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NI USB-621x User Manual

1. Ww NATIONAL Pp INSTRUMENTS D GND USER P0 0 IN P1 0 OUT PO 1 IN P0 2 IN P1 2 OUT P0 3 IN P1 3 OUT D GND D GND P0 4 IN P1 4 OUT PO 5 IN P1 5 OUT P0 6 IN P1 6 OUT P0 7 IN P1 7 OUT D GND D GND 45V AL GND D GND AI SENSE e Al x 4 Source 0 1 pF i 5kQ NZ AI GND USB 621 x Device EE oes Floating FS DZ S Ss sk ss eme A NI USB 6218 S e Al x 4 Et Aix EE GS Ground i Referenced FS Source Figure A 14 USB 6218 BNC Top Panel and Pinout NI USB 621x User Manual A 22 ni com Appendix A Device Specific Information Table A 7 Default NI DAQmx Counter Timer Pins Counter Timer Signal Default Terminal Name CTR 0 SRC PFI 0 CTR 0 GATE PFI 1 CTR 0 AUX PFI 9 CTR 0 OUT PFI 4 CTROA PFI 0 CTROZ PFI 1 CTROB PFI 9 CTR 1 SRC PFI 3 CTR 1 GATE PFI 2 CTR 1 AUX PFI 10 CTR 1 OUT PFI 5 CTR1A PFI3 CTR1Z PFI 2 CTR1B PFI 10 FREQ OUT PFI 6 hy Note For more information about default NI DAQmx counter inputs refer to Connecting Counter Signals in the NI DAQmx Help or the LabVIEW Help in versi
2. Al e o OO Bias Resistors o4 4 6 o e l z see text a x Floating Instrumentation Signal Vs 4 Amplifier Source i o bd so PGIA F Al 75 Measured Voltage Oo so 9 Bias Current a e s o e Return e ni Paths se O is o Input Multiplexers O4 9 W Al SENSE AI GND I O Connector USB 6210 621 1 6212 Device Configured in Differential Mode Figure 4 18 Differential Connections for Floating Signal Sources with Balanced Bias Resistors Both inputs of the NI PGIA require a DC path to ground in order for the NI PGIA to work If the source is AC coupled capacitively coupled the NI PGIA needs a resistor between the positive input and AI GND If the source has low impedance choose a resistor that is large enough not to significantly load the source but small enough not to produce significant input offset voltage as a result of input bias current typically 100 kQ to 1 MQ In this case connect the negative input directly to AI GND If the source has high output impedance balance the signal path as previously described using the same value resistor on both the positive and negative inputs be aware that there is some gain error from loading down the source as shown in Figure 4 19 National Instruments Corporation 4 29 NI USB 621x User Manual Chapter 4 Analog Input NI USB 621x
3. Wy NATIONAL P INSTRUMENTS D GND TL T n PFI 8 P2 0 PO 1 PFI9 P2 1 P0 2 PFI 10 P2 2 P0 3 PFI 11 P2 3 D GND D GND P0 4 PFI 12 P2 4 P0 5 PFI 13 P2 5 P0 6 PFI 14 P2 6 P0 7 PFI 15 P2 7 D GND D GND 45V AI GND D GND Al SENSE PFI 0 P1 0 PFI 1 P1 1 PFI 2 P1 2 PFI 3 P1 3 m MEE Grn Alx Floating oGS PFI 4 P1 4 PFI 5 P1 5 Source FS i O1 S5kQ NZ AI GND USB 621x Device Ae AT 2e AS ae i o Alx me 1 i Alx LES GS Ground i Referenced FS i ome P OdprT 5kn A NZ AI GND NiUSB0218 6216 USB 621x Device Figure A 5 USB 6212 6216 BNC Top Panel and Pinout NI USB 621x User Manual A 14 ni com Appendix A Device Specific Information Table A 5 Default NI DAQmx Counter Timer Pins Counter Timer Signal Default Terminal Name CTR 0 SRC PFI 8 CTR 0 GATE PFI 9 CTR 0 AUX PFI 10 CTR 0 OUT PFI 12 CTROA PFI 8 CTROZ PFI 9 CTROB PFI 10 CTR 1 SRC PFI 3 CTR 1 GATE PFI 4 CTR 1 AUX PFI 11 CTR 1 OUT PFI 13 CTR1A PFI3 CTR1Z PFI 4 CTR1B PFI 11 FREQ OUT PFI 14 Sy Note For more information about default NI DAQmx counter inputs refer to Connecting Counter Signals in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later Connecting Signals to the USB 6212 6216 BNC Analog Input You can use each analog input BNC connector for one
4. Filtered Input PFI Terminal Filtered input goes high when terminal is sampled Filter Clock 123 4 12 3 4 5 high on five consecutive 40 MHz filter clocks Prescaling NI USB 621x User Manual Figure 8 31 Filter Example Enabling filters introduces jitter on the input signal For the 125 ns and 6 425 us filter settings the jitter is up to 25 ns On the 2 56 ms setting the jitter is up to 10 025 us Referto the KnowledgeBase document Digital Filtering with M Series and CompactDAQ for more information about digital filters and counters To access this KnowledgeBase go to ni com info and enter the info code rddfms Prescaling allows the counter to count a signal that is faster than the maximum timebase of the counter USB 621x devices offer 8X and 2X prescaling on each counter prescaling can be disabled Each prescaler consists of a small simple counter that counts to eight or two and rolls over This counter can run faster than the larger counters which simply count the rollovers of this smaller counter Thus the prescaler acts as a frequency divider on the Source and puts out a frequency that is one eighth or one half of what it is accepting External Signal Prescaler Rollover Used as Source by Counter Counter Value 0 X 1 Figure 8 32 Prescaling
5. AO Sample Clock Timebase AO Start Trigger AO Sample Clock Delay i From Start Trigger Figure 5 6 AO Sample Clock and AO Start Trigger AO Sample Clock Timebase Signal The AO Sample Clock Timebase ao SampleClockTimebase signal is divided down to provide a source for AO Sample Clock You can route any of the following signals to be the AO Sample Clock Timebase signal e 20MBZz Timebase e 100 kHz Timebase e USB 6211 6215 Devices PFI lt 0 3 gt e USB 6212 6216 Devices PFI lt 0 15 gt e USB 6218 Devices PFI lt 0 3 gt PFI lt 8 11 gt AO Sample Clock Timebase is not available as an output on the I O connector You might use AO Sample Clock Timebase if you want to use an external sample clock signal but need to divide the signal down If you want to use an external sample clock signal but do not need to divide the signal then you should use AO Sample Clock rather than AO Sample Clock Timebase National Instruments Corporation 5 9 NI USB 621x User Manual Chapter 5 Analog Output Getting Started with AO Applications in Software You can use a USB 621x device in the following analog output applications e Single point on demand generation Finite generation e Continuous generation e Waveform generation You can perform these generations through programmed I O or USB Signal Stream data transfer mechanisms Some of the applicati
6. Frequency Generator e FREQ OUT Divisor 1 16 Figure 8 27 Frequency Generator Block Diagram The frequency generator generates the Frequency Output signal The Frequency Output signal is the Frequency Output Timebase divided by a number you select from to 16 The Frequency Output Timebase can be either the 20 MHz Timebase divided by 2 or the 100 kHz Timebase The duty cycle of Frequency Output is 50 if the divider is either 1 or an even number For an odd divider suppose the divider is set to D In this case Frequency Output is low for D 1 2 cycles and high for D 1 2 cycles of the Frequency Output Timebase Figure 8 28 shows the frequency generator output waveform when the divider is set to 5 Frequency Output Timebase FREQ OUT Divisor 5 Figure 8 28 Frequency Generator Output Waveform National Instruments Corporation 8 25 NI USB 621x User Manual Chapter 8 Counters Frequency Output can be routed out to any output PFI terminal All PFI terminals are set to high impedance at startup The FREQ OUT signal also can be routed to DO Sample Clock and DI Sample Clock In software program the frequency generator as you would program one of the counters for pulse train generation For information about connecting counter signals refer to the Default Counter Timer Pinouts s
7. N No NK Figure 8 11 Method 1b 8 11 NI USB 621x User Manual Chapter 8 Counters Method 2 Measure High Frequency with Two Counters lIn this method you measure one pulse of a known width using your signal and derive the frequency of your signal from the result This method is good for high frequency signals In this method you route a pulse of known duration T to the Gate of a counter You can generate the pulse using a second counter You also can generate the pulse externally and connect it to a PFI terminal You only need to use one counter if you generate the pulse externally Route the signal to measure F1 to the Source of the counter Configure the counter for a single pulse width measurement Suppose you measure the width of pulse T to be N periods of F1 Then the frequency of F1 is N T Figure 8 12 illustrates this method Another option would be to measure the width of a known period instead of a known pulse me Width of Pulse T Pulse Pulse _ Gate 1 2 zn N F1 4 Source F1 A 4 Pulse Width Width of y _N Measurement Pulse F1 Frequency of F1 2 NI USB 621x User Manual Figure 8 12 Method 2 8 12 ni com Chapter 8 Counters Method 3 Measure Large Range of Frequencies Using Two Counters By using two counters you can accurately measure a signal that might be high or low frequency This techniqu
8. Figure 1 3 USB Cable Strain Relief on USB 621x BNC Devices Note You can provide cable management for signal wires to from the screw terminals and BNC connectors on USB 621x BNC devices by threading a zip tie through the strain relief holes and tightening it around the signal wires and BNC cables as shown in Figure 1 3 National Instruments Corporation 1 5 NI USB 621x User Manual Chapter 1 Getting Started Mounting the USB 621x You can use the USB 621x on a desktop or mount it to a standard DIN rail or a panel Desktop Use You can use the USB 621x on a desktop USB 621x Screw Terminal Mass Termination devices have grooves on the underside that allow it to be stacked with other like sized USB 621x devices as shown in Figure 1 2 3 Note USB 621x BNC devices cannot be stacked USB 621x Screw Terminal Mass Termination Devices For secure desktop use adhere the supplied rubber non skid feet to the underside of the USB 621x device as shown in Figure 1 4 3 Note Do not apply the rubber feet if you are panel mounting the USB 621x or stacking the device on another USB 621x device Sea J Figure 1 4 Rubber Feet Application DIN Rail Mounting The DIN rail mounting kit part number 779689 01 not included in your USB 621x kit is an accessory you can use to mount the USB 621x family of products to a standard DIN rail iyi Note Apply strain relief as descri
9. 7v Figure A 18 Analog Output Circuitry National Instruments Corporation A 25 NI USB 621x User Manual Appendix A NI USB 621x User Manual Device Specific Information Refer to the Connecting Analog Output Signals section of Chapter 5 Analog Output for more information USER The USER BNC connector allows you to use a BNC connector for a digital or timing I O signal of your choice The USER BNC connector is routed internal to the USB 6218 BNC to the USER screw terminal as shown in Figure A 19 Internal USER BNC i Connection i USER r Px x Screw Pxx NA Terminal Px x D GND Block Px x Px x D GND Figure A 19 USER BNC Connection Figure A 20 shows an example of how to use the USER BNC To access the PFI 9 P0 5 signal from a BNC connect USER on the screw terminal block to PFI 9 P0 5 with a wire Internal USERBNC Connection CE D GND USER POO IN P1 0 OUT P0 1 IN P11 QUT VW P0 2 IN P1 2 OUT D GND PO 3 IN Wire P1 3 OUT D GND DGND PO 4 IN P1 4 OUT Screw PO 5 IN P1 5 OUT Terminal BNC Cable PO 6 IN P1 6 OUT Block PO 7 IN P1 7 OUT D GND D GND Mon Al GND Al SENSE Beis Signal Figure A 20 Connecting PFI 9 P0 5 to USER BNC A 26 ni com Troubleshooting Analog Input This section contains common questions about USB 621x devices I
10. AO GND Bv Figure A 9 Analog Output Circuitry Refer to the Connecting Analog Output Signals section of Chapter 5 Analog Output for more information Digital 1 0 and Timing 1 0 You can access digital I O and timing I O signals on the BNC connectors labeled PFI lt 0 7 gt P1 lt 0 7 gt Figure A 10 shows the DIO TIO circuitry on the USB 6212 6216 BNC e PFI x P1 x D GND Figure A 10 Digital 1 0 and Timing 1 0 Circuitry National Instruments Corporation A 17 NI USB 621x User Manual Appendix A NI USB 621x User Manual Device Specific Information Refer to the Digital I O on USB 6212 6216 Devices section of Chapter 6 Digital I O and the Connecting PFI Input Signals section of Chapter 7 PFI for more information USER The USER BNC connector allows you to use a BNC connector for a digital or timing I O signal of your choice The USER BNC connector is routed internal to the USB 6212 6216 BNC to the USER screw terminal as shown in Figure A 11 Internal USERBNC Connection USER Px x Screw Px x Terminal Px x D GND Block Px x Px x D GND Figure A 11 USER BNC Connection Figure A 12 shows an example of how to use the USER BNC To access the PFI 8 P2 0 signal from a BNC connect USER on the screw terminal block to PFI 8 P2 0 with a wire Internal USER BNC Connection e m eee D
11. cha SL TL ChB Lid pesao Counter Value 5X6 X7 8X9 TX ENT Y 8 X8 Figure 8 15 X2 Encoding 6 16 ni com Chapter 8 Counters e X4 Encoding Similarly the counter increments or decrements on each edge of channels A and B for X4 encoding Whether the counter increments or decrements depends on which channel leads the other Each cycle results in four increments or decrements as shown in Figure 8 16 Cha pee up E o l ChB Counter Value 5 X 6X 7X8 X 9X10X11X12 X13 13X12 X11 X10X 9X 8X7 XE 5 Figure 8 16 X4 Encoding Channel Z Behavior Some quadrature encoders have a third channel channel Z which is also referred to as the index channel A high level on channel Z causes the counter to be reloaded with a specified value in a specified phase of the quadrature cycle You can program this reload to occur in any one of the four phases in a quadrature cycle Channel Z behavior when it goes high and how long it stays high differs with quadrature encoder designs You must refer to the documentation for your quadrature encoder to obtain timing of channel Z with respect to channels A and B You must then ensure that channel Z is high during at least a portion of the phase you specify for reload For instance in Figure 8 17 channel Z is never high when channel A is high and channel B is low Thus the reload must oc
12. Figure 3 1 Grounding a USB 621x BNC Device through the Ground Lug Screw USB Device Fuse Replacement USB 621x Mass Termination Devices USB 621x Mass Termination devices have a replaceable 0 75A 125V fuse Littelfuse part number 0453 750 that protects the device from overcurrent through the 5 V terminal s To replace a broken fuse in the USB 621x Mass Termination complete the following steps while referring to Figure 3 2 1 Remove the USB cable and any I O signal wires from the device 2 Remove the four Phillips screws on the bottom of the device to remove the device top You may have to remove the rubber feet National Instruments Corporation 3 4 NI USB 621x User Manual Chapter 3 Connector and LED Information 3 Replace the broken fuse in the socket Figure 3 2 shows the fuse location 1 0 75A 125V Fuse Socketed Figure 3 2 USB 621x Mass Termination Fuse Location 4 Replace the device top and reattach with the screws ik Note Unscrewing and reinstalling the thread forming screws over time will produce a compromised connection between the device top and bottom NI USB 621x User Manual 3 5 ni com Chapter 3 Connector and LED Information PWR ACT LED Indicator The PWR ACT LED indicator indicates device status Table 3 2 shows the behavior of the PWR ACT LED Table 3 2 PWR ACT LED Status LED State Device Status Not lit Device not powered or device error Refer to
13. You can specify a delay from when the counter is armed to the beginning of the pulse The delay is measured in terms of a number of active edges of the Source input You can specify a pulse width The pulse width is also measured in terms of a number of active edges of the Source input You also can specify the active edge of the Source input rising or falling National Instruments Corporation 8 21 NI USB 621x User Manual Chapter 8 Counters NI USB 621x User Manual Figure 8 22 shows a generation of a pulse with a pulse delay of four and a pulse width of three using the rising edge of Source Counter Armed SOURCE OUT Figure 8 22 Single Pulse Generation Single Pulse Generation with Start Trigger The counter can output a single pulse in response to one pulse on a hardware Start Trigger signal The pulse appears on the Counter n Internal Output signal of the counter You can route the Start Trigger signal to the Gate input of the counter You can specify a delay from the Start Trigger to the beginning of the pulse You also can specify the pulse width The delay and pulse width are measured in terms of a number of active edges of the Source input After the Start Trigger signal pulses once the counter ignores the Gate input Figure 8 23 shows a generation of a pulse with a pulse delay of four and a pulse width of three using the rising
14. Each pin is called PFI x when used as a PFI each pin is named P1 x or P2 x when used as a digital input or output NI USB 621x User Manual 6 4 ni com Chapter 6 Digital I O Figure 6 3 shows the circuitry of one DIO line Each DIO line is similar The voltage input and output levels and the current drive levels of the DIO lines are listed in the NJ USB 621x Specifications Static DO Buffer Digital Line Direction Control l O Protection e PO x Static DI Weak Pull Down Figure 6 3 USB 6212 6216 Digital 1 0 Circuitry The following sections provide information about the various parts of the DIO circuit Static DIO on USB 6212 6216 Devices Each of the USB 6212 6216 DIO lines can be used as a static DI or DO line You can use static DIO lines to monitor or control digital signals Each DIO can be individually configured as a digital input DI or digital output DO All samples of static DI lines and updates of DO lines are software timed 1 0 Protection on USB 6212 6216 Devices Each DIO and PFI signal is protected against overvoltage undervoltage and overcurrent conditions as well as ESD events However you should avoid these fault conditions by following these guidelines National Instruments Corporation If you configure a PFI or DIO line as an output do not connect it to any external signal source ground signal or power supply If you configure a PFI or DIO line as an output
15. With single point on demand edge counting the counter counts the number of edges on the Source input after the counter is armed On demand refers to how the software can read the counter contents at any time without disturbing the counting process Figure 8 2 shows an example of single point edge counting Counter Armed SOURCE FLAL IL 1 2 3 4 5 Counter Value 0 Figure 8 2 Single Point Edge Counting You also can use a pause trigger to pause or gate the counter When the pause trigger is active the counter ignores edges on its Source input When the pause trigger is inactive the counter counts edges normally 8 2 ni com Chapter 8 Counters You can route the pause trigger to the Gate input of the counter You can configure the counter to pause counting when the pause trigger is high or when it is low Figure 8 3 shows an example of on demand edge counting with a pause trigger Counter Armed Pause Trigger Pause when Low G i i L HEELEETAT T LIERTA Oo 1 2 3 4 5 SOURCE f Counter Value 0 Figure 8 3 Single Point Edge Counting with Pause Trigger Buffered Sample Clock Edge Counting With buffered edge counting edge counting using a sample clock the counter counts the number of edges on the Source input after the counter is armed The value of the counter is sampled on each active edge of a sample clock A USB Signal Stream transfe
16. National Instruments support and services C 1 NET languages documentation xvii NI support and services C 1 NI DAQmx default counter terminals 8 32 documentation xiv device documentation browser xviii enabling duplicate count prevention 8 39 NI DAQmx Base documentation xiv NI PGIA 4 2 non referenced single ended connections using with floating signal sources 4 30 using with ground referenced signal sources 4 35 when to use with floating signal sources 4 26 when to use with ground referenced signal sources 4 32 NI USB 621x User Manual Index 0 on demand acquisitions 4 8 edge counting 8 2 timing 4 8 order of channels for scanning 4 6 other software 1 1 output signal glitches B 3 minimizing glitches 5 2 overview 2 1 P panel mounting 1 7 pause trigger 8 33 period measurement 8 6 buffered 8 7 single 8 6 PFI 7 1 connecting input signals 7 4 exporting timing output signals using PFI terminals 7 3 filters 7 4 T O protection 7 6 programmable power up states 7 6 terminals as static digital I Os 7 3 using terminals as static digital I Os 7 3 using terminals as timing input signals 7 2 pin assignments See pinouts pinouts counter default 8 32 device 1 2 USB 6210 A 2 USB 6211 A 4 USB 6212 BNC A 13 USB 6212 Mass Termination A 8 USB 6212 Screw Terminal A 6 USB 6215 A 4 NI USB 621x User Manual USB 6216 BNC A 13 USB 6216 Mass Termination A 8 USB 6216 Screw Te
17. When performing analog input measurements you either can perform software timed or hardware timed acquisitions Software Timed Acquisitions With a software timed acquisition software controls the rate of the acquisition Software sends a separate command to the hardware to initiate each ADC conversion In NI DAQmx software timed acquisitions are referred to as having on demand timing Software timed acquisitions are also referred to as immediate or static acquisitions and are typically used for reading a single sample of data 4 8 ni com Chapter 4 Analog Input e Hardware Timed Acquisitions With hardware timed acquisitions a digital hardware signal AI Sample Clock controls the rate of the acquisition This signal can be generated internally on your device or provided externally Hardware timed acquisitions have several advantages over software timed acquisitions The time between samples can be much shorter The timing between samples is deterministic Hardware timed acquisitions can use hardware triggering Hardware timed operations are buffered In a buffered acquisition data is moved from the DAQ device s onboard FIFO memory to a PC buffer using USB signal streams or programmed I O before it is transferred to application memory Buffered acquisitions typically allow for much faster transfer rates than non buffered acquisitions because data is moved in large blocks rather than one point at a time One pr
18. When using a EU d USB 6215 6218 i you must connect D GND i D GND and or Al GND l O Connector to the local ground on your system USB 6210 6211 6215 6218 Device Figure 6 2 USB 6210 6211 6215 6218 Digital 1 0 Connections N Caution Exceeding the maximum input voltage ratings which are listed in the NI USB 621x Specifications can damage the DAQ device and the computer NI is not liable for any damage resulting from such signal connections National Instruments Corporation 6 3 NI USB 621x User Manual Chapter 6 Digital I O Getting Started with DIO Applications in Software on USB 6210 6211 6215 6218 Devices You can use the USB 6210 6211 6215 6218 device in the following digital I O applications e Static digital input e Static digital output 3 Note For more information about programming digital I O applications and triggers in software refer to the NI DAQmx Help or the LabVIEW Help in version 8 0 or later Digital 1 0 on USB 6212 6216 Devices USB 6212 6216 devices contain e Upto 16 DIO signals P0 lt 0 15 gt Each signal can be individually configured as either Static digital input Static digital output e 16 PFI DIO signals PFI lt 0 7 gt P1 lt 0 7 gt and PFI lt 8 15 gt P2 lt 0 7 gt Each signal can be individually configured as either Static digital input Static digital output PFI input PFI output
19. Analog Input with this amplified voltage The amount of amplification the gain is determined by the analog input range as shown in Figure 4 2 Vin o Vin 9 3 Instrumentation Amplifier V Vm Vin Vin x Gain Measured Voltage ee Figure 4 2 NI PGIA Table 4 1 shows how signals are routed to the NI PGIA Table 4 1 Signals Routed to the NI PGIA AI Ground Reference Signals Routed to the Positive Signals Routed to the Negative Settings Input of the NI PGIA Vj Input of the NI PGIA Vj RSE AI 0 31 AI GND NRSE AI 0 31 AI SENSE DIFF AI lt 0 7 gt AI 8 15 AI lt 16 23 gt AI lt 24 31 gt For differential measurements AI 0 and AI 8 are the positive and negative inputs of differential analog input channel 0 For a complete list of signal pairs that form differential input channels refer to the O Connector Signal Descriptions section of Chapter 3 Connector and LED Information AI ground reference setting is sometimes referred to as AI terminal configuration UN Caution The maximum input voltages rating of AI signals with respect to AI GND and for differential signals with respect to each other are listed in the NJ USB 62 Ix Specifications Exceeding the maximum input voltage of AI signals distorts the measurement results Exceeding the maximum input voltage rating also can damage the device an
20. Figure 6 4 USB 6212 6216 Digital 1 0 Connections Caution Exceeding the maximum input voltage ratings which are listed in the NI USB 621x Specifications can damage the DAQ device and the computer NI is not liable for any damage resulting from such signal connections Getting Started with DIO Applications in Software on USB 6212 6216 Devices You can use the USB 6212 6216 device in the following digital I O applications e Static digital input e Static digital output 3 Note For more information about programming digital I O applications and triggers in software refer to the NI DA Qmx Help or the LabVIEW Help in version 8 0 or later National Instruments Corporation 6 7 NI USB 621x User Manual PFI USB 621x devices have multiple Programmable Function Interface PFI signals Each input PFI can be individually configured as the following e A Static digital input e A timing input signal for AI AO or counter timer functions Each output PFI can be individually configured as the following e A Static digital output e A timing output signal from AI AO or counter timer functions iyi Note USB 6212 6216 Devices PFI signals on USB 6212 6216 devices can be configured as input or output Each PFI input also has a programmable debouncing filter Figure 7 1 shows the circuitry of an input PFI line U Isolation lt 7 l Bamier sen USB 6215 6216 6218 i devices only PFI DIO Pin e4 I O Pro
21. LabVIEW Help in version 8 0 or later 8 32 ni com Chapter 8 Counters Counter Triggering Counters support three different triggering actions e Arm Start Trigger To begin any counter input or output function you must first enable or arm the counter Software can arm a counter or configure counters to be armed on a hardware signal Software calls this hardware signal the Arm Start Trigger Internally software routes the Arm Start Trigger to the Counter n HW Arm input of the counter For counter output operations you can use the arm start trigger in addition to the start and pause triggers For counter input operations you can use the arm start trigger to have start trigger like behavior The arm start trigger can be used for synchronizing multiple counter input and output tasks When using an arm start trigger the arm start trigger source is routed to the Counter n HW Arm signal Start Trigger For counter output operations a start trigger can be configured to begin a finite or continuous pulse generation Once a continuous generation has triggered the pulses continue to generate until you stop the operation in software For finite generations the specified number of pulses is generated and the generation stops unless you use the retriggerable attribute When you use this attribute subsequent start triggers cause the generation to restart When using a start trigger the start trigger source is routed to the Counte
22. NI USB 621x User Manual DAQ specifications and manuals are available as PDFs You must have Adobe Acrobat Reader with Search and Accessibility 5 0 5 or later installed to view the PDFs Refer to the Adobe Systems Incorporated Web site at www adobe com to download Acrobat Reader Refer to the National Instruments Product Manuals Library at ni com manuals for updated documentation resources xviii ni com Getting Started NI USB 621x devices feature up to 32 analog input AI channels up to two analog output AO channels two counters and up to eight lines of digital input DI and up to eight lines of digital output DO or 32 bidirectional static DIO lines Installing NI DAQmx The NI DAQmx for USB Devices Getting Started Guide which you can download from ni com manuals offers NI DAQmx users step by step instructions for installing software and hardware configuring channels and tasks and getting started developing an application Installing Other Software If you are using other software refer to the installation instructions that accompany your software Installing the Hardware The NI DAQmx for USB Devices Getting Started Guide contains non software specific information about how to install USB devices Before installing your DAQ device you must install the software you plan to use with the device National Instruments Corporation 1 1 NI USB 621x User Manual Chapter 1 Getting Started Device Sel
23. but my readings are random and drift rapidly What is wrong In differential mode if the readings from the DAQ device are random and drift rapidly you should check the ground reference connections The signal can be referenced to a level that is considered floating with reference to the device ground reference Even if you are in differential mode you must still reference the signal to the same ground level as the device National Instruments Corporation B 1 NI USB 621x User Manual Appendix B Troubleshooting NI USB 621x User Manual reference There are various methods of achieving this reference while maintaining a high common mode rejection ratio CMRR These methods are outlined in the Connecting Analog Input Signals on USB 6210 6211 6212 Devices and Connecting Analog Input Signals on USB 6215 6216 6218 Devices sections of Chapter 4 Analog Input AI GND is an AI common signal that routes directly to the ground connection point on the devices You can use this signal if you need a general analog ground connection point to the device Refer to the When to Use Differential Connections with Ground Referenced Signal Sources section of Chapter 4 Analog Input for more information How can I use the AI Sample Clock and AI Convert Clock signals on a USB 621x device to sample the AI channel s USB 621x devices use AI Sample Clock and AI Convert Clock to perform interval sampling As Figure B 1 shows AI Sample Clock controls the sa
24. edges occurring on the Source input between the two active edges of the Gate signal You can calculate the period of the Gate input by multiplying the period of the Source signal by the number of edges returned by the counter Single Period Measurement With single period measurement the counter counts the number of rising or falling edges on the Source input occurring between two active edges of the Gate input On the second active edge of the Gate input the counter stores the count in a hardware save register and ignores other edges on the Gate and Source inputs Software then reads the stored count Figure 8 7 shows an example of a single period measurement GATE SOURCE K A Si y Counter Value 0 1 2 3 4 5 HW Save Register 5 Figure 8 7 Single Period Measurement 8 6 ni com Chapter 8 Counters Buffered Period Measurement Buffered period measurement is similar to single period measurement but buffered period measurement measures multiple periods The counter counts the number of rising or falling edges on the Source input between each pair of active edges on the Gate input At the end of each period on the Gate signal the counter stores the count in a hardware save register A USB Signal Stream transfers the stored values to host memory The counter begins on the first active edge of the Gate after it is armed The arm usually occurs in th
25. generations analog output data 5 2 buffered hardware timed 5 3 clock 10 1 continuous pulse train 8 23 frequency 8 25 hardware timed 5 2 pulse for ETS 8 26 pulse train 8 23 retriggerable single pulse 8 22 simple pulse 8 21 single pulse 8 21 single pulse with start trigger 8 22 software timed 5 2 getting started 1 1 AI applications in software 4 22 AO applications in software 5 10 DIO applications in software USB 6210 6211 6215 6218 6 4 USB 6212 6216 6 7 ghost voltages when sampling multiple channels B 1 ground reference connections checking B 1 settings 4 1 4 3 analog input 4 3 ground referenced signal sources connecting 4 31 description 4 31 using in differential mode 4 34 using in non referenced single ended mode 4 35 when to use in differential mode 4 32 when to use in non referenced single ended mode 4 32 when to use in RSE mode 4 33 NI USB 621x User Manual I 6 H hardware 1 1 2 1 hardware timed acquisitions 4 9 generations 5 2 help technical support C 1 T O connector 3 1 USB 6210 pinout A 2 USB 6211 pinout A 4 USB 6212 BNC pinout A 13 USB 6212 Mass Termination pinout A 8 USB 6212 Screw Terminal pinout A 6 USB 6215 pinout A 4 USB 6216 BNC pinout A 13 USB 6216 Mass Termination pinout A 8 USB 6216 Screw Terminal pinout A 6 USB 6218 BNC pinout A 21 USB 6218 Screw Terminal pinout A 19 I O protection 6 2 6 5 7 6 input signals using PFI terminals as 7 2 inser
26. is sometimes referred to as a posttriggered acquisition Using a Digital Source To use AI Start Trigger with a digital source specify a source and an edge The source can be any of the following signals e USB 6210 6211 6215 Devices PFI lt 0 3 gt e USB 6212 6216 Devices PFI lt 0 15 gt e USB 6218 Devices PFI lt 0 3 gt PFI lt 8 11 gt e Counter n Internal Output The source also can be one of several other internal signals on your DAQ device Refer to Device Routing in MAX in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later for more information You also can specify whether the measurement acquisition begins on the rising edge or falling edge of AI Start Trigger Routing Al Start Trigger to an Output Terminal You can route AI Start Trigger out to any output PFI terminal The output is an active high pulse The device also uses AI Start Trigger to initiate pretriggered DAQ operations In most pretriggered applications a software trigger generates AI Start Trigger Refer to the AJ Reference Trigger Signal section for a complete description of the use of AI Start Trigger and AI Reference Trigger in a pretriggered DAQ operation 4 20 ni com Chapter 4 Analog Input Al Reference Trigger Signal Use a reference trigger ai ReferenceTrigger signal to stop a measurement acquisition To use a reference trigger specify a buffer of finite size and a number of pretrigger samples samples that occur b
