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National Instruments USB-621x User's Manual

1. measurement AUX ___4 L C GATE 4 A A SOURCE Counter Value 1 2 3 1 2 3 1 2 3 3 3 3 Buffer 7 7 Figure 9 21 Buffered Two Signal Edge Separation Measurement For information about connecting counter signals refer to the Default Counter Timer Pinouts section National Instruments Corporation 9 19 NI USB 621x User Manual Chapter 9 Counters Counter Output Applications Simple Pulse Generation NI USB 621x User Manual Single Pulse Generation The counter can output a single pulse The pulse appears 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 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 Figure 9 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 1 SOURCE OUT Figure 9 22 Single Pulse Generation Single Pulse Generation with Start Trigger The counter can output a sing
2. ai ConvertClock Channel Measured 0123 0123 0123 lt Sample 1 a Sample 2 Sample 3 e Convert Clock Too Fast for Sample Clock e Convert Clock Pulses are Gated Off Figure 4 11 ai ConvertClock Too Fast ai SampleClock ai ConvertClock Channel Measured 0 1 2 3 0 1 2 3 0 P Sample 1 E Sample 2 gt Sample 3 e Improperly Matched Sample Clock and Convert Clock e Leads to Aperiodic Sampling National Instruments Corporation Figure 4 12 ai SampleClock and ai ConvertClock Improperly Matched 4 19 NI USB 621x User Manual Chapter 4 Analog Input ai SampleClock 0123 0128 ai ConvertClock 0123 Sample 3 gt Channel Measured Sample 1 lt q gt q Sample 2 gt q e Properly Matched Sample Clock and Convert Clock Figure 4 13 ai SampleClock and ai ConvertClock Properly Matched It is also possible to use a single external signal to drive both ai SampleClock and ai ConvertClock at the same time In this mode each tick of the external clock will cause a conversion on the ADC Figure 4 14 shows this timing relationship ai SampleClock ai ConvertClock Channel Mea
3. devices only T RON Channel 0 Digital Load V OUT Isolators IE NZ Load V OUT tol ROI Channel 1 V M Series Device Figure 7 2 Analog Output Connections NI USB 621x User Manual 7 4 ni com Chapter 7 Analog Output Analog Output Timing Signals Figure 7 3 summarizes all of the timing options provided by the analog output timing engine B 20 MHz Timebase ao SampleClock PFI ao SampleClock Ctr n Internal Output o 100 kHz Timebase ke Timebase Programmable o Clock Divider SampleClock Timebase Divisor Figure 7 3 Analog Output Timing Options USB M Series devices feature the following AO waveform generation timing signals AO Start Trigger Signal AO Pause Trigger Signal AO Sample Clock Signal 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 StartTrigger specify a source and an edge The source can be one of the following signals National Instruments Corporation A software pulse PFI lt 0 3 gt PFI lt 8 11 gt ai StartTrigger 7 5 NI USB 621x User Manual Chapter 7 Analog Output The source also can be one of several internal signals on your DA
4. 4 18 AI Convert Clock Timebase Signal 4 20 AI Hold Complete Event Signal 4 21 Al Start Trigger Signal ass Loan intel dr dessins 4 21 Using a Digital Source tin E 4 21 Routing AI Start Trigger to an Output Terminal 4 21 AT Reference Trigger Signaleren ROT VERTE Tee ha ROT nus 4 22 Using a Digital Source ere urnes 4 23 Routing AI Reference Trigger Signal to an Output Terminal 4 23 NI USB 621x User Manual vi ni com Contents AT Pause Trigger TTT nine sabes pedasvivsonntseetes pedeees 4 23 Using Digital Source hist ht hiinitl tais ist 4 23 Getting Started with AI Applications in Software 4 24 Chapter 5 Connecting Al Signals on the USB 6210 6211 Devices Connecting Floating Signal Sources 5 3 What Are Floating Signal Sources 5 3 When to Use Differential Connections with Floating Signal Sources 5 3 When to Use Referenced Single Ended RSE Connections with Floating Signal Sources ss 5 3 When to Use Non Referenced Single Ended NRSE Connections with Floating Signal Sources 5 4 Using Differential Connections for Floating Signal Sources 5 5 Using Non Referenced Single Ended NRSE Connections for Floating Signal Sources ds dns mesh net S 5 8 Using Referenced Single Ended RSE Connections for Floating Signal TT S Let rar eae ee vets M tee 5 9 Connecting Ground Referenced Signal Sources ss 5 9 What Are
5. K i i USB 6215 and USB 6218 devices only 1 7 1 A Digital Routing Digital Bus and Clock Isolators Interface Bus Generation 1 i 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 Flexible AI and AO sample and convert timing Many triggering modes Independent AI 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 and static DO signals USB Hi Speed 2 0 interface Up to four USB Signal Streams for acquisition and generation functions The M Series 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 2 2 ni com Chapter 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 t
6. Bus Interface The bus interface circuitry of M Series devices efficiently moves data between host memory and the measurement and acquisition circuits All M Series devices are jumperless for complete plug and play operation The operating system automatically assigns the base address interrupt levels and other resources NI 621x devices incorporate USB STC2 technology to implement a Hi Speed USB interface USB Signal Streams M Series USB 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 e Analog input e Analog output e Counter 0 e Counter 1 Data Transfer Methods The two primary ways to transfer data across the USB bus are USB Signal Stream and programmed I O USB Signal Stream USB Signal Stream is 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 National Instruments Corporation 13 1 NI USB 621x User Manual Chapter 13 Bus Interface Programmed 1 0 Programmed I O is a data transfer mechanism where the user s program is responsible for transferring data Each read or write call in the program initiates the transfer of data Programmed
7. Divisor 1 16 Figure 9 26 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 1 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 9 27 shows the output waveform of the frequency generator when the divider is set to 5 Frequency Output Timebase FREQ OUT Divisor 5 Figure 9 27 Frequency Generator Output Waveform National Instruments Corporation 9 23 NI USB 621x User Manual Chapter 9 Counters Frequency Output can be routed out to any PFI lt 4 7 gt or PFI lt 12 15 gt 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 section Frequenc
8. Al GND Figure 5 4 Differential Connections for AC Coupled Floating Sources with Balanced Bias Resistors Using Non Referenced Single Ended NRSE 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 5 5 shows a floating source connected to the DAQ device in NRSE mode o Al Floating Signal o Source o Al SENSE R o Al GND Figure 5 5 NRSE 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 NRSE bias resistors as well Replace AI with AI SENSE in Figures 5 1 5 2 5 3 and 5 4 for configurations with zero to two bias resistors The noise rejection of NRSE mode is better than RSE mode because the AI SENSE connection is made remotely near the source However the noise rejection of NRSE mode is worse than DIFF mode because the AI SENSE NI USB 621x User Manual 5 8 ni com Chapter 5 Connecting Al Signals on the USB 6210 6211 Devices connection is shared with all channels rather than being cabled in a twisted pair with the AI signal Using the DAQ Assistant you can configure the channels for RSE or NRSE
9. ZE gt ED D gt gt gt gt gt gt 9LSLYLELZLLLOL6 8 L 9GSr EZ 12 ZE LE OF 62 80 LZ 92 GZ He EZ ce Lz OC pL BI LL NC No Connect Figure A 1 USB 6210 Pinout Table A 1 Default NI DAQmx Counter Timer Pins NI USB 621x User Manual 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 A 2 ni com Appendix Device Specific Information Table A 1 Default NI DAQmx Counter Timer Pins Continued Counter Timer Signal Default Terminal Number Name CTR 0 Z 2 PFI 1 CTROB 1 PFI 0 CTR 1 SRC 4 PFI 3 CTR 1 GATE 3 PFI 2 CTR 1 AUX 4 PFI 3 CTR 1 OUT 7 PFI 5 CTRIA 4 PFI 3 CTR1Z 3 PFI 2 CTR1B 4 PFI 3 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 8 x Help USB 6210 Specifications Refer to the NMI 621x Specifications for more detailed information about the USB 6210 device USB 6210 PWR ACT LED Indicator The PWR ACT LED indicator indicates device status Table A 2 PWR ACT LED Status LED State Device Status Not lit Device not powered or device error Refer to ni com support if device is powered On not blinking De
10. ChB L li base Li Li Counter Value 5 X 6 X 7 7 X 6 Y 5 Figure 9 15 X1 Encoding X2 Encoding The same behavior 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 9 16 Gh I es ChB LH Lee Counter Value 5X 6 X 7 X 8 X9 TX ENT ENE Figure 9 16 X2 Encoding 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 9 17 Counter Value Dane sanonenc 5 Ch A TE a ChB ee eee ea NI USB 621x User Manual Figure 9 17 X4 Encoding 9 16 ni com Chapter 9 Counters 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 quadra
11. Other Timing Requirements The sample and conversion level timing of M Series devices work such that clock signals are gated off unless the proper timing requirements are met For example the device ignores both ai SampleClock and ai ConvertClock until it receives a valid ai StartTrigger signal Once the device recognizes an ai SampleClock pulse it ignores subsequent ai SampleClock pulses until it receives the correct number of ai ConvertClock pulses Similarly the device ignores all ai ConvertClock pulses until it recognizes an ai SampleClock pulse Once the device receives the correct number of ai ConvertClock pulses it ignores subsequent ai ConvertClock pulses until it receives another ai SampleClock 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 SampleClock and ai ConvertClock NI USB 621x User Manual 4 18 ni com Chapter 4 Analog Input ai SampleClock ai ConvertClock t t t Channel Measured 0123 0123 0123 Sample 1 Sample 2 Sample 3 lt 4 gt lt gt lt e Sample Clock Too Fast for Convert Clock e Sample Clock Pulses are Gated Off Figure 4 10 ai SampleClock Too Fast ai SampleClock
12. Table A 5 Default NI DAQmx Counter Timer Pins NI USB 621x User Manual 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 A 8 ni com Appendix Device Specific Information Table A 5 Default NI DAQmx Counter Timer Pins Continued Counter Timer Signal Default Terminal Number Name 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 CTR 1 A 4 PFI 3 CTR 1 Z 3 PFI 2 CTR1B 35 PFI 10 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 8 x Help USB 6218 Specifications Refer to the MI 621x Specifications for more detailed information about the USB 6218 device USB 6218 PWR ACT LED Indicator The PWR ACT LED indicator indicates device status Table A 6 PWR ACT LED Status LED State Device Status Not lit Device not powered or device error Refer to ni com support if device is powered On not blinking Device error Refer to ni com support National Instruments Corporation A 9 NI USB 621x User Manual Appendix Device Specific Information Table A 6 PWR ACT LED Status Continued LED State Device Status Single blink
13. terminal terminal count tgn t gsu gw National Instruments Corporation G 17 Glossary A circuit whose output signal is present between one output terminal and ground The programs that run on your computer and perform a specific user oriented function such as accounting program development measurement or data acquisition In contrast operating system functions basically perform the generic housekeeping of the machine which is independent of any specific application Operating system functions include the saving of data file system handling of multiple programs at the same time multi tasking network interconnection printing and keyboard user interface interaction 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 sources 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 gen
14. A 7 specifications A 9 using low impedance sources 4 6 using PFI terminals as Static digital I Os 10 3 as timing input signals 10 2 to export timing output signals 10 3 NI USB 621x User Manual 1 10 W waveform generation signals 7 5 Web resources C 1 X X1 encoding 9 15 X2 encoding 9 16 X4 encoding 9 16 ni com
15. 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 National Instruments Corporation 9 35 NI USB 621x User Manual Chapter 9 NI USB 621x User Manual Counters Example Application That Works Correctly No Duplicate Counting Figure 9 32 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 Value __ 6 X7 lt X1 X2 Xd Buffer 17 2 7 Figure 9 32 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
16. 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 2 PFI 1 A 5 NI USB 621x User Manual Appendix Device Specific Information Table A 3 Default NI DAQmx Counter Timer Pins Continued Counter Timer Signal Default Terminal Number Name CTROB 1 PFI 0 CTR 1 SRC 4 PFI 3 CTR 1 GATE 3 PFI 2 CTR 1 AUX 4 PFI 3 CTR 1 OUT 7 PFI 5 CTRIA 4 PFI 3 CTR1Z 3 PFI 2 CTR 1B 4 PFI 3 FREQ OUT 8 PFI 6 le Note For more information about default NI DAQmx counter inputs refer to Connecting Counter Signals in the NI DAQmx Help or the LabVIEW 8 x Help USB 6211 6215 Specifications Refer to the NI 621x Specifications for more detailed information about the USB 6211 6215 device USB 6211 6215 PWR ACT LED Indicator The PWR ACT LED indicator indicates device status Table A 4 PWR ACT LED Status LED State Device Status Not lit Device not powered or device error Refer to ni com support if device is powered On not blinking Device error Refer to ni com support NI USB 621x User Manual A 6 ni com Appendix Device Specific Information Table A 4 PWR ACT LED Status Continued LED State Device Status Single blink Operating normally Connected to USB Hi Speed port Refer to the NI 621x Specifications for more information Double blink Connected to USB ful
17. 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 The PFI lt 0 3 gt or PFI lt 8 11 gt signals can be routed to each input Counter n Up_Down Signal Counter n Up Down is another name for the Counter n B signal Counter 7 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 counters or configure counters to be armed on the assertion of the Counter n HW Arm signal Routing Signals to Counter n HW Arm Input Any of the following signals can be routed to the Counter n HW Arm input e PFI lt 0 3 gt PFI lt 8 11 gt e ai ReferenceTrigger e ai StartTrigger Counter 1 Internal Output can be routed to Counter 0 HW Arm Counter 0 Internal Output can be routed to Counter 1 HW Arm 9 28 ni com Chapter 9 Counters Some of these options may not be available in som
18. input modes Refer to the Configuring AI Ground Reference Settings in Software section of Chapter 4 Analog Input for more information about the DAQ Assistant Using Referenced Single Ended RSE Connections for Floating Signal Sources Figure 5 6 shows how to connect a floating signal source to the NI 621x device configured for RSE mode 5 Programmable Gain Floating Instrumentation Signal M ol P Source Amplifier Input Multiplexers Al SENSE o Measured Voltage N m TT GND 1 0 Connector Selected Channel in RSE Configuration Figure 5 6 RSE Connections for Floating Signal Sources Using the DAQ Assistant you can configure the channels for RSE or NRSE input modes Refer to the Configuring AI Ground Reference Settings in Software section of Chapter 4 Analog Input 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 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 5 9 NI USB 621x User Manual Chapter 5 Connect
19. 2 AI Hold Complete Event signal 4 21 AI Pause Trigger signal 4 23 AI Reference Trigger signal 4 22 AI Sample Clock signal 4 14 AI Sample Clock Timebase signal 4 16 AI Start Trigger signal 4 21 National Instruments Corporation l 1 AI timing signals 4 11 ai ConvertClock 4 16 ai ConvertClockTimebase 4 20 ai HoldCompleteEvent 4 21 ai PauseTrigger 4 23 ai ReferenceTrigger 4 22 ai SampleClock 4 14 ai SampleClockTimebase 4 16 ai StartTrigger 4 21 analog input 4 1 charge injection B 1 circuitry 4 1 connecting signals 5 1 6 1 connecting through I O connector 4 1 crosstalk when sampling multiple channels B 1 data acquisition methods 4 9 differential troubleshooting B 1 getting started with applications in software 4 24 ghost voltages when sampling multiple channels B 1 ground reference settings 4 2 MUX 4 1 sampling channels with AI Sample Clock and AI Convert Clock B 2 timing signals 4 11 triggering 4 10 troubleshooting B 1 analog input data acquisitions 4 9 analog input signals 4 11 AI Convert Clock 4 16 AI Convert Clock Timebase 4 20 AI Hold Complete Event 4 21 AI Pause Trigger 4 23 AI Reference Trigger 4 22 AI Sample Clock 4 14 NI USB 621x User Manual Index AI Sample Clock Timebase 4 16 Al Start Trigger 4 21 analog output 7 1 circuitry 7 1 connecting signals 7 4 data generation methods 7 2 fundamentals 7 1 getting started with applications in software 7 9 glitches o
20. 2 Greater than or equal to Per S Degree Q Ohm A Amperes the unit of electric current A D Analog to Digital Most often used as A D converter AC Alternating current accuracy 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 ADE Application development environment National Instruments Corporation G 1 NI USB 621x User Manual Glossary AI AI GND AI SENSE analog analog input signal analog output signal analog signal analog trigger AO AO 0 AO 1 AO 2 AO 3 AO GND application arm NI USB 621x User Manual 1 Analog input 2 Analog input channel signal Analog input ground signal Analog input sense signal 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 signal representing a variable that can be observed and represented continuously 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 implement
21. 2 sig N Source F1 i 4 Pulse Width Width of _ N Measurement Pulse F1 a Width of Pulse T gt Pulse _ Frequency of F1 A NI USB 621x User Manual Figure 9 13 Method 2 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 technique 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 M Series 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 9 14 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 9 12 ni com Chapter 9 Counters Signal to K SOURCE OUT Measure F1 COUNTER 0 Signal of Known ___4 SOURCE OUT Frequency F2 COUNTER 1 GATE CTR_O_SOURCE C Signal to Measure 1 i CTR_0_OUT CTR_1_GATE Mtera p to Measure CTR_1_SOURCE JUUUUUUUUUUUUUUULUN Figure 9 14 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 Count