27. safety 3 A common reference point for an electrical system A form of triggering where you set the start time of an acquisition and gather data at a known position in time relative to a trigger signal 1 Hertz The SI unit for measurement of frequency One hertz Hz equals one cycle per second 2 The number of scans read or updates written per second Input Output The transfer of data to from a computer system involving communications channels operator interface devices and or data acquisition and control interfaces 1 The electrical characteristic of a circuit expressed in ohms and or capacitance inductance 2 Resistance Inch or inches A set of high level software functions that controls a specific GPIB VXI or RS232 programmable instrument or a specific plug in DAQ device Instrument drivers are available in several forms ranging from a function callable language to a virtual instrument VI in LabVIEW G 8 ni com instrumentation amplifier interchannel delay interface interrupt interrupt request line Ion IoL IRQ L LabVIEW LED lowpass filter LSB National Instruments Corporation G 9 Glossary A circuit whose output voltage with respect to ground is proportional to the difference between the voltages at its two inputs An instrumentation amplifier normally has high impedance differential inputs and high common mode rejection Amount of time that passes between sampling
28. to the instrument front end Common mode rejection is only a relevant specification for systems having a balanced or differential input 1 Any voltage present at the instrumentation amplifier inputs with respect to amplifier ground 2 The signal relative to the instrument chassis or computer s ground of the signals from a differential input This is often a noise signal such as 50 or 60 Hz hum Reciprocal of the interchannel delay The number of events such as zero crossings pulses or cycles 1 Software A memory location used to store a count of certain occurrences 2 Hardware A circuit that counts events When it refers to an instrument it refers to a frequency counter A circuit that counts external pulses or clock pulses timing G 4 ni com DAC DAQ DAQ STC2 data acquisition data transfer dB DC device Glossary Digital to Analog Converter An electronic device often an integrated circuit that converts a digital number into a corresponding analog voltage or current In the instrumentation world DACs can be used to generate arbitrary waveform shapes defined by the software algorithm that computes the digital data pattern which is fed to the DAC Data acquisition The process of collecting and measuring electrical signals from sensors transducers and test probes or fixtures and inputting them to a computer for processing Data acquisition system timing controller chip The gener
29. 0 3 gt e USB 6212 6216 Devices PFI lt 0 15 gt National Instruments Corporation 5 5 NI USB 621x User Manual Chapter 5 Analog Output e USB 6218 Devices PFI lt 0 3 gt PFI lt 8 11 gt e Al Start Trigger ai StartTrigger The source also can be one of several internal signals on your USB 621x device Refer to Device Routing in MAX in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later for more information You also can specify whether the waveform generation begins on the rising edge or falling edge of AO Start Trigger Routing AO Start Trigger to an Output Terminal You can route AO Start Trigger out to any output PFI terminal The output is an active high pulse AO Pause Trigger Signal Use the AO Pause Trigger signal ao PauseTrigger to pause the generation of AO samples in a DAQ sequence That is when AO Pause Trigger is active no samples occur If the AO Sample Clock is derived from AO Sample Clock Timebase for example when you choose the onboard 20 MHz or 100 kHz Timebase the AO Sample Clock Timebase is divided down by a programmable clock divider circuit and then drives AO Sample Clock as shown in Figure 5 3 In this case AO Pause Trigger masks off AO Sample Clock Timebase pulses from the programmable clock divider For example an internal timebase is routed to AO Sample Clock Timebase and the Timebase divisor is 5 as shown in Figure 5 4 AO Sample Clock normally asserts once for
30. 10 V and the input range of channel 1 is 200 mV to 200 mV You can connect channel 2 to AI GND or you can use the internal ground signal refer to Internal Channels in the NI DAQmx Help Set the input range of channel 2 to 200 mV to 200 mV to match channel 1 Then scan channels in the order 0 2 1 Inserting a grounded channel between signal channels improves settling time because the NI PGIA adjusts to the new input range setting faster when the input is grounded Minimize Voltage Step between Adjacent Channels When scanning between channels that have the same input range the settling time increases with the voltage step between the channels If you know the expected input range of your signals you can group signals with similar expected ranges together in your scan list For example suppose all channels in a system use a 5 to 5 V input range The signals on channels 0 2 and 4 vary between 4 3 V and 5 V The signals on channels 1 3 and 5 vary between 4 V and 0 V Scanning channels in the order 0 2 4 1 3 5 produces more accurate results than scanning channels in the order 0 1 2 3 4 5 4 7 NI USB 621x User Manual Chapter 4 Analog Input Avoid Scanning Faster Than Necessary Designing your system to scan at slower speeds gives the NI PGIA more time to settle to a more accurate level Consider the following examples Example 1 Averaging many AI samples can increase the accuracy of the reading by decreasi
31. 320 uV 5 V to5 V 160 uV 1VtolV 32 uV 200 mV to 200 mV 6 4 uV Analog Input Ground Reference Settings USB 621x devices support the following analog input ground reference settings Differential Mode In DIFF mode USB 621x devices measure the difference in voltage between two AI signals e Referenced Single Ended Mode In RSE mode USB 621x devices measure the voltage of an AI signal relative to AI GND Non Referenced Single Ended Mode In NRSE mode USB 621x devices measure the voltage of an AI signal relative to the AI SENSE input The AI ground reference setting determines how you should connect your AI signals to the USB 621x device For more information refer to one of the following sections depending on your device e Connecting Analog Input Signals on USB 6210 6211 6212 Devices e Connecting Analog Input Signals on USB 6215 6216 6218 Devices Ground reference settings are programmed on a per channel basis For example you might configure the device to scan 12 channels four differentially configured channels and eight single ended channels USB 621x devices implement the different analog input ground reference settings by routing different signals to the NI PGIA The NI PGIA is a differential amplifier That is the NI PGIA amplifies or attenuates the difference in voltage between its two inputs The NI PGIA drives the ADC National Instruments Corporation 4 3 NI USB 621x User Manual Chapter 4
32. 5 4 data generation methods 5 2 fundamentals 5 1 getting started with applications in software 5 10 glitches on the output signal 5 2 range 5 2 signals 5 5 timing signals 5 5 trigger signals 5 4 triggering 5 4 troubleshooting B 3 analog output signals 5 5 AO Pause Trigger 5 6 AO Sample Clock 5 8 AO Sample Clock Timebase 5 9 AO Start Trigger 5 5 analog to digital converter 4 2 ANSI C documentation xvii AO FIFO 5 1 AO Pause Trigger signal 5 6 AO Sample Clock 5 2 AO Sample Clock signal 5 8 AO Sample Clock Timebase signal 5 9 AO Start Trigger signal 5 5 ao PauseTrigger 5 6 ao SampleClock 5 8 ao StartTrigger 5 5 applications counter input 8 2 counter output 8 21 edge counting 8 2 applying rubber feet 1 6 arm start trigger 8 33 NI USB 621x User Manual l 2 BNC cables 2 4 connecting signals A 15 A 23 board mounting 1 7 buffered edge counting 8 3 hardware timed acquisitions 4 9 hardware timed generations 5 3 period measurement 8 7 position measurement 8 18 pulse width measurement 8 5 semi period measurement 8 9 two signal edge separation measurement 8 20 bus interface 11 1 C cable management 1 5 cables 2 4 custom 2 4 USB 6212 Mass Termination A 10 USB 6216 Mass Termination A 10 calibration 1 2 2 2 certificate NI resources C 2 circuitry 2 2 cascading counters 8 35 changing data transfer methods between USB Signal Stream and programmed I O 11 2 channel scan
33. 621x cable management 1 5 cables and accessories 2 4 cabling 2 4 chassis ground 3 4 NI USB 621x User Manual Index combicon 2 4 desktop use 1 6 device security 1 8 DIN rail mounting kit 1 6 fuse replacement 3 4 information A 1 labeling 1 3 LED 3 6 panel mounting 1 7 signal labels 1 3 signal wire management 1 5 specifications xviii stacking 1 6 USB cable strain relief 1 4 using low impedance sources 4 6 using PFI terminals as static digital I Os 7 3 as timing input signals 7 2 to export timing output signals 7 3 using short high quality cabling 4 6 W waveform generation signals 5 5 Web resources C 1 X X1 encoding 8 16 X2 encoding 8 16 X4 encoding 8 17 NI USB 621x User Manual I 12 ni com
34. 621x top screw hole into the panel USB Device Security Cable Slot USB 621x BNC Devices The security cable slot shown in Figure 1 3 allows you to attach an optional antitheft device to your USB device Note The security cable is designed to act as a deterrent but might not prevent the device from being mishandled or stolen For more information refer to the documentation that accompanied the security cable S Note The security cable slot on the USB 621x BNC might not be compatible with all antitheft cables NI USB 621x User Manual 1 8 ni com DAQ System Overview Figure 2 1 shows a typical DAQ system which includes the USB 621x device programming software and PC DAQ systems involving the USB 621x Mass Termination device can also include signal conditioning devices and a cable for accessory connection The following sections contain more information about the components of a typical DAQ system Sensors and Transducers USB 621x Mass Termination Devices Only i Signal Cables and DAQ DAQ Personal Computer Conditioning Accessories Hardware Software or Laptop USB 621x Mass Termination Devices Only Figure 2 1 Components of a Typical DAQ System DAQ Hardware DAQ hardware digitizes signals performs D A conversions to generate analog output signals and measures and controls digital I O signals National Instruments Corporation 2 1 NI USB 621x User Manual C
35. 7 gt D GND Input USB 6210 6211 6215 6218 Devices Programmable Function Interface or Static Digital Input Channels 0 to 7 Each PFI terminal can be used to supply an external source for AI AO or counter timer inputs You also can use these terminals as static digital input lines PFI lt 4 7 gt PFI lt 12 15 gt P1 lt 0 7 gt D GND Output USB 6210 6211 6215 6218 Devices Programmable Function Interface or Static Digital Output Channels 0 to 7 You can route many different internal AI AO or counter timer outputs to each PFI terminal You also can use these terminals as static digital output lines P0 0 15 D GND Input or Output USB 6212 6216 Devices Port 0 Digital I O Channels 0 to 15 You can individually configure each signal as an input or output PFI lt 0 7 gt P1 lt 0 7 gt PFI lt 8 15 gt P2 lt 0 7 gt D GND Input or Output USB 6212 6216 Devices Programmable Function Interface or Digital I O Channels 0 to 15 Each of these terminals can be individually configured as a PFI terminal or a digital I O terminal As a PFI input each terminal can be used to supply an external source for AI AO DI and DO timing signals or counter timer inputs As a PFI output you can route many different internal AI AO DI or DO timing signals to each PFI terminal You also can route the counter timer outputs to each PFI terminal As a Port 1 or Port 2 d
36. Chapter 9 Isolation and Digital Isolators on USB 6215 6216 6218 Devices for more information The AO range is 10 V for USB 621x devices Minimizing Glitches on the Output Signal When you use a DAC to generate a waveform you may observe glitches on the output signal These glitches are normal when a DAC switches from one voltage to another it produces glitches due to released charges The largest glitches occur when the most significant bit of the DAC code changes You can build a lowpass deglitching filter to remove some of these glitches depending on the frequency and nature of the output signal Visit ni com support for more information about minimizing glitches Analog Output Data Generation Methods When performing an analog output operation you can perform software timed or hardware timed generations NI USB 621x User Manual Software Timed Generations Software controls the rate at which data is generated Software sends a separate command to the hardware to initiate each DAC conversion In NI DAQmx software timed generations are referred to as on demand timing Software timed generations are also referred to as immediate or static operations They are typically used for writing a single value out such as a constant DC voltage Hardware Timed Generations A digital hardware signal controls the rate of the generation This signal can be generated internally on your device or provided externally Hardware
37. Device Specific Information Table A 3 Default NI DAQmx Counter Timer Pins Counter Timer Signal Default Terminal Number Name CTR 0 SRC 33 PFI 8 CTR 0 GATE 34 PFI 9 CTR 0 AUX 35 PFI 10 CTR 0 OUT 38 PFI 12 CTROA 33 PFI 8 CTROZ 34 PFI 9 CTROB 35 PFI 10 CTR 1 SRC 4 PFI 3 CTR 1 GATE 6 PFI 4 CTR 1 AUX 36 PFI 11 CTR 1 OUT 39 PFI 13 CTR1A 4 PFI 3 CTR1Z 6 PFI 4 CTR1B 36 PFI 11 FREQ OUT 40 PFI 14 3 Note For more information about default NI DAQmx counter inputs refer to Connecting Counter Signals in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later National Instruments Corporation A 7 NI USB 621x User Manual Appendix A Device Specific Information USB 6212 6216 Mass Termination USB 6212 6216 Mass Termination Pinout Figure A 4 shows the pinout of the USB 6212 Mass Termination and USB 6216 Mass Termination For a detailed description of each signal refer to the O Connector Signal Descriptions section of Chapter 3 Connector and LED Information NI USB 621x User Manual A 8 ni com Appendix A Device Specific Information T Al 8 34 68 AlO Al 1 33 67 Al GND Al GND 32 66 AI9 Al 10 31 65 Al2 Al3 30 64 Al GND Al GND 29 63 Al 11 Al 4 28 62 Al SENSE Al GND 27 61 Al 1
38. Figure 9 1 1 Analog Input E 1 Isolation Barrier Analog Output h 8 Digital c I Routing Digital Bus S Digital I O and Clock Isolators Interface Bus Oo Generation Counters al PFI NA L3 E Figure 9 1 USB 6215 6216 6218 Block Diagram The bus interface circuitry is referenced to a non isolated ground The following table lists the ground symbols Ground Type Symbol Isolated Ground EVA Non Isolated Ground J ZIF 1 USB 6216 devices have PFI static DIO circuitry National Instruments Corporation 9 1 NI USB 621x User Manual Chapter 9 Isolation and Digital Isolators on USB 6215 6216 6218 Devices The non isolated ground is connected to the chassis ground of the PC Each isolated ground is not connected to the chassis ground of the PC The isolated ground can be at a higher or lower voltage relative to the non isolated ground All analog measurements are made relative to the isolated ground signal The isolated ground is an input to the USB 6215 6216 6218 device The user must connect this ground to the ground of system being measured or controlled For more information refer to the following e The Connecting Analog Input Signals on USB 6215 6216 6218 Devices section of Chapter 4 Analog Input e The Connecting Analog Output Signals section of Chapter 5 Analog Output e The Connecti
39. Gated Off Al Sample Clock Al Convert Clock Channel Measured 0123 0128 0128 Sample 1 Sample 2 Sample 3 e l gt lt gt Figure 4 11 Al Convert Clock Too Fast For Al Sample Clock Al Convert Clock Pulses Are Gated Off Al Sample Clock IL TE 0 1 2 3 Sample 2 Al Convert Clock 0 1 2 3 Sample 1 0 Sample 3 Channel Measured q Figure 4 12 Al Sample Clock and Al Convert Clock Improperly Matched Leads To Aperiodic Sampling Al Sample Clock UU 012 3 Sample 2 i 012 3 Sample 3 Al Convert Clock 012 3 Sample 1 Channel Measured Figure 4 13 Al Sample Clock and Al Convert Clock Properly Matched NI USB 621x User Manual 4 18 ni com Chapter 4 Analog Input A single external signal can drive both AI Sample Clock and AI Convert Clock at the same time In this mode each tick of the external clock causes a conversion on the ADC Figure 4 14 shows this timing relationship Al Sample Clock Al Convert Clock Channel Measured 012 3 01 2 3 01 Sample 1 Sample 2 Sample 3 lt gt lt bod Figure 4 14 Single External Signal Driving Al Sample Clock and Al Convert Clock Simultaneously Al Convert Clock Ti
40. Instruments Web site at ni com info and enter the info code feedback 2006 2009 National Instruments Corporation All rights reserved Important Information Warranty The NI USB 6210 NI USB 6211 NI USB 6212 NI USB 6215 NI USB 6216 and NI USB 6218 are warranted against defects in materials and workmanship for a period of one year from the date of shipment as evidenced by receipts or other documentation National Instruments will at its option repair or replace equipment that proves to be defective during the warranty period This warranty includes parts and labor The media on which you receive National Instruments software are warranted not to fail to execute programming instructions due to defects in materials and workmanship for a period of 90 days from date of shipment as evidenced by receipts or other documentation National Instruments will at its option repair or replace software media that do not execute programming instructions if National Instruments receives notice of such defects during the warranty period National Instruments does not warrant that the operation of the software shall be uninterrupted or error free A Return Material Authorization RMA number must be obtained from the factory and clearly marked on the outside of the package before any equipment will be accepted for warranty work National Instruments will pay the shipping costs of returning to the owner parts which are covered by warranty Nation
41. PFI 4 CTR1B 46 PFI 11 FREQ OUT 1 PFI 14 3 Note For more information about default NI DAQmx counter inputs refer to Connecting Counter Signals in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later USB 6212 6216 Mass Termination Cables and Accessories This section describes some cable and accessory options for USB 6212 6216 Mass Termination devices Refer to ni com for other accessory options including new devices UN Caution For compliance with Electromagnetic Compatibility EMC requirements this product must be operated with shielded cables and accessories If unshielded cables or accessories are used the EMC specifications are no longer guaranteed unless all unshielded cables and or accessories are installed in a shielded enclosure with properly designed and shielded input output ports NI USB 621x User Manual A 10 ni com Appendix A Device Specific Information SCC Accessories SCC provides portable modular signal conditioning to your DAQ system To connect your USB 6212 6216 Mass Termination device to an SCC module carrier such as the SC 2345 SC 2350 or SCC 68 use an SH68 68 EPM shielded cable The SCC carrier must be externally powered when used with a USB 6212 6216 Mass Termination device Refer to the 5 V Power section of Chapter 3 Connector and LED Information and the NI USB 621x Specifications for more information Refer to the SCC Configuration Guide available by going to ni com info and enteri
42. Prescaling is intended to be used for frequency measurement where the measurement is made on a continuous repetitive signal The prescaling counter cannot be read therefore you cannot determine how many edges have occurred since the previous rollover Prescaling can be used for event counting provided it is acceptable to have an error of up to seven or one Prescaling can be used when the counter Source is an external signal 8 36 ni com Chapter 8 Counters Prescaling is not available if the counter Source is one of the internal timebases S0OMHzTimebase 20MHzTimebase or 100kHzTimebase Duplicate Count Prevention Duplicate count prevention or synchronous counting mode is used when taking frequency or period measurements on USB 621x devices which ensures that a counter returns correct data in applications that use a slow or non periodic external source Duplicate count prevention applies only to buffered counter applications such as measuring frequency or period In such buffered applications the counter should store the number of times an external Source pulses between rising edges on the Gate signal Example Application That Works Correctly No Duplicate Counting Figure 8 33 shows an external buffered signal as the period measurement Source Rising Edge of Gate Counter detects rising edge of Gate on the next rising edge of Source Gate Source Counter Valu
43. Signal Name Label 4 User Defined Custom Label Figure 1 1 USB 621x Screw Terminal Signal Labels National Instruments Corporation 1 3 NI USB 621x User Manual Chapter 1 Getting Started USB Cable Strain Relief You can provide strain relief for the USB cable in the following ways e Cable Strain Relief Groove Method USB 621x Screw Terminal Mass Termination Devices Press the USB cable into one of the two grooves on the underside of the USB 621x Choose the USB cable groove that matches your USB cable size as shown in Figure 1 2a Zip Tie Method USB 621x Screw Terminal Mass Termination Devices Thread a zip tie through the zip tie bar on the underside of the USB 621x and tighten around the USB cable as shown in Figure 1 2b 1 USB Cable Strain Relief Groove Large 4 Zip Tie 2 USB Cable Strain Relief Groove Small 5 Zip Tie Bar 3 USB Cable 6 Stacking Groove Figure 1 2 USB Cable Strain Relief Options on USB 621 x Screw Terminal Mass Termination Devices NI USB 621x User Manual 1 4 ni com Chapter 1 Getting Started Locking USB Cable Method USB 621x BNC Devices Use the jackscrew on the locking USB cable included in the USB 621x BNC kit to securely attach the cable to the device as shown in Figure 1 3 1 Security Cable Slot 3 Jackscrew Hole 2 Locking USB Cable Jackscrew 4 Signal Wire Strain Relief
44. Start Trigger Internally software routes the Arm Start Trigger to the Counter n HW Arm input of the counter 8 30 ni com Chapter 8 Counters Routing Signals to Counter n HW Arm Input Any of the following signals can be routed to the Counter n HW Arm input e USB 6210 6211 6215 Devices PFI lt 0 3 gt e USB 6212 6216 Devices PFI lt 0 15 gt e USB 6218 Devices PFI lt 0 3 gt PFI lt 8 11 gt e AI Reference Trigger ai ReferenceTrigger e AI Start Trigger ai StartTrigger Counter Internal Output can be routed to Counter 0 HW Arm Counter 0 Internal Output can be routed to Counter 1 HW Arm Some of these options may not be available in some driver software Counter 7 Internal Output and Counter n TC Signals The Counter n Internal Output signal changes in response to Counter n TC The two software selectable output options are pulse output on TC and toggle output on TC The output polarity is software selectable for both options With pulse or pulse train generation tasks the counter drives the pulse s on the Counter n Internal Output signal The Counter n Internal Output signal can be internally routed to be a counter timer input or an external source for AI AO DI or DO timing signals Routing Counter n Internal Output to an Output Terminal You can route Counter n Internal Output to any output PFI terminal Frequency Output Signal The Frequency Output FREQ OUT signal is the output of the frequen
45. Train Generation This function generates a train of pulses with programmable frequency and duty cycle The pulses appear on the Counter n Internal Output signal of the counter You can specify a delay from when the counter is armed to the beginning of the pulse train The delay is measured in terms of a number of active edges of the Source input You specify the high and low pulse widths of the output signal The pulse widths are also measured in terms of a number of active edges of the Source input You also can specify the active edge of the Source input rising or falling The counter can begin the pulse train generation as soon as the counter is armed or in response to a hardware start trigger You can route the Start Trigger to the Gate input of the counter National Instruments Corporation 8 23 NI USB 621x User Manual Chapter 8 NI USB 621x User Manual Counters You also can use the Gate input of the counter as a Pause Trigger if it is not used as a Start Trigger The counter pauses pulse generation when the Pause Trigger is active Figure 8 25 shows a continuous pulse train generation using the rising edge of Source source Jl I UUUUUULN LULU OUT l Counter Armed Figure 8 25 Continuous Pulse Train Generation Continuous pulse train generation is sometimes called frequency division If the high a
46. USB 621x User Manual 7 2 ni com Chapter 7 PFI AO Sample Clock Timebase ao SampleClockTimebase AO Pause Trigger ao PauseTrigger Counter input signals for either counter Source Gate Aux HW Arm A B Z Most functions allow you to configure the polarity of PFI inputs and whether the input is edge or level sensitive Exporting Timing Output Signals Using PFI Terminals You can route any of the following timing signals to any PFI output terminal AI Convert Clock ai ConvertClock AI Hold Complete Event ai HoldCompleteEvent AI Reference Trigger ai ReferenceTrigger AI Sample Clock ai SampleClock AI Start Trigger ai StartTrigger AO Sample Clock ao SampleClock AO Start Trigger ao StartTrigger Counter n Source Counter n Gate Counter n Internal Output Frequency Output 3 Note Signals with a are inverted before being driven to a terminal that is these signals are active low Using PFI Terminals as Static Digital I Os Each input PFI line can be individually configured as a static digital input called PO x Each output PFI line can be individually configured as a static digital output called P1 x On USB 6212 6216 devices all PFI lines can be individually configured as static digital inputs or static digital outputs called PO x National Instruments Corporation 7 8 NI USB 621x User Manual Chapter 7 PFI Connecting PFI Input Signals All PFI input connections are r
47. a capacitor between the device s isolated ground and earth ground National Instruments Corporation 9 4 NI USB 621x User Manual 10 Digital Routing and Clock Generation The digital routing circuitry has the following main functions e Manages the flow of data between the bus interface and the acquisition generation sub systems analog input analog output digital I O and the counters The digital routing circuitry uses FIFOs if present in each sub system to ensure efficient data movement e Routes timing and control signals The acquisition generation sub systems use these signals to manage acquisitions and generations These signals can come from the following sources Your USB 621x device User input through the PFI terminals e Routes and generates the main clock signals for the USB 621x device 80 MHz Timebase The 80 MHz Timebase can be used as the Source input to the 32 bit general purpose counter timers The 80 MHz Timebase is generated from the onboard oscillator 20 MHz Timebase The 20 MHz Timebase normally generates many of the AI and AO timing signals The 20 MHz Timebase also can be used as the Source input to the 32 bit general purpose counter timers The 20 MHz Timebase is generated by dividing down the 80 MHz Timebase 100 kHz Timebase The 100 kHz Timebase can be used to generate many of the AI and AO timing signals The 100 kHz Timebase also can be used as the Source input to the 32 bit
48. a common ground point with respect to the device assuming that the computer is plugged into the same power system as the source Non isolated outputs of instruments and devices that plug into the building power system fall into this category National Instruments Corporation 4 31 NI USB 621x User Manual Chapter 4 Analog Input NI USB 621x User Manual The difference in ground potential between two instruments connected to the same building power system is typically between 1 and 100 mV but the difference can be much higher if power distribution circuits are improperly connected If a grounded signal source is incorrectly measured this difference can appear as measurement error Follow the connection instructions for grounded signal sources to eliminate this ground potential difference from the measured signal When to Use Differential Connections with Ground Referenced Signal Sources Use differential input connections for any channel that meets any of the following conditions e The input signal is low level less than 1 V e The leads connecting the signal to the device are greater than 3 m 10 ft e The input signal requires a separate ground reference point or return signal e The signal leads travel through noisy environments Two analog input channels AI and AI are available Differential signal connections reduce noise pickup and increase common mode noise rejection Differential signal connections also allo
49. companies Members of the National Instruments Alliance Partner Program are business entities independent from National Instruments and have no agency partnership or joint venture relationship with National Instruments Patents For patents covering National Instruments products technology refer to the appropriate location Help Patents in your software the patents txt file on your media or the National Instruments Patent Notice at ni com patents WARNING REGARDING USE OF NATIONAL INSTRUMENTS PRODUCTS 1 NATIONAL INSTRUMENTS PRODUCTS ARE NOT DESIGNED WITH COMPONENTS AND TESTING FOR A LEVEL OF RELIABILITY SUITABLE FOR USE IN OR IN CONNECTION WITH SURGICAL IMPLANTS OR AS CRITICAL COMPONENTS IN ANY LIFE SUPPORT SYSTEMS WHOSE FAILURE TO PERFORM CAN REASONABLY BE EXPECTED TO CAUSE SIGNIFICANT INJURY TO A HUMAN 2 IN ANY APPLICATION INCLUDING THE ABOVE RELIABILITY OF OPERATION OF THE SOFTWARE PRODUCTS CAN BE IMPAIRED BY ADVERSE FACTORS INCLUDING BUT NOT LIMITED TO FLUCTUATIONS IN ELECTRICAL POWER SUPPLY COMPUTER HARDWARE MALFUNCTIONS COMPUTER OPERATING SYSTEM SOFTWARE FITNESS FITNESS OF COMPILERS AND DEVELOPMENT SOFTWARE USED TO DEVELOP AN APPLICATION INSTALLATION ERRORS SOFTWARE AND HARDWARE COMPATIBILITY PROBLEMS MALFUNCTIONS OR FAILURES OF ELECTRONIC MONITORING OR CONTROL DEVICES TRANSIENT FAILURES OF ELECTRONIC SYSTEMS HARDWARE AND OR SOFTWARE UNANTICIPATED USES OR MISUSES OR ERRORS ON THE PART OF THE USER OR APPLICATIONS DE
50. condition has occurred A software program that creates an end user function The process of getting an instrument ready to perform a function For example the trigger circuitry of a digitizer is armed meaning that it is ready to start acquiring data when an appropriate trigger condition is met Application specific integrated circuit A proprietary semiconductor component designed and manufactured to perform a set of specific functions for a specific customer G 2 ni com asynchronous BNC buffer bus buses C C calibration cascading CE National Instruments Corporation G 3 Glossary 1 Hardware A property of an event that occurs at an arbitrary time without synchronization to a reference clock 2 Software A property of a function that begins an operation and returns prior to the completion or termination of the operation Bit One binary digit either 0 or 1 Byte Eight related bits of data an eight bit binary number Also used to denote the amount of memory required to store one byte of data Bayonet Neill Concelman A type of coaxial connector used in situations requiring shielded cable for signal connections and or controlled impedance applications 1 Temporary storage for acquired or generated data 2 A memory device that stores intermediate data between two devices The group of electrical conductors that interconnect individual circuitry in a computer Typically a bus is the e
51. detailed information about USB 621x devices NI USB 621x User Manual 1 2 ni com Chapter 1 Getting Started Applying Signal Labels to the USB 621x USB 621x Screw Terminal Devices Your USB 621 x kit includes labels for the combicon connectors on USB 621x Screw Terminal devices You can choose labels with pin numbers or signal names or blank labels Choose one of the labels align the correct label with the terminals printed on the top panel of your device or the 16 position combicon connector and apply the label as shown in Figure 1 1 r P N 19XXXX REVX msi 6000 123456 7 8 9 10 11 12 13 14 15 16 o Gag PFIO PFI PFI2 PFI3 pap PFH PFIS PFI6 PEI 2 Flo PFI PFI2 PFIS pup PF PHIS PFI6 PFI 45v DGND NC NC RSVD Al AB P00 P0 1 P02 P03 pupP10 P1 1 P12 P13 45V DGND NC NC RSVD AD in in in in out ou out ou 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 An or Al 5 AM3 ap 6 AM4 A7 ANS All A2 AB AISN AM Ab Abl AB A7 AMO AB AIT AISN AM A12 Al or r or By oo A ee for OOK nooo HHHHHHHHHHOHHHHH 1 Terminal Number Label 3 Differential Signal Name Label 2 Single Ended
52. e Isolation Barrier and Digital Isolators Refer to Chapter 9 Isolation and Digital Isolators on USB 6215 6216 6218 Devices for more information Analog Input Range NI USB 621x User Manual The input range affects the resolution of the USB 621x device for an AI channel For example a 16 bit ADC converts analog inputs into one of 65 536 2 216 codes that is one of 65 536 possible digital values So for an input range of 10 V to 10 V the voltage of each code of a 16 bit ADC is 10 V 10 V _ 305 uV 516 USB 621x devices use a calibration method that requires some codes typically about 5 of the codes to lie outside of the specified range This calibration method improves absolute accuracy but it increases the nominal resolution of input ranges by about 596 over what the formula shown above would indicate Choose an input range that matches the expected input range of your signal A large input range can accommodate a large signal variation but reduces the voltage resolution Choosing a smaller input range improves the voltage resolution but may result in the input signal going out of range 4 2 ni com Chapter 4 Analog Input For more information about setting ranges refer to the NJ DAQmx Help or the LabVIEW Help in version 8 0 or later The following table shows the input ranges and resolutions supported by USB 621x devices Nominal Resolution Assuming Input Range 5 Over Range 10 V to 10 V
53. ei erae trt siveascoessdescuedseseepes 8 21 Single Pulse Generation esee 8 21 Single Pulse Generation with Start Trigger sess 8 22 Retriggerable Single Pulse Generation esee 8 22 Pulse Train Generation iiie ets Pa e dei ri Ee aias eges 8 23 Continuous Pulse Train Generation see 8 23 Finite Pulse Train Generation seen 8 24 Frequency Generation 5 nni ntt itn oaa Ee tpe dE ede EEA 8 25 Using the Frequency Generator eee 8 25 Frequency Division 2 dti i RE t vei a Ee ette i pe ine dese 8 26 Pulse Generation for ETS nter te ha tie de di eine 8 26 Counter Timing Signals cette dr dt eo rine dur d Dac avaro 8 27 Counter n Source Signal sinnser ite et tte re i isa pit 8 28 Routing a Signal to Counter n Source sese 8 28 Routing Counter n Source to an Output Terminal 8 28 National Instruments Corporation ix NI USB 621x User Manual Contents Counter 5 Gate Signal uie aee Seve a ebore Mend eh RR 8 29 Routing a Signal to Counter n Gate esee 8 29 Routing Counter n Gate to an Output Terminal 8 29 Counter n Aux Signal met iege ate ce eo a e aA 8 29 Routing a Signal to Counter n AUX sese 8 29 Counter n A Counter n B and Counter n Z Signals esses 8 30 Routing Sig
54. etd 9 2 Benefits of an Isolated DAQ Device ssssesssssseeeee eene nennen nnne 9 3 Reducing Common Mode Noise nennen nennen 9 3 Creating an AC Return Path niti tepida 9 4 Isolated Systems ee ra teet pedet en tp edteie 9 4 Non Isolated Systems eese eee 9 4 NI USB 621x User Manual X ni com Contents Chapter 10 Digital Routing and Clock Generation SO MIZ Time DaSC issn EE 10 1 20 MHZ Tiimebase i aiat ea i Ue Seva aive devas a Tent EQ ARI ve 10 1 100 KHz Timebase e tete er D er dere 10 1 Chapter 11 Bus Interface USB Signal Stream noe nte eter tte ten imp t pite 11 1 Data Transfer Methods ep temet estre Yeti rh tede etd rues gau 11 1 Changing Data Transfer Methods essere 11 2 Chapter 12 Triggering Triggering with a Digital Source esssssssesseseeeeeeeeeeneee nennen nennen 12 1 Appendix A Device Specific Information USB O210 oi ak reed oh rine aiti emt ertet nies A 2 USB36211 62 15 te ede ie eee e ER NRI ELO ES E A 4 USB 6212 6216 Scr w Terminal ertet a oe ee tue ient A 6 USB 6212 6216 Mass Termination cccesscssecesceceneeesceceaeecseecsaceeaeceaeeeaeecsaeeeeeesas A 8 USB 6212 6216 BNC setne teret ttp tt at a hoa ee heen o eas A 13 USB 6218 Screw Terminal erento veneti e eren E Rate Penes A 19 USB 6218 BNNC 2 tad itt eset Deed eben Etat be nested lah steatst tees A 21 Appendix B Troubleshooting Appendix C Tech
55. leads you through nested menu items and dialog box options to a final action The sequence File Page Setup Options directs you to pull down the File menu select the Page Setup item and select Options from the last dialog box This icon denotes a note which alerts you to important information This icon denotes a caution which advises you of precautions to take to avoid injury data loss or a system crash When this symbol is marked on a product refer to the Read Me First Safety and Electromagnetic Compatibility document for information about precautions to take Bold text denotes items that you must select or click in the software such as menu items and dialog box options Bold text also denotes parameter names Italic text denotes variables emphasis a cross reference or an introduction to a key concept Italic text also denotes text that is a placeholder for a word or value that you must supply National Instruments Corporation xiii NI USB 621x User Manual About This Manual monospace Platform Text in this font denotes text or characters that you should enter from the keyboard sections of code programming examples and syntax examples This font is also used for the proper names of disk drives paths directories programs subprograms subroutines device names functions operations variables filenames and extensions Text in this font denotes a specific platform and indicates that the text following it app
56. nasia tert iere des bep tpe P e ERE 1 1 Installing the Hardware eie HERI HN tudes sande Re e PR Ee ER reta d ego 1 1 Device Self Calibr ation e ettet te P c s ee ee ci eiie 1 2 Device Pinouts iis etg treu E ea d M o e ERE e E ud 1 2 Device Specifications dieta ee eet eee Re eris 1 2 Applying Signal Labels to the USB 621x eese eere 1 3 USB Cable Stram Relief etate tei tei pa 1 4 Mounting the USB 621x need tete sen Gath eade e epi y eee tie edes 1 6 Desktop Use nore tesque ep 1 6 DIN Rail Mounting tet ree eee eee et ete reed 1 6 Panel Mounting iiec Ne eat Vt E ERE ect eae 1 7 USB Device Security Cable Slot eese tentent tnnt netten 1 8 Chapter 2 DAQ System Overview DAO Ha VAE etes is eo Eee E P teste EAN 2 1 DAQSSTQC2 iet p RU RR UU ER e TES UG 2 2 Calibration Circuitry ertet ipi e d I Er Re ped 2 2 Signal Conditioning hee e edet t nitet e vi terim dnas 2 3 Sensors and Eransd cers sse e odo rs t e AS E 2 3 Cables and ACCeSSOFIES ope dede tertie ede rea eee ote Polus ia deo 2 4 USB 621x Mass Termination Custom Cabling eee 2 4 Programming Devices in Software essere rennen eene 2 5 National Instruments Corporation V NI USB 621x User Manual Contents Chapter 3 Connector and LED Information T O Connector Signal Descriptions nene nemen emen 3 1 HON POWOE dco ate o ro a do tee etit hae 3 3 4 5 V
57. on USB 6210 6211 6215 6218 Devices 6 3 Getting Started with DIO Applications in Software on USB 6210 6211 6215 6218 Devices eee 6 4 Digital I O on USB 6212 6216 Devices sssssseseseseeeeeeeee eene 6 4 Static DIO on USB 6212 6216 Devices sese 6 5 T O Protection on USB 6212 6216 Devices sessseeee 6 5 Programmable Power Up States on USB 6212 6216 Devices 6 6 Increasing Current Drive on USB 6212 6216 Devices sess 6 6 Connecting Digital I O Signals on USB 6212 6216 Devices 6 6 Getting Started with DIO Applications in Software on USB 6212 6216 Devices en tcn eerte er eo tette 6 7 Chapter 7 PFI Using PFI Terminals as Timing Input Signals eee 7 2 Exporting Timing Output Signals Using PFI Terminals ees 7 3 Using PFI Terminals as Static Digital I Os eee 7 3 Connecting PFI Input Signals eese eene eene 7 4 PRE uli x 7 4 VO Protection ute ahi tetas Sete ash nila ts int dita detest 7 6 Programmable Power Up States eese nennen eee 7 6 NI USB 621x User Manual viii ni com Contents Chapter 8 Counters Counter Input Applications ettet edt te estas e assess Hare epa 8 2 Counting Edges nae tein p E e E edid 8 2 Single Point On Demand Edge Counting sss 8 2 B
58. program initiates the transfer of data Programmed I O is typically used in software timed on demand operations Refer to the Analog Output Data Generation Methods section of Chapter 5 Analog Output for more information 11 1 NI USB 621x User Manual Chapter 11 Bus Interface Changing Data Transfer Methods USB 621x devices have four dedicated USB Signal Stream channels To change your data transfer mechanism between USB Signal Streams and programmed I O use the Data Transfer Mechanism property node function in NI DAQmx NI USB 621x User Manual 11 2 ni com Triggering A trigger is a signal that causes an action such as starting or stopping the acquisition of data When you configure a trigger you must decide how you want to produce the trigger and the action you want the trigger to cause All USB 621x devices support internal software triggering as well as external digital triggering For information about the different actions triggers can perform for each sub system of the device refer to the following sections e The Analog Input Digital Triggering section of Chapter 4 Analog Input e The Analog Output Digital Triggering section of Chapter 5 Analog Output e The Counter Triggering section of Chapter 8 Counters Triggering with a Digital Source Your USB 621x device can generate a trigger on a digital signal You must specify a source and an edge The digital source can be any input PFI signal The edge can b
59. the symbol T Programmable Function Interface Programmable Gain Instrumentation Amplifier See channel The technique used on a DAQ device to acquire a programmed number of samples after trigger conditions are met NI USB 621x User Manual Glossary power source ppm pretriggering pulse pulse width Q quadrature encoder range real time RSE NI USB 621x User Manual An instrument that provides one or more sources of AC or DC power Also known as power supply Parts per million The technique used on a DAQ device to keep a continuous buffer filled with data so that when the trigger conditions are met the sample includes the data leading up to the trigger condition A signal whose amplitude deviates from zero for a short period of time The time from the rising to the falling slope of a pulse at 50 amplitude An encoding technique for a rotating device where two tracks of information are placed on the device with the signals on the tracks offset by 90 from each other This makes it possible to detect the direction of the motion The maximum and minimum parameters between which a sensor instrument or device operates with a specified set of characteristics This may be a voltage range or a frequency range 1 Displays as it comes in no delays 2 A property of an event or system in which data is processed and acted upon as it is acquired instead of being accumulated and processed at a later
60. 2 Al 13 26 60 AI 5 Al 6 25 59 AI GND Al GND 24 58 Al 14 Al 15 23 57 AI7 AO 0 22 56 Al GND AO 1 21 55 AO GND NC 20 54 AO GND P0 4 19 53 D GND D GND 18 52 P0 0 PO 1 17 51 P0 5 P0 6 16 50 D GND D GND 15 49 P0 2 5V 14 48 PO 7 D GND 13 47 P0 3 D GND 12 46 PFI 11 P2 3 PFI 0 P1 0 11 45 PFI 10 P2 2 PFI 1 P1 1 10 44 DGND D GND 9 43 PFI 2 P1 2 45V 8 42 PFI 3 P1 3 D GND 7 41 PFI 4 P1 4 PFI 5 P1 5 6 40 PFI 13 P2 5 PFI 6 P1 6 5 39 PFI 15 P2 7 D GND 4 38 PFI 7 P1 7 PFI 9 P2 1 3 37 PFI 8 P2 0 PFI 12 P2 4 2 36 D GND PFI 14 P2 6 1 1 35 D GND a NC No Connect TERMINAL 34 TERMINAL 1 OL EN TERMINAL 68 TERMINAL 35 Figure A 4 USB 6212 6216 Mass Termination Pinout National Instruments Corporation A 9 NI USB 621x User Manual Appendix A Device Specific Information Table A 4 Default NI DAQmx Counter Timer Pins Counter Timer Signal Default Terminal Number Name CTR 0 SRC 37 PFI 8 CTR 0 GATE 3 PFI 9 CTR 0 AUX 45 PFI 10 CTR 0 OUT 2 PFI 12 CTROA 37 PFI 8 CTROZ 3 PFI 9 CTROB 45 PFI 10 CTR 1 SRC 42 PFI 3 CTR 1 GATE 41 PFI 4 CTR 1 AUX 46 PFI 11 CTR 1 OUT 40 PFI 13 CTRIA 42 PFI 3 CTR 1Z 41
61. 3 sources floating 4 25 ground referenced 4 31 Signal Stream USB 11 1 National Instruments Corporation I 9 Index signals AI Convert Clock 4 16 AI Convert Clock Timebase 4 19 AI Hold Complete Event 4 19 AI Pause Trigger 4 22 AI Reference Trigger 4 21 AI Sample Clock 4 14 AI Sample Clock Timebase 4 15 Al Start Trigger 4 20 analog input 4 11 analog output 5 5 AO Pause Trigger 5 6 AO Sample Clock 5 8 AO Sample Clock Timebase 5 9 AO Start Trigger 5 5 connecting analog input on USB 6210 621 1 6212 devices 4 23 on USB 6215 6216 6218 devices 4 36 connecting analog output 5 4 connecting digital I O on USB 6210 621 1 6215 6218 6 3 on USB 6212 6216 6 6 connecting PFI input 7 4 Counter n A 8 30 Counter n Aux 8 29 Counter n B 8 30 Counter n Gate 8 29 Counter n HW Arm 8 30 Counter n Internal Output 8 31 Counter n Source 8 28 Counter n TC 8 31 Counter n Up Down 8 30 Counter n Z 8 30 counters 8 27 exporting timing output using PFI terminals 7 3 FREQ OUT 8 31 Frequency Output 8 31 NI USB 621x User Manual Index minimizing output glitches B 3 output minimizing glitches on 5 2 simple pulse generation 8 21 single period measurement 8 6 point edge counting 8 2 pulse generation 8 21 retriggerable 8 22 with start trigger 8 22 pulse width measurement 8 4 semi period measurement 8 8 two signal edge separation measurement 8 20 single ended connections for floating signal sou
62. 4 19 AI FIFO 4 2 AI Hold Complete Event signal 4 19 AI Pause Trigger signal 4 22 AI Reference Trigger signal 4 21 AI Sample Clock signal 4 14 AI Sample Clock Timebase signal 4 15 AI Start Trigger signal 4 20 ai ConvertClock 4 16 National Instruments Corporation ai ConvertClockTimebase 4 19 ai HoldCompleteEvent 4 19 ai PauseTrigger 4 22 ai ReferenceTrigger 4 21 ai SampleClock 4 14 ai SampleClockTimebase 4 15 ai StartTrigger 4 20 analog input 4 1 channels sampling with AI Sample Clock and AI Convert Clock B 2 charge injection B 1 circuitry 4 1 connecting signals on USB 6210 6211 6212 devices 4 23 connecting signals on USB 6215 6216 6218 devices 4 36 connecting through I O connector 4 1 crosstalk when sampling multiple channels B 1 data acquisition methods 4 8 differential troubleshooting B 1 getting started with applications in software 4 22 ghost voltages when sampling multiple channels B 1 ground reference settings 4 1 MUX 4 1 sampling channels with AI Sample Clock and AI Convert Clock B 2 signals 4 11 timing signals 4 11 triggering 4 10 troubleshooting B 1 analog input signals 4 11 AI Convert Clock 4 16 AI Convert Clock Timebase 4 19 AI Hold Complete Event 4 19 AI Pause Trigger 4 22 NI USB 621x User Manual Index AI Reference Trigger 4 21 AI Sample Clock 4 14 AI Sample Clock Timebase 4 15 Al Start Trigger 4 20 analog output 5 1 circuitry 5 1 connecting signals
63. 6212 6216 Mass Termination NI DAQmx 8 7 1 and later USB 6212 6216 6218 BNC NI DAQmx 8 9 and later National Instruments Corporation 2 5 NI USB 621x User Manual Connector and LED Information The 1 O Connector Signal Descriptions and 5 V Power sections contain information about NI USB 621x connectors The PWR ACT LED Indicator section contains information about the NI USB 621x PWR ACT LED Refer to Appendix A Device Specific Information for device I O connector pinouts Refer to the Applying Signal Labels to the USB 621x section of Chapter 1 Getting Started for information about applying signal labels 1 0 Connector Signal Descriptions Table 3 1 describes the signals found on the I O connectors Not all signals are available on all devices Table 3 1 1 0 Connector Signals Signal Name Reference Direction Description AI GND Analog Input Ground These terminals are the reference point for single ended AI measurements in RSE mode and the bias current return point for differential measurements All three ground references AI GND AO GND and D GND are connected on the device AI lt 0 31 gt Varies Input Analog Input Channels 0 to 31 For single ended measurements each signal is an analog input voltage channel In RSE mode AI GND is the reference for these signals In NRSE mode the reference for each AI lt 0 31 gt signal is AI SENSE For differential measurements AI 0
64. AQ Assistant In LabWindows CVI select Help Contents then select Using LabWindows CVI Data Acquisition The NI DAQmx Library book of the LabWindows CVI Help contains API overviews and function reference for NI DAQmx Select Library Reference NI DAQmx Library in the LabWindows CVI Help Measurement Studio NI USB 621x User Manual If you program your NI DAQmx supported device in Measurement Studio using Visual C Visual C or Visual Basic NET you can interactively create channels and tasks by launching the DAQ Assistant from MAX or from within Visual Studio NET You can generate the configuration code based on your task or channel in Measurement Studio Refer to the DAQ Assistant Help for additional information about generating code You also can create channels and tasks and write your own applications in your ADE using the NI DAQmx API For help with NI DAQmx methods and properties refer to the NI DAQmx NET Class Library or the NI DAQmx Visual C Class Library included in the NI Measurement Studio Help For general help with programming xvi ni com About This Manual in Measurement Studio refer to the NJ Measurement Studio Help which is fully integrated with the Microsoft Visual Studio NET help To view this help file in Visual Studio NET select Measurement Studio NI Measurement Studio Help To create an application in Visual C Visual C or Visual Basic NET follow these general steps 1 In Visual
65. CE Counter Value 00001 2 3 4 5 6 7 8 8 8 HW Save Register 8 Figure 8 20 Single Two Signal Edge Separation Measurement Buffered Two Signal Edge Separation Measurement Buffered and single two signal edge separation measurements are similar but buffered measurement measures multiple intervals The counter counts the number of rising or falling edges on the Source input occurring between an active edge of the Gate signal and an active edge of the Aux signal The counter then stores the count in a hardware save register On the next active edge of the Gate signal the counter begins another measurement A USB Signal Stream transfers the stored values to host memory 8 20 ni com Chapter 8 Counters Figure 8 21 shows an example of a buffered two signal edge separation measurement AUX 4 E GATE amp amp SOURCE Counter Value 12 3 1 2 3 1 2 3 3 3 3 Buffer 3 3 Figure 8 21 Buffered Two Signal Edge Separation Measurement For information about connecting counter signals refer to the Default Counter Timer Pinouts section Counter Output Applications Simple Pulse Generation Single Pulse Generation The counter can output a single pulse The pulse appears on the Counter n Internal Output signal of the counter
66. DAQ M Series NI USB 621x User Manual Bus Powered M Series USB Devices Fran ais Deutsch H RE et O f en p ni com manuals April 2009 371931F 01 INSTRUMENTS Df NATIONAL Worldwide Technical Support and Product Information ni com National Instruments Corporate Headquarters 11500 North Mopac Expressway Austin Texas 78759 3504 USA Tel 512 683 0100 Worldwide Offices Australia 1800 300 800 Austria 43 662 457990 0 Belgium 32 0 2 757 0020 Brazil 55 11 3262 3599 Canada 800 433 3488 China 86 21 5050 9800 Czech Republic 420 224 235 774 Denmark 45 45 76 26 00 Finland 358 0 9 725 72511 France 01 57 66 24 24 Germany 49 89 7413130 India 91 80 41190000 Israel 972 3 6393737 Italy 39 02 41309277 Japan 0120 527196 Korea 82 02 3451 3400 Lebanon 961 0 1 33 28 28 Malaysia 1800 887710 Mexico 01 800 010 0793 Netherlands 31 0 348 433 466 New Zealand 0800 553 322 Norway 47 0 66 90 76 60 Poland 48 22 328 90 10 Portugal 351 210 311 210 Russia 7 495 783 6851 Singapore 1800 226 5886 Slovenia 386 3 425 42 00 South Africa 27 0 11 805 8197 Spain 34 91 640 0085 Sweden 46 0 8 587 895 00 Switzerland 41 56 2005151 Taiwan 886 02 2377 2222 Thailand 662 278 6777 Turkey 90 212 279 3031 United Kingdom 44 0 1635 523545 For further support information refer to the Technical Support and Professional Services appendix To comment on National Instruments documentation refer to the National
67. FI output signals Do not exceed the specified current output limits of the DAQ device NI has several signal conditioning solutions for digital applications requiring high current drive Donot drive a DI or PFI input line with voltages outside of its normal operating range The PFI or DI lines have a smaller operating range than the AI signals Treat the DAQ device as you would treat any static sensitive device Always properly ground yourself and the equipment when handling the DAQ device or connecting to it Programmable Power Up States At system startup and reset the hardware sets all output PFI and DO lines to high impedance by default The DAQ device does not drive the signal high or low Each line has a weak pull down resistor connected to it as described in the N7 USB 621x Specifications NI DAQmx supports programmable power up states for PFI and DIO lines Software can program any value at startup to the P1 lines The output PFI and DO lines can be set as e A high impedance input with a weak pull down resistor default e An output driving a 0 e An output driving a 1 Refer to the NI DAQmx Help or the LabVIEW Help in version 8 0 or later for more information about setting power up states in NI DAQmx or MAX NI USB 621x User Manual 7 6 ni com Counters USB 621x devices have two general purpose 32 bit counter timers and one frequency generator as shown in Figure 8 1 The general purpose counter timers can be us
68. GND Wire USER e v POO PFI 8 P2 0 pod PFI 9 P2 1 SONS POS PFI 10 P2 2 Pad PFI 11 P2 3 D GND E OND P0 4 PFI12 P2 4 Screw E PFI13 P2 5 Terminal BNC Cable 0 6 PFI 14 P2 6 Block PO 7 oc PFI 15 P2 7 D GND DONO 5 id AI GND i Al SENSE REIS Signal Figure A 12 Connecting PFI 8 P2 0 to USER BNC A 18 ni com Appendix A Device Specific Information USB 6218 Screw Terminal USB 6218 Screw Terminal Pinout Figure A 13 shows the pinout of the USB 6218 Screw Terminal For a detailed description of each signal refer to the O Connector Signal Descriptions section of Chapter 3 Connector and LED Information PFI 0 PO 0 In gl PFI 8 PO 4 In PFI 1 P0 1 In q E h PFI 9 P0 5 In PFI 2 P0 2 In Ee PFI 10 P0 6 In PFI 3 P0 3 In Ee PFI 11 P0 7 In D GND Ee D GND PFI 4 P1 0 Out Eme PFI 12 P1 4 Out PFI 5 P1 1 Out E PFI 13 P1 5 Out PFI 6 P1 2 Out Ee PFI 14 P1 6 Out PFI 7 P1 3 Out Ee PFI 15 P1 7 Out 45V Eme 45V D GND E D GND AO 0 Gls NC AO 1 Es NC AO GND Ez AI GND AIO Ea Al 16 AI8 mui E Al 24 Al 1 Gils g Al 17 AI 9 Es 2 Al 25 Al2 Gills B Al 18 Al 10 Es e Al 26 AI 3 Ee 8 AI 19 AI 11 E 3 Al 27 Al SENSE Eus 8 AI GND Al4 Ee 8 Al 20 Al 12 Eus D Al 28 AI5 E
69. Glossary differential input digital I O digital signal digital trigger DIO driver E edge detection EEPROM encoder external trigger NI USB 621x User Manual An input circuit that actively responds to the difference between two terminals rather than the difference between one terminal and ground Often associated with balanced input circuitry but also may be used with an unbalanced source The capability of an instrument to generate and acquire digital signals Static digital I O refers to signals where the values are set and held or rarely change Dynamic digital I O refers to digital systems where the signals are continuously changing often at multi MHz clock rates A representation of information by a set of discrete values according to a prescribed law These values are represented by numbers A TTL level signal having two discrete levels A high and a low level Digital input output Software unique to the device or type of device and includes the set of commands the device accepts A technique that locates an edge of an analog signal such as the edge of a square wave Electrically Erasable Programmable Read Only Memory ROM that can be erased with an electrical signal and reprogrammed Some SCXI modules contain an EEPROM to store measurement correction coefficients A device that converts linear or rotary displacement into digital or pulse signals The most popular type of encoder is the optic
70. Power as at Output eee pter repre repe perde 3 3 45 V Power asan Input icit e ng ee abd tei ee ces sia 3 3 USB Chassis Ground oer ee iet c a Et E att eee 3 4 USB Device Fuse Replacement sess rennen rennen 3 4 PWR ACT LED Indicatot erred erret trai e 3 6 Chapter 4 Analog Input Analog Input Range oh ett tette timere edendis 4 2 Analog Input Ground Reference Settings eese 4 3 Configuring AI Ground Reference Settings in Software 4 5 Multichannel Scanning Considerations eese 4 5 Analog Input Data Acquisition Methods esee 4 8 Analog Input Digital Triggering esee emen 4 10 Field Waring Consideratiotis tr ttt DE dons tee eg tecta 4 10 Analog Input Timing Signals rennen eene 4 11 AI Sample Clock Signal esee enne 4 14 Using an Internal Source eese 4 14 Using an External Source essere 4 14 Routing AI Sample Clock to an Output Terminal 4 14 Other Timing Requirements esee 4 14 AI Sample Clock Timebase Signal eere 4 15 Al Convert Clock Signal oie Ete tes 4 16 Using an Internal Source eese 4 16 Using an External Source eese 4 16 Routing AI Convert Clock to an Output Terminal 4 16 Using a Del
71. SIGNER ADVERSE FACTORS SUCH AS THESE ARE HEREAFTER COLLECTIVELY TERMED SYSTEM FAILURES ANY APPLICATION WHERE A SYSTEM FAILURE WOULD CREATE A RISK OF HARM TO PROPERTY OR PERSONS INCLUDING THE RISK OF BODILY INJURY AND DEATH SHOULD NOT BE RELIANT SOLELY UPON ONE FORM OF ELECTRONIC SYSTEM DUE TO THE RISK OF SYSTEM FAILURE TO AVOID DAMAGE INJURY OR DEATH THE USER OR APPLICATION DESIGNER MUST TAKE REASONABLY PRUDENT STEPS TO PROTECT AGAINST SYSTEM FAILURES INCLUDING BUT NOT LIMITED TO BACK UP OR SHUT DOWN MECHANISMS BECAUSE EACH END USER SYSTEM IS CUSTOMIZED AND DIFFERS FROM NATIONAL INSTRUMENTS TESTING PLATFORMS AND BECAUSE A USER OR APPLICATION DESIGNER MAY USE NATIONAL INSTRUMENTS PRODUCTS IN COMBINATION WITH OTHER PRODUCTS IN A MANNER NOT EVALUATED OR CONTEMPLATED BY NATIONAL INSTRUMENTS THE USER OR APPLICATION DESIGNER IS ULTIMATELY RESPONSIBLE FOR VERIFYING AND VALIDATING THE SUITABILITY OF NATIONAL INSTRUMENTS PRODUCTS WHENEVER NATIONAL INSTRUMENTS PRODUCTS ARE INCORPORATED IN A SYSTEM OR APPLICATION INCLUDING WITHOUT LIMITATION THE APPROPRIATE DESIGN PROCESS AND SAFETY LEVEL OF SUCH SYSTEM OR APPLICATION Contents About This Manual Conventions nette a NE eO OE EE ERE EH Hee ee xiii Related Documentation eeesseseeeeeeeeee nnn I eene eene enne nnne enne nenne nnns a Siea xiv Chapter 1 Getting Started Installing NI D AQinx 5 xr rd ere Ud eed Saeed ere ie eI US 1 1 Installing Other SoftWare isisisi
72. Studio NET select File New Project to launch the New Project dialog box 2 Findthe Measurement Studio folder for the language you want to create a program in 3 Choose a project type You add DAQ tasks as a part of this step ANSI C without NI Application Software The NI DAQmx Help contains API overviews and general information about measurement concepts Select Start All Programs National Instruments NI DAQmx Help The NI DAQmx C Reference Help describes the NI DAQmx Library functions which you can use with National Instruments data acquisition devices to develop instrumentation acquisition and control applications Select Start All Programs National Instruments NI DAQ NI DAQmx C Reference Help NET Languages without NI Application Software With the Microsoft NET Framework version 1 1 or later you can use NI DAQmx to create applications using Visual Cft and Visual Basic NET without Measurement Studio You need Microsoft Visual Studio NET 2003 or Microsoft Visual Studio 2005 for the API documentation to be installed The installed documentation contains the NI DAQmx API overview measurement tasks and concepts and function reference This help is fully integrated into the Visual Studio NET documentation To view the NI DAQmx NET documentation go to Start Programs National Instruments NI DAQ NI DAQmx NET Reference Help Expand NI Measurement Studio Help NI Measurement Studio NET Class Library Re
73. USB 6211 6215 USB 6211 6215 Pinout Figure A 2 shows the pinout of the USB 6211 and USB 6215 For a detailed description of each signal refer to the O Connector Signal Descriptions section of Chapter 3 Connector and LED Information PFI 0 PO O In PFI1 PO 1 In d PFI 2 PO 2 In PFI 3 P0 3 In D GND PFI 4 P1 0 Out PFI 5 P1 1 Out PFI 6 P1 2 Out PFI 7 P1 3 Out 5V D GND AO O0 AO 1 AO GND AIO AI8 9gigiviELCELILOLO 82 9G v EGZ HL Alt Al 9 AI 2 Al 10 Al 3 AI 11 Al SENSE Al 4 AI 12 ALS Al 13 Al GND Al6 Al 14 Il ALT Al 15 ZE LE 0 6c 8c Le 9c So vc Ez co Lc Oc 6L BI LI Figure A 2 USB 6211 6215 Pinout NI USB 621x User Manual A 4 ni com Appendix A Device Specific Information Table A 2 Default NI DAQmx Counter Timer Pins Counter Timer Signal Default Terminal Number Name CTR 0 SRC 1 PFI 0 CTR 0 GATE 2 PFI 1 CTR 0 AUX 1 PFI 0 CTR 0 OUT 6 PFI 4 CTROA 1 PFI 0 CTROZ 3 PFI 2 CTROB 2 PFI 1 CTR 1 SRC 4 PFI 3 CTR 1 GATE 3 PFI 2 CTR 1 AUX 4 PFI 3 CTR 1 OUT 7 PFI 5 CTR1A 4 PFI 3 CTR1Z 2 PFI 1 CTR1B 3 PFI 2 FREQ OUT 8 PFI 6 3 Note For more information about default NI DAQmx counter inputs refer to Connecting Counter Signals in the NI DAQmx Help or
74. User Manual AC Coupling 1 o Al AC Coupled Floating Signal Vs Source T o Al I o Al SENSE O4 Al GND Figure 4 19 Differential Connections for AC Coupled Floating Sources with Balanced Bias Resistors Using Non Referenced Single Ended Connections for Floating Signal Sources It is important to connect the negative lead of a floating signals source to AI GND either directly or through a resistor Otherwise the source may float out of the valid input range of the NI PGIA and the DAQ device returns erroneous data Figure 4 20 shows a floating source connected to the DAQ device in non referenced single ended mode O1 Al Floating Signal o Source o Al SENSE R o AI GND Figure 4 20 Non Referenced Single Ended Connections for Floating Signal Sources All of the bias resistor configurations discussed in the Using Differential Connections for Floating Signal Sources section apply to the non referenced single ended bias resistors as well Replace AI with AI SENSE in Figures 4 16 4 17 4 18 and 4 19 for configurations with zero to two bias resistors The noise rejection of non referenced single ended mode is better than referenced single ended mode because the AI SENSE connection is made remotely near the source However the noise rejection of non referenced single ended mode is worse than differential mode because the AI SENSE connection is sha
75. a from the PC buffer is continually downloaded to the FIFO to be written out New data can be written to the PC buffer at any time without disrupting the output With FIFO regeneration the entire buffer is downloaded to the FIFO and regenerated from there Once the data is downloaded new data cannot be written to the FIFO To use FIFO regeneration the entire buffer must fit within the FIFO size The advantage of using FIFO regeneration is that it does not require communication with the main host memory once the operation is started thereby preventing any problems that may occur due to excessive bus traffic With non regeneration old data is not repeated New data must be continually written to the buffer If the program does not write new data to the buffer at a fast enough rate to keep up with the generation the buffer underflows and causes an error 5 8 NI USB 621x User Manual Chapter 5 Analog Output Analog Output Digital Triggering Analog output supports two different triggering actions e Start trigger e Pause trigger A digital trigger can initiate these actions on USB 621x devices Refer to the AO Start Trigger Signal and AO Pause Trigger Signal sections for more information about these triggering actions Connecting Analog Output Signals NI USB 621x User Manual AO lt 0 1 gt are the voltage output signals for AO channels 0 and 1 AO GND is the ground reference for AO lt 0 1 gt Figure 5 2 shows how t
76. al Instruments believes that the information in this document is accurate The document has been carefully reviewed for technical accuracy In the event that technical or typographical errors exist National Instruments reserves the right to make changes to subsequent editions of this document without prior notice to holders of this edition The reader should consult National Instruments if errors are suspected In no event shall National Instruments be liable for any damages arising out of or related to this document or the information contained in it EXCEPT AS SPECIFIED HEREIN NATIONAL INSTRUMENTS MAKES NO WARRANTIES EXPRESS OR IMPLIED AND SPECIFICALLY DISCLAIMS ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE CUSTOMER S RIGHT TO RECOVER DAMAGES CAUSED BY FAULT OR NEGLIGENCE ON THE PART OF NATIONAL INSTRUMENTS SHALL BE LIMITED TO THE AMOUNT THERETOFORE PAID BY THE CUSTOMER NATIONAL INSTRUMENTS WILL NOT BE LIABLE FOR DAMAGES RESULTING FROM LOSS OF DATA PROFITS USE OF PRODUCTS OR INCIDENTAL OR CONSEQUENTIAL DAMAGES EVEN IF ADVISED OF THE POSSIBILITY THEREOF This limitation of the liability of National Instruments will apply regardless of the form of action whether in contract or tort including negligence Any action against National Instruments must be brought within one year after the cause of action accrues National Instruments shall not be liable for any delay in performance due to causes beyond its reasonable control The wa
77. al concept of acquiring data as in begin data acquisition or data acquisition and control See also DAQ A technique for moving digital data from one system to another Options for data transfer are DMA interrupt and programmed I O For programmed I O transfers the CPU in the PC reads data from the DAQ device whenever the CPU receives a software signal to acquire a single data point Interrupt based data transfers occur when the DAQ device sends an interrupt to the CPU telling the CPU to read the acquired data from the DAQ device DMA transfers use a DMA controller instead of the CPU to move acquired data from the device into computer memory Even though high speed data transfers can occur with interrupt and programmed I O transfers they require the use of the CPU to transfer data DMA transfers are able to acquire data at high speeds and keep the CPU free for performing other tasks at the same time Decibel The unit for expressing a logarithmic measure of the ratio of two signal levels dB 20log10 V1 V2 for signals in volts Direct current although the term speaks of current many different types of DC measurements are made including DC Voltage DC current and DC power An electronic board that performs general analog or digital I O functions on one or multiple channels connected to a PC through a bus or I O port such as PCI PXI Ethernet USB or serial National Instruments Corporation G 5 NI USB 621x User Manual
78. al encoder which uses a rotating disk with alternating opaque areas a light source and a photodetector A voltage pulse from an external source that causes a DAQ operation to begin G 6 ni com FIFO filter filtering floating signal sources frequency ft function Glossary First In First Out memory buffer A data buffering technique that functions like a shift register where the oldest values first in come out first Many DAQ products and instruments use FIFOs to buffer digital data from an A D converter or to buffer the data before or after bus transmission The first data stored is the first data sent to the acceptor FIFOs are often used on DAQ devices to temporarily store incoming or outgoing data until that data can be retrieved or output For example an analog input FIFO stores the results of A D conversions until the data can be retrieved into system memory a process that requires the servicing of interrupts and often the programming of the DMA controller This process can take several milliseconds in some cases During this time data accumulates in the FIFO for future retrieval With a larger FIFO longer latencies can be tolerated In the case of analog output a FIFO permits faster update rates because the waveform data can be stored on the FIFO ahead of time This again reduces the effect of latencies associated with getting the data from system memory to the DAQ device A physical device or digital algo
79. and AI 8 are the positive and negative inputs of differential analog input channel 0 Similarly the following signal pairs also form differential input channels AI 1 AI 9 gt AI 2 AI 10 gt AI 3 AI 11 AI 4 AI 12 gt AI 5 AI 13 gt AI 6 AI 14 gt AI 7 AI 15 AI 16 AI 24 gt AI 17 AI 25 AI 18 AI 26 gt AI 19 AI 27 gt AI 20 AI 28 gt AI 21 AI 295 AI 22 AI 30 gt AI 23 AI 31 AI SENSE Input Analog Input Sense In NRSE mode the reference for each AI lt 0 31 gt signal is AI SENSE National Instruments Corporation 3 1 NI USB 621x User Manual Chapter 3 Table 3 1 1 0 Connector Signals Continued Signal Name Reference Direction Description AO lt 0 1 gt AO GND Output Analog Output Channels 0 to 1 These terminals supply the voltage output of AO channels 0 to 1 AO GND Analog Output Ground AO GND is the reference for AO lt 0 1 gt All three ground references AI GND AO GND and D GND are connected on the device D GND Digital Ground D GND supplies the reference for PFI lt 0 15 gt P0 P1 and 5 V All three ground references AI GND AO GND and D GND are connected on the device 5 V D GND Input or Output 5 V Power These terminals provide a 5 V power source or can be used to externally power the digital outputs PFI lt 0 3 gt PFI lt 8 11 gt P0 lt 0