22. 4 1 shows the input ranges and resolutions supported by NI 621x devices Table 4 1 Input Ranges for NI 621x Nominal Resolution Assuming Input Range 5 Over Range 10 V to 10 V 320 uV 5 V 05 V 160 uV 1VtolV 32 uV 200 mV to 200 mV 6 4 uV Analog Input Ground Reference Settings NI 621x devices support the analog input ground reference settings shown in Table 4 2 Table 4 2 Analog Input Ground Reference Settings AI Ground Reference Settings Description DIFF In differential DIFF mode NI 621x devices measure the difference in voltage between two AI signals RSE In referenced single ended RSE mode NI 621x devices measure the voltage of an AI signal relative to AI GND NRSE In non referenced single ended NRSE mode NI 621x devices measure the voltage of an AI signal relative to the AI SENSE input National Instruments Corporation 4 3 NI USB 621x User Manual Chapter 4 Analog Input AI Ground Reference The A ground reference setting determines how you should connect your AI signals to the NI 621x device Refer to Chapter 5 Connecting AI Signals on the USB 6210 6211 Devices section for more information 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 NI 621x devices implement the different analog input
23. Al FIFO M Series 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 M Series devices can handle multiple A D conversion operations with DMA interrupts or programmed I O Analog Input Range NI USB 621x User Manual The input range affects the resolution of the M Series device for an AI channel For example a 16 bit ADC converts analog inputs into one of 65 536 2101 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 516 305 uV M Series devices use a calibration method that requires some codes typically about 5 of the codes to lie outside of the specified range This 4 2 ni com Chapter 4 Analog Input calibration method improves absolute accuracy but it increases the nominal resolution of input ranges by about 5 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 For more information about setting ranges refer to the NJ DAQmx Help or the LabVIEW 8 x Help Table
24. Ground Referenced Signal Sources sese eee 5 9 When to Use Differential Connections with Ground Referenced Signal SOULCES serre i re nn E Msn als A 5 10 When to Use Non Referenced Single Ended NRSE Connections with Ground Referenced Signal Sources 5 10 When to Use Referenced Single Ended RSE Connections with Ground Referenced Signal Sources 5 11 Using Differential Connections for Ground Referenced Signal Sources 5 12 Using Non Referenced Single Ended NRSE Connections for Ground Referenced Signal Sources 5 13 Chapter 6 Connecting Al Signals on the USB 6215 6218 Devices Differential Measurement sis 6 1 Differential Pairs arnir a einen nitrate M evra ed lee dde E eee 6 1 Referenced Single Ended RSE Measurements sese eee eee eee eee eee 6 3 Non Referenced Single Ended NRSE Measurements sese eee eee eee eee 6 4 National Instruments Corporation vij NI USB 621x User Manual Contents Chapter 7 Analog Output Analog Output Circuitry sissioni a nee ner seit en tennis 7 1 AO Ran pee si ns Mn A Mt A ben E bare tell ey 7 2 Minimizing Glitches on the Output Signal 7 2 Analog Output Data Generation Methods 7 2 Software Timed Generations 7 2 Hardware Timed Generations ss 7 2 Analog Output Digital Triggering ss 7 4 Connecting Analog Output Signals ss 7 4 Analog Output Timing Signals ss 7 5 AQ Start Tripper Signal en ten Seve gels 7 5 Using a Digital Source sfinnninni
25. I O is typically used in software timed on demand operations Refer to the Software Timed Generations section of Chapter 7 Analog Output for more information Changing Data Transfer Methods USB M Series 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 13 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 M Series 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 7 Analog Output e The Counter Triggering section of Chapter 9 Counters Triggering with a Digital Source Your DAQ 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 be either the rising edge or falling edge of the digital signal A rising edge is a transition from a low logic level to a h
26. 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 9 18 ni com Chapter 9 Counters Figure 9 20 shows an example of a single two signal edge separation measurement Counter Armed i a Measured Interval AUX 4 GATE i l L SOURCE Counter Value 00001 2 3 4 5 6 7 8 8 8 HW Save Register 8 Figure 9 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 Figure 9 21 shows an example of a buffered two signal edge separation
27. Scanning Order 4 7 Avoid Switching from a Large to a Small Input Range 4 7 Insert Grounded Channel between Signal Channels sss sese 4 7 Minimize Voltage Step between Adjacent Channels sss sees 4 8 Avoid Scanning Faster Than Necessary sees esse eee eee eee 4 8 Example sez secs chs enzenea oan he D UE E en ns hates 4 8 Example 2e int a a ee gs ee AA Sn es 4 9 Analog Input Data Acquisition Methods 4 9 Software Timed Acquisitions ss 4 9 Hardware Timed Acquisitions sss sese eee eee 4 9 Bulleted areen din Bs Ae Mie i eae a Lie aes oi Dites 4 10 Non Bu tlered 2652 Sens Tea Ne tie aino 4 10 Analog Input Digital Triggering ss 4 10 Field Wiring Considerations ss 4 11 Analog Input Timing Signals ss 4 11 Al Sample ClockKS16nal cic mesrine its is be ete ets 4 14 Using an Internal Source wo esse esse sees resen enen 4 15 Using an External Source ss 4 15 Routing AI Sample Clock Signal to an Output Terminal 4 15 Other Timing Requirement sss sese sees eee ee eee 4 15 AI Sample Clock Timebase Signal 4 16 Al Convert Clock Signalisation Mets 4 16 Using an Internal Source sss esse esse eee eee 4 17 Using an External Source ss 4 17 Routing AI Convert Clock Signal to an Output Terminal 4 17 Using a Delay from Sample Clock to Convert Clock sss esse ee 4 17 Other Timing Requirement
28. and two counters lt gt gt g bold italic monospace 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 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 Radio Frequency Interference document which can be found at ni com manuals 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 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
29. are sampled in finite mode e After a hardware reference trigger in finite mode e With a software command in continuous mode An acquisition that uses a start trigger but not a reference trigger is sometimes referred to as a posttriggered acquisition Using a Digital Source To use ai StartTrigger with a digital source specify a source and an edge The source can be any of the following signals e PHL 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 8 x Help for more information You also can specify whether the measurement acquisition begins on the rising edge or falling edge of ai StartTrigger Routing Al Start Trigger to an Output Terminal You can route ai StartTrigger out to any PFI lt 4 8 gt or PFI lt 12 15 gt terminal The output is an active high pulse National Instruments Corporation 4 21 NI USB 621x User Manual Chapter 4 Analog Input The device also uses ai StartTrigger to initiate pretriggered DAQ operations In most pretriggered applications a software trigger generates ai StartTrigger Refer to the AJ Reference Trigger Signal section for a complete description of the use of ai StartTrigger and ai ReferenceTrigger in a pretriggered DAQ operation Al Reference Trigger Signal Use a reference trigger ai ReferenceTrigger signal to stop a
30. choosing frequency measurement 9 13 circular buffered acquisition 4 10 clock generation 12 1 sample 9 32 common mode noise 11 2 configuring AI ground reference settings in software 4 5 connecting analog input signals 5 1 6 1 analog output signals 7 4 digital I O signals 8 3 floating signal sources 5 3 ni com ground referenced signal sources 5 9 PFI input signals 10 3 connections for floating signal sources 5 9 single ended for floating signal sources 5 9 single ended RSE configuration 5 9 connector information 3 1 USB 6210 pinout A 1 USB 6211 pinout A 4 USB 6215 pinout A 4 USB 6218 pinout A 7 considerations for field wiring 4 11 for multichannel scanning 4 6 continuous pulse train generation 9 22 controlling counting direction 9 2 conventions used in the manual xiii counter input and output 9 29 Counter n A signal 9 28 Counter n Aux signal 9 27 Counter n B signal 9 28 Counter n Gate signal 9 27 Counter n HW Arm signal 9 28 Counter n Internal Output signal 9 29 Counter n Source signal 9 26 Counter n TC signal 9 29 Counter n Up_Down signal 9 28 Counter n Z signal 9 28 counter output applications 9 20 counter signals Counter n A 9 28 Counter n Aux 9 27 Counter n B 9 28 Counter n Gate 9 27 Counter n HW Arm 9 28 Counter n Internal Output 9 29 Counter n Source 9 26 Counter n TC 9 29 Counter n Up_Down 9 28 National Instruments Corporation 1 3 I
31. drives paths directories programs subprograms subroutines device names functions operations variables filenames and extensions National Instruments Corporation xiii NI USB 621x User Manual About This Manual 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 3 or later and where applicable version 7 0 or later of the NI application software NI DAQmx for Windows LabVIEW NI USB 621x User Manual 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 DAQm x Help If you are a new user use the Getting Started with LabVIEW manual to familiarize yourself with the LabVIEW graphical programming
32. environment and the basic LabVIEW features you use to build data acquisition and instrument control applications Open the Getting Started with 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 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 XIV ni com About This Manual tools Refer to the following locations on the Contents tab of the LabVIEW Help for information about NI DAQmx e Getting Started 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 e VI and 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 LabWindows CVI 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 wh
33. human being or computer can determine the value DAQ devices such as the M Series multifunction I O MIO devices SCXI signal conditioning modules and switch modules Megahertz A unit of frequency 1 MHz 10 Hz 1 000 000 Hz The numerical prefix designating 106 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 MXI Interface To Everything A custom ASIC designed by National Instruments that implements the PCI bus interface The MITE supports bus mastering for high speed data transfers over the PCI bus 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 NI USB 621x User Manual Glossary monotonicity multichannel multifunction DAQ multiplex mux NI NI DAQ NI DAQmx NI PGIA non referenced signal sources NI USB 621x User Manual 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 T
34. 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 Lag between making a change and the effect of the change Input Output The transfer of data to from a computer system involving communications channels operator interface devices and or data acquisition and control interfaces NI USB 621x User Manual Glossary impedance in instrument driver instrumentation amplifier interchannel delay interface interrupt interrupt request line kHz KS NI USB 621x User Manual 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 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 consecutive channels in an Al scan list The interchannel delay must be short enough to allow sampling of all the channels in th
35. is designated by the symbol T The number of periods of a signal Programmable Function Interface Programmable Gain Instrumentation Amplifier See channel NI USB 621x User Manual Glossary Plug and Play devices posttriggering power source ppm pretriggering pulse pulse width PXI PXI Express PXI_STAR NI USB 621x User Manual Devices that do not require DIP switches or jumpers to configure resources on the devices Also called switchless devices port 1 A communications connection on a computer or a remote controller 2 A digital port consisting of four or eight lines of digital input and or output The technique used on a DAQ device to acquire a programmed number of samples after trigger conditions are met 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 A rugged open system for modular instrumentation based on CompactPCI with special mechanical electrical and software features The PXIbus standard was originally developed by National Instruments in 1997 and is now managed by the PXIbus Sy
36. measurement acquisition To use a reference trigger specify a buffer of finite size and a number of pretrigger samples samples that occur before 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 Once 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 T Complete Buffer Figure 4 15 Reference Trigger Final Buffer NI USB 6
37. on 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 9 36 ni com Chapter 9 Counters Example Application That Works Incorrectly Duplicate Counting In Figure 9 33 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 eg oi i ae Source Counter Value _6 X7 Buffer Figure 9 33 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 timebase 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 9 34 Gate Source Counter detects rising Gate edge Counter value increments only one time for each Source pulse 80 MHz Timebase Counter Value Buffer z Ve EA Figure 9 34 Duplicate Count Prevention Example National Instru
38. or hardware timed acquisitions Hardware timed acquisitions can be buffered or non buffered 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 Hardware Timed Acquisitions With hardware timed acquisitions a digital hardware signal ai SampleClock 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 e The time between samples can be much shorter e The timing between samples is deterministic e Hardware timed acquisitions can use hardware triggering Hardware timed operations can be buffered or non buffered National Instruments Corporation 4 9 NI USB 621x User Manual Chapter 4 Analog Input 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
39. sese eee Chapter 12 Digital Routing and Clock Generation EOS NTT sentis ut ut 20 MHZ Timebase ss nd End ste 100 KHz Timebase oe eee cece eeeceeeeseeseeeseeseeeaeeseeeas Chapter 13 Bus Interface USB Signal Streams Data Transfer Methods USB Signal Stream Programmed W O sinni aaa Changing Data Transfer Methods sss Chapter 14 Triggering Triggering with a Digital Source Appendix A Device Specific Information ORI s PA O EEE ihe nine ni tnt eee SK e ETT USB OZI het m mo ti Mer diet fre A National Instruments Corporation xi Contents NI USB 621x User Manual Contents Appendix B Troubleshooting Appendix C Technical Support and Professional Services Glossary Index Device Pinouts Figure A 1 USB 6210 Pinout osaisi enie instants A 2 Figure A 2 USB 6211 6215 Pinout A 5 Figure AS oUSB 621 8 PINOUt at aise mienne ue mine unes A 8 NI USB 621x User Manual xii ni com About This Manual Conventions The NI 621x User Manual contains information about using the National Instruments USB 621x data acquisition DAQ devices with NI DAQmx 8 3 and later NI 621x devices feature up to 32 analog input AD channels up to two analog output AO channels up to eight lines of digital input DI up to eight lines of digital output DO
40. signal channels 4 7 installation hardware 1 3 NI DAQ 1 2 other software 1 2 instrument drivers NI resources C 1 NI USB 621x User Manual Index instrumentation amplifier 4 2 interface bus 13 1 isolated DAQ devices 11 1 benefits 11 2 common mode noise 11 2 isolators 11 1 K KnowledgeBase C 1 L LabVIEW documentation xiv LabWindows CVI documentation xv LED USB 6210 A 3 USB 6211 A 6 USB 6215 A 6 USB 6218 A 9 low impedance sources 4 6 M Series information A 1 specifications xvi A 1 Measurement Studio documentation xv measurements buffered period 9 7 buffered pulse width 9 5 buffered semi period 9 9 buffered two signal edge separation 9 19 choosing frequency 9 13 frequency 9 10 period 9 6 position 9 15 pulse width 9 5 semi period 9 9 single period 9 7 single pulse width 9 5 NI USB 621x User Manual 1 6 single semi period 9 9 single two signal edge separation 9 18 two signal edge separation 9 18 using quadrature encoders 9 15 using two pulse encoders 9 17 measuring high frequency with two counters 9 11 large range of frequencies using two counters 9 12 low frequency with one counter 9 10 averaged 9 11 methods data transfer 13 1 minimizing glitches on the output signal 7 2 output signal glitches B 3 voltage step between adjacent channels 4 8 multichannel scanning considerations 4 6 MUX 4 1 National Instruments support and servic
41. sources to the USB 6210 6211 device in NRSE mode 1 0 Connector Al lt 0 15 gt gt or Al lt 16 n gt O D P soe Ground Instrumentation Referenced v e Amplifier Signal s gs o Source PGIA Input Multiplexers Measured S V sli i Al SENSE Voltage Mode AI GND Noise ot E and Ground Potential 4 D Vem 2 M Series Device Configured in NRSE Mode 777 Figure 5 8 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 NRSE ground reference setting Connect the signal to one of AI lt 0 31 gt 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 inputs 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 RSE ground reference setting this difference in ground potentials would appear as an error in the measured voltage Using the DAQ Assistant you can configure the channels for RSE o
42. that counts events When it refers to an instrument it refers to a frequency counter G 4 ni com counter timer D D GND D SUB connector DAC DAQ DAQ device DAQ STC2 data acquisition Glossary A circuit that counts external pulses or clock pulses timing Digital ground signal A serial connector 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 1 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 2 Data acquisition The process of collecting and measuring the same kinds of electrical signals with A D and or DIO devices plugged into a computer and possibly generating control signals with D A and or DIO devices in the same computer A device that acquires or generates data and can contain multiple channels and conversion devices DAQ devices include plug in devices PCMCIA cards and DAQPad devices which connect to a computer USB or 1394 FireWire port SCXI modules are considered DAQ devices Data acquisition system timing controller chip The general concept of acquiring data a