80. and the ground potential difference between the signal source and the device ground Refer to the Using Non Referenced Single Ended Connections for Floating Signal Sources section for more information about non referenced single ended connections 4 26 ni com Chapter 4 Analog Input Using Differential Connections for Floating Signal Sources It is important to connect the negative lead of a floating source to AI GND either directly or through a bias resistor Otherwise the source may float out of the maximum working voltage range of the NI PGIA and the DAQ device returns erroneous data The easiest way to reference the source to AI GND is to connect the positive side of the signal to AI and connect the negative side of the signal to AI GND as well as to AI without using resistors This connection works well for DC coupled sources with low source impedance less than 100 Q O4 Al Floating m Signal V Source 3 o Al Impedance O4 Al GND Figure 4 16 Differential Connections for Floating Signal Sources without Bias Resistors However for larger source impedances this connection leaves the differential signal path significantly off balance Noise that couples electrostatically onto the positive line does not couple onto the negative line because it is connected to ground This noise appears as a differential mode signal instead of a common mode signal and thus appears in your data I
81. apter 4 Analog Input software or hardware can stop it once a finite acquisition completes When using an internally generated AI Sample Clock you also can specify a configurable delay from AI Start Trigger to the first AI Sample Clock pulse By default this delay is set to two ticks of the AI Sample Clock Timebase signal When using an externally generated AI Sample Clock you must ensure the clock signal is consistent with respect to the timing requirements of AI Convert Clock Failure to do so may result in AI Sample Clock pulses that are masked off and acquisitions with erratic sampling intervals Refer to the AI Convert Clock Signal section for more information about the timing requirements between AI Convert Clock and AI Sample Clock Figure 4 8 shows the relationship of AI Sample Clock to AI Start Trigger Al Sample Clock Timebase Al Start Trigger Al Sample Clock lt gt Delay From Start Trigger Figure 4 8 Al Sample Clock and Al Start Trigger Al Sample Clock Timebase Signal You can route any of the following signals to be the AI Sample Clock Timebase ai SampleClockTimebase signal e 20 MHz Timebase e 100 kHz Timebase e USB 6210 6211 6215 Devices PFI lt 0 3 gt e USB 6212 6216 Devices PFI lt 0 15 gt e USB 6218 Devices PFI lt 0 3 gt PFI lt 8 11 gt AI Sample Clock Timebase is not available as an output on the I O connect
82. ase the counter detects edges on Gate even if the Source does not pulse This enables the correct current count to be stored in the buffer even if no Source edges occur between Gate signals as shown in Figure 8 35 8 38 ni com Chapter 8 Counters Counter detects rising Gate edge Counter value increments only Gate one time for each Source pulse Source 80 MHzTimebase UUUUBUUUUUUUUBUUUULUL Counter Value 6 X 7 Xo X1 Buffer 7 0 7 Figure 8 35 Duplicate Count Prevention Example Even if the Source pulses are long the counter increments only once for each Source pulse Normally the counter value and Counter n Internal Output signals change synchronously to the Source signal With duplicate count prevention the counter value and Counter n Internal Output signals change synchronously to the 80 MHz Timebase Enabling Duplicate Count Prevention in NI DAQmx Duplicate count prevention is automatically used with USB 621x devices Disabling duplicate count prevention is not supported National Instruments Corporation 8 39 NI USB 621x User Manual Isolation and Digital Isolators on USB 6215 6216 6218 Devices USB 6215 6216 6218 devices are isolated data acquisition devices The analog input analog output counters PFI static DI and PFI static DO circuitry and digital routing and clock generation are referenced to an isolated ground as shown in
83. ay from Sample Clock to Convert Clock 4 17 Other Timing Requirements esee 4 17 AI Convert Clock Timebase Signal eere 4 19 AI Hold Complete Event Signal essere 4 19 Al Start Drigger Signal ois bp ee ete ep es 4 20 Using a Digital Source eeesesesseeeeeeeeneen eee 4 20 Routing AI Start Trigger to an Output Terminal 4 20 AI Reference Trigger Signal essen 4 21 Using a Digital Source reet rete 4 22 Routing AI Reference Trigger to an Output Terminal 4 22 A Pa se Trgger Signal 4 2 tenet ee t reet eer teen 4 22 Using a Digital Source eese eene 4 22 NI USB 621x User Manual vi ni com Contents Getting Started with AI Applications in Software eee ec eeeeseeeeeeseeseeeseeneeeeeeeenaes 4 22 Connecting Analog Input Signals on USB 6210 6211 6212 Devices 4 23 Connecting Floating Signal Sources eee 4 25 What Are Floating Signal Sources sse 4 25 When to Use Differential Connections with Floating Signal Sources sese 4 25 When to Use Referenced Single Ended Connections with Floating Signal Sources essen 4 25 When to Use Non Referenced Single Ended Connections with Floating Signal Sources eee 4 26 Using Differential Conn
84. bed in the USB Cable Strain Relief section before mounting the USB 621x to a DIN rail NI USB 621x User Manual 1 6 ni com Chapter 1 Getting Started Panel Mounting USB 621x Screw Terminal Mass Termination Devices To mount the USB 621x to a board or panel complete the following steps while referring to Figure 1 5 Figure 1 5 Mounting the USB 621x on a Panel E Note Do not apply the rubber feet to the USB 621x when panel mounting the device yi Note Apply strain relief as described in the USB Cable Strain Relief section before panel mounting the USB 621x 1l Download and print the panel mounting template PDF attached in the KnowledgeBase document USB 621x Panel Mounting Template Go to ni com info and enter the info code ex3x98 to locate the KnowledgeBase 2 Using the template mark the bottom point and top point on the panel USB 621x Screw Terminal Devices The points will be 171 45 mm 6 75 in from each other USB 621x Mass Termination Devices The points will be 182 56 mm 7 188 in from each other National Instruments Corporation 1 7 NI USB 621x User Manual Chapter 1 Getting Started 3 Remove the USB cable from the connector on the USB 621 x 4 Screw a 8 or MA screw into the bottom point on the panel 5 Setthe USB 621x on the screw by fitting it into the bottom screw notch on the underside of the USB 621x 6 Screw a 8 or M4 screw through the USB
85. can be used to provide timing for undersampling applications where a digitizing system can sample repetitive waveforms that are higher in frequency than the Nyquist 6 26 ni com Chapter 8 Counters frequency of the system Figure 8 29 shows an example of pulse generation for ETS the delay from the trigger to the pulse increases after each subsequent Gate active edge D1 D2 D1 AD D3 D1 2AD Figure 8 29 Pulse Generation for ETS For information about connecting counter signals refer to the Default Counter Timer Pinouts section Counter Timing Signals USB 621x devices feature the following counter timing signals e Counter n Source Signal e Counter n Gate Signal e Counter n Aux Signal e Counter n A Signal e Counter n B Signal e Counter n Z Signal e Counter n Up Down Signal e Counter n HW Arm Signal e Counter n Internal Output Signal e Counter n TC Signal e Frequency Output Signal In this section n refers to either Counter 0 or 1 For example Counter n Source refers to two signals Counter 0 Source the source input to Counter 0 and Counter 1 Source the source input to Counter 1 National Instruments Corporation 8 27 NI USB 621x User Manual Chapter 8 Counters Counter 7 Source Signal NI USB 621x User Manual The selected edge of the Counter n Source signal increments and decrements the counter value depending on the application the counter is performing Table 8 3 lists how this
86. cause you cannot ensure that the input signal is within 10 V of AI GND National Instruments Corporation 4 37 NI USB 621x User Manual Chapter 4 Analog Input Ald i i Mux PGIA ADC 2 C2 e jALGND 7v An MM USB 6215 6216 6218 Figure 4 25 Connecting to the USB 6215 6216 6218 in Referenced Single Ended Mode In an referenced single ended connection configuration each input channel is measured with respect to AI GND Taking Non Referenced Single Ended Measurements NI USB 621x User Manual To reach a compromise between referenced single ended and differential measurements you can use an non referenced single ended measurement configuration This configuration allows for a remote sense for the negative input of the instrumentation amplifier PGIA that is shared among all channels configured for non referenced single ended mode The behavior of this configuration is similar to that of referenced single ended connections except it provides improved noise rejection Figure 4 26 shows an non referenced single ended connection configuration rcHEME oes e i C2 Mux PGIA ADC AIO l C Al SENSE e AIGND V USB 6215 6216 6218 Figure 4 26 Connecting to the USB 6215 6216 6218 in Non Referenced Single Ended Mode In non referenced single ended co
87. ce are greater than 3 m 10 ft e The input signal requires a separate ground reference point or return signal e The signal leads travel through noisy environments e Two analog input channels AI and AI are available for the signal Differential signal connections reduce noise pickup and increase common mode noise rejection Differential signal connections also allow input signals to float within the common mode limits of the NI PGIA Refer to the Using Differential Connections for Floating Signal Sources section for more information about differential connections When to Use Referenced Single Ended Connections with Floating Signal Sources Only use referenced single ended input connections if the input signal meets the following conditions e The input signal can share a common reference point AI GND with other signals that use referenced single ended e The input signal is high level greater than 1 V e The leads connecting the signal to the device are less than 3 m 10 ft National Instruments Corporation 4 25 NI USB 621x User Manual Chapter 4 Analog Input NI USB 621x User Manual Differential input connections are recommended for greater signal integrity for any input signal that does not meet the preceding conditions In the single ended modes more electrostatic and magnetic noise couples into the signal connections than in differential configurations The coupling is the result of differences in the
88. ces The total internal current limit for digital outputs and power drawn from the 5 V terminals is 50 mA You can increase this internal current limit by supplying an external 5 V supply Refer to the 5 V Power as an Input section of Chapter 3 Connector and LED Information Connecting Digital 1 0 Signals on USB 6212 6216 Devices The DIO signals P0 0 15 P1 lt 0 7 gt and P2 lt 0 7 gt are referenced to D GND You can individually program each line as an input or output Figure 6 4 shows P0 lt 0 3 gt configured for digital input and P1 lt 0 3 gt configured for digital output Digital input applications include receiving TTL signals and sensing external device states such as the state of the switch shown in the figure Digital output applications include sending TTL signals and driving external devices such as the LED shown in the figure NI USB 621x User Manual 6 6 ni com Chapter 6 Digital I O 5 V Isolation Ly Barrier i USB 6216 LED dd devices only VVV o 4 i o i P1 lt 0 3 gt A o K 4 4 Digital ole Isolators D a TTL Signal T a P0 0 3 4 5 V NN t Switch V A Vo When using a a Z USB 6216 D GND i you must connect gU D GND and or Al GND l O Connector E S to the local ground on your system USB 6212 6216 Device
89. coders You can choose either a single point on demand position measurement or a buffered sample clock position measurement You must arm a counter to begin position measurements NI USB 621x User Manual Chapter 8 NI USB 621x User Manual Counters Measurements Using Quadrature Encoders The counters can perform measurements of quadrature encoders that use X1 X2 or X4 encoding A quadrature encoder can have up to three channels channels A B and Z X1 Encoding When channel A leads channel B in a quadrature cycle the counter increments When channel B leads channel A in a quadrature cycle the counter decrements The amount of increments and decrements per cycle depends on the type of encoding X1 X2 or X4 Figure 8 14 shows a quadrature cycle and the resulting increments and decrements for X1 encoding When channel A leads channel B the increment occurs on the rising edge of channel A When channel B leads channel A the decrement occurs on the falling edge of channel A ChA ChB Li Lee i Counter Value 5 Y 6 X 7 7 Y 6 X 5 Figure 8 14 X1 Encoding X2 Encoding The same behavior for X1 encoding holds for X2 encoding except the counter increments or decrements on each edge of channel A depending on which channel leads the other Each cycle results in two increments or decrements as shown in Figure 8 15
90. consecutive channels in an Alscan list The interchannel delay must be short enough to allow sampling of all the channels in the channel list within the sample interval The greater the interchannel delay the more time the PGIA is allowed to settle before the next channel is sampled The interchannel delay is regulated by AI Convert Clock Connection between one or more of the following hardware software and the user For example hardware interfaces connect two other pieces of hardware 1 A means for a device to notify another device that an event occurred 2 A computer signal indicating that the CPU should suspend its current task to service a designated activity Current output high Current output low See interrupt interrupt request line A graphical programming language Light Emitting Diode A semiconductor light source A filter that passes signals below a cutoff frequency while blocking signals above that frequency Least Significant Bit NI USB 621x User Manual Glossary m M Series measurement MIO module monotonicity multichannel multifunction DAQ multiplex mux NI USB 621x User Manual Meter An architecture for instrumentation class multichannel data acquisition devices based on the earlier E Series architecture with added new features The quantitative determination of a physical characteristic In practice measurement is the conversion of a physical quantity or observati
91. counts the number of rising or falling edges on the Source The counter ignores additional edges on the Aux input The counter stops counting upon receiving an active edge on the Gate input The counter stores the count in a hardware save register You can configure the rising or falling edge of the Aux input to be the active edge You can configure the rising or falling edge of the Gate input to be the active edge Use this type of measurement to count events or measure the time that occurs between edges on two signals This type of measurement is sometimes referred to as start stop trigger measurement second gate measurement or A to B measurement National Instruments Corporation 8 19 NI USB 621x User Manual Chapter 8 NI USB 621x User Manual Counters Single Two Signal Edge Separation Measurement With single two signal edge separation measurement the counter counts the number of rising or falling edges on the Source input occurring between an active edge of the Gate signal and an active edge of the Aux signal The counter then stores the count in a hardware save register and ignores other edges on its inputs Software then reads the stored count Figure 8 20 shows an example of a single two signal edge separation measurement Counter Armed 4 Measured Interval 39 NEN i AUX GATE SOUR
92. ction You can enable a programmable debouncing filter on each PFI signal When the filters are enabled your device samples the input on each rising edge of a filter clock USB 621x devices use an onboard oscillator to generate the filter clock with a 40 MHz frequency 3 Note NI DAQmx only supports filters on counter inputs The following is an example of low to high transitions of the input signal High to low transitions work similarly Assume that an input terminal has been low for a long time The input terminal then changes from low to high but glitches several times When the filter clock has sampled the signal high on N consecutive edges the low to high transition is propagated to the rest of the circuit The value of N depends on the filter setting refer to Table 8 5 Table 8 5 Filters N Filter Clocks Pulse Width Pulse Width Needed to Guaranteed to Guaranteed to Filter Setting Pass Signal Pass Filter Not Pass Filter 125 ns 5 125 ns 100 ns 6 425 us 257 6 425 us 6 400 us 2 56 ms 101 800 2 56 ms 2 54 ms Disabled The filter setting for each input can be configured independently On power up the filters are disabled Figure 8 31 shows an example of a low to high transition on an input that has its filter set to 125 ns N 5 National Instruments Corporation NI USB 621x User Manual Chapter 8 Counters
93. cur in some other phase In Figure 8 17 the reload phase is when both channel A and channel B are low The reload occurs when this phase is true and channel Z is high Incrementing and decrementing takes priority over reloading Thus when the channel B goes low to enter the reload phase the increment occurs first The reload occurs within one maximum timebase period after the reload phase becomes true After the reload occurs the counter continues to count as before The figure illustrates channel Z reload with X4 decoding National Instruments Corporation 8 17 NI USB 621x User Manual Chapter 8 Counters NI USB 621x User Manual Max Timebase Counter Value 5 6 7 y Thay 1 X 2 X 3 Y4 0 0 1 Figure 8 17 Channel Z Reload with X4 Decoding Measurements Using Two Pulse Encoders The counter supports two pulse encoders that have two channels channels A and B The counter increments on each rising edge of channel A The counter decrements on each rising edge of channel B as shown in Figure 8 18 Ch A Ch B gt lt kan A Counter Value 2X 3 X 4 X 5 4 3 Figure 8 18 Measurements Using Two Pulse Encoders For information about connecting counter signals refer to the Default Counter Timer Pinouts section Buffered Sample Clock Pos
94. curacy is affected by settling time When your USB 621x device switches from one AI channel to another AI channel the device configures the NI PGIA with the input range of the new channel The NI PGIA then amplifies the input signal with the gain for the new input range Settling time refers to the time it takes the NI PGIA to amplify the input signal to the desired accuracy before it is sampled by the ADC The NI USB 621x Specifications lists settling time USB 621x devices are designed to have fast settling times However several factors can increase the settling time which decreases the accuracy National Instruments Corporation 4 5 NI USB 621x User Manual Chapter 4 Analog Input NI USB 621x User Manual of your measurements To ensure fast settling times you should do the following in order of importance e Use Low Impedance Sources To ensure fast settling times your signal sources should have an impedance of 1 kQ Large source impedances increase the settling time of the NI PGIA and so decrease the accuracy at fast scanning rates Settling times increase when scanning high impedance signals due to a phenomenon called charge injection Multiplexers contain switches usually made of switched capacitors When one of the channels for example channel 0 is selected in a multiplexer those capacitors accumulate charge When the next channel for example channel 1 is selected the accumulated charge leaks backward through chann
95. cy output generator Routing Frequency Output to a Terminal You can route Frequency Output to any output PFI terminal National Instruments Corporation 8 31 NI USB 621x User Manual Chapter 8 Counters Default Counter Timer Pinouts By default NI DAQmx routes the counter timer inputs and outputs to the USB 6210 6211 6215 device PFI pins as shown in Table 8 4 Table 8 4 Default NI DAQmx Counter Timer Pins for USB 6210 6211 6215 Devices Counter Timer Signal Default Terminal Number Name CTR 0 SRC 1 PFI 0 CTR 0 GATE 2 PFI 1 CTR 0 AUX 1 PFI 0 CTR 0 OUT 6 PFI 4 CTROA 1 PFI 0 CTROZ 3 PFI 2 CTROB 2 PFI 1 CTR 1 SRC 4 PFI 3 CTR 1 GATE 3 PFI 2 CTR 1 AUX 4 PFI 3 CTR 1 OUT 7 PFI 5 CTR1A 4 PFI 3 CTR1Z 2 PFI 1 CTR1IB 3 PFI 2 FREQ OUT 8 PFI 6 yi Note You can find the default NI DAQmx counter timer pins for all USB 621x devices in the applicable section of Appendix A Device Specific Information NI USB 621x User Manual You can use these defaults or select other sources and destinations for the counter timer signals in NI DAQmx Refer to Connecting Counter Signals in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later for more information about how to connect your signals for common counter measurements and generations USB 621x default PFI lines for counter functions are listed in Physical Channels in the NI DAQmx Help or the
96. d I O 11 1 USB Signal Stream 11 1 Declaration of Conformity NI resources C 2 default counter terminals 8 32 NI DAQmx counter timer pins 8 32 pins 8 32 desktop use 1 6 device information A 1 pinouts 1 2 specifications 1 2 A 1 NI USB 621x User Manual l 4 USB 6210 A 2 USB 6211 A 4 USB 6212 BNC A 13 USB 6212 Mass Termination A 8 USB 6212 Screw Terminal A 6 USB 6215 A 4 USB 6216 BNC A 13 USB 6216 Mass Termination A 8 USB 6216 Screw Terminal A 6 USB 6218 BNC A 21 USB 6218 Screw Terminal A 19 diagnostic tools NI resources C 1 differential connections analog input troubleshooting B 1 using with floating signal sources 4 27 using with ground referenced signal sources 4 34 when to use with floating signal sources 4 25 when to use with ground referenced signal sources 4 32 digital isolation 9 2 isolators 4 2 5 2 9 1 routing 10 1 signals connecting USB 6210 6211 6215 6218 6 3 USB 6212 6216 6 6 source triggering 12 1 digital I O triggering 12 1 USB 6210 6211 6215 6218 6 1 block diagram 6 2 circuitry 6 2 connecting signals 6 3 getting started with applications in software 6 4 TO protection 6 2 static DIO 6 2 ni com USB 6212 6216 6 4 block diagram 6 5 circuitry 6 5 connecting signals 6 6 getting started with applications in software 6 7 I O protection 6 5 programmable power up states 6 6 static DIO 6 5 DIN rail mounting kit 1 6 documentation conventions u
97. d the computer NI is not liable for any damage resulting from such signal connections NI USB 621x User Manual 4 4 ni com Chapter 4 Analog Input Configuring Al Ground Reference Settings in Software You can program channels on an USB 621x device to acquire with different ground references To enable multimode scanning in LabVIEW use NI DAQmx Create Virtual Channel vi of the NI DAQmx API You must use a new VI for each channel or group of channels configured in a different input mode In Figure 4 3 channel 0 is configured in differential mode and channel is configured in referenced single ended mode Differential Y DIO mx amp Devifeit E Tun Figure 4 3 Enabling Multimode Scanning in LabVIEW Pg Dev jai 7 To configure the input mode of your voltage measurement using the DAQ Assistant use the Terminal Configuration drop down list Refer to the DAQ Assistant Help for more information about the DAQ Assistant To configure the input mode of your voltage measurement using the NI DAQmx C API set the terminalConfig property Refer to the NI DAQmx C Reference Help for more information Multichannel Scanning Considerations USB 621x devices can scan multiple channels at high rates and digitize the signals accurately However you should consider several issues when designing your measurement system to ensure the high accuracy of your measurements In multichannel scanning applications ac
98. data on the device and still achieve accurate results For example if a USB 621x device has a sampling rate of 250 kS s this sampling rate is aggregate one channel at 250 kS s or two channels at 125 kS s per channel illustrates the relationship NI USB 621x User Manual Posttriggered data acquisition allows you to view only data that is acquired after a trigger event is received A typical posttriggered DAQ sequence is shown in Figure 4 6 The sample counter is loaded with the specified number of posttrigger samples in this example five The value decrements with each pulse on AI Sample Clock until the value reaches zero and all desired samples have been acquired Al Start Trigger Al Sample Clock l E Il I HELP LES Sample Counter 004 1 8 Figure 4 6 Posttriggered Data Acquisition Example 4 12 ni com Chapter 4 Analog Input Pretriggered data acquisition allows you to view data that is acquired before the trigger of interest in addition to data acquired after the trigger Figure 4 7 shows a typical pretriggered DAQ sequence AI Start Trigger ai StartTrigger can be either a hardware or software signal If AI Start Trigger is set up to be a software start trigger an output pulse appears on the AI Start Trigger line when the acquisition begins When the AI Start Trigger pulse occurs the sample counter is loaded with the number of pretriggered samples in this example
99. driver and additional signal labels You can use the combicon accessory to create custom connection solutions for USB 621x Screw Terminal devices Cables and Accessories for USB 621x Mass Termination Devices Refer to the USB 6212 6216 Mass Termination Cables and Accessories section of Appendix A Device Specific Information for a list of cables and accessories for USB 621x Mass Termination devices BNC Cables for USB 621x BNC Devices Use standard BNC cables with the USB 621x BNC device The BNC Male Plug to BNC Male Plug Cables Kit part number 779697 01 contains four one meter BNC cables for use with USB 621x BNC devices USB 621x Mass Termination Custom Cabling NI offers cables and accessories for many applications However if you want to develop your own cable adhere to the following guidelines for best results NI USB 621x User Manual For AI signals use shielded twisted pair wires for each AI pair of differential inputs Connect the shield for each signal pair to the ground reference at the source Route the analog lines separately from the digital lines When using a cable shield use separate shields for the analog and digital sections of the cable Failure to do so results in noise coupling into the analog signals from transient digital signals For more information about the connectors used for DAQ devices refer to the KnowledgeBase document Specifications and Manufacturers for Board Mating Connectors by go
100. e 6 X7 X1 X2 Xa Buffer 7 2 7 Figure 8 33 Duplicate Count Prevention Example On the first rising edge of Gate the current count of 7 is stored On the next rising edge of Gate the counter stores a 2 since two Source pulses occurred after the previous rising edge of Gate The counter synchronizes or samples the Gate signal with the Source signal so the counter does not detect a rising edge in Gate until the next Source pulse In this example the counter stores the values in the buffer on National Instruments Corporation 8 37 NI USB 621x User Manual Chapter 8 NI USB 621x User Manual Counters the first rising Source edge after the rising edge of Gate The details of when exactly the counter synchronizes the Gate signal vary depending on the synchronization mode Example Application That Works Incorrectly Duplicate Counting In Figure 8 34 after the first rising edge of Gate no Source pulses occur so the counter does not write the correct data to the buffer No Source edge so no value written to buffer Gate Source Counter Value 6 X7 X1 Buffer 7 Figure 8 34 Duplicate Count Example Example Application That Prevents Duplicate Count With duplicate count prevention the counter synchronizes both the Source and Gate signals to the 80 MHz Timebase By synchronizing to the timeb
101. e either the rising edge or falling edge of the digital signal A rising edge is a transition from a low logic level to a high logic level A falling edge is a high to low transition Figure 12 1 shows a falling edge trigger 5V Digital Trigger OV Falling Edge Initiates Acquisition Figure 12 1 Falling Edge Trigger National Instruments Corporation 12 1 NI USB 621x User Manual Chapter 12 Triggering NI USB 621x User Manual You also can program your USB 621x device to perform an action in response to a trigger from a digital source The action can affect the following e Analog input acquisition Analog output generation e Counter behavior 12 2 ni com Device Specific Information This appendix contains device pinouts and other information for the following USB 621x devices USB 6210 USB 621 1 6215 USB 6212 6216 Screw Terminal USB 6212 6216 Mass Termination USB 6212 6216 BNC USB 6218 Screw Terminal USB 6218 BNC Refer to the NI USB 621x Specifications available on the NI DAQ Device Documentation Browser or from ni com manuals for more detailed information about USB 621x devices To obtain documentation for devices not listed here refer to ni com manuals National Instruments Corporation A 1 NI USB 621x User Manual Appendix A Device Specific Information USB 6210 USB 6210 Pinout NI USB 621x User Manual Figure A 1 shows the pinout of the USB 6210 For a deta
102. e is called reciprocal frequency measurement In this method you generate a long pulse using the signal to measure You then measure the long pulse with a known timebase The USB 621x device can measure this long pulse more accurately than the faster input signal You can route the signal to measure to the Source input of Counter 0 as shown in Figure 8 13 Assume this signal to measure has frequency F1 Configure Counter 0 to generate a single pulse that is the width of N periods of the source input signal Signal to e SOURCE OUT Measure F1 COUNTER 0 Signal of Known A SOURCE OUT Frequency F2 COUNTER 1 L p GATE 0123 N CTR 0 SOURCE Signal to Measure CTR 0 OUT CTR 1 GATE Interval to Measure CTR 1 SoURCE JU National Instruments Corporation Figure 8 13 Method 3 Then route the Counter 0 Internal Output signal to the Gate input of Counter 1 You can route a signal of known frequency F2 to the Counter 1 Source input F2 can be 830MHzTimebase For signals that might be slower than 0 02 Hz use a slower known timebase Configure Counter 1 to perform a single pulse width measurement Suppose the result is that the pulse width is J periods of the F2 clock 8 13 NI USB 621x User Manual Chapter 8 Counters From Counter 0 the length of the pulse is V F1 From Counter 1 the length of the same pulse is J F2 Th
103. e measurements take more time and consume some of the available USB bandwidth NI USB 621x User Manual 6 14 ni com Chapter 8 e Method 2 is accurate for high frequency signals However the accuracy decreases as the frequency of the signal to measure decreases At very low frequencies Method 2 may be too inaccurate for your application Another disadvantage of Method 2 is that it requires two counters if you cannot provide an external signal of known width An advantage of Method 2 is that the measurement completes in a known amount of time e Method 3 measures high and low frequency signals accurately However it requires two counters Table 8 2 summarizes some of the differences in methods of measuring frequency Table 8 2 Frequency Measurement Method Comparison Measures High Measures Low Number of Number of Frequency Frequency Counters Measurements Signals Signals Method Used Returned Accurately Accurately 1 1 1 Poor Good 1b 1 Many Fair Good 2 or2 1 Good Poor 3 2 1 Good Good For information about connecting counter signals refer to the Default Counter Timer Pinouts section Position Measurement You can use the counters to perform position measurements with quadrature encoders or two pulse encoders You can measure angular position with X1 X2 and X4 angular encoders Linear position can be National Instruments Corporation 8 15 Counters measured with two pulse en
104. e middle of a period of the Gate input The counter does not store a measurement for this incomplete period Figure 8 8 shows an example of a buffered period measurement In this example a period is defined by two consecutive rising edges GATE SOURCE Counter Value Buffer Time N Counter Armed L wicguiecdu ores imeem 3 8 to h to ty rising edges of Source in the buffer in the buffer to At t the counter is armed No measurements are taken until the counter is armed t The rising edge of Gate indicates the beginning of the first period to measure The counter begins counting t The rising edge of Gate indicates the end of the first period The USB 621x device stores the counter value tz The rising edge of Gate indicates the end of the second period The USB 621 x device stores the counter value Figure 8 8 Buffered Period Measurement National Instruments Corporation 8 7 NI USB 621x User Manual Chapter 8 Counters Note that if you are using an external signal as the Source at least one Source pulse should occur between each active edge of the Gate signal This condition ensures that correct values are returned by the counter If this condition is not met the counter returns a zero Refer to the Duplicate Count Prevention section for more information For information about c
105. e period Figure 8 10 illustrates method 1 ECL Interval Measured H F1 F1 Gate 1 2 3 ite N Ft Source Ft 4 4 Single Period Period of F1 ON Measurement Ft Ft Frequency of F1 q y N Figure 8 10 Method 1 8 10 ni com Chapter 8 Counters Method 1b Measure Low Frequency with One Counter Averaged In this method you measure several periods of your signal using a known timebase This method is good for low to medium frequency signals You can route the signal to measure F1 to the Gate of a counter You can route a known timebase Ft to the Source of the counter The known timebase can be 80MHzTimebase For signals that might be slower than 0 02 Hz use a slower known timebase You can configure the counter to make K 1 buffered period measurements Recall that the first period measurement in the buffer should be discarded Average the remaining K period measurements to determine the average period of F1 The frequency of F1 is the inverse of the average period Figure 8 11 illustrates this method National Instruments Corporation Intervals Measured CO a Ta g i Tki es a a REED a F1 Gate zi Ft 4 Source 12 N41 nm No ak ee Nx r JUNI Buffered Period Measurement N No Nk 1 Average Period of F1 x K Ft K x Ft Frequency of F1