43. using a pause trigger the pause trigger source is routed to the Counter n Gate signal input of the counter 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 9 29 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 soo LLL LALLA COUNTER VALUE 1 2 8 4 1 2 1 2 3i 1 SAMPLE CLOCK ee ee i 3 BUFFER i i TIME N to ty t tg L ts Figure 9 29 Sample Clock Example NI USB 621x User Manual 9 32 ni com Chapter 9 Counters Table 9 7 Time N Descriptions to At to the counter is armed No measurements are taken until the counter is armed ty The rising edge of Gate indicates the beginning of the first period to measure The counter begins counting rising edges of Source to The rising edge of the Sample Clock indicates that the USB M Series device should store the result of the measurement of the current period when the period ends ts The rising edge of Gate indicates the end of the first period The USB M Series device stores the counter value in the buffer t
44. with each pulse on ai SampleClock until the value reaches zero The sample counter is then loaded with the number of posttriggered samples in this example three National Instruments Corporation 4 13 NI USB 621x User Manual Chapter 4 Analog Input ai StartTrigger ai ReferenceTrigger n a ai SampleClock ai ConvertClock NON WANT Scan Counter 3 121141012121 2 1 14 1 O1 Figure 4 7 Pretriggered Data Acquisition Example If an ai ReferenceTrigger pulse occurs before the specified number of pretrigger samples are acquired the trigger pulse is ignored Otherwise when the ai ReferenceTrigger pulse occurs the sample counter value decrements until the specified number of posttrigger samples have been acquired USB M Series devices feature the following analog input timing signals e AL Sample Clock Signal e AI Sample Clock Timebase Signal e AI Convert Clock Signal e AI Convert Clock Timebase Signal e AIT Hold Complete Event Signal e AL Start Trigger Signal e AI Reference Trigger Signal e AIT Pause Trigger Signal Al Sample Clock Signal NI USB 621x User Manual Use the AI Sample Clock ai SampleClock signal to initiate a set of measurements Your M Series device samples the AI signals of every channel in the task once for every ai SampleClock A measurement acquisition consists of one or more samples You can specify an in
45. 21x User Manual 4 22 ni com Chapter 4 Analog Input Using a Digital Source To use ai ReferenceTrigger with a digital source specify a source and an edge The source can be the PFI lt 0 3 gt or PFI lt 8 11 gt signals 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 8 x Help for more information You also can specify whether the measurement acquisition stops on the rising edge or falling edge of ai ReferenceTrigger Routing Al Reference Trigger Signal to an Output Terminal You can route ai ReferenceTrigger out to any PFI lt 4 7 gt or PFI lt 12 15 gt 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 SampleClock specify a source and a polarity The source can be the PFI lt 0 3 gt or PFI lt 8 11 gt signals 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 8 x Help for more information National Instruments Corporation 4 23 NI USB 621x User Manual Chapter 4 Analog Input Getting Started with AI Applications i
46. 3 2 1 Good Good For information about connecting counter signals refer to the Default Counter Timer Pinouts section Position Measurement National Instruments Corporation 9 15 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 measured with two pulse encoders You can choose to do either a single point on demand position measurement or a buffered sample clock position measurement You must arm a counter to begin position measurements 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 NI USB 621x User Manual Chapter 9 Counters Figure 9 15 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 l wee
47. 4 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 ts The rising edge of Gate indicates the end of the third period Sample Clock asserts during this period so the USB M Series device stores the measurement in the buffer Cascading Counters 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 Measure Large Range of Frequencies Using Two Counters section Counter Filters 3 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 M Series devices use an onboard oscillator to generate the filter clock with a 40 MHz frequency 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 cloc
48. 9 4 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 PFI lt 0 3 gt PFI lt 8 11 gt In addition Counter 1 TC or Counter 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 PFI lt 4 7 gt or PFII lt 12 15 gt terminal ni com Chapter 9 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 selectors for the Counter n Gate signal Any of the following signals can be routed to the Counter n Gate inpu
49. Aux HW_Arm A B Z 10 2 ni com Chapter 10 PFI 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 e AI Convert Clock e AI Hold Complete Event e AI Reference Trigger e AI Sample Clock e AI Start Trigger e AO Sample Clock e AO Start Trigger e Counter n Source e Counter n Gate e Counter n Internal Output e Frequency Output le 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 Connecting PFI Input Signals All PFI input connections are referenced to D GND Figure 10 3 shows this reference and how to connect an external PFI 0 source and an external PFI 2 source to two PFI terminals National Instruments Corporation 10 3 NI USB 621x User Manual Chapter 10 PFI PFI Filters om 9 S PFI O PFI 2 PFI 0 PFI 2 Source Source D GND VY I O Connctor M Series Device Figure 10 3 PFI Input Signals Connections You can e
50. B 13 1 signals AI Convert Clock 4 16 AI Convert Clock Timebase 4 20 AI Hold Complete Event 4 21 AI Pause Trigger 4 23 AI Reference Trigger 4 22 AI Sample Clock 4 14 AI Sample Clock Timebase 4 16 AI Start Trigger 4 21 analog input 4 11 NI USB 621x User Manual l 8 analog output 7 5 AO Pause Trigger 7 6 AO Sample Clock 7 7 AO Sample Clock Timebase 7 8 AO Start Trigger 7 5 connecting analog input 5 1 6 1 connecting analog output 7 4 connecting digital I O 8 3 connecting PFI input 10 3 Counter n A 9 28 Counter n Aux 9 27 Counter n B 9 28 Counter n Gate 9 27 Counter n HW Arm 9 28 Counter n Internal Output 9 29 Counter n Source 9 26 Counter n TC 9 29 Counter n Up_Down 9 28 Counter n Z 9 28 counters 9 25 exporting timing output using PFI terminals 10 3 FREQ OUT 9 29 Frequency Output 9 29 minimizing output glitches B 3 output minimizing glitches on 7 2 simple pulse generation 9 20 single period measurement 9 7 point edge counting 9 2 pulse generation 9 20 retriggerable 9 21 with start trigger 9 20 pulse width measurement 9 5 semi period measurement 9 9 two signal edge separation measurement 9 18 single ended connections RSE configuration 5 9 single ended connections for floating signal sources 5 9 ni com software configuring AI ground reference settings 4 5 programming devices 2 4 software NI resources C 1 software timed acquisitions 4 9 generations 7 2 specific
51. Base 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 M Series 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 9 34 ni com Chapter 9 Counters External Signal Prescaler Rollover Used as Source by Counter Counter Value 0 X 1 Figure 9 31 Prescaling 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 Prescaling is not available if the counter Source is one of the internal timebases 80MH7Timebase 20MHzTimebase or 100kHzTimebase Duplicate Count Prevention
52. C A L AL JA eno Vom FH A GND Single Ended Non Referenced Signal Source DAQ Device Signal Source DAQ Device NRSE Al ALS LA SENSE LA SENSE AI GND v Al GND P cm E LLL Single Ended Referenced RSE Signal Source DAQ Device NOT RARES ALT USB 6210 6211 o Signal Source DAQ Device AI E GND amp Va v AA B AI GND Ground loop potential VA Vg are added to measured signal Refer to the Analog Input Ground Reference Settings section of Chapter 4 Analog Input for descriptions of the RSE NRSE and DIFF modes and software considerations Refer to the Connecting Ground Referenced Signal Sources section for more information NI USB 621x User Manual 5 2 ni com Chapter 5 Connecting Al Signals on the USB 6210 6211 Devices 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 DIFF 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 c
53. Chapter 10 PFI for more information Digital Isolation The USB 6215 6218 uses 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 e 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 e Improved accuracy lIsolation improves measurement accuracy by physically preventing ground loops Ground loops a common source of error and noise are the result of a measurement system having multiple grounds at different potentials e Improved safety Isolation creates an insulation barrier so you can make floating measurements while protecting the USB host computer against large transient voltage spikes Reducing Common Mode Noise NI USB 621x User Manual Isolated product
54. DAQ M Series NI USB 621 x User Manual Bus Powered M Series USB Devices August 2006 371931A 01 INSTRUMENTS 1 2 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 0 662 45 79 90 0 Belgium 32 0 2 757 00 20 Brazil 55 11 3262 3599 Canada 800 433 3488 China 86 21 6555 7838 Czech Republic 420 224 235 774 Denmark 45 45 76 26 00 Finland 385 0 9 725 725 11 France 33 0 1 48 14 24 24 Germany 49 0 89 741 31 30 India 91 80 41190000 Israel 972 0 3 6393737 Italy 39 02 413091 Japan 81 3 5472 2970 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 3390150 Portugal 351 210 311 210 Russia 7 095 783 68 51 Singapore 1800 226 5886 Slovenia 386 3 425 4200 South Africa 27 0 11 805 8197 Spain 34 91 640 0085 Sweden 46 0 8 587 895 00 Switzerland 41 56 200 51 51 Taiwan 886 02 2377 2222 Thailand 662 278 6777 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 Instruments Web site at ni com info and enter the info code feedback 2006 National Instruments Cor
55. E mode 5 9 when to use in differential mode 5 3 when to use in NRSE mode 5 4 when to use in RSE mode 5 3 FREQ OUT signal 9 29 frequency division 9 24 generation 9 23 generator 9 23 frequency measurement 9 10 Frequency Output signal 9 29 G generations analog output data 7 2 buffered hardware timed 7 3 clock 12 1 continuous pulse train 9 22 frequency 9 23 hardware timed 7 2 pulse for ETS 9 24 pulse train 9 22 retriggerable single pulse 9 21 simple pulse 9 20 single pulse 9 20 single pulse with start trigger 9 20 software timed 7 2 getting started 1 2 National Instruments Corporation l 5 Index AI applications in software 4 24 AO applications in software 7 9 DIO applications in software 8 4 ghost voltages when sampling multiple channels B 1 ground reference connections checking B 1 ground reference settings 4 2 4 3 analog input 4 3 ground referenced signal sources connecting 5 9 description 5 9 using in differential mode 5 12 using in NRSE mode 5 13 when to use in differential mode 5 10 when to use in NRSE mode 5 10 when to use in RSE mode 5 11 H hardware 1 3 2 1 hardware timed acquisitions 4 9 hardware timed generations 7 2 help technical support C 1 I O connector 3 1 USB 6210 pinout A 1 USB 6211 pinout A 4 USB 6215 pinout A 4 USB 6218 pinout A 7 T O protection 8 2 10 6 input signals using PFI terminals as 10 2 insertion of grounded channels between
56. ET installed to view the NI Measurement Studio Help Device Documentation and Specifications Training Courses The NI 621x Specifications contains all specifications for the USB 6210 USB 6211 USB 6215 and USB 6218 M Series devices NI DAQ 7 0 and later includes the Device Document Browser which contains online documentation for supported DAQ SCXI and switch devices such as help files describing device pinouts features and operation and PDF files of the printed device documents You can find view and or print the documents for each device using the Device Document Browser at any time by inserting the CD After installing the Device Document Browser device documents are accessible from Start All Programs National Instruments NI DAQ Browse Device Documentation 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 le Note You can download these documents at ni com manuals NI USB 621x User Manual DAQ specifications and some DAQ 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 In
57. KL Note The sampling rate is the fastest you can acquire data on the device and still achieve accurate results For example if an M Series 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 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 SampleClock until the value reaches zero and all desired samples have been acquired ai StartTrigger ai SampleClock ai ConvertClock Sample Counter Figure 4 6 Posttriggered Data Acquisition Example 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 StartTrigger can be either a hardware or software signal If ai StartTrigger is set up to be a software start trigger an output pulse appears on the ai StartTrigger line when the acquisition begins When the ai StartTrigger pulse occurs the sample counter is loaded with the number of pretriggered samples in this example four The value decrements
58. Manual Chapter 8 Digital I O Getting Started with DIO Applications in Software You can use the M Series device in the following digital I O applications e Static digital input e Static digital output e Digital waveform generation e Digital waveform acquisition e DI change detection le Note For more information about programming digital I O applications and triggers in software refer to the NJ DAQmx Help or the LabVIEW 8 x Help NI USB 621x User Manual 8 4 ni com Counters M Series devices have two general purpose 32 bit counter timers and one frequency generator as shown in Figure 9 1 The general purpose counter timers can be used for many measurement and pulse generation applications Input Selection Muxes Counter 0 Counter 0 Source Counter 0 Timebase Gana Counter 0 Internal Output Counter 0 Aux Counter 0 HW Arm Counter 0 A Counter 0 TC Counter 0 B Counter 0 Up Down x Counter 0 Z Input Selection Muxes Counter 1 Counter 1 Source Counter 1 Timebase lt Counter 1 Gale Counter 0 Internal Output ka D Counter 1 Aux D Counter 1 HW Arm A Counter 1 A Counter 0 TC D Counter 1 B Counter 1 Up_Down a D Counter 1 Z Input Selection Muxes Frequency Generator D Frequency Output Timebase National Instruments Corporation Figure 9 1 M Series Counters 9 1 Freq Out NI USB 621x User Man
59. National Instruments Corporation 7 7 NI USB 621x User Manual Chapter 7 Analog Output Figure 7 5 shows the relationship of ao SampleClock to ao StartTrigger ao SampleClockTimebase ao StartTrigger ao SampleClock Delay From Start Trigger Figure 7 5 ao SampleClock and ao StartTrigger AO Sample Clock Timebase Signal The AO Sample Clock Timebase ao SampleClockTimebase signal is divided down to provide a source for ao SampleClock You can route any of the following signals to be the AO Sample Clock Timebase ao SampleClockTimebase signal s 20 MHz Timebase N 100 kHz Timebase e PFI lt 0 3 gt PFI lt 8 11 gt ao SampleClockTimebase is not available as an output on the I O connector You might use ao SampleClockTimebase 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 SampleClock rather than ao SampleClockTimebase NI USB 621x User Manual 7 8 ni com Chapter 7 Analog Output Getting Started with AO Applications in Software You can use an NI 621x device in the following analog output applications e Single point on demand generation e Finite generation e Continuous generation e Waveform generation You can perform these generations through programmed I O or USB Signal Stream data t
60. 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 DIFF input connections are recommended for greater signal integrity for any input signal that does not meet the preceding conditions 5 10 ni com Chapter 5 Connecting Al Signals on the USB 6210 6211 Devices In the single ended modes more electrostatic and magnetic noise couples into the signal connections than in DIFF 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 NRSE Connections for Ground Referenced Signal Sources section for more information about NRSE connections When to Use Referenced Single Ended RSE Connections with Ground Referenced Signal Sources Do not use RSE connections with ground referenced signal sources Use NRSE or DIFF connections instead As shown in the bottom rightmost ce
61. Operating normally Connected to USB Hi Speed port Refer to the NI 621x Specifications for more information Double blink Connected to USB full speed port Device performance might be affected Refer to the NI 621x Specifications for more information NI USB 621x User Manual A 10 ni com Troubleshooting Analog Input This section contains common questions about M Series devices If 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 an M Series device Otherwise you must decrease the sample rate for each channel Another common cause of chann
62. Period Measurement 9 7 Buffered Period Measurement 9 7 Semi Period Measurement nenen 9 9 Single Semi Period Measurement 9 9 Buffered Semi Period Measurement 9 9 Frequency Measurement 2 20 23 cccusssssedsssssassassescscsuesis eadasescdpessseasicegsasessdges eves 9 10 Method 1 Measure Low Frequency with One Counter 9 10 Method 1b Measure Low Frequency with One Counter Averaged TT 9 11 Method 2 Measure High Frequency with Two Counters 9 11 Method 3 Measure Large Range of Frequencies Using TWo Counters sssisssis disent sinus umo 9 12 Choosing a Method for Measuring Frequency sss sees eee eee 9 13 Position Measurement assez ss ss zeis ssg os veizo 2o csxe arto Ta cyo Z Ten eestas Tan es 9 15 Measurements Using Quadrature Encoders sss sees 9 15 Measurements Using Two Pulse Encoders sss sese 9 17 Two Signal Edge Separation Measurement 9 18 Single Two Signal Edge Separation Measurement sss sese sees 9 18 Buffered Two Signal Edge Separation Measurement sss sees 9 19 Counter Output Applications enseri aie a RS ERE E 9 20 Simple Pulse Generation ss 9 20 Single Pulse Generation 9 20 Single Pulse Generation with Start Trigger 9 20 Retriggerable Single Pulse Generation sees sees eee eee 9 21 Pulse Train G n ration he misent ig dated Nantai
63. Q device Refer to Device Routing in MAX in the NI DAQmx Help or the LabVIEW 8 x Help for more information You also can specify whether the waveform generation begins on the rising edge or falling edge of ao StartTrigger Routing AO Start Trigger Signal to an Output Terminal You can route ao StartTrigger out to any PFI lt 4 7 gt or PFI lt 12 15 gt terminal The output is an active high pulse AO Pause Trigger Signal Use the AO Pause Trigger signal ao PauseTrigger to mask off samples in a DAQ sequence That is when ao PauseTrigger is active no samples occur ao PauseTrigger does not stop a sample that is in progress The pause does not take effect until the beginning of the next sample If you are using any signal other than the onboard clock as the source of your sample clock the generation resumes as soon as the pause trigger is deasserted and another edge of the sample clock is received as shown in Figure 7 4 Pause Trigger Sample Clock Figure 7 4 ao PauseTrigger with Other Signal Source Using a Digital Source To use ao PauseTrigger specify a source and a polarity The source can be the PFI lt 0 3 gt or PFI lt 8 11 gt signals NI USB 621x User Manual 7 6 ni com Chapter 7 Analog 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 8