106. easurement system having multiple grounds at different potentials Improved Safety The isolation barrier allows you to make floating measurements while protecting the USB host computer against large transient voltage spikes Reducing Common Mode Noise Isolated products require an isolated power supply to deliver power to the isolated side from the non isolated side Isolated power supplies work by switching voltages through a transformer with high speed transistors Switching voltages through the transformer cause charging and discharging of the parasitic capacitances and inductances in the switching power supplies that occur on every switch cycle resulting in high speed currents flowing through the isolated side and returning to the non isolated side which is earth ground These parasitic currents interact with parasitic and non parasitic resistances causing voltage spikes These voltage spikes are called common mode noise a noise source that travels in the ground and is therefore common to both the ground and any signal referenced to the ground such as AI AO and digital signals Common mode noise appears at the harmonics of the switching power supply frequency and can corrupt measurements depending on the system setup You can perform some tasks to reduce common mode noise e Better grounding from the front connector AI GND to the signal source ground can reduce common mode noise Use low resistance cabling and connections a
107. ection Frequency Division The counters can generate a signal with a frequency that is a fraction of an input signal This function is equivalent to continuous pulse train generation For information about connecting counter signals refer to the Default Counter Timer Pinouts section Pulse Generation for ETS NI USB 621x User Manual In the equivalent time sampling ETS application the counter produces a pulse on the output a specified delay after an active edge on Gate After each active edge on Gate the counter cumulatively increments the delay between the Gate and the pulse on the output by a specified amount Thus the delay between the Gate and the pulse produced successively increases The increase in the delay value can be between 0 and 255 For instance if you specify the increment to be 10 the delay between the active Gate edge and the pulse on the output increases by 10 every time a new pulse is generated Suppose you program your counter to generate pulses with a delay of 100 and pulse width of 200 each time it receives a trigger Furthermore suppose you specify the delay increment to be 10 On the first trigger your pulse delay is 100 on the second it is 110 on the third it is 120 the process repeats in this manner until the counter is disarmed The counter ignores any Gate edge that is received while the pulse triggered by the previous Gate edge is in progress The waveform thus produced at the counter s output
108. ections for Floating Signal Sources 4 27 Using Non Referenced Single Ended Connections for Floating Signal Sources sse 4 30 Using Referenced Single Ended Connections for Floating Signal Sources sese 4 31 Connecting Ground Referenced Signal Sources eese 4 31 What Are Ground Referenced Signal Sources 4 31 When to Use Differential Connections with Ground Referenced Signal Sources sess 4 32 When to Use Non Referenced Single Ended Connections with Ground Referenced Signal Sources sss 4 32 When to Use Referenced Single Ended Connections with Ground Referenced Signal Sources sess 4 33 Using Differential Connections for Ground Referenced Signal Sources iet ea ted Ice ie dane 4 34 Using Non Referenced Single Ended Connections for Ground Referenced Signal Sources sess 4 35 Connecting Analog Input Signals on USB 6215 6216 6218 Devices 4 36 Taking Differential Measurement essere 4 36 Taking Referenced Single Ended Measurements esse 4 37 Taking Non Referenced Single Ended Measurements 4 38 Chapter 5 Analog Output AQ Ranges 255 oae d OR ERU ER EE EE ene Ev cet eo Dee D ER Red 5 2 Minimizing Glitches on the Output Signal sene 5 2 Analog O
109. ed for many measurement and pulse generation applications Input Selection Muxes Counter 0 Counter 0 Source Counter 0 Timebase Counter D Gate Counter 0 Internal Output Counter 0 Aux Counter 0 HW Arm Counter 0 A Counter 0 TC Counter 0 B Counter 0 Up_Down T Counter 0 Z Input Selection Muxes Counter 1 Counter 1 Source Counter 1 Timebase Gounter i Gale Counter 0 Internal Output Counter 1 Aux N Counter 1 HW Arm N Counter 1 A Counter 0 TC Counter 1 B Counter 1 Up_Down 7 Counter 1 Z Input Selection Muxes Frequency Generator Frequency Output Timebase National Instruments Corporation Figure 8 1 USB 621x Counters 8 1 Freq Out NI USB 621x User Manual Chapter 8 Counters The counters have seven input signals although in most applications only a few inputs are used For information about connecting counter signals refer to the Default Counter Timer Pinouts section Counter Input Applications Counting Edges NI USB 621x User Manual In edge counting applications the counter counts edges on its Source after the counter is armed You can configure the counter to count rising or falling edges on its Source input You also can control the direction of counting up or down The counter values can be read on demand or with a sample clock Single Point On Demand Edge Counting
110. edge of Source GATE Start Trigger source __ IU LI LI OUT NM Figure 8 23 Single Pulse Generation with Start Trigger Retriggerable Single Pulse Generation The counter can output a single pulse in response to each pulse on a hardware Start Trigger signal The pulses appear on the Counter n Internal Output signal of the counter 6 22 ni com Chapter 8 Counters You can route the Start Trigger signal to the Gate input of the counter You can specify a delay from the Start Trigger to the beginning of each pulse You also can specify the pulse width The delay and pulse width are measured in terms of a number of active edges of the Source input The counter ignores the Gate input while a pulse generation is in progress After the pulse generation is finished the counter waits for another Start Trigger signal to begin another pulse generation Figure 8 24 shows a generation of two pulses with a pulse delay of five and a pulse width of three using the rising edge of Source GATE i Start Trigger M SOURCE OUT Figure 8 24 Retriggerable Single Pulse Generation For information about connecting counter signals refer to the Default Counter Timer Pinouts section Pulse Train Generation Continuous Pulse
111. eferenced to D GND Figure 7 3 shows this reference and how to connect an external PFI 0 source and an external PFI 2 source to two PFI terminals PFI O pag PFI 2 PFI O PFI 2 Source Source D GND yF Vv l O Connector USB 621x Device Figure 7 3 PFI Input Signals Connections PFI Filters You can enable a programmable debouncing filter on each PFI signal When the filters are enabled your device samples the input on each rising edge of a filter clock USB 621x devices use an onboard oscillator to generate the filter clock with a 40 MHz frequency B Note NI DAQmx only supports filters on counter inputs The following is an example of low to high transitions of the input signal High to low transitions work similarly NI USB 621x User Manual 7 4 ni com Chapter 7 PFI Assume that an input terminal has been low for a long time The input terminal then changes from low to high but glitches several times When the filter clock has sampled the signal high on N consecutive edges the low to high transition is propagated to the rest of the circuit The value of N depends on the filter setting refer to Table 7 1 Table 7 1 Filters N Filter Clocks Pulse Width Pulse Width Needed to Guaranteed to Guaranteed to Filter Setting Pass Signal Pass Filter Not Pass Filter 125 ns 5 125 ns 100 ns 6 425 u
112. efore the reference trigger The number of posttrigger samples samples that occur after the reference trigger desired is the buffer size minus the number of pretrigger samples After the acquisition begins the DAQ device writes samples to the buffer After the DAQ device captures the specified number of pretrigger samples the DAQ device begins to look for the reference trigger condition If the reference trigger condition occurs before the DAQ device captures the specified number of pretrigger samples the DAQ device ignores the condition If the buffer becomes full the DAQ device continuously discards the oldest samples in the buffer to make space for the next sample This data can be accessed with some limitations before the DAQ device discards it Refer to the KnowledgeBase document Can a Pretriggered Acquisition be Continuous for more information To access this KnowledgeBase go to ni com info and enter the info code rdcanq When the reference trigger occurs the DAQ device continues to write samples to the buffer until the buffer contains the number of posttrigger samples desired Figure 4 15 shows the final buffer Reference Trigger Pretrigger Samples Posttrigger Samples l l Complete Buffer Figure 4 15 Reference Trigger Final Buffer National Instruments Corporation 4 21 NI USB 621x User Manual Chapter 4 Analog Input Using a Digital Source To use AI Reference Trigger wi
113. el 1 If the output impedance of the source connected to channel 1 is high enough the resulting reading of channel 1 can be partially affected by the voltage on channel 0 This effect is referred to as ghosting If your source impedance is high you can decrease the scan rate to allow the NI PGIA more time to settle Another option is to use a voltage follower circuit external to your DAQ device to decrease the impedance seen by the DAQ device Refer to the KnowledgeBase document Decreasing the Source Impedance of an Analog Input Signal by going to ni com info and entering the info code rdbbis Use Short High Quality Cabling Using short high quality cables can minimize several effects that degrade accuracy including crosstalk transmission line effects and noise The capacitance of the cable also can increase the settling time National Instruments recommends using individually shielded twisted pair wires that are 2 m or less to connect AI signals to the device Refer to the Connecting Analog Input Signals on USB 6210 6211 6212 Devices or Connecting Analog Input Signals on USB 6215 6216 6218 Devices section for more information e Carefully Choose the Channel Scanning Order Avoid Switching from a Large to a Small Input Range Switching from a channel with a large input range to a channel with a small input range can greatly increase the settling time Suppose a 4 V signal is connected to channel 0 and a mV signal is con
114. ent configuration A differential measurement configuration requires two inputs for each measurement The AI lt 0 31 gt description in Table 3 1 O Connector Signals lists the signal pairs that are valid for differential connection configurations with USB 621x devices 4 36 ni com Chapter 4 Analog Input Figure 4 24 shows a differential connection configuration Al 0 i Al 0 AI 8 i Vi A fans ADC 4 1 Al 1 Vem WVC Al 1 AI 9 ptos pa AND This signal name indicates the differential pair Refer to Table 3 1 O Connector Signals for a list of differential signal pairs Figure 4 24 Connecting to the USB 6215 6216 6218 in Differential Mode The differential connection configuration allows the common mode noise voltage Vm to be rejected during the measurement of V4 You must connect the negative lead of your sensors and AI GND to a local ground signal on your system Taking Referenced Single Ended Measurements 3 Using the referenced single ended measurement configuration allows the USB 6215 6216 6218 to take measurements on all AI channels when all channels share a common ground Figure 4 25 shows an referenced single ended connection configuration Note Ifyou leave the AI GND pin unconnected the signals float outside the working input range of the USB 6215 6216 6218 This can result in unreliable measurements be
115. er counts the number of edges on the Source input while the Gate input remains active On each trailing edge of the Gate signal the counter stores the count in a hardware save register A USB Signal Stream transfers the stored values to host memory Figure 8 6 shows an example of a buffered pulse width measurement Counter Value Buffer N Figure 8 6 Buffered Pulse Width Measurement Note that if you are using an external signal as the Source at least one Source pulse should occur between each active edge of the Gate signal This condition ensures that correct values are returned by the counter If this National Instruments Corporation 8 5 NI USB 621x User Manual Chapter 8 Counters condition is not met consider using duplicate count prevention described in the Duplicate Count Prevention section For information about connecting counter signals refer to the Default Counter Timer Pinouts section Period Measurement NI USB 621x User Manual In period measurements the counter measures a period on its Gate input signal after the counter is armed You can configure the counter to measure the period between two rising edges or two falling edges of the Gate input signal You can route an internal or external periodic clock signal with a known period to the Source input of the counter The counter counts the number of rising or falling
116. erefore the frequency of F1 is given by F1 F2 N J Choosing a Method for Measuring Frequency The best method to measure frequency depends on several factors including the expected frequency of the signal to measure the desired accuracy how many counters are available and the measurement duration e Method 1 uses only one counter It is a good method for many applications However the accuracy of the measurement decreases as the frequency increases Consider a frequency measurement on a 50 KHz signal using an 80 MHz Timebase This frequency corresponds to 1 600 cycles of the 80 MHz Timebase Your measurement may return 1 600 1 cycles depending on the phase of the signal with respect to the timebase As your frequency becomes larger this error of 1 cycle becomes more significant Table 8 1 illustrates this point Table 8 1 Frequency Measurement Method 1 Task Equation Example 1 Example 2 Actual Frequency to Measure F1 50 kHz 5 MHz Timebase Frequency Ft 80 MHz 80 MHz Actual Number of Timebase FUF1 1 600 16 Periods Worst Case Measured Number of Ft F1 1 1 599 15 Timebase Periods Measured Frequency Ft F1 Ft F1 50 031 kHz 5 33 MHz Error Ft F1 Ft F1 F1 31 Hz 333 kHz Error Ft Ft F1 1 0 06 6 67 e Method 1b measuring K periods of F1 improves the accuracy of the measurement A disadvantage of Method 1b is that you have to take K 1 measurements Thes
117. errupt or programmed I O data transfer mechanisms Some of the applications also use start reference and pause triggers 4 22 ni com Chapter 4 Analog Input B Note For more information about programming analog input applications and triggers in software refer to the NI DA Qmx Help or the LabVIEW Help in version 8 0 or later Connecting Analog Input Signals on USB 6210 6211 6212 Devices Table 4 2 summarizes the recommended input configuration for both types of signal sources on USB 6210 6211 6212 devices National Instruments Corporation 4 23 NI USB 621x User Manual Chapter 4 Analog Input Table 4 2 USB 6210 6211 6212 Analog Input Configuration AI Ground Reference Floating Signal Sources Not Connected to Ground Referenced Building Ground Signal Sources Examples Example Ungrounded thermocouples Signal conditioning with isolated outputs Plug in instruments with non isolated outputs Setting Battery devices Differential DIFF Signal Source DAQ Device Signal Source DAQ Device Ale Ale t C Al C Al Al GND Al GND Vom Non Referenced Signal Source DAQ Device Signal Source DAQ Device Single Ended NRSE Al Al e AI SENSE ES SENSE AI GND V AI GND TI Pa dr d m Referenced S
118. every five periods of AO Sample Clock Timebase the programmable clock divider counts down from 4 to 0 When AO Pause Trigger is asserted the programmable clock divider ignores pulses of AO Sample Clock Timebase NI USB 621x User Manual 5 6 ni com Chapter 5 Analog Output AO Sample Clock AO Sample Clock Timebase Programmable Clock Divider Cout 0 4 3 2 1 0 4 3 2 1 0 AO Pause Trigger The Programmable Clock Divider ignores AO Sample Clock Timebase when AO Pause Trigger is true Figure 5 4 AO Pause Trigger Example If you are using any signal as the source of your sample clock the generation resumes as soon as AO Pause Trigger is deasserted and another edge of the sample clock is received as shown in Figure 5 5 Pause Trigger Sample Clock JES LE Figure 5 5 AO Pause Trigger with Other Signal Source Using a Digital Source To use AO Pause Trigger specify a source and a polarity The source can be any input PFI signal The source also can be one of several other internal signals on your USB 621x device Refer to Device Routing in MAX in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later for more information You also can specify whether the samples are paused when AO Pause Trigger is at a logic high or low level National Instruments Corporat
119. f Calibration NI recommends that you self calibrate your USB 621x device after installation and whenever the ambient temperature changes Self calibration should be performed after the device has warmed up for the recommended time period Refer to the NJ USB 621x Specifications to find your device warm up time This function measures the onboard reference voltage of the device and adjusts the self calibration constants to account for any errors caused by short term fluctuations in the environment Disconnect all external signals when you self calibrate a device You can initiate self calibration using Measurement amp Automation Explorer MAX by completing the following steps 1 Launch MAX 2 Select My System Devices and Interfaces NI DAQmx Devices your device 3 Initiate self calibration using one of the following methods Click Self Calibrate in the upper right corner of MAX e Right click the name of the device in the MAX configuration tree and select Self Calibrate from the drop down menu ER Note You can also programmatically self calibrate your device with NI DAQmx as described in Device Calibration in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later Device Pinouts Refer to Appendix A Device Specific Information for USB 621x device pinouts Device Specifications Refer to the NJ USB 621x Specifications available on the NI DAQ Device Documentation Browser or from ni com manuals for more
120. f your questions are not answered here refer to the National Instruments KnowledgeBase at ni com kb I am seeing crosstalk or ghost voltages when sampling multiple channels What does this mean You may be experiencing a phenomenon called charge injection which occurs when you sample a series of high output impedance sources with a multiplexer Multiplexers contain switches usually made of switched capacitors When a channel for example AI 0 is selected in a multiplexer those capacitors accumulate charge When the next channel for example AI 1 is selected the accumulated current or charge leaks backward through channel 1 If the output impedance of the source connected to AI 1 is high enough the resulting reading can somewhat affect the voltage in AI 0 To circumvent this problem use a voltage follower that has operational amplifiers op amps with unity gain for each high impedance source before connecting to a USB 621x device Otherwise you must decrease the sample rate for each channel Another common cause of channel crosstalk is due to sampling among multiple channels at various gains In this situation the settling times can increase For more information about charge injection and sampling channels at different gains refer to the Multichannel Scanning Considerations section of Chapter 4 Analog Input I am using my device in differential analog input ground reference mode and I have connected a differential input signal
121. ference to view the function reference Expand NI Measurement Studio Help NI Measurement Studio NET Class Library Using the Measurement Studio NET Class Libraries to view conceptual topics for using NI DAQmx with Visual Cft and Visual Basic NET National Instruments Corporation xvii NI USB 621x User Manual About This Manual To get to the same help topics from within Visual Studio go to Help Contents Select Measurement Studio from the Filtered By drop down list and follow the previous instructions Device Documentation and Specifications Training Courses The NI USB 621x Specifications contains all specifications for the USB 6210 USB 6211 USB 6212 USB 6215 USB 6216 and USB 6218 M Series devices Documentation for supported devices and accessories including PDF and help files describing device terminals specifications features and operation are on the NI DAQmx media that includes Device Documentation Insert the media open the Device Documentation directory and double click the Device Documents shortcut for your language to find view and print device documents If you need more help getting started developing an application with NI products NI offers training courses To enroll in a course or obtain a detailed course outline refer to ni com training Technical Support on the Web For additional support refer to ni com support or zone ni com 3 Note You can download these documents at ni com manuals
122. ffer SOURCE E A A E A Counter Value O0 1 2 3 1 1 B 1 H 3 dm 2 Ive Figure 8 9 Buffered Semi Period Measurement Note that if you are using an external signal as the Source at least one Source pulse should occur between each active edge of the Gate signal This condition ensures that correct values are returned by the counter If this condition is not met the counter returns a zero Refer to the Duplicate Count Prevention section for more information For information about connecting counter signals refer to the Default Counter Timer Pinouts section National Instruments Corporation 8 9 NI USB 621x User Manual Chapter 8 Counters Frequency Measurement You can use the counters to measure frequency in several different ways You can choose one of the following methods depending on your application NI USB 621x User Manual Method 1 Measure Low Frequency with One Counter In this method you measure one period of your signal using a known timebase This method is good for low frequency signals You can route the signal to measure F1 to the Gate of a counter You can route a known timebase Ft to the Source of the counter The known timebase can be 80MHzTimebase For signals that might be slower than 0 02 Hz use a slower known timebase You can configure the counter to measure one period of the gate signal The frequency of F1 is the inverse of th
123. for more information about non referenced single ended connections When to Use Referenced Single Ended Connections with Ground Referenced Signal Sources Do not use referenced single ended connections with ground referenced signal sources Use non referenced single ended or differential connections instead As shown in the bottom rightmost cell of Table 4 2 there can be a potential difference between AI GND and the ground of the sensor In referenced single ended mode this ground loop causes measurement errors National Instruments Corporation 4 33 NI USB 621x User Manual Chapter 4 Analog Input NI USB 621x User Manual Using Differential Connections for Ground Referenced Signal Sources Figure 4 22 shows how to connect a ground referenced signal source to the USB 6210 6211 6212 device configured in differential mode 1s Al oo oO Co Ground Aa Referenced i u Instrumentation Eu en ee ee Al 4 Measured Common oc eee o o e vs Mode V o o o 4 Noise and Xem 4 Ground i N Potential 77 2 ve Input Multiplexers O1 9 AI SENSE AI GND 1 O Connector USB 6210 6211 6212 Configured in DIFF Mode Figure 4 22 Differential Connections for Ground Referenced Signal Sources With this type of connection the NI PGIA rejects both the common mode noise in the signal and the ground p
124. four The value decrements with each pulse on AI Sample Clock until the value reaches zero The sample counter is then loaded with the number of posttriggered samples in this example three Al Start Trigger Al Reference Trigger n a UN T Al Sample Clock l l Al Convert Clock Scan Counter 3 Figure 4 7 Pretriggered Data Acquisition Example If an AI Reference Trigger ai ReferenceTrigger pulse occurs before the specified number of pretrigger samples are acquired the trigger pulse is ignored Otherwise when the AI Reference Trigger pulse occurs the sample counter value decrements until the specified number of posttrigger samples have been acquired USB 621x devices feature the following analog input timing signals e AI Sample Clock Signal e Al Sample Clock Timebase Signal e AI Convert Clock Signal e AI Convert Clock Timebase Signal e AI Hold Complete Event Signal e Al Start Trigger Signal e AI Reference Trigger Signal e AI Pause Trigger Signal National Instruments Corporation 4 13 NI USB 621x User Manual Chapter 4 Analog Input Al Sample Clock Signal NI USB 621x User Manual Use the AI Sample Clock ai SampleClock signal to initiate a set of measurements Your USB 621x device samples the AI signals of every channel in the task once for every AI Sample Clock A measurement acqui
125. frequency range and linearity 1 Electronic equipment that makes transducer or other signals suitable in level and range to be transmitted over a distance or to interface with voltage input instruments 2 The manipulation of signals to prepare them for digitizing A generic term for any instrument in the family of signal generators Signals are waveforms containing information Although physical signals can be in the form of mechanical electromagnetic or other forms they are most often converted to electronic form for measurement When the arbitrary waveform generator goes through the staging list only once Describes a device that acquires a specified number of samples from one or more channels and returns the data when the acquisition is complete A circuit that responds to the voltage on one input terminal and ground See also differential input NI USB 621x User Manual Glossary single ended output software triggering source impedance synchronous task TC terminal terminal count tgh lgs tew Timebase t out transducer NI USB 621x User Manual A circuit whose output signal is present between one output terminal and ground A method of triggering in which you simulate an analog trigger using software Also called conditional retrieval A parameter of signal sources that reflects current driving ability of voltage sources lower is better and the voltage driving ability of current source
126. general purpose counter timers The 100 kHz Timebase is generated by dividing down the 20 MHz Timebase by 200 National Instruments Corporation 10 1 NI USB 621x User Manual Bus Interface The bus interface circuitry of USB 621x devices efficiently moves data between host memory and the measurement and acquisition circuits All USB 621x devices are jumperless for complete plug and play operation The operating system automatically assigns the base address interrupt levels and other resources USB 621x devices incorporate USB STC2 technology to implement a Hi Speed USB interface USB Signal Stream USB 621x devices have four fully independent USB Signal Streams for high performance transfers of data blocks One USB Signal Stream is available for each measurement and acquisition block Analog input Analog output Counter 0 Counter 1 Data Transfer Methods The two primary ways to transfer data across the USB bus are as follows National Instruments Corporation USB Signal Stream A method to transfer data between the device and computer memory using USB bulk transfers without intervention of the microcontroller on the NI device NI uses USB Signal Stream hardware and software technology to achieve high throughput rates and increase system utilization in USB devices Programmed I O A data transfer mechanism where the user s program is responsible for transferring data Each read or write call in the
127. h LabVIEW manual by selecting Start All Programs National Instruments LabVIEW LabVIEW Manuals or by navigating to the labview manuals directory and opening Lv_Getting_Started pdf National Instruments Corporation XV NI USB 621x User Manual About This Manual LabWindows CVI Use the LabVIEW Help available by selecting Help Search the LabVIEW Help in LabVIEW to access information about LabVIEW programming concepts step by step instructions for using LabVIEW and reference information about LabVIEW VIs functions palettes menus and tools Refer to the following locations on the Contents tab of the LabVIEW Help for information about NI DAQmx Getting Started with LabVIEW Getting Started with DAQ Includes overview information and a tutorial to learn how to take an NI DAQmx measurement in LabVIEW using the DAQ Assistant Vland Function Reference Measurement I O VIs and Functions Describes the LabVIEW NI DAQmx VIs and properties e Taking Measurements Contains the conceptual and how to information you need to acquire and analyze measurement data in LabVIEW including common measurements measurement fundamentals NI DAQmx key concepts and device considerations The Data Acquisition book of the LabWindows CVI Help contains measurement concepts for NI DAQmx This book also contains Taking an NI DAQmx Measurement in LabWindows CVI which includes step by step instructions about creating a measurement task using the D
128. hapter 2 DAQ System Overview Figure 2 2 features components common to all USB 621x devices Isolation Barrier USB 6215 6216 6218 devices only Digital Routing Digital Bus and Clock Isolators F Interface pug Generation T EU Analog Input Analog Output 8 o e Sr Digital I O O Q Counters y PFI ith DAQ STC2 Figure 2 2 USB 621x Block Diagram The DAQ STC2 implements a high performance digital engine for M Series data acquisition hardware Some key features of this engine include the following Calibration Circuitry The USB 621x analog inputs and outputs have calibration circuitry to correct gain and offset errors You can calibrate the device to minimize AI and AO errors caused by time and temperature drift at run time No external circuitry is necessary an internal reference ensures high accuracy and stability over time and temperature changes NI USB 621x User Manual Flexible AI and AO sample and convert timing Many triggering modes Independent AL AO and CTR FIFOs Generation and routing of internal and external timing signals Two flexible 32 bit counter timer modules with hardware gating Static DI DO and DIO signals USB Hi Speed 2 0 interface Up to four USB Signal Streams for acquisition and generation functions 2 2 ni com C
129. hapter 2 DAQ System Overview Factory calibration constants are permanently stored in an onboard EEPROM and cannot be modified When you self calibrate the device software stores new constants in a user modifiable section of the EEPROM To return a device to its initial factory calibration settings software can copy the factory calibration constants to the user modifiable section of the EEPROM Refer to the NI DAQmx Help or the LabVIEW Help in version 8 0 or later for more information about using calibration constants For a detailed calibration procedure for USB 621x devices refer to the B E M S Series Calibration Procedure for NI DAQmx by clicking Manual Calibration Procedures on ni com calibration Signal Conditioning Many sensors and transducers require signal conditioning before a measurement system can effectively and accurately acquire the signal The front end signal conditioning system can include functions such as signal amplification attenuation filtering electrical isolation simultaneous sampling and multiplexing In addition many transducers require excitation currents or voltages bridge completion linearization or high amplification for proper and accurate operation Therefore most computer based measurement systems include some form of signal conditioning in addition to plug in data acquisition DAQ devices Sensors and Transducers Sensors can generate electrical signals to measure physical phenomena such as
130. he NJ USB 621x Specifications Refer to Chapter 7 PFI for more information on PFI inputs and outputs National Instruments Corporation 6 1 NI USB 621x User Manual Chapter 6 Digital I O Figure 6 1 shows the circuitry of one DI line and one DO line The following sections provide information about the various parts of the DIO circuit Static DI I O Protection e PO x 47 kQ Pull Down Static DO I O Protection e P1 x 47 kQ Pull Down Figure 6 1 USB 6210 6211 6215 6218 Digital 1 0 Circuitry The DI terminals are named PO lt 0 7 gt on the USB 6210 6211 6215 6218 device I O connector The DO terminals are named P1 lt 0 7 gt on the USB 6210 6211 6215 6218 device I O connector The voltage input and output levels and the current drive levels of the DIO lines are listed in the NJ USB 621x Specifications Static DIO on USB 6210 6211 6215 6218 Devices You can use static DI and DO lines to monitor or control digital signals All samples of static DI lines and updates of DO lines are software timed 1 0 Protection on USB 6210 6211 6215 6218 Devices Each DI DO and PFI signal is protected against overvoltage undervoltage and overcurrent conditions as well as ESD events However you should avoid these fault conditions by following these guidelines e Donot connect a DO or PFI output lines to any external signal source ground signal or power supply e Understand the current req
131. igital I O signal you can individually configure each signal as an input or output National Instruments Corporation 3 2 NI USB 621x User Manual Connector and LED Information Chapter 3 Connector and LED Information Table 3 1 1 0 Connector Signals Continued Signal Name Reference Direction Description USER USB 621x BNC Devices User Defined Channel The USER BNC connector allows you to use a BNC connector for a digital or timing T O signal of your choice The USER BNC connector is internally routed to the USER screw terminal Refer to the appropriate USER section for your USB 621x BNC device in Appendix A Device Specific Information for more information about the USER signal NC No connect Do not connect signals to these terminals USB 6212 6216 BNC Mass Termination devices have eight digital T O lines P0 lt 0 7 gt 5 V Power The 5 V terminals on the I O connector can be use as either an output or an input Both terminals are internally connected on the USB 621x 5 V Power as an Output Because the USB 621x devices are bus powered there is a 50 mA limit on the total current that can be drawn from the 5 V terminals and the digital outputs The USB 621x monitors the total current and drops the voltage on all of the digital outputs and the 5 V terminals if the 50 mA limit is exceeded 5 V Power as an Input If you have high current loads for the d
132. igital outputs to drive you can exceed the 50 mA internal limit by connecting an external 5 V power source to the 5 V terminals These terminals are protected against undervoltage and overvoltage and they have a fuse to protect them from short circuit conditions If your USB 621x device has more than one 5 V terminal you can connect the external power supply to one terminal and use the other as a power source 1 USB 621x Screw Terminal BNC devices have a 350 mA self resetting fuse USB 621x Mass Termination devices have a 750 mA user replaceable socketed fuse Refer to the USB Device Fuse Replacement section for information about replacing socketed fuses NI USB 621x User Manual 3 3 ni com Chapter 3 Connector and LED Information USB Chassis Ground USB 621x BNC Devices For EMC compliance the chassis of the USB 621x BNC device must be connected to earth ground through the chassis ground The wire should be AWG 16 or larger solid copper wire with a maximum length of 1 5 m 5 ft Attach the wire to the earth ground of the facility s power system For more information about earth ground connections refer to the KnowledgeBase document Earth Grounding for Test and Measurement Devices by going to ni com info and entering the info code earthground You can attach a wire to the ground lug screw of any USB 621x BNC device as shown in Figure 3 1