64. SE Connections In the NRSE connection configuration each input channel is measured with respect to AI SENSE 6 4 ni com Analog Output Many M Series devices have analog output functionality NI 621x devices that support analog output have two AO channels controlled by a single clock and capable of waveform generation Refer to Appendix A Device Specific Information for information about the capabilities of your device Figure 7 1 shows the analog output circuitry of M Series devices AO 0 AO 1 Isolation Barrier i USB 6215 and USB 6218 devices only Digital AO FIFO Isolators AO Data AO Sample Clock Figure 7 1 M Series Analog Output Circuitry Analog Output Circuitry DACs Digital to analog converters DACs convert digital codes to analog voltages 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 National Instruments Corporation 7 1 NI USB 621x User Manual Chapter 7 Analog Output DACs It allows you to download the points of a waveform to your M Series device without host computer interaction AO Sample Clock The AO Sample Clock signal reads a sample from the DAC FIFO and generates the AO voltage AO Range The AO Range is 10 V for NI 621x devices Minimizing Glitches on the Output Signal When you use a DAC to generate a w
65. The rising edge of Gate indicates the end of the second period The USB M Series device stores the counter value in the buffer 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 NI USB 621x User Manual 9 8 ni com Chapter 9 Counters Semi Period Measurement 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 Buffered Semi Period Measurement In buffered semi period measurement on each edge of the Gate signal th
66. Training Courses hisiorio e aa ee E r E E anis tt xvi Technical Support on the Web xvi Chapter 1 Getting Started Installing NEDAQMX s Aeara a i ee aa e 1 2 Installing Other Rofe ss inier r er a a EE EEEE EEE REE 1 2 Installing the Hardware na aa OR a A i 1 3 D vice Pin outs Siessen activi ae A a E A E EAA Ae Ai EREE 1 3 Device Specifications sister tentent paso ia soara ZTE RRR OER AIE Sanapa DR Ta 1 3 IS le 1 3 Chapter 2 DAQ System Overview DAQ Hard Ware issus A nes time ten rene ennemis seit EN Ey 2 1 DAQOSTEZ ss nee med st NY ne HO eed 2 2 Calibration Circuitry sisi mn hit item S 2 2 Signal Const OMI ss Mes Al Herr its dr a e seen en 2 3 Sensors and Transducers x cisscceccccssessiccssavevcecvscsestenscuvecseaccduscesaaceaad RR NEUI ov het 2 3 Programming Devices in Software 2 4 Chapter 3 Connector Information UO Connector Signal Descriptions ss 3 1 FES V POWEL uen nn ter mener ent ea Din QE 3 2 5V Power as an Outpuliey i ler wane nee alka es 3 2 X Vi POWEL AS an T ET uns mien menant 3 3 National Instruments Corporation v NI USB 621x User Manual Contents Chapter 4 Analog Input Analog Input Circultty sorserien ss trie rime ni niet ess 4 1 Analog Input TT e nn n a a 4 2 Analog Input Ground Reference Settings ss 4 3 Configuring AI Ground Reference Settings in Software 4 5 Multichannel Scanning Considerations sss sees ee ee ee eee eee eee 4 6 Use Low Impedance Sources 4 6 Carefully Choose the Channel
67. ULD 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 sis nement ent eme tn Nina sn en xiii Related Documentations atiet E EEEE AE xiv NEDA Qmx for Windows xiv LabVIEW souien aa aa a aa aaia ie xiv LabWindowst M CVIM re a E E R totes ede E EEA XV Measurement Studios ste an 70273 a aT a TE Sarr XV ANSI C without NI Application Software ss XV NET Languages without NI Application Software sss see eee ee eee xvi Device Documentation and Specifications xvi
68. ase Frequency Ft 80 MHz 80 MHz Actual Number of Timebase Ft F1 1600 16 Periods Worst Case Measured Number of Ft F1 1 1599 15 Timebase Periods Measured Frequency Ft F1 Ft F1 50 125 kHz 5 33 MHz Error Ft F1 Ft F1 F1 125 kHz 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 disadvantage of Method 1b is that you have to take K 1 measurements These measurements take more time and consume some of the available USB bandwidth 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 NI USB 621x User Manual 9 14 ni com Chapter 9 Counters Table 9 3 summarizes some of the differences in methods of measuring frequency Table 9 3 Frequency Measurement Method Comparison Measures High Measures Low Number of Frequency Frequency Number of Measurements Signals Signals Method Counters Used Returned Accurately Accurately 1 1 1 Poor Good 1b 1 Many Fair Good 2 lor2 1 Good Poor
69. ations A 1 device 1 3 USB 6210 A 3 USB 6211 A 6 USB 6215 A 6 USB 6218 A 9 start trigger 9 31 static DIO 8 2 using PFI terminals as 10 3 support technical C 1 switching from a large to a small input range 4 7 synchronous counting mode 9 35 T technical support xvi C 1 terminal configuration 4 3 analog input 4 1 terminals connecting counter 9 29 NI DAQmx default counter 9 29 Timebase 100 kHz 12 2 20 MHz 12 1 80 MHz 12 1 timed acquisitions 4 9 timing output signals exporting using PFI terminals 10 3 training xvi training and certification NI resources C 1 National Instruments Corporation 1 9 Index transducers 2 3 trigger 14 1 arm start 9 31 pause 9 31 start 9 31 triggering 14 1 analog input 4 10 counter 9 31 with a digital source 14 1 troubleshooting analog input B 1 analog output B 3 troubleshooting NI resources C 1 two signal edge separation measurement 9 18 buffered 9 19 single 9 18 USB Signal Streams 13 1 USB bulk transfers 13 1 USB signal stream as a transfer method 13 1 changing data transfer methods 13 2 USB 6210 A 1 analog input signals 5 1 LED A 3 pinout A 1 specifications A 3 USB 6211 A 4 analog input signals 5 1 LED A 6 pinout A 4 specifications A 6 USB 6215 A 4 analog input signals 6 1 LED A 6 pinout A 4 specifications A 6 NI USB 621x User Manual Index USB 6218 A 7 analog input signals 6 1 LED A 9 pinout
70. aveform 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 either can perform software timed or hardware timed generations Software Timed Generations With a software timed generation 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 With a hardware timed generation a digital hardware signal controls the rate of the generation This signal can be generated internally on your device or provided externally NI USB 621x User Manual 7 2 ni com Chapter 7 Analog Output Hardware timed generations have several advantages over software timed acquisitions e The time between samples can be much short
71. 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 refer to the appropriate location Help Patents in your software the patents txt file on your CD or 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 DESIGNER ADVERSE FACTORS SUCH AS THESE ARE HEREAFTER COLLECTIVELY TERMED SYSTEM FAILURES ANY APPLICATION WHERE A SYSTEM FAILURE WO
72. ce 1 3 USB 6210 A 1 USB 6211 A 4 USB 6215 A 4 USB 6218 A 7 pins default 9 29 position measurement 9 15 power 5 V 3 2 power 5 V input 3 3 power 5 V output 3 2 power up states 10 6 prescaling 9 34 programmable function interface 10 1 programmable power up states 10 6 programmed I O 13 2 changing data transfer methods 13 2 programming devices in software 2 4 programming examples NI resources C 1 pulse encoders 9 17 pulse generation for ETS 9 24 pulse train generation 9 22 continuous 9 22 pulse width measurement 9 5 buffered 9 5 single 9 5 Q quadrature encoders 9 15 R reciprocal frequency measurement 9 12 referenced single ended connections using with floating signal sources 5 9 when to use with floating signal sources 5 3 NI USB 621x User Manual Index when to use with ground referenced signal sources 5 11 related documentation xiv retriggerable single pulse generation 9 21 routing digital 12 1 RSE configuration 5 9 RSE connections using With floating signal sources 5 9 when to use with floating signal sources 5 3 when to use with ground referenced signal sources 5 11 S sample clock 9 32 edge counting 9 3 scanning speed 4 8 semi period measurement 9 9 buffered 9 9 single 9 9 sensors 2 3 settings analog input ground reference 4 3 signal conditioning 2 3 signal descriptions 3 1 signal sources floating 5 3 ground referenced 5 9 Signal Stream US
73. ct 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 Avoid Scanning Faster Than Necessary NI USB 621x User Manual Designing your system to scan at slower speeds gives the NI PGIA more time to settle to a more accurate level Here are two examples to consider Example 1 Averaging many AI samples can increase the accuracy of the reading by decreasing noise effects In general the more points you average the more accurate the final result However y
74. d PFI lt 12 15 gt P1 lt 0 7 gt The USB 621x monitors the total current and will drop the voltage on all of the digital outputs and the 5 V terminals if the 50 mA limit is exceeded NI USB 621x User Manual 3 2 ni com Chapter 3 Connector Information 5 V Power as an Input If you have high current loads for the digital 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 350 mA self resetting 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 National Instruments Corporation 3 3 NI USB 621x User Manual Analog Input Figure 4 1 shows the analog input circuitry of NI 621x devices Isolation Barrier USB 6215 and USB 6218 devices only z Al lt 0 n gt 2 O DIFF RSE Digital c N U S or NRSE NI PGIA ADC Al FIFO isolators Al Data O AI SENSE Input Range AI GND Selection i i 1 1 Al Terminal i i Configuration f i Selection i H Figure 4 1 M Series Analog Input Circuitry Analog Input Circuitry 1 0 Connector You can connect analog input signals to the M Series device through the I O connector The prope
75. d conversion devices Plug in products PCMCIA cards and devices such as the DAQPad 1200 which connects to your computer parallel port are all examples of DAQ devices SCXI modules are distinct from devices with the exception of the SCXI 1200 which is a hybrid Differential mode An analog input mode consisting of two terminals both of which are isolated from computer ground whose difference is measured 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 G 6 ni com digital trigger DIO DMA DMA controller chip driver E E Series edge detection EEPROM encoder EXTCLK external trigger EXTREF National Instruments Corporation G 7 Glossary A TTL level signal having two discrete levels A high and a low level Digital input output Direct Memory Access A method by which data can be transferred to f
76. e 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 9 10 shows an example of a buffered semi period measurement Counter Armed GATE SOURCE Fa L m L E ne ER eee gt Le Counter Value 0 NO 02 Buffer Figure 9 10 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 National Instruments Corporation 9 9 NI USB 621x User Manual Chapter 9 Counters 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 Frequency Measurement NI USB 621x User Manual You can use the counters to measure frequency in several different ways You can choose one of the following methods depending on your application Method 1 Measure Low Frequency with One Counter I
77. e 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 ConvertClock 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 Kilohertz A unit of frequency 1 kHz 10 1 000 Hz 1 000 samples G 10 ni com L LabVIEW LED lowpass filter LSB m M Series measurement measurement device MHz micro u MIO MITE module National Instruments Corporation G 11 Glossary 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 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 observation to a domain where a
78. e driver software Counter n Internal Output and Counter n TC Signals Counter n TC is an internal signal that asserts when the counter value is 0 The Counter n Internal Output signal changes in response to Counter n TC The two software selectable output options are pulse on TC and toggle output polarity on TC The output polarity is software selectable for both options Routing Counter n Internal Output to an Output Terminal You can route Counter n Internal Output to any PFI lt 4 7 gt or PFI lt 12 15 gt terminal Frequency Output Signal The Frequency Output FREQ OUT signal is the output of the frequency output generator Routing Frequency Output to a Terminal You can route Frequency Output to any PFI lt 4 7 gt or PFI lt 12 15 gt terminal Default Counter Timer Pinouts By default NI DAQmx routes the counter timer inputs and outputs to the PFI pins shown in Tables 9 5 and 9 6 Table 9 5 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 National Instruments Corporation 9 29 NI USB 621x User Manual Chapter 9 Counters Table 9 5 Default NI DAQmx Counter Timer Pins for USB 6210 6211 6215 Devices Continued Counter Timer Signal Default Terminal N
79. e impedances if possible The parasitic currents react with these impedances Creating an AC Return Path A Caution Adding a capacitor will degrade the USB M Series device withstand voltage and isolation specifications Withstand voltage must be retested by an approved testing facility after adjustments are made to the measurement system 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 lsolated Systems A non isolated measurement system is one where the device s isolated front end connects to earth ground National Instruments Corporation 11 3 NI USB 621x User Manual Chapter 11 Isolation and Digital Isolators 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 a capacitor between the device s isolated ground and earth ground NI USB 621x User Manual 11 4 ni com Digital Routing and Clock Generation The digital routing circuitry has the following main functions e Manages the flow of data be
80. e 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 5 5 NI USB 621x User Manual Chapter 5 Connecting Al Signals on the USB 6210 6211 Devices NI USB 621x User Manual Floating Signal Source C R is about 100 times source impedance of sensor Al o lt Al o Al SENSE o Al GND Figure 5 2 Differential Connections for Floating Signal Sources with Single Bias 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 621x device as shown in Figure 5 3 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 ni com Chapter 5 Connecting Al Signals on the USB 6210 6211 Devices Floating Signal Y S
81. ed either in software or in hardware When implemented in software Lab VIEW 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 condition has occurred Analog output Analog channel 0 output signal Analog channel 1 output signal Analog channel 2 output signal Analog channel 3 output signal Analog output ground signal 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 G 2 ni com ASIC asynchronous block diagram BNC buffer bus buses C C calibration calibrator National Instruments Corporation G 3 Glossary Application specific integrated circuit A proprietary semiconductor component designed and manufactured to perform a set of specific functions for a specific customer 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 A
82. either software or hardware can stop it once a finite acquisition completes When using an internally generated ai SampleClock you also can specify a configurable delay from ai StartTrigger to the first ai SampleClock pulse By default this delay is set to two ticks of the ai SampleClockTimebase signal When using an externally generated ai SampleClock you must ensure the clock signal is consistent with respect to the timing requirements of ai ConvertClock Failure to do so may result in ai SampleClock pulses that are masked off and acquisitions with erratic sampling intervals Refer National Instruments Corporation 4 15 NI USB 621x User Manual Chapter 4 Analog Input to AI Convert Clock Signal for more information about the timing requirements between ai ConvertClock and ai SampleClock Figure 4 8 shows the relationship of ai SampleClock to ai StartTrigger ai SampleClockTimebase ai StartTrigger 1 ai SampleClock Delay From Start Trigger Figure 4 8 ai SampleClock and ai StartTrigger Al Sample Clock Timebase Signal You can route any of the following signals to be the AI Sample Clock Timebase ai SampleClockTimebase signal s 20 MHz Timebase N 100 kHz Timebase e PFI lt 0 3 gt PFI lt 8 11 gt ai SampleClockTimebase is not available as an output on the I O connector ai SampleClockTimebase is divided down to provide one of the possible sources fo
83. el 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 but my readings are random and drift rapidly What is wrong In DIFF 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 DIFF mode you must still reference the signal to the same ground level as the device reference There National Instruments Corporation B 1 NI USB 621x User Manual Appendix B Troubleshooting NI USB 621x User Manual are various methods of achieving this reference while maintaining a high common mode rejection ratio CMRR These methods are outlined in Chapter 5 Connecting AI Signals on the USB 6210 6211 Devices and Chapter 6 Connecting AI Signals on the USB 6215 6218 Devices 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 Con
84. en aa 9 31 Start RT nn Eine are AE wea em eee es 9 31 Pause Re T hits rm th hrs A Ulis a Esie dns 9 31 Other Counter Features a E E a ETE nina 9 32 Sample Clock nsss sains rein A uses meta rte NE 9 32 Cascading Count rsss sus iienaa ann ia a EEA teen 9 33 Counter Filters es isimni inpri iape tisse tn it son 9 33 Precise edhe MUR Bagh a ads RTE nee ler ie 9 34 Duplicate Count Prevention 9 35 Example Application That Works Correctly No Duplicate Counting RL 9 36 Example Application That Works Incorrectly Duplicate Counting c2 ccesessesestescsssecvteecssdsostanetsdeebvagsasaveseoeeseees 9 37 Example Application That Prevents Duplicate Count 9 37 Enabling Duplicate Count Prevention in NI DAQmx eee 9 38 Chapter 10 PFI Using PFI Terminals as Timing Input Signals oo sees 10 2 Exporting Timing Output Signals Using PFI Terminals eee eeeeeeeeeeeeeeeees 10 3 Using PFI Terminals as Static Digital I Os sss sese 10 3 Connecting PFI Input Signals s 10 3 BEL Falters sees Sess docs en at Recs ost tec a deve tends ne rire et naines 10 4 VO Protection 5eme aah ale ia oan weaves ees Eine 10 6 Programmable Power Up States 10 6 NI USB 621x User Manual X ni com Chapter 11 Isolation and Digital Isolators Digital Isola on ennn oneen ein ares EEE Benefits of an Isolated DAQ Device sss Reducing Common Mode Noise sss Creating an AC Return Path Isolated Systems Non Isolated Systems
85. er e The timing between samples can be deterministic e Hardware timed acquisitions can use hardware triggering Hardware timed operations can be buffered or non buffered During hardware timed AO generation data is moved from a PC buffer to the onboard FIFO on the DAQ 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 Once the specified number of samples has been written out the generation stops 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 several different 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 data 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 regeneratio
86. er 1 Source input F2 can be 80MHzTimebase 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 From Counter 0 the length of the pulse is N F1 From Counter 1 the length of the same pulse is J F2 Therefore the frequency of F1 is given by Fl 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 measures the desired accuracy how many counters are available and how long the measurement can take 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 1600 cycles of the National Instruments Corporation 9 13 NI USB 621x User Manual Chapter 9 Counters 80 MHz Timebase Your measurement may return 1600 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 9 2 illustrates this point Table 9 2 Frequency Measurement Method 1 Task Equation Example 1 Example 2 Actual Frequency to Measure F1 50 kHz 5 MHz Timeb
87. eration 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 NI USB 621x User Manual Glossary Timebase tout Traditional NI DAQ Legacy transducer trigger USB cm NI USB 621x User Manual 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 An upgrade to the earlier version of NI DAQ Traditional NI DAQ Legacy has the same VIs and functions and works the same way as NI DAQ 6 9 x You can use both Traditional NI DAQ Legacy and NI DAQm x on the same computer which is not possible with NI DAQ 6 9 x 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 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 Source clock period Source pulse width Transistor Transistor Logic A digital circuit composed of bipolar tra
88. es C 1 NI support and services C 1 NI DAQ documentation xiv device documentation browser xvi NI DAQmx default counter terminals 9 29 enabling duplicate count prevention 9 38 NI PGIA 4 2 non buffered hardware timed acquisitions 4 10 non cumulative buffered edge counting 9 4 non referenced single ended connections using with floating signal sources 5 8 using with ground referenced signal sources 5 13 when to use with floating signal sources 5 4 ni com when to use with ground referenced signal sources 5 10 NRSE connections using with floating signal sources 5 8 using with ground referenced signal sources 5 13 when to use with floating signal sources 5 4 when to use with ground referenced signal sources 5 10 0 on demand acquisitions 4 9 edge counting 9 2 timing 4 9 order of channels for scanning 4 7 other software 1 2 output signal glitches B 3 output signals minimizing glitches 7 2 overview 2 1 P pause trigger 9 31 period measurement 9 6 buffered 9 7 single 9 7 PFI 10 1 connecting input signals 10 3 exporting timing output signals using PFI terminals 10 3 filters 10 4 I O protection 10 6 programmable power up states 10 6 using terminals as static digital I Os 10 3 using terminals as timing input signals 10 2 PFI terminals as static digital I Os 10 3 pin assignments See pinouts National Instruments Corporation 1 7 Index pinouts counter default 9 29 devi
89. eveloping 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 and LabWindows CVI examples open the National Instruments Example Finder In LabVIEW select Help Find Examples e In LabWindows CVI select Help NI Example Finder Measurement Studio Visual Basic and ANSI C examples are located in the following directories e NI DAQmx examples for Measurement Studio supported languages are in the following directories Measurement Studio VCNET Examples NIDaq MeasurementStudio DotNET Examples NIDaq e NI DAQmx examples for ANSI C are in the NI DAQ Examples DAQmx ANSI C Dev directory For additional examples refer to zone ni com NI USB 621x User Manual 2 4 ni com Connector Information The I O Connector Signal Descriptions and 5 V Power sections contain information about NI 621x connectors Refer to Appendix A Device Specific Information for device I O connector pinouts 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
90. example of the symbols for isolated ground and non isolated ground Table 11 1 Ground Symbols Isolated Ground Non Isolated Ground Isolation 1 Barrier 1 1 1 1 Analog Input USB 6215 and USB 6218 devices only 1 1 Analog Output 8 Digital K Routing Digital Bus 8 Digital VO and Clock Isolators Interface O Generation Counters i H 7 477 Figure 11 1 General NI 621x Block Diagram 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 National Instruments Corporation 11 1 NI USB 621x User Manual Chapter 11 Isolation and Digital Isolators The isolated ground is an input to the USB 6215 6218 device The user must connect this ground to the ground of system being measured or controlled Refer to Chapter 5 Connecting AI Signals on the USB 6210 6211 Devices Chapter 6 Connecting AI Signals on the USB 6215 6218 Devices the Connecting Analog Output Signals section of Chapter 7 Analog Output the Connecting Digital I O Signals section of Chapter 8 Digital I O and the Connecting PFI Input Signals section of
91. f a single pulse width measurement GATE ee ee eee L SOURCE A A Counter Value 0 1 2 HW Save Register 2 Figure 9 6 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 National Instruments Corporation 9 5 NI USB 621x User Manual Chapter 9 Counters The counter 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 9 7 shows an example of a buffered pulse width measurement GATE SOURCE COUNTER VALUE BUFFER MIC Figure 9 7 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 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 secti
92. floating signal sources 5 5 using with ground referenced signal sources 5 12 when to use with floating signal sources 5 3 when to use with ground referenced signal sources 5 10 digital isolation 11 2 isolators 11 1 digital I O 8 1 block diagram 8 1 circuitry 8 1 connecting signals 8 3 getting started with applications in software 8 4 I O protection 8 2 NI USB 621x User Manual l 4 static DIO 8 2 triggering 14 1 digital routing 12 1 digital signals connecting 8 3 digital source triggering 14 1 documentation conventions used in manual xiii NI resources C 1 related documentation xiv double buffered acquisition 4 10 drivers NI resources C 1 duplicate count prevention 9 35 enabling in NI DAQmx 9 38 example 9 36 prevention example 9 37 E edge counting 9 2 buffered 9 3 non cumulative buffered 9 4 on demand 9 2 sample clock 9 3 single point 9 2 edge separation measurement buffered two signal 9 19 single two signal 9 18 enabling duplicate count prevention in NI DAQmx 9 38 encoders quadrature 9 15 encoding X1 9 15 X2 9 16 X4 9 16 equivalent time sampling 9 24 examples NI resources C 1 exporting timing output signals using PFI terminals 10 3 ni com F features counter 9 32 field wiring considerations 4 11 filters counter 9 33 PFI 10 4 floating signal sources connecting 5 3 description 5 3 using in differential mode 5 5 using in NRSE mode 5 8 using in RS
93. for DIFF 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 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 lt AI 1 AI 9 gt lt AI 2 AI 10 gt lt AI 3 AI 11 gt lt AI 4 AI 12 gt lt AI 5 AI 13 gt lt AI 6 AI 14 gt lt AI 7 AI 15 gt lt AI 16 AI 24 gt lt AI 17 AI 25 gt lt AI 18 AI 26 gt lt AI 19 AI 27 gt lt AI 20 AI 28 gt lt AI 21 AI 29 gt lt AI 22 AI 30 gt lt AI 23 AI 31 gt AI SENSE Input Analog Input Sense In NRSE mode the reference for each AI lt 0 31 gt signal is AI SENSE 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 National Instruments Corporation 3 1 NI USB 621x User Manual Chapter 3 Connector Information Table 3 1 1 0 Connector Signals Continued Signal Name Reference Direction Description AO GND Analog Output Ground AO GND is the reference for AO lt 0 1 gt All t
94. gital 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 that is common to both the positive and negative polarities of the input leads 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 1 A device that provides electrical connection 2 A fixture either male or female attached to a cable or chassis for quickly making and breaking one or more circuits A symbol that connects points on a flowchart 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
95. gnal AI Reference Trigger Signal and AI Pause Trigger Signal sections for information about these triggers 4 10 ni com Chapter 4 Analog Input A digital trigger can initiate these actions All NI 621x devices support digital triggering NI 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 DIFF 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 Analog Input Timing Signals In orde
96. 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 with this amplified voltage The amount of amplification the gain is determined by the analog input range as shown in Figure 4 2 Instrumentation Amplifier Vin o Measured Vin o Voltage Vm Vins Vin x Gain Figure 4 2 NI PGIA Table 4 3 shows how signals are routed to the NI PGIA Table 4 3 Signals Routed to the NI PGIA Signals Routed to the Positive Signals Routed to the Negative Settings Input of the NI PGIA V Input of the NI PGIA V _ RSE AI lt 0 31 gt AI GND NRSE AI lt 0 31 gt AI SENSE DIFF AI lt 0 7 gt AI lt 8 15 gt 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 NI USB 621x User Manual 4 4 ni com Chapter 4 Analog Input pairs that form differential input channels refer to the 7 0 Connector Signal Descriptions section of Chapter 3 Connector Information A 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 specifications document for your device Exceeding t
97. he factory calibration constants to the user modifiable section of the EEPROM Refer to the NJ DAQmx Help or the LabVIEW 8 x Help for more information about using calibration constants 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 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 the
98. he 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 input channel National Instruments The driver software needed to use National Instruments DAQ devices and SCXI components Some devices use Traditional NI DAQ Legacy others use NI DAQmx 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 c
99. he maximum input voltage of AI signals distorts the measurement results Exceeding the maximum input voltage rating also can damage the device and the computer NI is not liable for any damage resulting from such signal connections AI ground reference setting is sometimes referred to as AJ terminal configuration Configuring Al Ground Reference Settings in Software You can program channels on an M Series 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 RSE mode Differential Y DAGmx 4 Dev1 ait v patatas AI Voltage AI Voltage fi Dev jai v Figure 4 3 Enabling Multimode Scanning in LabVIEW 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 National Instruments Corporation 4 5 NI USB 621x User Manual Chapter 4 Analog Input Multichannel Scanning Considerations M Serie
100. he world System Integration If you have time constraints limited in house technical resources or other project challenges National Instruments Alliance Partner members can help To learn more call your local NI office or visit ni com alliance 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 electronic compatibility EMC and product safety You can obtain the DoC for your product by visiting ni com certification C 1 NI USB 621x User Manual Appendix C Technical Support and Professional Services 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 Numbers 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
101. hree 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 5 V Power These terminals provide a 5 V power Output source or can be used to externally power the PFI outputs PFI lt 0 3 gt D GND Input Programmable Function Interface or Static Digital PFI lt 8 11 gt P0 lt 0 7 gt 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 DGND Output Programmable Function Interface or Static Digital PFI lt 12 15 gt P1 lt 0 7 gt 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 NC No connect Do not connect signals to these terminals 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 PFI lt 4 7 gt an
102. ich includes step by step instructions about creating a measurement task using the DAQ 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 The NI Measurement Studio Help contains function reference measurement concepts and a walkthrough for using the Measurement Studio NI DAQmx NET and Visual C class libraries This help collection is integrated into the Microsoft Visual Studio NET documentation In Visual Studio NET select Help Contents le Note You must have Visual Studio NET installed to view the NJ Measurement Studio Help 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 National Instruments Corporation XV NI USB 621x User Manual About This Manual NET Languages without NI Application Software The NI Measurement Studio Help contains function reference and measurement concepts for using the Measurement Studio NI DAQmx NET and Visual C class libraries This help collection is integrated into the Visual Studio NET documentation In Visual Studio NET select Help Contents B Note You must have Visual Studio N
103. igh logic level A falling edge is a high to low transition Figure 14 1 shows a falling edge trigger 5V Digital Trigger OV Falling Edge Initiates Acquisition Figure 14 1 Falling Edge Trigger National Instruments Corporation 14 1 NI USB 621x User Manual Chapter 14 Triggering You also can program your DAQ device to perform an action in response to a trigger from a digital source The action can affect the following e Analog input acquisition e Analog output generation e Counter behavior NI USB 621x User Manual 14 2 ni com Device Specific Information This appendix contains device pinouts specifications cable and accessory choices and other information for the following USB M Series devices e USB 6210 e USB 6211 6215 e USB 6218 To obtain documentation for devices not listed here refer to ni com manuals USB 6210 USB 6210 Pinout Figure A 1 shows the pinout of the NI 6210 For a detailed description of each signal refer to the 7 0 Connector Signal Descriptions section of Chapter 3 Connector Information National Instruments Corporation A 1 NI USB 621x User Manual Appendix Device Specific Information PFI 0 P0 0 In PFI 1 P0 1 In q PFI 2 P0 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 NC NC RESERVED AIO AI 8 11 9 12 10 13 11 SENSE 112
104. igure 8 1 M Series Digital 1 0 Circuitry The DI terminals are named P0 lt 0 7 gt on the NI 621x device I O connector The DO terminals are named P1 lt 0 7 gt on the NI 621x device I O connector National Instruments Corporation 8 1 NI USB 621x User Manual Chapter 8 Digital I O The voltage input and output levels and the current drive levels of the DIO lines are listed in the specifications of your device Static DIO 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 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 Do not 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 PFI 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 Do not 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 Increasing Current Drive The total internal current limit for digital outputs and power down from the 5 V ter
105. ing Al Signals on the USB 6210 6211 Devices 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 DIFF 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 e Two analog input channels AI and AI are available DIFF signal connections reduce noise pickup and increase common mode noise rejection DIFF signal connections also allow 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 NRSE Connections with Ground Referenced Signal Sources NI USB 621x User Manual
106. ing 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 RSE Connections for Floating Signal Sources section for more information about RSE connections When to Use Non Referenced Single Ended NRSE Connections with Floating Signal Sources Only use NRSE 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 DIFF 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 DIFF 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 g
107. ing 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 channel 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 4 6 ni com Chapter 4 Analog Input 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 How Do I Create a Buffer to Decrease the Source Impedance of My Analog Input Signal by going to ni com info and entering the info code rdbbis 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 connected to channel 1 The input range for channel 0 is 10 V to 10 V and the input range
108. k 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 9 8 National Instruments Corporation 9 33 NI USB 621x User Manual Chapter 9 Counters Table 9 8 Filters N Filter Clocks Pulse Width Pulse Width Needed to Pass Guaranteed to Pass Guaranteed to Not Filter Setting Signal Filter Pass Filter 125 ns 5 125 ns 100 ns 6 425 us 257 6 425 us 6 400 us 2 55 ms 101 800 2 55 ms 2 54 ms Disabled The filter setting for each input can be configured independently On power up the filters are disabled Figure 9 30 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 1 2 3 4 1 2 3 4 5 high on five consecutive 40 MHz filter clocks Filtered Input Prescaling NI USB 621x User Manual Figure 9 30 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 55 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 Knowledge
109. l speed port Device performance might be affected Refer to the MI 621x Specifications for more information USB 6218 USB 6218 Pinout Figure A 3 shows the pinout of the NI 6218 For a detailed description of each signal refer to the 7 0 Connector Signal Descriptions section of Chapter 3 Connector Information National Instruments Corporation A 7 NI USB 621x User Manual Appendix Device Specific Information PFI 0 P0 0 In PFI 1 P0 1 In q PFI 2 P0 2 In PFI 3 P0 3 In D GND PFI 4 P1 0 Out PFI 5 P1 1 Out PEI 6 P1 2 Out PFI 7 P1 3 Out 5V D GND AO 0 AO 1 AO GND AIO AI 8 SL SL FL EL SL LL 0L 6 8L 99 t E lt a AI AI Al2 AI 10 A13 Al 11 Al SENSE Al 4 Al 12 AIS Al 13 AI GND l A16 AI 14 AI7 AI 15 ZE LE OE Be Be Le 92 GZ pe Ez ce IC OC pL BI LL PFI 8 P0 4 In h PFI 9 P0 5 In PFI 10 P0 6 In PFI 11 P0 7 In D GND PFI 12 P1 4 Out PFI 13 P1 5 Out PFI 14 P1 6 Out PFI 15 P1 7 Out 5 V D GND NC NC Al GND Al 16 Al 24 Al 17 Al 25 Al 18 Al 26 Al 19 Al 27 AI GND AI 20 AI 28 AI 21 AI 29 HAI GND AI 22 Al 30 Al 23 Al 31 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 NC No Connect Figure A 3 USB 6218 Pinout