133. ignals 4 23 default counter timer pins A 3 digital I O 6 1 pinout A 2 USB 6211 A 4 analog input signals 4 23 default counter timer pins A 5 digital I O 6 1 pinout A 4 USB 6212 BNC A 13 analog input signals 4 23 chassis ground 3 4 connecting signals A 15 default counter timer pins A 15 digital I O 6 4 pinout A 13 USB 6212 Mass Termination A 8 accessories A 10 analog input signals 4 23 cables A 10 default counter timer pins A 10 digital I O 6 4 pinout A 8 USB 6212 Screw Terminal A 6 analog input signals 4 23 default counter timer pins A 7 digital I O 6 4 pinout A 6 National Instruments Corporation l 11 Index USB 6215 A 4 analog input signals 4 36 default counter timer pins A 5 digital I O 6 1 pinout A 4 USB 6216 BNC A 13 analog input signals 4 23 chassis ground 3 4 connecting signals A 15 default counter timer pins A 15 digital I O 6 4 pinout A 13 USB 6216 Mass Termination A 8 accessories A 10 analog input signals 4 36 cables A 10 default counter timer pins A 10 digital I O 6 4 pinout A 8 USB 6216 Screw Terminal A 6 analog input signals 4 36 default counter timer pins A 7 digital I O 6 4 pinout A 6 USB 6218 BNC A 21 analog input signals 4 36 chassis ground 3 4 connecting signals A 23 digital I O 6 1 pinout A 21 USB 6218 Screw Terminal A 19 analog input signals 4 36 default counter timer pins A 20 A 23 digital I O 6 1 pinout A 19 USB
134. iled description of each signal refer to the O Connector Signal Descriptions section of Chapter 3 Connector and LED Information PFI 0 PO 0 In B PFI1 PO 1 In d S PFI 2 P0 2 In e PFIS PO 3 In gt D GND on PFI 4 P1 0 Out l o PFI 5 P1 1 Out 3 PFI 6 P1 2 Out o PFI 7 P1 3 Out 45V 3 D GND NC S NC p RESERVED AlO a Al8 8 Al 1 5 AL9 EJ Al 2 Al 10 8 Al3 x Al 11 8 Al SENSE 8 Al4 X Al 12 S AI 5 8 Al 13 N AI GND I B Al 6 8 Al 14 ll 8 ALT 2 Al 15 8 J f NC No Connect Figure A 1 USB 6210 Pinout A 2 ni com Appendix A Device Specific Information Table A 1 Default NI DAQmx Counter Timer Pins Counter Timer Signal Default Terminal Number Name CTR 0 SRC 1 PFI 0 CTR 0 GATE 2 PFI 1 CTR 0 AUX 1 PFI 0 CTR 0 OUT 6 PFI 4 CTROA 1 PFI 0 CTROZ 3 PFI 2 CTROB 2 PFI 1 CTR 1 SRC 4 PFI 3 CTR 1 GATE 3 PFI 2 CTR 1 AUX 4 PFI 3 CTR 1 OUT 7 PFI 5 CTR1A 4 PFI 3 CTR1Z 2 PFI 1 CTR1B 3 PFI 2 FREQ OUT 8 PFI 6 3 Note For more information about default NI DAQmx counter inputs refer to Connecting Counter Signals in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later National Instruments Corporation A 3 NI USB 621x User Manual Appendix A Device Specific Information
135. ime N to t t ts te ts ts ts At tg the counter is armed No measurements are taken until the counter is armed The rising edge of Gate indicates the beginning of the first period to measure The counter begins counting rising edges of Source The rising edge of Sample Clock indicates that the USB 621 x device should store the result of the measurement of the current period when the period ends The rising edge of Gate indicates the end of the first period The USB 621x device stores the counter value in the buffer The rising edge of Gate indicates the end of the second period Sample Clock did not assert during this period So the counter discards the measurement of the second period The rising edge of Gate indicates the end of the third period Sample Clock asserts during this period so the USB 621 x device stores the measurement in the buffer Figure 8 30 Sample Clock Example NI USB 621x User Manual 6 34 ni com Chapter 8 Counters Cascading Counters Counter Filters You can internally route the Counter n Internal Output and Counter n TC signals of each counter to Gate inputs of the other counter By cascading two counters together you can effectively create a 64 bit counter By cascading counters you also can enable other applications For example to improve the accuracy of frequency measurements use reciprocal frequency measurement as described in the Method 3 bullet of the Frequency Measurement se
136. information about these triggers A digital trigger can initiate these actions All USB 621x devices support digital triggering USB 621x devices do not support analog triggering Field Wiring Considerations Environmental noise can seriously affect the measurement accuracy of the device if you do not take proper care when running signal wires between signal sources and the device The following recommendations apply mainly to AI signal routing to the device although they also apply to signal routing in general Minimize noise pickup and maximize measurement accuracy by taking the following precautions e Use differential AI connections to reject common mode noise e Use individually shielded twisted pair wires to connect AI signals to the device With this type of wire the signals attached to the positive and negative input channels are twisted together and then covered with a shield You then connect this shield only at one point to the signal source ground This kind of connection is required for signals traveling through areas with large magnetic fields or high electromagnetic interference Refer to the NI Developer Zone document Field Wiring and Noise Considerations for Analog Signals for more information To access this document go to ni com info and enter the info code rdfwn3 UN Caution Electromagnetic interference can adversely affect the measurement accuracy of this product Refer to the NJ USB 621x Specifications for
137. ing to ni com info and entering the info code rdspmb 2 4 ni com Chapter 2 DAQ System Overview Programming Devices in Software National Instruments measurement devices are packaged with NI DAQ driver software an extensive library of functions and VIs you can call from your application software such as LabVIEW or LabWindows CVI to program all the features of your NI measurement devices Driver software has an application programming interface API which is a library of VIs functions classes attributes and properties for creating applications for your device USB 621x devices use the NI DAQmx driver NI DAQmx includes a collection of programming examples to help you get started developing an application You can modify example code and save it in an application You can use examples to develop a new application or add example code to an existing application To locate LabVIEW LabWindows CVI Measurement Studio Visual Basic and ANSI C examples refer to the KnowledgeBase document Where Can I Find NI DAQmx Examples by going to ni com info and entering the info code dagmxexp For additional examples refer to zone ni com Table 2 1 lists the earliest NI DAQmx support version for each NI USB 621x device Table 2 1 NI USB 621x NI DAQmx Software Support Device NI DAQmx Version Support USB 6210 6211 6215 6218 Screw NI DAQmx 8 3 and later Terminal USB 6212 6216 Screw Terminal NI DAQmx 8 6 and later USB
138. ingle Ended NOT RECOMMENDED for the RSE USB 6210 6211 6212 Signal Source DAQ Device Signal Source DAQ Device AL ips AL f 2 Va AI GND oA Ve WIBLGND Ground loop potential V4 Vg are added to measured signal software considerations device Refer to the Analog Input Ground Reference Settings section for descriptions of the RSE NRSE and DIFF modes and Refer to the Connecting Ground Referenced Signal Sources section for more information Note USB 621x BNC Devices Refer to the appropriate Analog Input section for your USB 621x BNC device in Appendix A Device Specific Information for more information about using grounded and floating signal sources with your NI USB 621x User Manual 4 24 ni com Chapter 4 Analog Input Connecting Floating Signal Sources What Are Floating Signal Sources A floating signal source is not connected to the building ground system but has an isolated ground reference point Some examples of floating signal sources are outputs of transformers thermocouples battery powered devices optical isolators and isolation amplifiers An instrument or device that has an isolated output is a floating signal source When to Use Differential Connections with Floating Signal Sources Use differential input connections for any channel that meets any of the following conditions e The input signal is low level less than 1 V e The leads connecting the signal to the devi
139. ion Support Technical support at ni com support includes the following resources Self Help Technical Resources For answers and solutions visit ni com support for software drivers and updates a searchable KnowledgeBase product manuals step by step troubleshooting wizards thousands of example programs tutorials application notes instrument drivers and so on Registered users also receive access to the NI Discussion Forums at ni com forums NI Applications Engineers make sure every question submitted online receives an answer Standard Service Program Membership This program entitles members to direct access to NI Applications Engineers via phone and email for one to one technical support as well as exclusive access to on demand training modules via the Services Resource Center NI offers complementary membership for a full year after purchase after which you may renew to continue your benefits For information about other technical support options in your area visit ni com services or contact your local office at ni com contact Training and Certification Visit ni com training for self paced training eLearning virtual classrooms interactive CDs and Certification program information You also can register for instructor led hands on courses at locations around the world System Integration If you have time constraints limited in house technical resources or other project challenges National Instruments A
140. ion 5 7 NI USB 621x User Manual Chapter 5 Analog Output AO Sample Clock Signal Use the AO Sample Clock ao SampleClock signal to initiate AO samples Each sample updates the outputs of all of the DACs You can specify an internal or external source for AO Sample Clock You also can specify whether the DAC update begins on the rising edge or falling edge of AO Sample Clock Using an Internal Source One of the following internal signals can drive AO Sample Clock e AO Sample Clock Timebase divided down e Counter n Internal Output A programmable internal counter divides down the AO Sample Clock Timebase signal Using an External Source Use any input PFI line as the source of AO Sample Clock Routing AO Sample Clock to an Output Terminal You can route AO Sample Clock as an active low signal out to any output PFI terminal Other Timing Requirements A counter on your device internally generates AO Sample Clock unless you select an external source AO Start Trigger starts the counter and either the software or hardware can stop it once a finite generation completes When using an internally generated AO Sample Clock you also can specify a configurable delay from AO Start Trigger to the first AO Sample Clock pulse By default this delay is two ticks of AO Sample Clock Timebase NI USB 621x User Manual 5 8 ni com Chapter 5 Analog Output Figure 5 6 shows the relationship of AO Sample Clock to AO Start Trigger
141. ition Measurement With buffered position measurement position measurement using a sample clock the counter increments based on the encoding used after the counter is armed The value of the counter is sampled on each active edge of a sample clock A DMA controller transfers the sampled values to host memory The count values returned are the cumulative counts since the counter armed event that is the sample clock does not reset the counter You can route the counter sample clock to the Gate input of the counter You can configure the counter to sample on the rising or falling edge of the sample clock 8 18 ni com Chapter 8 Counters Figure 8 19 shows an example of a buffered X1 position measurement Sample Clock Armed i Sample on Rising Edge Counter CA en Te 3p TEST e LR ELT RE Count K 0 X 1 K 2 K 4 K 5 Buffer m d 4 Figure 8 19 Buffered Position Measurement Two Signal Edge Separation Measurement Two signal edge separation measurement is similar to pulse width measurement except that there are two measurement signals Aux and Gate An active edge on the Aux input starts the counting and an active edge on the Gate input stops the counting You must arm a counter to begin a two edge separation measurement After the counter has been armed and an active edge occurs on the Aux input the counter
142. l Using an Internal Source One of the following internal signals can drive AI Convert Clock e Al Convert Clock Timebase divided down e Counter n Internal Output A programmable internal counter divides down the AI Convert Clock Timebase to generate AI Convert Clock Started by AI Sample Clock the counter counts down to zero produces an AI Convert Clock reloads itself and repeats the process until the sample is finished It then reloads itself in preparation for the next AI Sample Clock pulse Using an External Source Use any input PFI line as the source of AI Convert Clock Routing Al Convert Clock to an Output Terminal You can route AI Convert Clock as an active low signal out to any output PFI terminal 4 16 ni com Chapter 4 Analog Input Using a Delay from Sample Clock to Convert Clock When using an internally generated AI Convert Clock you also can specify a configurable delay from AI Sample Clock to the first AI Convert Clock pulse within the sample By default this delay is three ticks of AI Convert Clock Timebase Figure 4 9 shows the relationship of AI Sample Clock to AI Convert Clock Al Convert Clock Timebase Al Sample Clock Al Convert Clock Delay Convert From Period Sample Clock Figure 4 9 Al Sample Clock and Al Co
143. l to Per a Degree Q Ohm National Instruments Corporation G 1 NI USB 621x User Manual Glossary A A A D AC accuracy ADE analog analog input signal analog output signal analog trigger application arm ASIC NI USB 621x User Manual Amperes the unit of electric current Analog to Digital Most often used as A D converter Alternating current A measure of the capability of an instrument or sensor to faithfully indicate the value of the measured signal This term is not related to resolution however the accuracy level can never be better than the resolution of the instrument Application development environment A signal whose amplitude can have a continuous range of values An input signal that varies smoothly over a continuous range of values rather than in discrete steps An output signal that varies smoothly over a continuous range of values rather than in discrete steps A trigger that occurs at a user selected point on an incoming analog signal Triggering can be set to occur at a specific level on either an increasing or a decreasing signal positive or negative slope Analog triggering can be implemented either in software or in hardware When implemented in software LabVIEW all data is collected transferred into system memory and analyzed for the trigger condition When analog triggering is implemented in hardware no data is transferred to system memory until the trigger
144. lectors for the Counter n Gate signal Any of the following signals can be routed to the Counter n Gate input e USB 6210 6211 6215 Devices PFI lt 0 3 gt e USB 6212 6216 Devices PFI lt 0 15 gt e USB 6218 Devices PFI lt 0 3 gt PFI lt 8 11 gt e AI Reference Trigger ai ReferenceTrigger e AI Start Trigger ai StartTrigger e AT Sample Clock ai SampleClock e Al Convert Clock ai ConvertClock e AO Sample Clock ao SampleClock In addition Counter 1 Internal Output or Counter 1 Source can be routed to Counter 0 Gate Counter 0 Internal Output or Counter 0 Source can be routed to Counter 1 Gate Some of these options may not be available in some driver software Routing Counter n Gate to an Output Terminal You can route Counter n Gate out to any output PFI terminal Counter 7 Aux Signal The Counter n Aux signal indicates the first edge in a two signal edge separation measurement Routing a Signal to Counter n Aux Each counter has independent input selectors for the Counter n Aux signal Any of the following signals can be routed to the Counter n Aux input e USB 6210 6211 6215 Devices PFI lt 0 3 gt e USB 6212 6216 Devices PFI 0 15 e USB 6218 Devices PFI lt 0 3 gt PFI lt 8 11 gt National Instruments Corporation 8 29 NI USB 621x User Manual Chapter 8 Counters e AI Reference Trigger ai ReferenceTrigger e Al Start Trigger ai StartTrigger In addition Counter 1 Inter
145. lies only to that platform Related Documentation Each application software package and driver includes information about writing applications for taking measurements and controlling measurement devices The following references to documents assume you have NI DAQ 8 9 or later and where applicable version 7 1 or later of the NI application software NI DAQmx for Windows The NI DAQmx for USB Devices Getting Started Guide describes how to install your NI DAQmx for Windows software your NI DAQmx supported DAQ device and how to confirm that your device is operating properly Select Start All Programs National Instruments NI DAQ NI DAQmx for USB Devices Getting Started The NI DAQ Readme lists which devices are supported by this version of NI DAQ Select Start All Programs National Instruments NI DAQ NI DAQ Readme The NI DAQmx Help contains general information about measurement concepts key NI DAQmx concepts and common applications that are applicable to all programming environments Select Start All Programs National Instruments NI DAQ NI DA Qmx Help NI DAQmx Base Linux Mac OS X LabVIEW Mobile Module 8 x LabVIEW Touch Panel Module 8 x NI USB 621x User Manual The NI DAQmx Base Getting Started Guide describes how to install your NI DAQmx Base software your NI DAQmx Base supported DAQ device and how to confirm that your device is operating properly In Windows select Start All Programs National Ins
146. lliance Partner members can help To learn more call your local NI office or visit ni com alliance C 1 NI USB 621x User Manual Appendix C Technical Support and Professional Services Declaration of Conformity DoC A DoC is our claim of compliance with the Council of the European Communities using the manufacturer s declaration of conformity This system affords the user protection for electromagnetic compatibility EMC and product safety You can obtain the DoC for your product by visiting ni com certification e Calibration Certificate If your product supports calibration you can obtain the calibration certificate for your product at ni com calibration If you searched ni com and could not find the answers you need contact your local office or NI corporate headquarters Phone numbers for our worldwide offices are listed at the front of this manual You also can visit the Worldwide Offices section of ni com niglobal to access the branch office Web sites which provide up to date contact information support phone numbers email addresses and current events NI USB 621x User Manual C 2 ni com Glossary Symbol Prefix Value p pico 10 2 n nano 107 u micro 10 6 m milli 103 k kilo 103 M mega 106 Symbols Percent Positive of or plus Negative of or minus Plus or minus lt Less than gt Greater than lt Less than or equal to 2 Greater than or equa
147. mebase Signal The AI Convert Clock Timebase ai ConvertClockTimebase signal is divided down to provide one of the possible sources for AI Convert Clock Use one of the following signals as the source of AI Convert Clock Timebase e AI Sample Clock Timebase e 20 MHz Timebase AI Convert Clock Timebase is not available as an output on the I O connector Al Hold Complete Event Signal The AI Hold Complete Event ai HoldCompleteEvent signal generates a pulse after each A D conversion begins You can route AI Hold Complete Event out to any output PFI terminal The polarity of AI Hold Complete Event is software selectable but is typically configured so that a low to high leading edge can clock external AI multiplexers indicating when the input signal has been sampled and can be removed National Instruments Corporation 4 19 NI USB 621x User Manual Chapter 4 Analog Input Al Start Trigger Signal NI USB 621x User Manual Use the AI Start Trigger ai StartTrigger signal to begin a measurement acquisition A measurement acquisition consists of one or more samples If you do not use triggers begin a measurement with a software command After the acquisition begins configure the acquisition to stop e When a certain number of points are sampled in finite mode e After a hardware reference trigger in finite mode With a software command in continuous mode An acquisition that uses a start trigger but not a reference trigger
148. more information about the performance of this product NI USB 621x User Manual 4 10 ni com Analog Input Timing Signals Chap ter 4 Analog Input In order to provide all of the timing functionality described throughout this section USB 621x devices have a flexible timing engine Figure 4 4 summarizes all of the timing options provided by the analog input timing engine 20 MHz Timebase 100 kHz Timebase V Analog Comparison Event 4 Ctr n Internal Output SW Pulse a Al Sample Clock Timebase Programmable Clock Divider Al Convert Ctr n Internal Output Clock Timebase Programmable e Clock Divider Lo Al Sample Clock Al Convert Clock o Figure 4 4 Analog Input Timing Options USB 621x devices use AI Sample Clock ai SampleClock and AI Convert Clock ai ConvertClock to perform interval sampling As Figure 4 5 shows AI Sample Clock controls the sample period which is determined by the following equation National Instruments Corporation 1 Sample Period Sample Rate NI USB 621x User Manual Chapter 4 Analog Input Channel 0 Channel 1 l Convert Period Sample Period Figure 4 5 Interval Sampling AI Convert Clock controls the Convert Period which is determined by the following equation 1 Convert Period Convert Rate ER Note The sampling rate is the fastest you can acquire
149. mple period which is determined by the following equation l sample period sample rate Channel 0 Channel 1 l Convert Period Sample Period Figure B 1 Al Sample Clock and Al Convert Clock AI Convert Clock controls the convert period which is determined by the following equation 1 convert period convert rate This method allows multiple channels to be sampled relatively quickly in relationship to the overall sample rate providing a nearly simultaneous effect with a fixed delay between channels B 2 ni com Appendix B Troubleshooting Analog Output I am seeing glitches on the output signal How can I minimize it When you use a DAC to generate a waveform you may observe glitches on the output signal These glitches are normal when a DAC switches from one voltage to another it produces glitches due to released charges The largest glitches occur when the most significant bit of the DAC code changes You can build a lowpass deglitching filter to remove some of these glitches depending on the frequency and nature of the output signal Visit ni com support for more information about minimizing glitches National Instruments Corporation B 3 NI USB 621x User Manual Technical Support and Professional Services Visit the following sections of the award winning National Instruments Web site at ni com for technical support and professional services National Instruments Corporat
150. n this case instead of directly connecting the negative line to AI GND connect the negative line to AI GND through a resistor that is about 100 times the equivalent source impedance The resistor puts the signal path nearly in balance so that about the same amount of noise couples onto both connections yielding better rejection of electrostatically coupled noise This configuration does not load down the source other than the very high input impedance of the NI PGIA National Instruments Corporation 4 27 NI USB 621x User Manual Chapter 4 Analog Input NI USB 621x User Manual O1 Al Floating Signal Vs Source A ot Al R is about R fi 100 times S RAL SENSE source Al GND impedance of sensor Figure 4 17 Differential Connections for Floating Signal Sources with Single Bias Resistor You can fully balance the signal path by connecting another resistor of the same value between the positive input and AI GND on the USB 6210 6211 6212 device as shown in Figure 4 18 This fully balanced configuration offers slightly better noise rejection but has the disadvantage of loading the source down with the series combination sum of the two resistors If for example the source impedance is 2 kQ and each of the two resistors is 100 kQ the resistors load down the source with 200 kQ and produce a 1 gain error 4 28 ni com Chapter 4 Analog Input
151. n most applications you can use the following cables SH68 68 EPM High performance cable with individual bundles separating analog and digital signals Each differential analog input channel is routed on an individually shielded twisted pair of wires Analog outputs are also individually shielded e R68 68 Highly flexible unshielded ribbon cable Custom Cabling and Connectivity The CA 1000 is a configurable enclosure that gives user defined connectivity and flexibility through customized panelettes Visit ni com for more information about the CA 1000 Refer to the USB 621x Mass Termination Custom Cabling section of Chapter 2 DAQ System Overview for more information about custom cabling solutions NI USB 621x User Manual A 12 ni com Appendix A Device Specific Information USB 6212 6216 BNC USB 6212 6216 BNC Pinout Figure A 5 shows the pinout of the USB 6212 BNC and USB 6216 BNC For a detailed description of each signal refer to the O Connector Signal Descriptions section of Chapter 3 Connector and LED Information National Instruments Corporation A 13 NI USB 621x User Manual Appendix A Device Specific Information
152. nal Output Counter 1 Gate Counter 1 Source or Counter 0 Gate can be routed to Counter 0 Aux Counter 0 Internal Output Counter 0 Gate Counter 0 Source or Counter 1 Gate can be routed to Counter 1 Aux Some of these options may not be available in some driver software Counter n A Counter n B and Counter n Z Signals Counter n B can control the direction of counting in edge counting applications Use the A B and Z inputs to each counter when measuring quadrature encoders or measuring two pulse encoders Routing Signals to A B and Z Counter Inputs Each counter has independent input selectors for each of the A B and Z inputs You can route any input PFI signal to each input Counter n Up Down Signal Counter n Up Down is another name for the Counter n B signal Counter n HW Arm Signal NI USB 621x User Manual The Counter n HW Arm signal enables a counter to begin an input or output function To begin any counter input or output function you must first enable or arm the counter In some applications such as buffered semi period measurement the counter begins counting when it is armed In other applications such as single pulse width measurement the counter begins waiting for the Gate signal when it is armed Counter output operations can use the arm signal in addition to a start trigger Software can arm a counter or configure counters to be armed on a hardware signal Software calls this hardware signal the Arm
153. nals to A B and Z Counter Inputs 8 30 Counter n Up Down Signal eese 8 30 Counter n HW Arm Signal eese eren 8 30 Routing Signals to Counter n HW Arm Input sess 8 31 Counter n Internal Output and Counter n TC Signals eects 8 31 Routing Counter n Internal Output to an Output Terminal 8 31 Frequency Output Signal esee 8 31 Routing Frequency Output to a Terminal ess 8 31 Default Counter Timer Pinouts eeseseeeeeeeeeeeeeeee eene nennen eere 8 32 Counter Triggering ien dre re te niece tate Rene 8 33 Other Counter Fe tu res i 4 ete tee er etc d devote epe uda eto i o s el 8 34 sample Clock 5 ettet ite era etes 8 34 Cascading Counters ete et elg e rue Yr n do ron 8 35 Counter Lalters ean aee Greta ius 8 35 Prescaling iicet e S ded a dem ge d e d eth 8 36 Duplicate Count Prevention iseitis iois resze eene eene 8 37 Example Application That Works Correctly No Duplicate Counting esee 8 37 Example Application That Works Incorrectly Duplicate Counting eese 8 38 Example Application That Prevents Duplicate Count 8 38 Enabling Duplicate Count Prevention in NI DAQmx 8 39 Chapter 9 Isolation and Digital Isolators on USB 6215 6216 6218 Devices Digital Isolation eet t e pie seb
154. nd low pulse widths of the output signal are M and N periods then the frequency of the Counter n Internal Output signal is equal to the frequency of the Source input divided by M N For information about connecting counter signals refer to the Default Counter Timer Pinouts section Finite Pulse Train Generation This function generates a train of pulses of predetermined duration This counter operation requires both counters The first counter for this example Counter 0 generates a pulse of desired width The second counter Counter 1 generates the pulse train which is gated by the pulse of the first counter The routing is done internally Figure 8 26 shows an example finite pulse train timing diagram Counter 0 Paired Counter Counter 1 Generation Complete Figure 8 26 Finite Pulse Train Timing Diagram 6 24 ni com Chapter 8 Counters Frequency Generation 20 MHz Timebase e You can generate a frequency by using a counter in pulse train generation mode or by using the frequency generator circuit Using the Frequency Generator The frequency generator can output a square wave at many different frequencies The frequency generator is independent of the two general purpose 32 bit counter timer modules on USB 621x devices Figure 8 27 shows a block diagram of the frequency generator Frequency Output 100 kHz Timebase e 2 Timebase
155. nd verify that all ground connections are kept short Keep the number of connections to a minimum If the device s isolated ground is being connected back to earth ground verify that this is done in the most direct way possible e Reduce source impedances if possible The parasitic currents react with these impedances Creating an AC Return Path Caution Adding a capacitor will degrade the USB 6215 6216 6218 device withstand voltage and isolation specifications Withstand voltage must be retested by an approved testing facility after adjustments are made to the measurement system NI USB 621x User Manual 9 3 ni com Chapter 9 Isolation and Digital Isolators on USB 6215 6216 6218 Devices Isolated Systems A fully isolated measurement system is one where the device s isolated front end is not connected back to earth ground Create an AC path back to earth ground from the device s isolated ground by connecting a high voltage capacitor between the isolated board ground and earth ground The voltage rating of the capacitor must be larger than the voltage drop between the isolated ground and earth ground Non Isolated Systems A non isolated measurement system is one where the device s isolated front end connects to earth ground Add an AC return path from the device isolated ground to earth ground For non isolated systems an AC return path is only needed for high or source impedances An AC return path can be created by connecting
156. nected to channel 1 The input range for channel 0 is 10 V to 10 V and the input range of channel 1 is 200 mV to 200 mV When the multiplexer switches from channel 0 to channel 1 the input to the NI PGIA switches from 4 V to 1 mV The approximately 4 V step from 4 V to 1 mV is 1 000 of the new 4 6 ni com National Instruments Corporation Chapter 4 Analog Input full scale range For a 16 bit device to settle within 0 0015 15 ppm or 1 LSB of the 200 mV full scale range on channel 1 the input circuitry must settle to within 0 000031 0 31 ppm or 1 50 LSB of the 10 V range Some devices can take many microseconds for the circuitry to settle this much To avoid this effect you should arrange your channel scanning order so that transitions from large to small input ranges are infrequent In general you do not need this extra settling time when the NI PGIA is switching from a small input range to a larger input range Insert Grounded Channel between Signal Channels Another technique to improve settling time is to connect an input channel to ground Then insert this channel in the scan list between two of your signal channels The input range of the grounded channel should match the input range of the signal after the grounded channel in the scan list Consider again the example above where a4 V signal is connected to channel 0 anda mV signal is connected to channel 1 Suppose the input range for channel 0 is 10 V to
157. ng Digital I O Signals on USB 6210 6211 6215 6218 Devices or Connecting Digital I O Signals on USB 6212 6216 Devices section of Chapter 6 Digital I O e The Connecting PFI Input Signals section of Chapter 7 PFI Digital Isolation USB 6215 6216 6218 devices use digital isolators Unlike analog isolators digital isolators do not introduce any analog error in the measurements taken by the device The A D converter used for analog input is on the isolated side of the device The analog inputs are digitized before they are sent across the isolation barrier Similarly the D A converters used for analog output are on the isolated side of the device Benefits of an Isolated DAQ Device With isolation engineers can safely measure a small signal in the presence of a large common mode voltage signal Some advantages of isolation are as follows Improved Rejection Isolation increases the ability of the measurement system to reject common mode voltages Common mode voltage is the signal that is present or common to both the positive and negative input of a measurement device but is not part of the signal to be measured Improved Accuracy Isolation improves measurement accuracy by physically preventing ground loops Ground loops a common source National Instruments Corporation 9 2 NI USB 621x User Manual Chapter 9 Isolation and Digital Isolators on USB 6215 6216 6218 Devices of error and noise are the result of a m