110. 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 acquisition refers to the acquisition of a specific predetermined number of data samples Once the specified number of samples has been written out the generation stops If you use a reference trigger you must use finite sample mode 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 Non Buffered Hardware timed non buffered mode is not supported for USB M series devices Analog Input Digital Triggering NI USB 621x User Manual Analog input supports three different triggering actions e Start trigger e Reference trigger e Pause trigger Refer to the AJ Start Trigger Si
111. le 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 9 20 ni com Chapter 9 Counters Figure 9 23 shows a generation of a pulse with a pulse delay of four and a pulse width of three using the rising edge of Source GATE i Start Trigger l SOURCE L LU L ET EN OUT 4 Figure 9 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 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 gene
112. les Signal Conditioning eXtensions for Instrumentation The National Instruments product line for conditioning low level signals within an external chassis near sensors so that only high level signals are sent to DAQ devices in the noisy PC environment 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 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 G 16 ni com single ended output software applications software triggering source impedance synchronous task TC
113. ll of Table 5 1 there can be a potential difference between AI GND and the ground of the sensor In RSE mode this ground loop causes measurement errors National Instruments Corporation 5 11 NI USB 621x User Manual Chapter 5 Connecting Al Signals on the USB 6210 6211 Devices Using Differential Connections for Ground Referenced Signal Sources Figure 5 7 shows how to connect a ground referenced signal source to the USB 6210 6211 device configured in DIFF mode Al lol O D o So Ground Referenced Instrumentation Signal Vs 4 Amplifier Source of o Al l L Measured m Voltage Common oo t ooe Mode a H T Noise and cm 4 Ground S Potential 77 Input Multiplexers Creed AI SENSE Lot Al GND 1 0 Connector M Series Device Configured in DIFF Mode Figure 5 7 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 potential difference between the signal source and the device ground shown as V in the figure AILL and AI must both remain within 11 V of AI GND NI USB 621x User Manual 5 12 ni com Chapter 5 Connecting Al Signals on the USB 6210 6211 Devices Using Non Referenced Single Ended NRSE Connections for Ground Referenced Signal Sources Figure 5 8 shows how to connect ground reference signal
114. lso used to denote the amount of memory required to store one byte of data A pictorial description or representation of a program or algorithm 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 expansion 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 A precise traceable signal source used to calibrate instruments NI USB 621x User Manual Glossary cascading CE channel clock CMOS CMRR common mode rejection common mode signal connector convert rate count counter NI USB 621x User Manual Process of extending the counting range of a counter chip by connecting to the next higher counter European emissions control standard Pin or wire lead to which you apply or from which you read the analog or di
115. lways 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 9 4 ni com Chapter 9 Counters 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 pulses 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 will be 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 will wait 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 Figure 9 6 shows an example o
116. m 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 e Ifyou are using other application software refer to Common Sensors in the NI DAQmx Help or the LabVIEW 8 x Help National Instruments Corporation 2 3 NI USB 621x User Manual 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 NI DAQ 7 3 and later includes two NI DAQ drivers Traditional NI DAQ Legacy and NI DAQmx M Series devices use the NI DAQm x driver Each driver has its own API hardware configuration and software configuration Refer to the NJ DAQmx for USB Devices Getting Started Guide for more information about the two drivers NI DAQmx includes a collection of programming examples to help you get started d
117. ments Corporation 9 37 NI USB 621x User Manual Chapter 9 Counters 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 the USB 621x devices Disabling duplicate count prevention is not supported NI USB 621x User Manual 9 38 ni com PFI NI 621x devices have up to eight input and eight output Programmable Function Interface PFI signals which also can be used as static digital input or static digital output 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 Each PFI input also has a programmable debouncing filter Figure 10 1 shows the circuitry of an input PFI line PFI lt 0 3 gt P0 PFI lt 8 11 gt p0 HO Protection Weak Pull Down w gt Static DI Isolation Barrier USB 6215 and USB 6218 devices only PFI Filter
118. minals 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 Information NI USB 621x User Manual 8 2 ni com Chapter 8 Digital I O Connecting Digital 1 0 Signals The DI and DO signals PO lt 0 7 gt 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 8 2 5 V Isolation Barrier Ae USB 6215 and USB 6218 cr m C La devices only amp P1 lt 0 3 gt ote a Digital ola Isolators E of gt l TTL Signal P0 lt 0 3 gt 5 V ww oF gt Switch a Le z D GND UO Connector r M Series Device When using a USB 6215 6218 you must connect D GND and or AI GND to the local ground on your system Figure 8 2 Digital 1 0 Connections A Caution Exceeding the maximum input voltage ratings which are listed in the specifications document for each M Series device can damage the DAQ device and the computer NI is not liable for any damage resulting from such signal connections National Instruments Corporation 8 3 NI USB 621x User
119. n 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 will not be repeated New data must be continually written to the buffer If the program does not write new data to National Instruments Corporation 7 3 NI USB 621x User Manual Chapter 7 Analog Output the buffer at a fast enough rate to keep up with the generation the buffer will underflow and cause an error Analog Output Digital Triggering Analog output supports two different triggering actions e Sart trigger e Pause trigger A digital trigger can initiate these actions on the 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 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 7 2 shows how to make AO connections to the device Isolation Barrier USB 6215 and USB 6218 a Analog Output Channels
120. n Software You can use the M Series device in the following analog input applications e Single point analog input e Finite analog input e Continuous analog input You can perform these applications through DMA interrupt or programmed I O data transfer mechanisms Some of the applications also use start reference and pause triggers Sy Note For more information about programming analog input applications and triggers in software refer to the NJ DAQmx Help or the LabVIEW 8 x Help NI USB 621x User Manual 4 24 ni com Connecting Al Signals on the USB 6210 6211 Devices Table 5 1 summarizes the recommended input configuration for both types of signal sources on NI 6210 6211 devices National Instruments Corporation 5 1 NI USB 621x User Manual Chapter 5 Connecting Al Signals on the USB 6210 6211 Devices Table 5 1 Analog Input Configuration Floating Signal Sources Not Ground Referenced Signal Connected to Building Ground Sources Al Examples Example Ground Reference e Ungrounded thermocouples e Plug in instruments with Setting e Signal conditioning with non isolated outputs isolated outputs e Battery devices Differential Signal Source DAQ Device Signal Source DAQ Device Al A
121. n 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 National Instruments Web site at ni com for technical support and professional services National Instruments Corporation Support Online technical support resources at ni com support include the following Self Help Resources For answers and solutions visit the award winning National Instruments Web site 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 Free Technical Support All registered users receive free Basic Service which includes access to hundreds of Application Engineers worldwide in the NI Discussion Forums at ni com forums National Instruments Application Engineers make sure every question receives an answer For information about other technical support options in your area visitni 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 t
122. n the output signal 7 2 timing signals 7 5 triggering 7 4 troubleshooting B 3 analog output data generation 7 2 analog output signals 7 5 AO Pause Trigger 7 6 AO Sample Clock 7 7 AO Sample Clock Timebase 7 8 AO Start Trigger 7 5 analog output trigger signals 7 4 analog to digital converter 4 2 ANSI C documentation xv AO FIFO 7 1 AO Pause Trigger signal 7 6 AO range 7 2 AO Sample Clock 7 2 Timebase signal 7 8 AO sample clock signal 7 7 AO Sample Clock signal 7 7 AO Sample Clock Timebase signal 7 8 AO Start Trigger signal 7 5 ao PauseTrigger 7 6 ao SampleClock 7 7 ao StartTrigger 7 5 applications counter input 9 2 counter output 9 20 edge counting 9 2 arm start trigger 9 31 avoiding scanning faster than necessary 4 8 NI USB 621x User Manual 1 2 buffered edge counting 9 3 non cumulative 9 4 buffered hardware timed acquisitions 4 10 buffered hardware timed generations 7 3 buffered period measurement 9 7 buffered pulse width measurement 9 5 buffered semi period measurement 9 9 buffered two signal edge separation measurement 9 19 bus interface 13 1 C calibration 2 2 calibration certificate NI resources C 2 calibration circuitry 2 2 cascading counters 9 33 changing data transfer methods between USB signal stream and programmed I O 13 2 channel scanning order 4 7 channel Z behavior 9 17 channels sampling with AI Sample Clock and AI Convert Clock B 2 charge injection B 1
123. n 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 the period Figure 9 11 illustrates this method Interval Measured gt F1 F1 Gate 1 2 3 a ad N Ft Source Ft 4 Single Period Period of F1 N Measurement Ft Ft Frequency of F1 q y N Figure 9 11 Method 1 9 10 ni com Chapter 9 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 t
124. nable 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 M Series devices use an onboard oscillator to generate the filter clock with a 40 MHz frequency KI Note NI DAQmx only supports filters on counter inputs NI USB 621x User Manual 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 10 1 10 4 ni com Table 10 1 Filters Chapter 10 PFI Filtered Input N Filter Clocks Pulse Width Pulse Width Needed to Pass Guaranteed to Pass Guaranteed to Not Filter Setting Signal Filter Pass Filter 125 ns 5 125 ns 100 ns 6 425 us 257 6 425 us 6 400 us 2 55 ms 101 800 2 55 ms 2 54 ms Disabled The filter setting for each input can be configured independently On power up the filters are disabled Figure 10 4 shows an example of a low to high transition on an input that has its filter set t
125. ndex FREQ OUT 9 29 Frequency Output 9 29 counter terminals default 9 29 counters 9 1 cascading 9 33 connecting terminals 9 29 duplicate count prevention 9 35 edge counting 9 2 filters 9 33 generation 9 20 input applications 9 2 other features 9 32 output applications 9 20 prescaling 9 34 pulse train generation 9 22 retriggerable single pulse generation 9 21 simple pulse generation 9 20 single pulse generation 9 20 single pulse generation with start trigger 9 20 timing signals 9 25 triggering 9 31 counting edges 9 2 creating an AC return path 11 3 crosstalk when sampling multiple channels B 1 D DACs 7 1 DAQ hardware 2 1 DAQ system 2 1 DAQ STC2 2 2 data acquisition methods 4 9 generation methods 7 2 transfer methods 13 1 changing 13 2 programmed I O 13 2 USB signal stream 13 1 NI USB 621x User Manual Index Declaration of Conformity NI resources C 1 default counter terminals 9 29 NI DAQmx counter timer pins 9 29 pins 9 29 device information A 1 pinouts 1 3 specifications 1 3 A 1 USB 6210 A 1 USB 6211 A 4 USB 6215 A 4 USB 6218 A 7 diagnostic tools NI resources C 1 DIFF connections using with floating signal sources 5 5 using with ground referenced signal sources 5 12 when to use with floating signal sources 5 3 when to use with ground referenced signal sources 5 10 differential analog input troubleshooting B 1 differential connections using with
126. nections with Ground Referenced Signal Sources section of Chapter 5 Connecting AI Signals on the USB 6210 6211 Devices for more information How can I use the AI Sample Clock and AI Convert Clock signals on an M Series device to sample the AI channel s M Series devices use ai SampleClock and ai ConvertClock to perform interval sampling As Figure B 1 shows ai SampleClock controls the sample period which is determined by the following equation 1 sample period sample rate Channel 0 Channel 1 Convert Period Sample Period gt Figure B 1 ai SampleClock and ai ConvertClock ai ConvertClock 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 o
127. nsistors 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 G 18 ni com virtual channel W waveform Ground loop voltage Volts input high Volts input low Volts in Measured voltage Volts output high Volts output low Volts out Signal source voltage See channel Glossary 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 National Instruments Corporation G 19 NI USB 621x User Manual Index Symbols 5 V power input 3 3 5 V power output 3 2 5 V power source 3 2 NET languages documentation xvi Numerics 100 kHz Timebase 12 2 20 MHz Timebase 12 1 80 MHz Timebase 12 1 A A D converter 4 2 AC return path creating 11 3 accessories choosing for your device 1 3 acquisition circular buffered 4 10 double buffered 4 10 acquisitions hardware timed 4 9 on demand 4 9 software timed 4 9 AI channels sampling with AI Sample Clock and AI Convert Clock B 2 AI Convert Clock signal 4 16 AI Convert Clock Timebase signal 4 20 AI data acquisition methods 4 9 AI FIFO 4
128. nspires so results of the computation can be used in guiding the physical process Referenced Single Ended configuration All measurements are made with respect to a common reference measurement system or a ground Also called a grounded measurement system Real Time System Integration Real Time System Integration bus The National Instruments timing bus that connects DAQ devices directly by means of connectors on top of the devices for precise synchronization of functions 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 NI USB 621x User Manual Glossary scan scan interval scan rate SCC SCXI sensor signal conditioning signal source signals single trigger mode single buffered single ended input NI USB 621x User Manual 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 Signal Conditioning Carriers A compact modular form factor for signal conditioning modu
129. o 125 ns N 5 PFI Terminal Filtered input goes high when terminal is sampled Filter Clock 1 2 3 4 1 2 34 5 high on five consecutive 40 MHz filter clocks Figure 10 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 55 ms setting the jitter is up to 10 025 us When a PFI input is routed directly to RTSL or a RTSI input is routed directly to PFI the M Series device does not use the filtered version of the input signal 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 National Instruments Corporation 10 5 NI USB 621x User Manual Chapter 10 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 Do not 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 PFI 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 Do not drive a DI or PFI in
130. o determine the average period of F1 The frequency of F1 is the inverse of the average period Figure 9 12 illustrates this method Intervals Measured Toi To i T Tk DD gt F1 Gate F1 Ft Source 12 Ny1 No s 1 Nk Fi UUU Buffered Period Measurement N No Nk 1 Average Period of F1 x K Ft K x Ft Frequency of F1 _ N No LN Figure 9 12 Method 1b Method 2 Measure High Frequency with Two Counters In 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 National Instruments Corporation 9 11 NI USB 621x User Manual Chapter 9 Counters 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 9 13 illustrates this method Another option would be to measure the width of a known period instead of a known pulse Pulse 4 F1 Gate 1
131. 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 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 00003 1 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 a 4 V signal is connected to channel 0 and a mV signal is connected to channel 1 Suppose 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 National Instruments Corporation 4 7 NI USB 621x User Manual Chapter 4 Analog Input You can conne
132. ommon example of non referenced signal sources are batteries transformers or thermocouples G 12 ni com NRSE 0 offset P PCI PCI Express PCIe period periods PFI PGIA physical channel National Instruments Corporation G 13 Glossary 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 Peripheral Component Interconnect A high performance expansion bus architecture originally developed by Intel to replace ISA and EISA It offers a theoretical maximum transfer rate of 132 MB s A high performance expansion bus architecture originally developed by Intel to replace PCI PCI Express offers a theoretical maximum transfer rate that is dependent upon lane width A x1 link theoretically provides 250 MB s in each direction to and from the device Once overhead is accounted for a x1 link can provide approximately 200 MB s of input capability and 200 MB s of output capability Increasing the number of lanes in a link increases maximum throughput by approximately the same factor See PCI Express 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
133. on 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 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 9 6 ni com Chapter 9 Counters 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 9 8 shows an example of a single period measurement source I TATALATAT TT 1 2 3 4 5 Counter Value 0 HW Save Register 5 Figure 9 8 Single Period Measurement Buffered Period Measurement Buffered period measurement is similar to single period measurement but buffered period measu
134. onnecting 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 e Two analog input channels AI and AI are available for the signal DIFF signal connections reduce noise pickup and increase common mode noise rejection DIFF 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 RSE Connections with Floating Signal Sources Only use RSE 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 RSE 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 DIFF input connections are recommended for greater signal integrity for any input signal that does not meet the preceding conditions National Instruments Corporation 5 3 NI USB 621x User Manual Chapter 5 Connecting Al Signals on the USB 6210 6211 Devices In the single ended modes more electrostatic and magnetic noise couples into the signal connections than in DIFF configurations The coupling is the result of differences in the signal path Magnetic coupl
135. ou 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 4 8 ni com Chapter 4 Analog Input 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 less often and is affected much less by settling time Analog Input Data Acquisition Methods When performing analog input measurements you either can perform software timed
136. ounter s output 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 9 24 ni com Chapter 9 Counters frequency of the system Figure 9 28 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 Di AD D3 D1 2AD Figure 9 28 Pulse Generation for ETS For information about connecting counter signals refer to the Default Counter Timer Pinouts section Counter Timing Signals USB M Series devices feature the following counter timing signals e Counter n Source e Counter n Gate e Counter n Aux e Counter n A e Counter n B e Counter n Z e Counter n Up_Down e Counter n HW Arm e Counter n Internal Output e Counter n TC e Frequency Output 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 9 25 NI USB 621x User Manual Chapter 9 Counters Counter n Source Signal The selected edge of the Counter n Source signal increments and decrements the counter value depending on the application the counter is performing Table 9 4 lists how this terminal is used in various NI USB 621x User Manual applications Table
137. ounter 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 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 Counter n Gate signal input of the counter Counter input operations can use the arm start trigger to have start trigger like behavior 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 National Instruments Corporation 9 31 NI USB 621x User Manual Chapter 9 Counters 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
138. ource Al Lo O Resistors o Co see text xI MG 6 Instrumentation Amplifier Ses So PGIA Measured Bias Current Return Paths 1 0 Connector J Le So m Voltage Input Multiplexers oeo Al SENSE AI GND M Series Device Configured in DIFF Mode Figure 5 3 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 National Instruments Corporation 5 7 NI USB 621x User Manual Chapter 5 Connecting Al Signals on the USB 6210 6211 Devices inputs be aware that there is some gain error from loading down the source as shown in Figure 5 4 AC Coupling AC Coupled tt G AI Floating Signal Vs Source GL Al GL Al SENSE
139. own in Figure 9 19 ChA ChB Counter Value 2 X 3 X 4 X 5 4 Y 3 X 4 Figure 9 19 Measurements Using Two Pulse Encoders For information about connecting counter signals refer to the Default Counter Timer Pinouts section Two Signal Edge Separation Measurement NI USB 621x User Manual 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 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 Single Two Signal Edge Separation
140. pause trigger is high or when it is low Figure 9 3 shows an example of on demand edge counting with a pause trigger 9 2 ni com Chapter 9 Counters Counter Armed Pause Trigger Pause When Low LFL TT FT 0 1 2 3 4 5 SOURCE Counter Value 0 Figure 9 3 Single Point On Demand 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 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 Figure 9 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 F Sample on Rising Edge l l SOURCE LATALALATAT AE Counter Value 0 1 2 3 4 5 6 7 i 3 3 Buffer Figure 9 4 Buffered Sample Clock Edge Coun
141. poration All rights reserved Important Information Warranty The USB 6210 USB 6211 USB 6215 and USB 6218 devices are warranted against defects in materials and workmanship for a period of three years 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 National Instruments believes that the information in this document is accurate The document has been carefully reviewed for technical accuracy In
142. put line with voltages outside of its normal operating range The PFI or DI lines have a smaller operating range than the AI signals e 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 specifications document for your device NI DAQm x 8 3 and later supports programmable power up states for PFI and DIO lines Software can program any value at power up 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 8 x Help for more information about setting power up states in NI DAQmx or MAX NI USB 621x User Manual 10 6 ni com Isolation and Digital Isolators USB 6215 6218 devices are isolated data acquisition devices As shown in Figure 11 1 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 The bus interface circuitry is referenced to a non isolated ground Refer to Table 11 1 for an
143. r NRSE input modes Refer to the Configuring AI Ground Reference Settings in Software section of Chapter 4 Analog Input for more information about the DAQ Assistant National Instruments Corporation 5 13 NI USB 621x User Manual Connecting Al Signals on the USB 6215 6218 Devices You can connect the USB 6215 6218 directly to a variety of devices and other signal sources Make sure the devices you connect to the USB 6215 6218 are compatible with the input specifications of the module When connecting various sources to the USB 6215 6218 you can use differential single ended or a combination of single ended and differential connections Refer to Figures 6 1 6 2 and 6 3 for diagrams of each connection type 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 Differential Measurements To attain more accurate measurements and less noise use a differential measurement configuration A differential measurement configuration requires two inputs for each measurement Differential Pairs Table 6 1 the signal pairs that are valid for differential connection configurations with the USB 6215 6218 Table 6 1 1 0 Connector Signals Channel Signal Signal 0 AIO AI 8 1 AI1 AI9 2 AI 2 AI 10 Na
144. r ai SampleClock You can configure the polarity selection for ai SampleClockTimebase as either rising or falling edge 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 ConvertClock You also can specify whether the measurement sample begins on the rising edge or falling edge of ai ConvertClock 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 NI USB 621x User Manual 4 16 ni com Chapter 4 Analog Input 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 UN Caution Setting the conversion rate higher than the maximum rate specified for your device will result in errors Using an Internal Source One of the following internal signals can drive ai ConvertClock e AT Convert Clock Timebase divided down e Coun
145. r to provide all of the timing functionality described throughout this section M Series devices have a flexible timing engine Figure 4 4 summarizes all of the timing options provided by the analog input timing engine National Instruments Corporation 4 11 NI USB 621x User Manual Chapter 4 Analog Input 20 MHz Timebase 100 kHz Timebase ae Analog Comparison Event ai SampleClock er Ctr n Internal Output ai SampleClock SW Pulse Timebase Programmable D Clock Divider p ai ConvertClock Ctr n Internal Output ai ConvertClock Timebase Programmable Clock Divider Figure 4 4 Analog Input Timing Options M Series devices use ai SampleClock and ai ConvertClock to perform interval sampling As Figure 4 5 shows ai SampleClock controls the sample period which is determined by the following equation 1 Sample Period Sample Rate Channel 0 Channel 1 l Convert Period Sample Period gt Figure 4 5 Interval Sampling ai ConvertClock controls the Convert Period which is determined by the following equation 1 Convert Period Convert Rate NI USB 621x User Manual 4 12 ni com Chapter 4 Analog Input NI DAQm x chooses the default convert rate to allow for the maximum settling time between conversions Typically this rate is the sampling rate for the task multiplied by the number of channels in the task
146. r 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 MUX Each M Series device has one analog to digital converter ADC The multiplexers MUX route one AI channel at a time to the ADC through the NI PGIA National Instruments Corporation 4 1 NI USB 621x User Manual Chapter 4 Analog Input Ground Reference Settings The analog input ground reference settings circuitry selects between differential referenced single ended and non referenced single ended input modes Each AI channel can use a different mode Instrumentation Amplifier 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 M Series devices use the NI PGIA to deliver high accuracy even when sampling multiple channels with small input ranges at fast rates M Series 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 A D Converter The analog to digital converter ADC digitizes the AI signal by converting the analog voltage into a digital number
147. ransfer mechanisms Some of the applications 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 8 x Help National Instruments Corporation 7 9 NI USB 621x User Manual Digital 1 0 NI 621x devices have eight static digital input lines PO lt 0 7 gt These lines also can be used as PFI inputs NI 621x devices have eight static digital output lines P1 lt 0 8 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 s Set a line to a static 0 s Seta 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 the M 621x Specifications Refer to Chapter 10 PFT for more information on PFI inputs and outputs Figure 8 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 47kQ Pull Down Static DO I O Protection e P1 x 47 kQ Pull Down F
148. ration is finished the counter waits for another Start Trigger signal to begin another pulse generation Figure 9 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 Start Trigger R source SUUUUUU UU UU UU UU Figure 9 24 Retriggerable Single Pulse Generation For information about connecting counter signals refer to the Default Counter Timer Pinouts section National Instruments Corporation 9 21 NI USB 621x User Manual Chapter 9 Counters Pulse Train Generation NI USB 621x User Manual Continuous Pulse 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 You also can use the Gate inpu
149. rement 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 the middle of a period of the Gate input The counter does not store a measurement for this incomplete period Figure 9 9 shows an example of a buffered period measurement In this example a period is defined by two consecutive rising edges National Instruments Corporation 9 7 NI USB 621x User Manual Chapter 9 Counters Counter Armed GATE source PL A FLAT ALL Counter Value i 2 B14 2 B24 NE NE 3 Buffer i i i Time N i i i to ty t2 ts Figure 9 9 Buffered Period Measurement Table 9 1 Time N Descriptions to At t the counter is armed No measurements are taken until the counter is armed ti The rising edge of Gate indicates the beginning of the first period to measure The counter begins counting rising edges of Source to The rising edge of Gate indicates the end of the first period The USB M Series device stores the counter value in the buffer t3
150. rom computer memory from to a device or memory on the bus while the processor does something else DMA is the fastest method of transferring data to from computer memory Performs the transfers between memory and I O devices independently of the CPU Software unique to the device or type of device and includes the set of commands the device accepts A standard architecture for instrumentation class multichannel data acquisition devices 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 optical encoder which uses a rotating disk with alternating opaque areas a light source and a photodetector External clock signal A voltage pulse from an external source that causes a DAQ operation to begin External reference signal NI USB 621x User Manual Glossary FIFO filter filtering floating floating signal sources FREQ OUT frequency ft NI USB 621x User Manual 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 FIFO
151. round Refer to the Using Non Referenced Single Ended NRSE Connections for Floating Signal Sources section for more information about NRSE connections NI USB 621x User Manual 5 4 ni com Chapter 5 Connecting Al Signals on the USB 6210 6211 Devices 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 o Al Floating Signal Source o Al Inpedance Al GND Figure 5 1 Differential Connections for Floating Signal Sources without Bias Resistors However for larger source impedances this connection leaves the DIFF 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 DIFF mode signal instead of a common mode signal and thus appears in your data In this case instead of directly connecting the negative lin
152. s Digital Isolators To Input Timing Signal Selectors Figure 10 2 shows the circuitry of an output PFI line National Instruments Corporation Figure 10 1 NI 621x PFI Input Circuitry 10 1 NI USB 621x User Manual Chapter 10 PFI Timing Signals 4 Isolation Barrier USB 6215 and USB 6218 devices only 1 1 Digital Isolators UO Protection RAP Sta PFI lt 12 15 gt P1 Buffer Y 47 KQ Pull Down Direction Control Figure 10 2 NI 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 or P1 x On the I O connector each terminal is labeled PFI x PO or PFI x P1 The voltage input and output levels and the current drive levels of the PFI signals are listed in the specifications of your device Using PFI Terminals as Timing Input Signals NI USB 621x User Manual Use PFI terminals to route external timing signals to many different M Series functions Each input PFI terminal can be routed to any of the following signals AI Convert Clock AI Sample Clock Al Start Trigger AI Reference Trigger AI Pause Trigger AI Sample Clock Timebase AO Start Trigger AO Sample Clock AO Sample Clock Timebase AO Pause Trigger Counter input signals for either counter Source Gate
153. s or may exist between earth ground and the instrument or circuit of interest Neither the high nor the low side of a circuit is at earth potential 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 Frequency Output signal The number of alternating signals that occur per unit time Feet G 8 ni com function glitch GND ground H hardware hardware triggering Hz hysteresis UO National Instruments Corporation G 9 Glossary 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 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 safety 3 A common reference point for an electrical system The physical components of a computer system such as the circuit boards plug in devices chassis enclosures peripherals and cables A form of triggering where you set the start time of an acquisition and gather data at a known position
154. s 9 22 Continuous Pulse Train Generation 9 22 Frequency Generation stainless E E ea 9 23 Using the Frequency Generator 9 23 Frequency Division ssh unis tnt at nr natifs 9 24 Pulse Generation for BTS essen dosis zs oasse adao iaoi dR Tiag 9 24 Counter Timing TTT nn Atteint urnes 9 25 Counter n Source Signal ssissss ssh a R aE ttes 9 26 Routing a Signal to Counter n Sources sees essere 9 26 Routing Counter n Source to an Output Terminal 9 26 Counterin Gate Signal atipiese aeaeaie EEEE ERE E 9 27 Routing a Signal to Counter n Gate 9 27 Routing Counter n Gate to an Output Terminal 9 27 Counter m AUX Signal sine teen unten tint Ta 9 27 Routing a Signal to Counter n AUX 9 27 National Instruments Corporation ix NI USB 621x User Manual Contents Counter n A Counter n B and Counter n Z Signals sse eee 9 28 Routing Signals to A B and Z Counter Inputs sss eee 9 28 Counter n Up Down Signal ss 9 28 Counter n HW Arm Signal ss sms ins a hT 9 28 Routing Signals to Counter n HW Arm Input 9 28 Counter n Internal Output and Counter n TC Signals 9 29 Routing Counter n Internal Output to an Output Terminal 9 29 Frequency Output Signal insiste titine 9 29 Routing Frequency Output to a Terminal 9 29 Default Counter Timer Pinouts ss 9 29 Counter Triggering sis itunes tee nent init noisettes 9 31 Arm Start KST thin sntes ne se ptet mi
155. s 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 accuracy is affected by settling time When your NI 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 specifications document for your DAQ device lists its settling time NI 621x devices are designed to have fast settling times However several factors can increase the settling time which decreases the accuracy of your measurements To ensure fast settling times you should do the following in order of importance e Use low impedance sources e Use short high quality cabling e Carefully choose the channel scanning order e Avoid scanning faster than necessary The following sections contain more information about these factors Use Low Impedance Sources NI USB 621x User Manual To ensure fast settling times your signal sources should have an impedance of lt 1 KQ Large source impedances increase the settling time of the NI PGIA and so decrease the accuracy at fast scann
156. s in begin data acquisition or data acquisition and control See also DAQ National Instruments Corporation G 5 NI USB 621x User Manual Glossary data transfer dB DC device DIFF differential input digital I O digital signal NI USB 621x User Manual 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 A plug in data acquisition product card or pad that can contain multiple channels an
157. s 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 11 2 ni com Chapter 11 Isolation and Digital Isolators 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 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 and 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 sourc