158. ng noise effects In general the more points you average the more accurate the final result However you may choose to decrease the number of points you average and slow down the scanning rate Suppose you want to sample 10 channels over a period of 20 ms and average the results You could acquire 250 points from each channel at a scan rate of 125 kS s Another method would be to acquire 500 points from each channel at a scan rate of 250 kS s Both methods take the same amount of time Doubling the number of samples averaged from 250 to 500 decreases the effect of noise by a factor of 1 4 the square root of 2 However doubling the number of samples in this example decreases the time the NI PGIA has to settle from 8 us to 4 us In some cases the slower Scan rate system returns more accurate results Example 2 If the time relationship between channels is not critical you can sample from the same channel multiple times and scan less frequently For example suppose an application requires averaging 100 points from channel 0 and averaging 100 points from channel 1 You could alternate reading between channels that is read one point from channel 0 then one point from channel 1 and so on You also could read all 100 points from channel 0 then read 100 points from channel 1 The second method switches between channels much often and is affected less by settling time Analog Input Data Acquisition Methods NI USB 621x User Manual
159. ng the info code rdscav for more information BNC Accessories You can use the SH68 68 EPM shielded cable to connect the USB 6212 6216 Mass Termination device to BNC accessories such as the following e BNC 2110 Provides BNC connectivity to all analog signals some digital signals and spring terminals for other digital signals e BNC 2111 Provides BNC connectivity to 16 single ended analog input signals two analog output signals five DIO PFI signals and the external reference voltage for analog output BNC 2120 Similar to the BNC 2110 and also has a built in function generator quadrature encoder temperature reference and thermocouple connector e BNC 2090A Desktop rack mountable device with 22 BNCs for connecting analog digital and timing signals Screw Terminal Accessories National Instruments offers several styles of screw terminal connector blocks Use an SH68 68 EPM shielded cable to connect a USB 6212 6216 Mass Termination device to a connector block such as the following e CB 68LP and CB 68LPR Unshielded connector blocks e SCC 68 I O connector block with screw terminals general breadboard area bus terminals and four expansion slots for SCC signal conditioning modules e SCB 68 Shielded connector block with temperature sensor TBX 68 DIN rail mountable connector block National Instruments Corporation A 11 NI USB 621x User Manual Appendix A Device Specific Information Cables I
160. ngle Ended Mode For each BNC connector that you use for two single ended channels set the source type switch to the GS position This setting disconnects the built in ground reference resistor from the negative terminal of the BNC connector allowing the connector to be used as a single ended channel as shown in Figure A 17 Ground Ref Source GS USB 621x BNC Device Figure A 17 Single Ended Channels When you set the source type to the GS position and configure the device for single ended input in software each BNC connector provides access to two single ended channels AI x and AI x 8 For example the BNC connector labeled AI 0 provides access to single ended channels AI 0 and AI 8 the BNC connector labeled AI 1 provides access to single ended channels AI 1 and AI 9 and so on Up to 32 single ended channels are available in single ended measurement modes For information on how to connect your signals in single ended mode AI GND and or AI SENSE refer to the Connecting Analog Input Signals on USB 6215 6216 6218 Devices section of Chapter 4 Analog Input For a detailed description of each signal refer to the O Connector Signal Descriptions section of Chapter 3 Connector and LED Information Analog Output You can access analog output signals on the BNC connectors labeled AO 0 and AO 1 Figure A 18 shows the analog output circuitry on the USB 6218 BNC E C 1o AO GND
161. ni com support if device is powered On not blinking Device error Refer to ni com support Single blink Operating normally Connected to USB Hi Speed port Refer to the NI USB 621x Specifications for more information Double blink Connected to USB Full Speed port Device performance might be affected Refer to the NI USB 621x Specifications for more information National Instruments Corporation 3 6 NI USB 621x User Manual Analog Input Figure 4 1 shows the analog input circuitry of USB 621x devices Isolation i Barrier i USB 6215 6216 6218 devices only _ Al lt 0 n gt 9 o 2 DIFF RSE Digital 5 orNRSE NIPGIA ADC ALIRO Isolators m Al Data O Al SENSE 9 1 i Input Range i Al GND Selection Al Ground Reference Settings Figure 4 1 USB 621x Analog Input Circuitry The main blocks featured in the USB 621x analog input circuitry are as follows e T O Connector You can connect analog input signals to the USB 621x device through the I O connector The proper way to connect analog input signals depends on the analog input ground reference settings described in the Analog Input Ground Reference Settings section Also refer to Appendix A Device Specific Information for device I O connector pinouts e Mux Each USB 621x device has one analog to digital converter ADC The multi
162. nical Support and Professional Services National Instruments Corporation Xi NI USB 621x User Manual Contents Glossary Index Device Pinouts Figure A 1 USB 6210 Pinout essent nennen neret A 2 Figure A 2 USB 6211 6215 Pinout essen eene A 4 Figure A 3 USB 6212 6216 Screw Terminal Pinout eee A 6 Figure A 4 USB 6212 6216 Mass Termination Pinout eee A 9 Figure A 5 USB 6212 6216 BNC Top Panel and Pinout ses A 14 Figure A 13 USB 6218 Screw Terminal Pinout esee A 19 Figure A 14 USB 6218 BNC Top Panel and Pinout eee A 22 NI USB 621x User Manual Xii ni com About This Manual Conventions lt gt bold italic The NI USB 621x User Manual contains information about using the National Instruments USB 621x data acquisition DAQ devices with NI DAQmx 8 9 and later NI USB 6210 USB 6211 USB 6212 USB 6215 USB 6216 and USB 6218 devices feature up to 32 analog input AT channels up to two analog output AO channels two counters and up to eight lines of digital input DI and up to eight lines of digital output DO or 32 bidirectional static DIO lines The following conventions are used in this manual Angle brackets that contain numbers separated by an ellipsis represent a range of values associated with a bit or signal name for example AO lt 3 0 gt The symbol
163. ning order 4 6 channel Z behavior 8 17 channels sampling with AI Sample Clock and AI Convert Clock B 2 charge injection B 1 chassis ground 3 4 choosing frequency measurement 8 14 circular buffered acquisition 4 9 ni com clock generation 10 1 sample 8 34 combicon 2 4 common mode noise 9 3 configuring AI ground reference settings in software 4 5 connecting analog input signals on USB 6210 621 1 6212 devices 4 23 on USB 6215 6216 6218 devices 4 36 analog output signals 5 4 digital I O signals on USB 6210 6211 6215 6218 6 3 on USB 6212 6216 6 6 floating signal sources 4 25 ground referenced signal sources 4 31 PFI input signals 7 4 to earth ground 3 4 connections for floating signal sources 4 31 single ended for floating signal sources 4 31 single ended referenced configuration 4 31 connector information 3 1 labels for USB 621x Screw Terminal 1 3 USB 6210 pinout A 2 JSB 6211 pinout A 4 JSB 6212 BNC pinout A 13 SB 6212 Mass Termination pinout A 8 JSB 6212 Screw Terminal pinout A 6 SB 6215 pinout A 4 JSB 6216 BNC pinout A 13 SB 6216 Mass Termination pinout A 8 JSB 6216 Screw Terminal pinout A 6 SB 6218 BNC pinout A 21 JSB 6218 Screw Terminal pinout A 19 cccccocccoc c National Instruments Corporation F3 Index USB 6259 BNC pinout A 13 A 21 considerations for field wiring 4 10 for multichannel scanning 4 5 continuous pulse train generation 8 23 controlling cou
164. nnection configuration each input channel is measured with respect to AI SENSE 4 38 ni com Analog Output Most USB 621x devices have analog output functionality USB 621x devices that support analog output have two AO channels controlled by a single clock and capable of waveform generation Refer to the NI USB 621x Specifications for information about your device capabilities Figure 5 1 shows the analog output circuitry of USB 621x devices Isolation Barrier USB 6215 6216 6218 devices only AO 0 Digital AO FIFO Isolators AO Data AO 1 AO Sample Clock Figure 5 1 USB 621x Analog Output Circuitry The main blocks featured in the USB 621x analog output circuitry are as follows e DACO and DAC1 Digital to analog converters DACs convert digital codes to analog voltages e AO FIFO The AO FIFO enables analog output waveform generation It is a first in first out FIFO memory buffer between the computer and the DACs It allows you to download the points of a waveform to your USB 621x device without host computer interaction National Instruments Corporation 5 1 NI USB 621x User Manual Chapter 5 Analog Output AO Range AO Sample Clock The AO Sample Clock signal reads a sample from the DAC FIFO and generates the AO voltage Refer to the AO Sample Clock Signal section for more information Isolation Barrier and Digital Isolators Refer to
165. nting direction 8 2 conventions used in the manual xiii counter input and output 8 32 Counter n A signal 8 30 Counter n Aux signal 8 29 Counter n B signal 8 30 Counter n Gate signal 8 29 Counter n HW Arm signal 8 30 Counter n Internal Output signal 8 31 Counter n Source signal 8 28 Counter n TC signal 8 31 Counter n Up Down signal 8 30 Counter n Z signal 8 30 counter signals Counter n A 8 30 Counter n Aux 8 29 Counter n B 8 30 Counter n Gate 8 29 Counter n HW Arm 8 30 Counter n Internal Output 8 31 Counter n Source 8 28 Counter n TC 8 31 Counter n Up_Down 8 30 FREQ OUT 8 31 Frequency Output 8 31 counters 8 1 cascading 8 35 connecting terminals 8 32 duplicate count prevention 8 37 edge counting 8 2 filters 8 35 generation 8 21 input applications 8 2 other features 8 34 output applications 8 21 NI USB 621x User Manual Index prescaling 8 36 pulse train generation 8 23 retriggerable single pulse generation 8 22 simple pulse generation 8 21 single pulse generation 8 21 single pulse generation with start trigger 8 22 terminals default 8 32 timing signals 8 27 triggering 8 33 counting edges 8 2 creating an AC return path 9 4 crosstalk when sampling multiple channels B 1 custom cabling 2 4 D DACs 5 1 DAQ hardware 2 1 system 2 1 DAQ STC2 2 2 data acquisition methods 4 8 generation methods 5 2 transfer methods 11 1 changing 11 2 programme
166. nvert Clock Other Timing Requirements The sample and conversion level timing of USB 621x devices work such that clock signals are gated off unless the proper timing requirements are met For example the device ignores both AI Sample Clock and AI Convert Clock until it receives a valid AI Start Trigger signal Once the device recognizes an AI Sample Clock pulse it ignores subsequent AI Sample Clock pulses until it receives the correct number of AI Convert Clock pulses Similarly the device ignores all AI Convert Clock pulses until it recognizes an AI Sample Clock pulse Once the device receives the correct number of AI Convert Clock pulses it ignores subsequent AI Convert Clock pulses until it receives another AI Sample Clock Figures 4 10 4 11 4 12 and 4 13 show timing sequences for a four channel acquisition using AI channels 0 1 2 and 3 and demonstrate proper and improper sequencing of AI Sample Clock and AI Convert Clock National Instruments Corporation 4 17 NI USB 621x User Manual Chapter 4 Analog Input Al Sample Clock nnn nul 0123 0123 uil Al Convert Clock Channel Measured 012 3 Sample 1 Sample 2 Sample 3 lt lt 4 gt lt Figure 4 10 Al Sample Clock Too Fast For Al Convert Clock Al Sample Clock Pulses Are
167. o make AO connections to the device Isolation 3 i Barrier i L Analog Output Channels USB 6215 6216 6218 AO 0 i i z Channel 0 1 devices only Load V OUT Digital Lo gt AO GND Isolators 3 V Load V OUT 1 t BT Channel 1 rd USB 621 x Device i Figure 5 2 Analog Output Connections 5 4 ni com Chapter 5 Analog Output Analog Output Timing Signals Figure 5 3 summarizes all of the timing options provided by the analog output timing engine PFI 20 MHz Timebase 100 kHz Timebase PFI Ctr n Internal Output e AO Sample Clock AO Sample Clock Timebase Programmable e Clock Divider Sample Clock Timebase Divisor Figure 5 3 Analog Output Timing Options USB 621x devices feature the following AO waveform generation timing signals AO Start Trigger Signal e AO Pause Trigger Signal e AO Sample Clock Signal e AO Sample Clock Timebase Signal AO Start Trigger Signal Use the AO Start Trigger ao StartTrigger signal to initiate a waveform generation If you do not use triggers you can begin a generation with a software command Using a Digital Source To use AO Start Trigger specify a source and an edge The source can be one of the following signals e A pulse initiated by host software e USB 6211 6215 Devices PFI lt
168. on 8 0 or later Connecting Signals to the USB 6218 BNC Analog Input You can use each analog input BNC connector for one signal in differential mode or two signals in single ended mode e Differential Mode To connect signals in differential mode determine the type of signal source you are using a floating signal FS source or a ground referenced signal GS source Refer to the Connecting Analog Input Signals on USB 6215 6216 6218 Devices section of Chapter 4 Analog Input for more information To measure a floating signal source move the switch to the FS position To measure a ground referenced signal source move the switch to the GS position Figure A 15 shows the AI 0 BNC and corresponding FS GS switch on the top panel of the USB 6218 BNC National Instruments Corporation A 23 NI USB 621x User Manual Appendix A Device Specific Information Figure A 15 FS GS Switch Figure A 16 shows the analog input circuitry on the USB 6218 BNC When the switch is set to the FS position AI x is grounded through a 0 1 UF capacitor in parallel with a 5 KQ resistor an e88 oas Floating Ground Source FS Referenced 9FS Source ii 0 1 UF 5 kQ O1 pF S5k2 L3 NZ AI GND NZ AI GND USBE G21xDevie E USE G21xDevie 4 Figure A 16 Analog Input Circuitry NI USB 621x User Manual A 24 ni com Appendix A Device Specific Information Si
169. on to a domain where a human being or computer can determine the value Multifunction I O DAQ module Designates a family of data acquisition products that have multiple analog input channels digital I O channels timing and optionally analog output channels An MIO product can be considered a miniature mixed signal tester due to its broad range of signal types and flexibility Also known as multifunction DAQ A board assembly and its associated mechanical parts front panel optional shields and so on A module contains everything required to occupy one or more slots in a mainframe SCXI and PXI devices are modules A characteristic of a DAC in which the analog output always increases as the values of the digital code input to it increase Pertaining to a radio communication system that operates on more than one channel at the same time The individual channels might contain identical information or they might contain different signals See MIO To assign more than one signal to a channel See also mux Multiplexer A set of semiconductor or electromechanical switches arranged to select one of many inputs to a single output The majority of DAQ cards have a multiplexer on the input which permits the selection of one of many channels at a time A switching device with multiple inputs that sequentially connects each of its inputs to its output typically at high speeds in order to measure several signals with a single analog inpu
170. onnecting counter signals refer to the Default Counter Timer Pinouts section Semi Period Measurement NI USB 621x User Manual In semi period measurements the counter measures a semi period on its Gate input signal after the counter is armed A semi period is the time between any two consecutive edges on the Gate input You can route an internal or external periodic clock signal with a known period to the Source input of the counter The counter counts the number of rising or falling edges occurring on the Source input between two edges of the Gate signal You can calculate the semi period of the Gate input by multiplying the period of the Source signal by the number of edges returned by the counter Single Semi Period Measurement Single semi period measurement is equivalent to single pulse width measurement 8 8 ni com Chapter 8 Counters Buffered Semi Period Measurement In buffered semi period measurement on each edge of the Gate signal the counter stores the count in a hardware save register A USB Signal Stream transfers the stored values to host memory The counter begins counting on the first active edge of the Gate after it is armed The arm usually occurs between edges on the Gate input The counter does not store a value for this incomplete semi period Figure 8 9 shows an example of a buffered semi period measurement Counter Armed GATE EN 1 Bu
171. ons also use start triggers and pause triggers 3 Note For more information about programming analog output applications and triggers in software refer to the NI DAQmx Help or the LabVIEW Help in version 8 0 or later NI USB 621x User Manual 5 10 ni com Digital 1 0 Refer to one of the following sections depending on your device e Digital I O on USB 6210 6211 6215 6218 Devices USB 6210 6211 6215 6218 devices have up to eight lines of digital inputs DI and up to eight lines of digital output DO e Digital I O on USB 6212 6216 Devices USB 6212 6216 devices have 32 bidirectional static digital I O DIO lines Digital 1 0 on USB 6210 6211 6215 6218 Devices USB 6210 6211 6215 6218 devices have up to eight static digital input lines P0 lt 0 7 gt These lines also can be used as PFI inputs USB 6210 6211 6215 6218 devices have up to eight static digital output lines P1 lt 0 7 gt These lines also can be used as PFI output By default the digital output lines are disabled high impedance with a 47 kQ pull down resistor on power up Software can enable or disable the entire port software cannot enable individual lines Once the port is enabled you can individually configure each line to the following e Setaline to a static 0 e Set a line to a static 1 e Export a timing output signal to a line as a PFI pin The voltage input and output levels and the current drive level of the DI and DO lines are listed in t
172. operty of buffered I O operations is the sample mode The sample mode can be either finite or continuous Finite sample mode acquisition refers to the acquisition of a specific predetermined number of data samples After the specified number of samples has been read in the acquisition stops If you use a reference trigger you must use finite sample mode A Continuous acquisition refers to the acquisition of an unspecified number of samples Instead of acquiring a set number of data samples and stopping a continuous acquisition continues until you stop the operation Continuous acquisition is also referred to as double buffered or circular buffered acquisition If data cannot be transferred across the bus fast enough the FIFO becomes full New acquisitions will overwrite data in the FIFO before it can be transferred to host memory The device generates an error in this case With continuous operations if the user program does not read data out of the PC buffer fast enough to keep up with the data transfer the buffer could reach an overflow condition causing an error to be generated National Instruments Corporation 4 9 NI USB 621x User Manual Chapter 4 Analog Input Analog Input Digital Triggering Analog input supports three different triggering actions e Start trigger e Reference trigger e Pause trigger Refer to the AJ Start Trigger Signal AI Reference Trigger Signal and AI Pause Trigger Signal sections for
173. or AI Sample Clock Timebase is divided down to provide one of the possible sources for AI Sample Clock You can configure the polarity selection for AI Sample Clock Timebase as either rising or falling edge National Instruments Corporation 4 15 NI USB 621x User Manual Chapter 4 Analog Input Al Convert Clock Signal Use the AI Convert Clock ai ConvertClock signal to initiate a single A D conversion on a single channel A sample controlled by the AI Sample Clock consists of one or more conversions You can specify either an internal or external signal as the source of AI Convert Clock You also can specify whether the measurement sample begins on the rising edge or falling edge of AI Convert Clock By default NI DAQmx chooses the fastest conversion rate possible based on the speed of the A D converter and adds 10 us of padding between each channel to allow for adequate settling time This scheme enables the channels to approximate simultaneous sampling and still allow for adequate settling time If the AI Sample Clock rate is too fast to allow for this 10 us of padding NI DAQmx chooses the conversion rate so that the AI Convert Clock pulses are evenly spaced throughout the sample To explicitly specify the conversion rate use AI Convert Clock Rate DAQmx Timing property node or function N Caution Setting the conversion rate higher than the maximum rate specified for your device will result in errors NI USB 621x User Manua
174. otential difference between the signal source and the device ground shown as V in the figure AI and AI must both remain within 11 V of AI GND 4 34 ni com Chapter 4 Analog Input Using Non Referenced Single Ended Connections for Ground Referenced Signal Sources Figure 4 23 shows how to connect ground reference signal sources to the USB 6210 6211 6212 device in non referenced single ended mode I O Connector Al lt 0 15 gt or Al lt 16 n gt Ground Instrumentation Referenced V Amplifier Signal Source T Input Multiplexers Measured e e Al SENSE Voltage Al GND Noise e and Ground Potential 4 V ui USB 6210 6211 6212 Configured in NRSE Mode Figure 4 23 Single Ended Connections for Ground Referenced Signal Sources NRSE Configuration AI and AIl must both remain within 11 V of AI GND To measure a single ended ground referenced signal source you must use the non referenced single ended ground reference setting Connect the signal to one of AI 0 31 and connect the signal local ground reference to AI SENSE AI SENSE is internally connected to the negative input of the NI PGIA Therefore the ground point of the signal connects to the negative input of the NI PGIA Any potential difference between the device ground and the signal ground appears as a common mode signal at both the positive and negative input
175. plexers mux route one AI channel at a time to the ADC through the NI PGIA Al Ground Reference Settings The analog input ground reference settings circuitry selects between differential DIFF referenced single ended RSE and non referenced single ended NRSE input modes Each AI channel can use a different mode National Instruments Corporation 4 1 NI USB 621x User Manual Chapter 4 Analog Input NI PGIA The NI programmable gain instrumentation amplifier NI PGIA is a measurement and instrument class amplifier that minimizes settling times for all input ranges The NI PGIA can amplify or attenuate an AI signal to ensure that you use the maximum resolution of the ADC USB 621x devices use the NI PGIA to deliver high accuracy even when sampling multiple channels with small input ranges at fast rates USB 621x devices can sample channels in any order at the maximum conversion rate and you can individually program each channel in a sample with a different input range e ADC The analog to digital converter ADC digitizes the AI signal by converting the analog voltage into a digital number e AI FIFO USB 621x devices can perform both single and multiple A D conversions of a fixed or infinite number of samples A large first in first out FIFO buffer holds data during AI acquisitions to ensure that no data is lost USB 621x devices can handle multiple A D conversion operations with DMA interrupts or programmed I O
176. r n Gate signal input of the counter Counter input operations can use the arm start trigger to have start trigger like behavior e Pause Trigger You can use pause triggers in edge counting and continuous pulse generation applications For edge counting acquisitions the counter stops counting edges while the external trigger signal is low and resumes when the signal goes high or vice versa For continuous pulse generations the counter stops generating pulses while the external trigger signal is low and resumes when the signal goes high or vice versa When using a pause trigger the pause trigger source is routed to the Counter n Gate signal input of the counter National Instruments Corporation 8 33 NI USB 621x User Manual Chapter 8 Counters Other Counter Features Sample Clock When taking counter measurements you can enable a sample clock When you use a sample clock measurements are saved after an active edge of the sample clock Figure 8 30 shows an example of using a sample clock with a buffered period measurement In this example a period is defined by two consecutive rising edges of the Gate Counter Armed GATE SOURCE LEELA ALAA amp 141 4 4j Counter Value 1 2 3 4 1 2 1 2 8 1 Sample Clock ipi d i 1 i i i 3 Buffer T
177. rces 4 31 referenced single ended configuration 4 31 software configuring AI ground reference settings 4 5 NI resources C 1 programming devices 2 5 software timed acquisitions 4 8 generations 5 2 specifications A 1 device 1 2 stacking 1 6 start trigger 8 33 static DIO USB 6210 6211 6215 6218 6 2 USB 6212 6216 6 5 using PFI terminals as 7 3 strain relief 1 4 support technical C 1 switching from a large to a small input range 4 6 synchronous counting mode 8 37 NI USB 621x User Manual T technical support C 1 xviii terminal configuration 4 3 analog input 4 1 terminals connecting counter 8 32 NI DAQmx default counter 8 32 Timebase 100 KHz 10 1 20 MHz 10 1 80 MEZ 10 1 timed acquisitions 4 8 timing output signals exporting using PFI terminals 7 3 top panel USB 6212 BNC A 13 USB 6216 BNC A 13 USB 6218 BNC A 21 training xviii training and certification NI resources C 1 transducers 2 3 trigger 12 1 arm start 8 33 pause 8 33 start 8 33 triggering 12 1 analog input 4 10 counter 8 33 with a digital source 12 1 troubleshooting analog input B 1 analog output B 3 NI resources C 1 two signal edge separation measurement 8 19 buffered 8 20 single 8 20 ni com USB bulk transfers 11 1 cable strain relief 1 4 1 8 chassis ground 3 4 Signal Stream 11 1 USB Signal Stream as a transfer method 11 1 changing data transfer methods 11 2 USB 6210 A 2 analog input s
178. red with all channels rather than being cabled in a twisted pair with the AI signal 4 30 ni com Chapter 4 Analog Input Using the DAQ Assistant you can configure the channels for referenced single ended or non referenced single ended input modes Refer to the Configuring AI Ground Reference Settings in Software section for more information about the DAQ Assistant Using Referenced Single Ended Connections for Floating Signal Sources Figure 4 21 shows how to connect a floating signal source to the USB 6210 6211 6212 device configured for referenced single ended mode Al lt 0 n gt OO o So hd e so 4 Programmable Gain Floating E l Instrumentation Signal G RE E Amplifier Source PGIA Input Multiplexers _ Measured o Al SENSE Vin Voltage o Pid Al GND l O Connector Selected Channel in RSE Configuration Figure 4 21 Referenced Single Ended Connections for Floating Signal Sources Using the DAQ Assistant you can configure the channels for referenced single ended or non referenced single ended input modes Refer to the Configuring AI Ground Reference Settings in Software section for more information about the DAQ Assistant Connecting Ground Referenced Signal Sources What Are Ground Referenced Signal Sources A ground referenced signal source is a signal source connected to the building system ground It is already connected to
179. rithm that selectively removes noise from a signal or emphasizes certain frequency ranges and de emphasizes others Electronic filters include lowpass band pass and highpass types Digital filters can operate on numeric data to perform equivalent operations on digitized analog data or to enhance video images A type of signal conditioning that allows you to filter unwanted frequency components from the signal you are trying to measure Signal sources with voltage signals that are not connected to an absolute reference of system ground Also called non referenced signal sources Some common examples of floating signal sources are batteries transformers and thermocouples The number of alternating signals that occur per unit time Feet 1 A built in execution element comparable to an operator function or statement in a conventional language 2 A set of software instructions executed by a single line of code that may have input and or output parameters and returns a value when executed National Instruments Corporation G 7 NI USB 621x User Manual Glossary G glitch GND ground H hardware triggering Hz I O impedance in instrument driver NI USB 621x User Manual An unwanted signal excursion of short duration that is usually unavoidable See ground 1 A pin 2 An electrically neutral wire that has the same potential as the surrounding earth Normally a noncurrent carrying circuit intended for
180. rminal A 6 USB 6218 BNC A 21 USB 6218 Screw Terminal A 19 pins default 8 32 position measurement 8 15 buffered 8 18 power 5 V 3 3 input 3 3 output 3 3 power up states PFI 7 6 USB 6212 6216 6 6 prescaling 8 36 programmable function interface 7 1 power up states PFI 7 6 USB 6212 6216 6 6 programmed I O 11 1 changing data transfer methods 11 2 programming devices in software 2 5 programming examples NI resources C 1 pulse encoders 8 18 generation for ETS 8 26 train generation 8 23 continuous 8 23 pulse width measurement 8 4 buffered 8 5 single 8 4 PWR LED 3 6 Q quadrature encoders 8 16 ni com R reciprocal frequency measurement 8 13 referenced single ended configuration 4 31 referenced single ended connections using with floating signal sources 4 31 when to use with floating signal sources 4 25 when to use with ground referenced signal sources 4 33 related documentation xiv retriggerable single pulse generation 8 22 routing digital 10 1 RSE connections when to use with ground referenced signal sources 4 33 rubber feet 1 6 S sample clock 8 34 edge counting 8 3 measurement 8 18 scan speed 4 8 scanning speed 4 8 self calibration 1 2 semi period measurement 8 8 buffered 8 9 single 8 8 sensors 2 3 settings analog input ground reference 4 3 short high quality cabling 4 6 signal conditioning 2 3 descriptions 3 1 labels for USB 621x Screw Terminal 1
181. rranty provided herein does not cover damages defects malfunctions or service failures caused by owner s failure to follow the National Instruments installation operation or maintenance instructions owner s modification of the product owner s abuse misuse or negligent acts and power failure or surges fire flood accident actions of third parties or other events outside reasonable control Copyright Under the copyright laws this publication may not be reproduced or transmitted in any form electronic or mechanical including photocopying recording storing in an information retrieval system or translating in whole or in part without the prior written consent of National Instruments Corporation National Instruments respects the intellectual property of others and we ask our users to do the same NI software is protected by copyright and other intellectual property laws Where NI software may be used to reproduce software or other materials belonging to others you may use NI software only to reproduce materials that you may reproduce in accordance with the terms of any applicable license or other legal restriction Trademarks National Instruments NI ni com and LabVIEW are trademarks of National Instruments Corporation Refer to the Terms of Use section on ni com legal for more information about National Instruments trademarks Other product and company names mentioned herein are trademarks or trade names of their respective
182. rs the sampled values to host memory The count values returned are the cumulative counts since the counter armed event that is the sample clock does not reset the counter You can route the counter sample clock to the Gate input of the counter You can configure the counter to sample on the rising or falling edge of the sample clock Figure 8 4 shows an example of buffered edge counting Notice that counting begins when the counter is armed which occurs before the first active edge on Gate Counter Armed Sample Clock Sample on Rising Edge SOURCE LALELE UAL AU FLS Counter Value 0 1 2 3 4 5 6 7 i S 3 Buffer F1 F1 6 Figure 8 4 Buffered Sample Clock Edge Counting National Instruments Corporation 8 3 NI USB 621x User Manual Chapter 8 Counters Controlling the Direction of Counting In edge counting applications the counter can count up or down You can configure the counter to do the following e Always count up e Always count down e Count up when the Counter n B input is high count down when it is low For information about connecting counter signals refer to the Default Counter Timer Pinouts section Pulse Width Measurement In pulse width measurements the counter measures the width of a pulse on its Gate input signal You can configure the counter to measure the width of high pulses or low pulse
183. s higher is better 1 Hardware A property of an event that is synchronized to a reference clock 2 Software A property of a function that begins an operation and returns only when the operation is complete A synchronous process is therefore locked and no other processes can run during this time In NI DAQmx a collection of one or more channels timing and triggering and other properties that apply to the task itself Conceptually a task represents a measurement or generation you want to perform See terminal count An object or region on a node through which data passes The highest value of a counter Gate hold time Gate setup time Gate pulse width The reference signals for controlling the basic accuracy of time or frequency based measurements For instruments timebase refers to the accuracy of the internal clock Output delay time A device that responds to a physical stimulus heat light sound pressure motion flow and so on and produces a corresponding electrical signal See also sensor G 14 ni com trigger USB Glossary 1 Any event that causes or starts some form of data capture 2 An external stimulus that initiates one or more instrument functions Trigger stimuli include a front panel button an external input voltage pulse or a bus trigger command The trigger may also be derived from attributes of the actual signal to be acquired such as the level and slope of the signal So