158. s 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 algorithm 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 The condition where a common mode voltage exist
159. stems Alliance PCI Express eXtensions for Instrumentation The PXI implementation of PCI Express a scalable full simplex serial bus standard that operates at 2 5 Gbps and offers both asynchronous and isochronous data transfers A special set of trigger lines in the PXI backplane for high accuracy device synchronization with minimal latencies on each PXI slot Only devices in the PXI Star controller Slot 2 can set signal on this line For additional information concerning PXI star signal specifications and capabilities read the PXI Specification located at www pxisa org specs G 14 ni com Q quadrature encoder range real time RSE RTSI RTSI bus sample counter National Instruments Corporation G 15 Glossary 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 time 3 Pertaining to the performance of a computation during the actual time that the related physical process tra
160. struments Product Manuals Library at ni com manuals for updated documentation resources xvi ni com Getting Started 6210 6211 1 USB Figure 1 NI USB 621x User Manual 1 1 National Instruments Corporation Chapter 1 Getting Started Figure 1 2 USB 6215 6218 NI 621x devices feature up to 32 analog input AJ channels up to two analog output AO channels 8 lines of digital input DI 8 lines of digital output DO and two counters If you have not already installed your device refer to the NJ DAQmx for USB Devices Getting Started Guide For specifications refer to the NI 621x Specifications document on ni com manuals Before installing your DAQ device you must install the software you plan to use with the device Installing NI DAQmx The NI DAQmx for USB Devices Getting Started Guide which you can download at 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 NI USB 621x User Manual 1 2 ni com Chapter 1 Getting Started Installing the Hardware The NI DAQmx for USB Devices Getting Started Guide contains non software specific information about how to install USB devices Device Pinouts Refer to Appendi
161. struments 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 FireWire is the registered trademark of Apple Computer Inc Other product and company names mentioned herein are trademarks or trade names of their respective companies Members of the National Instruments Alliance Partner Program are
162. sured 0123012301 1 Sample 1 Sample 2 Sample 3 i K gt a e One External Signal Driving Both Clocks Figure 4 14 Single External Signal Driving ai SampleClock and ai ConvertClock Simultaneously Al Convert Clock Timebase Signal NI USB 621x User Manual The AI Convert Clock Timebase ai ConvertClockTimebase signal is divided down to provide on of the possible sources for ai ConvertClock Use one of the following signals as the source of ai ConvertClockTimebase e ai SampleClockTimebase e 20 MHz Timebase ai ConvertClockTimebase is not available as an output on the I O connector 4 20 ni com Chapter 4 Analog Input 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 HoldCompleteEvent out to any PFI lt 4 8 gt or PFI lt 12 15 gt terminal The polarity of ai HoldCompleteEvent 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 Al Start Trigger Signal 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 Once the acquisition begins configure the acquisition to stop e When a certain number of points
163. t e PHL lt 0 3 gt PFI lt 8 11 gt e ai ReferenceTrigger e ai StartTrigger e ai SampleClock e ai ConvertClock e 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 PFI lt 4 7 gt or PFI lt 12 15 gt terminal Counter n 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 PFI lt 0 3 gt PFI lt 8 11 gt e ai ReferenceTrigger e ai StartTrigger In addition Counter 1 Internal Output Counter 1 Gate Counter 1 Source or Counter 0 Gate can be routed to Counter 0 Aux Counter 0 Internal National Instruments Corporation 9 27 NI USB 621x User Manual Chapter 9 Counters 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 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
164. t 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 9 25 shows a continuous pulse train generation using the rising edge of Source SOURCE UN ULN UUU OUT Counter Armed Figure 9 25 Continuous Pulse Train Generation Continuous pulse train generation is sometimes called frequency division If the high and 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 9 22 ni com Chapter 9 Counters Frequency Generation 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 M Series devices Figure 9 26 shows a block diagram of the frequency generator Frequency Output 20 MHz Timebase 100 kHz Timebase 2 Timebase Frequency Generator e FREQ OUT
165. ter n Internal Output A programmable internal counter divides down the AI Convert Clock Timebase to generate ai ConvertClock The counter is started by ai SampleClock and continues to count down to zero produces an ai ConvertClock reloads itself and repeats the process until the sample is finished It then reloads itself in preparation for the next ai SampleClock pulse Using an External Source Use the external signals PFI lt 0 3 gt or PFI lt 8 11 gt as the source of ai ConvertClock Routing Al Convert Clock Signal to an Output Terminal You can route ai ConvertClock as an active low signal out to any PFI lt 4 7 gt or PFI lt 12 15 gt terminal Using a Delay from Sample Clock to Convert Clock When using an internally generated ai ConvertClock you also can specify a configurable delay from ai SampleClock to the first ai ConvertClock pulse within the sample By default this delay is three ticks of ai ConvertClockTimebase National Instruments Corporation 4 17 NI USB 621x User Manual Chapter 4 Analog Input Figure 4 9 shows the relationship of ai SampleClock to ai ConvertClock ai ConvertClockTimebase ai SampleClock ai ConvertClock gt gt Delay Convert From Period Sample Clock Figure 4 9 ai SampleClock and ai ConvertClock
166. ternal or external source for ai SampleClock You also can specify whether the measurement sample begins on the rising edge or falling edge of ai SampleClock 4 14 ni com Chapter 4 Analog Input Using an Internal Source One of the following internal signals can drive ai SampleClock e Counter n Internal Output e AI Sample Clock Timebase divided down e A software pulse A programmable internal counter divides down the sample clock timebase Using an External Source Use the external signals PFI lt 0 3 gt or PFI lt 8 11 gt as the source of ai SampleClock Routing Al Sample Clock Signal to an Output Terminal You can route ai SampleClock out to any PFI lt 4 7 gt or PFI lt 12 15 gt 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 SampleClock 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 SampleClock when a measurement acquisition is not in progress During a measurement acquisition you can cause your DAQ device to ignore ai SampleClock using the ai PauseTrigger signal A counter on your device internally generates ai SampleClock unless you select some external source ai StartTrigger starts this counter and
167. 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 warranty provided herein does not cover damages defects malfunctions or service failures caused by owner s failure to follow the National In
168. ting National Instruments Corporation 9 3 NI USB 621x User Manual Chapter 9 Counters NI USB 621x User Manual Non Cumulative Buffered Edge Counting Non cumulative edge counting is similar to buffered sample clock edge counting However the counter resets after each active edge of the Sample Clock You can route the Sample Clock to the Gate input of the counter Figure 9 5 shows an example of non cumulative buffered edge counting Counter Sample Clock aii 1 1 Sample on i Rising Edge i 1 i 1 SOURCE AL FIF AT FIF FF Counter Value O 1 2 11 2 3 1 2 3 1 2 2 IE Buffer E 2 7 Figure 9 5 Non Cumulative Buffered Edge Counting Notice that the first count interval begins when the counter is armed which occurs before the first active edge on Gate 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 consider using duplicate count prevention described in the Duplicate Count Prevention section 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 A
169. tional Instruments Corporation 6 1 NI USB 621x User Manual Chapter 6 Connecting Al Signals on the USB 6215 6218 Devices NI USB 621x User Manual Table 6 1 1 0 Connector Signals Continued Channel Signal Signal 3 A 13 AT11 4 A I4 AI 12 5 A IS AI 13 6 A 16 AI 14 7 AU AI 15 16 AI 16 AI 24 17 AI 17 AI 25 18 AI 18 AI 26 19 AI 19 AI 27 20 AI 20 AI 28 21 AI 21 AI 29 22 AI 22 AI 30 23 AI 23 AI 31 USB 6218 devices only Refer to Figure 6 1 for an illustration of a differential connection configuration 1 This signal name indicates the differential pair Refer to Table for a list of differential signal pairs Figure 6 1 Connecting a Device to a USB 6215 6218 Using Differential Connections 6 2 ni com Chapter 6 Connecting Al Signals on the USB 6215 6218 Devices The differential connection configuration allows the common mode noise voltage V m 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 Referenced Single Ended RSE Measurements Using the RSE measurement configuration allows the USB 6215 6218 to take measurements on all AI channels when all channels share a common ground Refer to Figure 6 2 for an illustration of an RSE connection configuration Note If you leave the AI GND pin unconnected the signals
170. ture 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 9 18 channel Z is never high when channel A is high and channel B is low Thus the reload must occur in some other phase In Figure 9 18 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 ChA ChB Ch Z L L 17 Max Timebase L LO Lit LJ Counter Value IE E woe aa aa a A B Z 0 0 1 Figure 9 18 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 National Instruments Corporation 9 17 NI USB 621x User Manual Chapter 9 Counters The counter increments on each rising edge of channel A The counter decrements on each rising edge of channel B as sh
171. tween 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 M Series device User input through the PFI terminals e Routes and generates the main clock signals for the M Series 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 National Instruments Corporation 12 1 NI USB 621x User Manual Chapter 12 Digital Routing and Clock Generation 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 general purpose counter timers The 100 kHz Timebase is generated by dividing down the 20 MHz Timebase by 200 NI USB 621x User Manual 12 2 ni com
172. ual Chapter 9 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 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 the fact that software can read the counter contents at any time without disturbing the counting process Figure 9 2 shows an example of single point edge counting Counter Armed SEE ai FF 1 2 3 4 5 SOURCE Counter Value 0 Figure 9 2 Single Point On Demand 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 You can route the pause trigger to the Gate input of the counter You can configure the counter to pause counting when the
173. uanniinstnianite te 7 5 Routing AO Start Trigger Signal to an Output Terminal sss 7 6 AO Pause Trigser Signal sn tn nn Mt nue let units 7 6 Using 4 Digital SOUrCe 235 er remettre ent sees 7 6 AO Sample Clock Signals sr deve Ain A 7 7 Using an Internal Source ts 7 7 Using an External Source ss 7 7 Routing AO Sample Clock Signal to an Output Terminal 7 7 Other Timing Requirement ss 7 7 AO Sample Clock Timebase Signal 7 8 Getting Started with AO Applications in Software 7 9 Chapter 8 Digital 1 0 Statie DIO 2 re nn nd en ett es nuit nie ten eae Me en 8 2 VO ProtectiOn E ei ae aia et ai ieee ei aad 8 2 Incredsing Current Drives cpio entier nr te re a dant ie 8 2 Connecting Digital I O Signals ss 8 3 Getting Started with DIO Applications in Software 8 4 Chapter 9 Counters Counter Input Applications sise 9 2 Counting Edees tri ee ter AO este teen byte 9 2 Single Point On Demand Edge Counting 00 0 0 sese eee ee 9 2 Buffered Sample Clock Edge Counting 9 3 Non Cumulative Buffered Edge Counting sss esse sese see eee eee 9 4 Controlling the Direction of Counting sese sees eee eee ee eee 9 4 NI USB 621x User Manual Vili ni com Contents Pulse Width Measurement 9 5 Single Pulse Width Measurement 9 5 Buffered Pulse Width Measurement 9 5 Period M asur ment ss stories e aa estate teste 9 6 Single
174. umber Name CTR 0 B 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 CTR 1 A 4 PFI 3 CTR 1 Z 2 PFI 1 CTR 1 B 3 PFI 2 FREQ OUT 8 PFI 6 Table 9 6 Default NI DAQmx Counter Timer Pins for USB 6218 Devices 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 CTR 1 A 4 PFI 3 CTR 1 Z 3 PFI 2 CTR1B 35 PFI 10 FREQ OUT 8 PFI 6 NI USB 621x User Manual 9 30 ni com Chapter 9 Counters 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 NJ DAQmx Help or the LabVIEW 8 x Help for more information about how to connect your signals for common counter measurements and generations M Series default PFI lines for counter functions are listed in Physical Channels in the NI DAQmx Help or the LabVIEW 8 x Help Counter Triggering Arm Start Trigger Start Trigger Pause Trigger Counters support three different triggering actions arm start start and pause Any counter operation can use the arm start trigger For counter output operations you can use it in addition to the start and pause triggers For c
175. vice error Refer to ni com support National Instruments Corporation A 3 NI USB 621x User Manual Appendix Device Specific Information Table A 2 PWR ACT LED Status Continued LED State Device Status Single blink Operating normally Connected to USB Hi Speed port Refer to the NI 621x Specifications for more information Double blink Connected to USB full speed port Device performance might be affected Refer to the M 621x Specifications for more information USB 6211 6215 USB 6211 6215 Pinout Figure A 2 shows the pinout of the NI 6211 6215 For a detailed description of each signal refer to the 7 0 Connector Signal Descriptions section of Chapter 3 Connector Information NI USB 621x User Manual A 4 ni com Appendix Device Specific Information PFI 0 P0 0 In PFI 1 P0 1 In PFI 2 P0 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 0 AO 1 AO GND AIO AI 8 11 9 12 10 13 11 SENSE 4 112 5 113 GND gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt I ll Figure A 2 USB 6211 6215 Pinout Table A 3 Default NI DAQmx Counter Timer Pins National Instruments Corporation Counter Timer Signal Default Terminal Number
176. will float outside the working input range of the USB 6215 6218 which may result in unreliable measurements because there is no way to ensure that the input signal is within 10 V of AI GND 1 Alt ka 1 i MUX PGIA ADC AI2 O f Al GND e 1 L tie oe el USB 6215 6218 Figure 6 2 Connecting a Device to a USB 6215 6218 Using RSE Connections In an RSE connection configuration each input channel is measured with respect to AI GND National Instruments Corporation 6 3 NI USB 621x User Manual Chapter 6 Connecting Al Signals on the USB 6215 6218 Devices Non Referenced Single Ended NRSE Measurements NI USB 621x User Manual To reach a compromise between RSE and differential measurements you can use an NRSE measurement configuration This configuration allows for a remote sense for the negative input of the programmable gain instrumentation amplifier PGIA that is shared among all channels configured for NRSE mode The behavior of this configuration is similar to the behavior of RSE connections but it provides improved noise rejection Refer to Figure 6 3 for an illustration of an NRSE connection configuration ANT Po ee re MUX M PGIA ADC AIO ha i AISENSE de e i Al GND i V USB 6215 6218 Figure 6 3 Connecting a Device to a USB 6215 6218 Using NR
177. x A Device Specific Information for NI 621x device pinouts Device Specifications Refer to the NI 621x Specifications available on the NI DAQ Device Document Browser or ni com manuals for more detailed information about NI 621x devices Device Accessories NI offers a variety of accessories to use with your DAQ device Refer to Appendix A Device Specific Information or ni com for more information National Instruments Corporation 1 3 NI USB 621x User Manual DAQ System Overview Figure 2 1 shows a typical DAQ system which includes sensors transducers signal conditioning devices cables that connect the various devices to the accessories the M Series device programming software and PC The following sections cover the components of a typical DAQ system DAQ DAQ Personal Computer Hardware Software or Laptop 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 Figure 2 2 features components common to all USB M Series devices National Instruments Corporation 2 1 NI USB 621x User Manual Chapter 2 DAQ System Overview Isolation Barrier 1 Analog Input g Inp Analog Output S O o E es 5 Digital UO O Q Counters SJ PFI
178. x Help for more information You also can specify whether the samples are paused when ao PauseTrigger is at a logic high or low level 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 SampleClock You also can specify whether the DAC update begins on the rising edge or falling edge of ao SampleClock Using an Internal Source One of the following internal signals can drive ao SampleClock 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 the external signals PFI lt 0 3 gt or PFI lt 8 11 gt as the source of ao SampleClock Routing AO Sample Clock Signal to an Output Terminal You can route ao SampleClock as an active low signal out to any PFI lt 4 7 gt or PFI lt 12 15 gt terminal Other Timing Requirements A counter on your device internally generates ao SampleClock unless you select some external source ao StartTrigger starts the counter and either the software or hardware can stop it once a finite generation completes When using an internally generated ao SampleClock you also can specify a configurable delay from ao StartTrigger to the first ao SampleClock pulse By default this delay is two ticks of ao SampleClockTimebase
179. y 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 In this 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 3 Note ETS Equivalent Time Sampling NI USB 621x User Manual 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 will increase 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 will be 100 on the second it will be 110 on the third it will be 120 the process will repeat 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 c

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