184. s of the NI PGIA and this difference is rejected by the amplifier If the input circuitry of a device were referenced to ground as it is in the referenced single ended ground reference setting this difference in ground potentials would appear as an error in the measured voltage National Instruments Corporation 4 35 NI USB 621x User Manual Chapter 4 Analog Input Using the DAQ Assistant you can configure the channels for referenced single ended or non referenced single ended input modes Refer to the Configuring AI Ground Reference Settings in Software section for more information about the DAQ Assistant Connecting Analog Input Signals on USB 6215 6216 6218 Devices You can connect the USB 6215 6216 6218 directly to a variety of devices and other signal sources Make sure the devices you connect to the USB 6215 6216 6218 are compatible with the input specifications of the module When connecting various sources to the USB 6215 6216 6218 you can use differential single ended or a combination of single ended and differential connections 3 Note You must always connect AI GND to a local ground signal in your system using a low impedance connection If you leave AI GND unconnected you cannot ensure that AI lt 0 31 gt are within 10 V of AI GND and your measurement may be unreliable Taking Differential Measurements NI USB 621x User Manual To attain more accurate measurements and less noise use a differential measurem
185. s 257 6 425 us 6 400 us 2 56 ms 101 800 2 56 ms 2 54 ms Disabled The filter setting for each input can be configured independently On power up the filters are disabled Figure 7 4 shows an example of a low to high transition on an input that has its filter set to 125 ns N 5 PFI Terminal Filtered input goes high when terminal is sampled Filter Clock 12 3 4 12 34 5 high on five consecutive 40 MHz filter clocks Filtered Input National Instruments Corporation 7 5 Figure 7 4 Filter Example Enabling filters introduces jitter on the input signal For the 125 ns and 6 425 us filter settings the jitter is up to 25 ns On the 2 56 ms setting the jitter is up to 10 025 us Refer to the KnowledgeBase document Digital Filtering with M Series for more information about digital filters and counters To access this KnowledgeBase go to ni com info and enter the info code rddfms NI USB 621x User Manual Chapter 7 PFI 1 0 Protection Each DI DO and PFI signal is protected against overvoltage undervoltage and overcurrent conditions as well as ESD events However you should avoid these fault conditions by following these guidelines e Donot connect a DO or PFI output lines to any external signal source ground signal or power supply e Understand the current requirements of the load connected to DO or P
186. s 8 AL 21 Al 13 EN 3 AI 29 AI GND Jl Eu 3 Al GND Al6 ES z AI 22 Al 14 Il Es a Al 30 AI7 Ee 8 Al 23 AI 15 Ef e bj AI 31 OI J SM j NC No Connect Figure A 13 USB 6218 Screw Terminal Pinout National Instruments Corporation A 19 NI USB 621x User Manual Appendix A Device Specific Information Table A 6 Default NI DAQmx Counter Timer Pins Counter Timer Signal Default Terminal Number Name CTR 0 SRC 1 PFI 0 CTR 0 GATE 2 PFI 1 CTR 0 AUX 34 PFI 9 CTR 0 OUT 6 PFI 4 CTROA 1 PFI 0 CTROZ 2 PFI 1 CTROB 34 PFI 9 CTR 1 SRC 4 PFI 3 CTR 1 GATE 3 PFI 2 CTR 1 AUX 35 PFI 10 CTR 1 OUT 7 PFI 5 CTR1A 4 PFI 3 CTR1Z 3 PFI 2 CTR1B 35 PFI 10 FREQ OUT 8 PFI 6 ER Note For more information about default NI DAQmx counter inputs refer to Connecting Counter Signals in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later NI USB 621x User Manual A 20 ni com Appendix A Device Specific Information USB 6218 BNC USB 6218 BNC Pinout Figure A 14 shows the pinout of the USB 6218 BNC For a detailed description of each signal refer to the O Connector Signal Descriptions section of Chapter 3 Connector and LED Information National Instruments Corporation A 21 NI USB 621x User Manual Appendix A Device Specific Information
187. s on the Gate signal You can route an internal or external periodic clock signal with a known period to the Source input of the counter The counter counts the number of rising or falling edges on the Source signal while the pulse on the Gate signal is active You can calculate the pulse width by multiplying the period of the Source signal by the number of edges returned by the counter A pulse width measurement is accurate even if the counter is armed while a pulse train is in progress If a counter is armed while the pulse is in the active state it waits for the next transition to the active state to begin the measurement Single Pulse Width Measurement With single pulse width measurement the counter counts the number of edges on the Source input while the Gate input remains active When the Gate input goes inactive the counter stores the count in a hardware save register and ignores other edges on the Gate and Source inputs Software then reads the stored count NI USB 621x User Manual 8 4 ni com Chapter 8 Counters Figure 8 5 shows an example of a single pulse width measurement GATE L J o c T SOURCE A A Counter Value 0 1 2 HW Save Register 2 Figure 8 5 Single Pulse Width Measurement Buffered Pulse Width Measurement Buffered pulse width measurement is similar to single pulse width measurement but buffered pulse width measurement takes measurements over multiple pulses The count
188. sed in manual xiii NI resources C 1 related documentation xiv double buffered acquisition 4 9 drivers NI resources C 1 duplicate count prevention 8 37 enabling in NI DAQmx 8 39 example 8 37 prevention example 8 38 E earth ground connecting 3 4 edge counting 8 2 buffered 8 3 on demand 8 2 sample clock 8 3 single point 8 2 edge separation measurement buffered two signal 8 20 single two signal 8 20 enabling duplicate count prevention in NI DAQmx 8 39 encoders quadrature 8 16 encoding X1 8 16 X2 8 16 XA 8 17 equivalent time sampling 8 26 National Instruments Corporation l 5 Index examples NI resources C 1 exporting timing output signals using PFI terminals 7 3 F features counter 8 34 field wiring considerations 4 10 filters counter 8 35 PFI 7 4 finite pulse train timing generation 8 24 floating signal sources connecting 4 25 description 4 25 using in differential mode 4 27 using in non referenced single ended mode 4 30 using in referenced single ended mode 4 31 when to use in differential mode 4 25 when to use in non referenced single ended mode 4 26 when to use in referenced single ended mode 4 25 FREQ OUT signal 8 31 frequency division 8 26 generation 8 25 generator 8 25 measurement 8 10 Frequency Output signal 8 31 front panel USB 6212 6216 A 13 USB 6218 A 21 fuse replacement USB devices 3 4 NI USB 621x User Manual Index G
189. signal in differential mode or two signals in single ended mode Differential Mode To connect signals in differential mode determine the type of signal source you are using a floating signal FS source or a ground referenced signal GS source Refer to the Connecting Analog Input Signals on USB 6210 6211 6212 Devices or Connecting Analog Input Signals on USB 6215 6216 6218 Devices section of Chapter 4 Analog Input for more information To measure a floating signal source move the switch to the FS position To measure a ground referenced signal source move the switch to the GS position Figure A 6 shows the AI 0 BNC and corresponding FS GS switch on the top panel of the USB 6212 6216 BNC National Instruments Corporation A 15 NI USB 621x User Manual Appendix A Device Specific Information Figure A 6 FS GS Switch Figure A 7 shows the analog input circuitry on the USB 6212 6216 BNC When the switch is set to the FS position AI x is grounded through a 0 1 UF capacitor in parallel with a 5 KQ resistor e eGS ID GS o Floating FS Ground oFS Source Referenced Source l 0 1 UF 5 kQ O1 pF 3 5k2 L3 NZ AI GND NZ AI GND 1 USB 621xDevice i 1 USB 621x Device Figure A 7 Analog Input Circuitry Single Ended Mode For each BNC connector that you use for two single ended channels set the source type switch to the GS posi
190. signal path Magnetic coupling is proportional to the area between the two signal conductors Electrical coupling is a function of how much the electric field differs between the two conductors With this type of connection the NI PGIA rejects both the common mode noise in the signal and the ground potential difference between the signal source and the device ground Refer to the Using Referenced Single Ended Connections for Floating Signal Sources section for more information about referenced single ended connections When to Use Non Referenced Single Ended Connections with Floating Signal Sources Only use non referenced single ended input connections if the input signal meets the following conditions e The input signal is high level greater than 1 V e The leads connecting the signal to the device are less than 3 m 10 ft Differential input connections are recommended for greater signal integrity for any input signal that does not meet the preceding conditions In the single ended modes more electrostatic and magnetic noise couples into the signal connections than in differential configurations The coupling is the result of differences in the signal path Magnetic coupling is proportional to the area between the two signal conductors Electrical coupling is a function of how much the electric field differs between the two conductors With this type of connection the NI PGIA rejects both the common mode noise in the signal
191. sition consists of one or more samples You can specify an internal or external source for AI Sample Clock You also can specify whether the measurement sample begins on the rising edge or falling edge of AI Sample Clock Using an Internal Source One of the following internal signals can drive AI Sample Clock e Counter n Internal Output e AI Sample Clock Timebase divided down e A pulse initiated by host software A programmable internal counter divides down the sample clock timebase Using an External Source Use any input PFI line as the source of AI Sample Clock Routing Al Sample Clock to an Output Terminal You can route AI Sample Clock out to any output PFI terminal This pulse is always active high You can specify the output to have one of two behaviors With the pulse behavior your DAQ device briefly pulses the PFI terminal once for every occurrence of AI Sample Clock With level behavior your DAQ device drives the PFI terminal high during the entire sample Other Timing Requirements Your DAQ device only acquires data during an acquisition The device ignores AI Sample Clock when a measurement acquisition is not in progress During a measurement acquisition you can cause your DAQ device to ignore AI Sample Clock using the AI Pause Trigger signal A counter on your device internally generates AI Sample Clock unless you select some external source AI Start Trigger starts this counter and either 4 14 ni com Ch
192. t channel G 10 ni com NI DAQmx NI PGIA non referenced signal sources NRSE offset period PFI PGIA physical channel posttriggering National Instruments Corporation G 11 Glossary The latest NI DAQ driver with new VIs functions and development tools for controlling measurement devices The advantages of NI DAQmx over earlier versions of NI DAQ include the DAQ Assistant for configuring channels and measurement tasks for your device for use in LabVIEW LabWindows CVI and Measurement Studio increased performance such as faster single point analog I O and a simpler API for creating DAQ applications using fewer functions and VIs than earlier versions of NI DAQ See instrumentation amplifier Signal sources with voltage signals that are not connected to an absolute reference or system ground Also called floating signal sources Some common example of non referenced signal sources are batteries transformers or thermocouples Non Referenced Single Ended mode All measurements are made with respect to a common NRSE measurement system reference but the voltage at this reference can vary with respect to the measurement system ground The unwanted DC voltage due to amplifier offset voltages added to a signal The period of a signal most often measured from one zero crossing to the next zero crossing of the same slope The period of a signal is the reciprocal of its frequency in Hz Period is designated by
193. tection Qo Digital To Input Timing Weak Pull Down ai PFI Isolators Signal Selectors Filters 8 Figure 7 1 USB 621x PFI Input Circuitry National Instruments Corporation 7 1 NI USB 621x User Manual Chapter 7 PFI Figure 7 2 shows the circuitry of an output PFI line Isolation Barrier USB 6215 6216 6218 devices only Digital Timing Signals isolators l O Protection PFI DIO Pin Static DO Buffer 47 kQ Pull Down Direction Control Figure 7 2 USB 621x PFI Output Circuitry When a terminal is used as a timing input or output signal it is called PFI x When a terminal is used as a static digital input or output it is called PO x P1 x or P2 x The voltage input and output levels and the current drive levels of the PFI signals are listed in the NJ USB 621x Specifications Using PFI Terminals as Timing Input Signals Use PFI terminals to route external timing signals to many different USB 621x functions Each input PFI terminal can be routed to any of the following signals e AT Convert Clock ai ConvertClock e ATI Sample Clock ai SampleClock e Al Start Trigger ai StartTrigger e AI Reference Trigger ai ReferenceTrigger e AIT Pause Trigger ai PauseTrigger e AI Sample Clock Timebase ai SampleClockTimebase e AO Start Trigger ao StartTrigger e AO Sample Clock ao SampleClock NI
194. temperature force sound or light Some commonly used sensors are strain gauges thermocouples thermistors angular encoders linear encoders and resistance temperature detectors RTDs To measure signals from these various transducers you must convert them into a form that a DAQ device can accept For example the output voltage of most thermocouples is very small and susceptible to noise Therefore you may need to amplify or filter the thermocouple output before digitizing it The manipulation of signals to prepare them for digitizing is called signal conditioning For more information about sensors refer to the following documents e For general information about sensors visit ni com sensors e Ifyou are using LabVIEW refer to the LabVIEW Help by selecting Help Search the LabVIEW Help in LabVIEW and then navigate to the Taking Measurements book on the Contents tab National Instruments Corporation 2 3 NI USB 621x User Manual Chapter 2 DAQ System Overview If you are using other application software refer to Common Sensors in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later Cables and Accessories Cable and accessory options for USB 621x devices are as follows Combicon Accessory for USB 621x Screw Terminal Devices Optional Your USB 621x kit includes combicon connectors with signal labels The NI USB 621x Accessory Kit part number 779807 01 contains four combicon connectors with screws a screw
195. terminal is used in various applications Table 8 3 Counter Applications and Counter n Source Application Purpose of Source Terminal Pulse Generation Counter Timebase One Counter Time Measurements Counter Timebase Two Counter Time Measurements Input Terminal Non Buffered Edge Counting Input Terminal Buffered Edge Counting Input Terminal Two Edge Separation Counter Timebase Routing a Signal to Counter n Source Each counter has independent input selectors for the Counter n Source signal Any of the following signals can be routed to the Counter n Source input e 80 MHz Timebase e 20 MHz Timebase e 100 kHz Timebase e USB 6210 6211 6215 Devices PFI lt 0 3 gt e USB 6212 6216 Devices PFI lt 0 15 gt e USB 6218 Devices PFI lt 0 3 gt PFI lt 8 11 gt In addition Counter 1 TC or Counter 1 Gate can be routed to Counter 0 Source Counter 0 TC or Counter 0 Gate can be routed to Counter 1 Source Some of these options may not be available in some driver software Routing Counter n Source to an Output Terminal You can route Counter n Source out to any output PFI terminal 8 28 ni com Chapter 8 Counters Counter n Gate Signal The Counter n Gate signal can perform many different operations depending on the application including starting and stopping the counter and saving the counter contents Routing a Signal to Counter n Gate Each counter has independent input se
196. th a digital source specify a source and an edge The source can be any input PFI signal The source also can be one of several internal signals on your DAQ device Refer to Device Routing in MAX in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later for more information You also can specify whether the measurement acquisition stops on the rising edge or falling edge of AI Reference Trigger Routing Al Reference Trigger to an Output Terminal You can route AI Reference Trigger out to any output PFI terminal Al Pause Trigger Signal You can use the AI Pause Trigger ai PauseTrigger signal to pause and resume a measurement acquisition The internal sample clock pauses while the external trigger signal is active and resumes when the signal is inactive You can program the active level of the pause trigger to be high or low Using a Digital Source To use AI Sample Clock specify a source and a polarity The source can be any input PFI signal The source also can be one of several other internal signals on your DAQ device Refer to Device Routing in MAX in the NI DAQmx Help or the LabVIEW Help in version 8 0 or later for more information Getting Started with Al Applications in Software NI USB 621x User Manual You can use the USB 621x device in the following analog input applications e Single point analog input Finite analog input e Continuous analog input You can perform these applications through DMA int
197. the LabVIEW Help in version 8 0 or later National Instruments Corporation A 5 NI USB 621x User Manual Appendix A Device Specific Information USB 6212 6216 Screw Terminal USB 6212 6216 Screw Terminal Pinout Figure A 3 shows the pinout of the USB 6212 Screw Terminal and USB 6216 Screw Terminal For a detailed description of each signal refer to the O Connector Signal Descriptions section of Chapter 3 Connector and LED Information PFI 0 P1 0 gI PFI 8 P2 0 PFI 1 P1 1 d m S o h PFI 9 P2 1 PFI 2 P1 2 e 3 m PFI 10 P2 2 PFI 3 P1 3 gt Sm PFI 11 P2 3 D GND e Sil D GND PFI 4 P1 4 ll o 8 ll PFI 12 P2 4 RIS PARS S PFI 13 P2 5 PFI 6 P1 6 eo S IE PFI 14 P2 6 PFI 7 P1 7 o PFI 15 P2 7 5V 3 S 45V D GND z emm D GND AO 0 5 O P0 0 AO 1 ror EI imm POS AO GND x S EHI P0 2 ALO a s o P0 3 Als a sm D GND AI 1 3 S IE D GND AI 9 c5 2O P0 4 Al 2 o iso P0 5 Al 10 B SI P0 6 AI 3 bs 2 m POZ Al 11 8 zO D GND Al SENSE B 8E P0 8 Al 4 m 8 P0 9 Al 12 X t5 P0 10 Al5 S si Pott Al 18 N 3 E D GND Al GND I B S P0 12 Al6 8 IO P0 13 Al 14 8 SH Po 14 Al7 2 2O P0 15 Al 15 8 zi I D GND J BJ Figure A 3 USB 6212 6216 Screw Terminal Pinout NI USB 621x User Manual A 6 ni com Appendix A
198. time 3 Pertaining to the performance of a computation during the actual time that the related physical process transpires so results of the computation can be used in guiding the physical process Referenced Single Ended mode All measurements are made with respect to a common reference measurement system or a ground Also called a grounded measurement system G 12 ni com sample counter scan scan interval scan rate sensor signal conditioning signal source signals single trigger mode single buffered single ended input National Instruments Corporation G 13 Glossary Seconds Samples The clock that counts the output of the channel clock in other words the number of samples taken On devices with simultaneous sampling this counter counts the output of the scan clock and hence the number of scans One or more analog or digital input samples Typically the number of input samples in a scan is equal to the number of channels in the input group For example one pulse from the scan clock produces one scan which acquires one new sample from every analog input channel in the group Controls how often a scan is initialized is regulated by the AI Sample Clock signal Reciprocal of the scan interval A device that responds to a physical stimulus heat light sound pressure motion flow and so on and produces a corresponding electrical signal Primary characteristics of sensors are sensitivity
199. timed generations have several advantages over software timed acquisitions The time between samples can be much shorter The timing between samples can be deterministic 5 2 ni com National Instruments Corporation Chapter 5 Analog Output Hardware timed acquisitions can use hardware triggering Hardware timed operations are buffered During hardware timed AO generation data is moved from a PC buffer to the onboard FIFO on the USB 621x device using USB Signal Streams before it is written to the DACs one sample at a time Buffered acquisitions allow for fast transfer rates because data is moved in large blocks rather than one point at a time One property of buffered I O operations is the sample mode The sample mode can be either finite or continuous Finite sample mode generation refers to the generation of a specific predetermined number of data samples After the specified number of samples has been written out the generation stops e Continuous generation refers to the generation of an unspecified number of samples Instead of generating a set number of data samples and stopping a continuous generation continues until you stop the operation There are three methods of continuous generation that control what data is written These methods are regeneration FIFO regeneration and non regeneration modes Regeneration is the repetition of the data that is already in the buffer Standard regeneration is when dat
200. tion This setting disconnects the built in ground reference resistor from the negative terminal of the BNC connector allowing the connector to be used as a single ended channel as shown in Figure A 8 Al x Al x 8 Ground Ref Source GS USB 621x BNC Device Figure A 8 Single Ended Channels NI USB 621x User Manual A 16 ni com Appendix A Device Specific Information When you set the source type to the GS position and configure the device for single ended input in software each BNC connector provides access to two single ended channels AI x and AI x 8 For example the BNC connector labeled AI 0 provides access to single ended channels AI 0 and AI 8 the BNC connector labeled AI 1 provides access to single ended channels AI 1 and AI 9 and so on Up to 16 single ended channels are available in single ended measurement modes For information on how to connect your signals in single ended mode AI GND and or AI SENSE refer to the Connecting Analog Input Signals on USB 6210 6211 6212 Devices or Connecting Analog Input Signals on USB 6215 6216 6218 Devices section of Chapter 4 Analog Input For a detailed description of each signal refer to the I O Connector Signal Descriptions section of Chapter 3 Connector and LED Information Analog Output You can access analog output signals on the BNC connectors labeled AO 0 and AO 1 Figure A 9 shows the analog output circuitry on the USB 6212 6216 BNC ia
201. tion of grounded channels between signal channels 4 7 installation hardware 1 1 NI DAQ 1 1 other software 1 1 instrument drivers NI resources C 1 instrumentation amplifier 4 2 interface bus 11 1 isolated DAQ devices 9 1 benefits 9 3 common mode noise 9 3 isolation barrier 4 2 5 2 isolators 9 1 ni com K KnowledgeBase C 1 L LabVIEW documentation xv Mobile Module 8 x xiv Touch Panel Module 8 x xiv LabWindows CVI documentation xvi LED 3 6 Linux xiv low impedance sources 4 6 Mac OS X xiv Measurement Studio documentation xvi measurements buffered period 8 7 buffered pulse width 8 5 buffered semi period 8 9 buffered two signal edge separation 8 20 choosing frequency 8 14 frequency 8 10 period 8 6 position 8 15 pulse width 8 4 semi period 8 8 single period 8 6 single pulse width 8 4 single semi period 8 8 single two signal edge separation 8 20 two signal edge separation 8 19 using quadrature encoders 8 16 using two pulse encoders 8 18 National Instruments Corporation I 7 Index measuring high frequency with two counters 8 12 large range of frequencies using two counters 8 13 low frequency with one counter 8 10 averaged 8 11 methods data transfer 11 1 minimizing glitches on the output signal 5 2 output signal glitches B 3 voltage step between adjacent channels 4 7 mounting DIN rail 1 6 panel 1 7 multichannel scanning considerations 4 5 MUX 4 1
202. truments NI DAQmx Base Documentation Getting Started Guide xiv ni com About This Manual Getting Started with NI DAQmx Base for Linux and Mac Users describes how to install your NI DAQmx Base software your NI DAQmx Base supported DAQ device and how to confirm that your device is operating properly on your Mac Linux machine The NI DAQmx Base Readme lists which devices are supported by this version of NI DAQmx Base In Windows select Start All Programs National Instruments NI DAQmx Base DAQmx Base Readme The NI DAQmx Base VI Reference Help contains VI reference and general information about measurement concepts In LabVIEW select Help NI DAQmx Base VI Reference Help The NI DAQmx Base C Reference Help contains C reference and general information about measurement concepts In Windows select Start All Programs National Instruments NI DA Qmx Base Documentation C Function Reference Help iyi Note All NI DAQmx Base documentation for Linux is installed at usr local natinst nidaqmxbase documentation 3 Note All NI DAQmx Base documentation for Mac OS X is installed at Applications National Instruments NI DAQmx Base documentation LabVIEW If you are a new user use the Getting Started with LabVIEW manual to familiarize yourself with the LabVIEW graphical programming environment and the basic LabVIEW features you use to build data acquisition and instrument control applications Open the Getting Started wit
203. uffered Sample Clock Edge Counting sess 8 3 Controlling the Direction of Counting esee 8 4 Pulse Width Measurement 00 0 0 cece eseesseesecesesseeeseeseeeseceecesseseeeaeseeeeaeenaes 8 4 Single Pulse Width Measurement esee 8 4 Buffered Pulse Width Measurement esee 8 5 Period Measurement esten i o ode d e rep ret EDU 8 6 Single Period Measurement essen 8 6 Buffered Period Measurement essere 8 7 Semi Period Measurement ssssesssseseeeeerenen rennen eene 8 8 Single Semi Period Measurement esee 8 8 Buffered Semi Period Measurement sss 8 9 Frequency Measurement 5 itr rede i e t epi 8 10 Choosing a Method for Measuring Frequency ssss 8 14 Position Measurement tie iie e a e Pei pee 8 15 Measurements Using Quadrature Encoders sss 8 16 Measurements Using Two Pulse Encoders sss 8 18 Buffered Sample Clock Position Measurement 8 18 Two Signal Edge Separation Measurement sese 8 19 Single Two Signal Edge Separation Measurement 8 20 Buffered Two Signal Edge Separation Measurement 8 20 Counter Output Applications oo eee eee rca a A 8 21 Simple Pulse Generation n
204. uirements of the load connected to DO or PFIoutput signals Do not exceed the specified current output limits of the DAQ device NI has several signal conditioning solutions for digital applications requiring high current drive e Donot drive a DI or PFI input line with voltages outside of its normal operating range The PFI or DI lines have a smaller operating range than the AI signals NI USB 621x User Manual 6 2 ni com Chapter 6 Digital I O Increasing Current Drive on USB 6210 6211 6215 6218 Devices The total internal current limit for digital outputs and power drawn from the 5 V terminals is 50 mA You can increase this internal current limit by supplying an external 5 V supply Refer to the 5 V Power as an Input section of Chapter 3 Connector and LED Information Connecting Digital 1 0 Signals on USB 6210 6211 6215 6218 Devices The DI and DO signals P0 0 7 and P1 lt 0 7 gt are referenced to D GND Digital input applications include receiving TTL signals and sensing external device states such as the state of the switch shown in the figure Digital output applications include sending TTL signals and driving external devices such as the LED shown in Figure 6 2 Isolation j Barrier t USB 6215 5V LED AR and USB 6218 VW o devices only o 4 4 Digital Isolators JT U U L gt a TTL Signal P0 lt 0 3 gt M lt 0 5V VWV Switch y
205. understand the current requirements of the load connected to these signals Do not exceed the specified current output limits of the DAQ device NI has several signal conditioning solutions for digital applications requiring high current drive If you configure a PFI or DIO line as an input do not drive the line with voltages outside of its normal operating range The PFI or DIO lines have a smaller operating range than the AI signals Treat the DAQ device as you would treat any static sensitive device Always properly ground yourself and the equipment when handling the DAQ device or connecting to it 6 5 NI USB 621x User Manual Chapter 6 Digital I O Programmable Power Up States on USB 6212 6216 Devices At system startup and reset the hardware sets all PFI and DIO lines to high impedance inputs by default The DAQ device does not drive the signal high or low Each line has a weak pull down resistor connected to it as described in the NJ USB 621x Specifications NI DAQmx supports programmable power up states for PFI and DIO lines Software can program any value at startup to the PO P1 or P2 lines The PFI and DIO lines can be set as e A high impedance input with a weak pull down resistor default e An output driving a 0 e An output driving a 1 Refer to the NI DAQmx Help or the LabVIEW Help in version 8 0 or later for more information about setting power up states in NI DAQmx or MAX Increasing Current Drive on USB 6212 6216 Devi
206. urce clock period Source pulse width Transistor Transistor Logic A digital circuit composed of bipolar transistors wired in a certain manner A typical medium speed digital technology Nominal TTL logic levels are 0 and 5 V Universal Serial Bus A 480 Mbit s serial bus with up to 12 Mbps bandwidth for connecting computers to keyboards printers and other peripheral devices USB 2 0 retains compatibility with the original USB specification Volts Common mode voltage Ground loop voltage Volts input high Volts input low Volts in Measured voltage Volts output high Volts output low Volts out National Instruments Corporation G 15 NI USB 621x User Manual Glossary V Signal source voltage s virtual channel See channel W waveform 1 The plot of the instantaneous amplitude of a signal as a function of time 2 Multiple voltage readings taken at a specific sampling rate NI USB 621x User Manual G 16 ni com Index Symbols 5 V power input 3 3 output 3 3 source 3 3 Numerics 100 kHz Timebase 10 1 20 MHz Timebase 10 1 80 MHz Timebase 10 1 A A D converter 4 2 AC return path creating 9 4 accessories 2 4 USB 6212 Mass Termination A 10 USB 6216 Mass Termination A 10 acquisition circular buffered 4 9 double buffered 4 9 hardware timed 4 9 on demand 4 8 software timed 4 8 ACT LED 3 6 ADC 4 2 AI Convert Clock signal 4 16 AI Convert Clock Timebase signal
207. utput Data Generation Methods eese 5 2 Analog Output Digital Triggering esseseeeeeeeeeeneeeneeeen nennen eee 5 4 Connecting Analog Output Signals esee eee 5 4 Analog Output Timing Signals ceceeeseeeeeeseceeesseeeseeseceeeeaeenseeaesneeeaeenseeaes 5 5 AO Start Trigger Sign l 5 eget e RE ei 5 5 Using a Digital Source acisini ot arnie ii ia 5 5 Routing AO Start Trigger to an Output Terminal 5 6 National Instruments Corporation vij NI USB 621x User Manual Contents AO Pause Trigger Signal oncion teste etis E A RERO d 5 6 Using a Digital Source ette pedet 5 7 AO Sample Clock Signal 5 2 ettet eter Prud 5 8 Using an Internal Source esee 5 8 Using an External Source eese 5 8 Routing AO Sample Clock to an Output Terminal 5 8 Other Timing Requirements eese 5 8 AO Sample Clock Timebase Signal eee 5 9 Getting Started with AO Applications in Software esee 5 10 Chapter 6 Digital 1 0 Digital I O on USB 6210 6211 6215 6218 Devices sss 6 1 Static DIO on USB 6210 6211 6215 6218 Devices eese 6 2 T O Protection on USB 6210 6211 6215 6218 Devices 6 2 Increasing Current Drive on USB 6210 6211 6215 6218 Devices 6 3 Connecting Digital I O Signals
208. w input signals to float within the common mode limits of the NI PGIA Refer to the Using Differential Connections for Ground Referenced Signal Sources section for more information about differential connections When to Use Non Referenced Single Ended Connections with Ground Referenced Signal Sources Only use non referenced single ended input connections if the input signal meets the following conditions e The input signal is high level greater than 1 V e The leads connecting the signal to the device are less than 3 m 10 ft e The input signal can share a common reference point with other signals Differential input connections are recommended for greater signal integrity for any input signal that does not meet the preceding conditions 4 32 ni com Chapter 4 Analog Input In the single ended modes more electrostatic and magnetic noise couples into the signal connections than in differential configurations The coupling is the result of differences in the signal path Magnetic coupling is proportional to the area between the two signal conductors Electrical coupling is a function of how much the electric field differs between the two conductors With this type of connection the NI PGIA rejects both the common mode noise in the signal and the ground potential difference between the signal source and the device ground Refer to the Using Non Referenced Single Ended Connections for Ground Referenced Signal Sources section
209. xpansion vehicle to which I O or other devices are connected Examples of PC buses are the PCI AT ISA and EISA bus Celsius The process of determining the accuracy of an instrument In a formal sense calibration establishes the relationship of an instrument s measurement to the value provided by a standard When that relationship is known the instrument may then be adjusted calibrated for best accuracy Process of extending the counting range of a counter chip by connecting to the next higher counter European emissions control standard NI USB 621x User Manual Glossary channel clock CMOS CMRR common mode rejection common mode signal convert rate count counter counter timer NI USB 621x User Manual Pin or wire lead to which you apply or from which you read the analog or digital signal Analog signals can be single ended or differential For digital signals you group channels to form ports Ports usually consist of either four or eight digital channels Hardware component that controls timing for reading from or writing to groups Complementary metal oxide semiconductor Common mode rejection ratio A measure of the ability of a differential amplifier to reject interference from a common mode signal usually expressed in decibels dB The ability of an electronic system to cancel any electronic noise pick up thatis common to both the positive and negative polarities of the input leads

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