National Instruments Computer-Based Instruments Digital Oscilloscope for PCI NI 5911 User's Manual
Contents
1. Analog Input AC DC Coupling Connector e LE Protect Calibration 1 MQ PGA b A D Converter a Mux 100 MHz 8 bit 10 KQ a Noise Shaper aa m gt p Calibration Generator o Timing 10 Reference Digital IO Memory Control Clock Connector S Digital Signal K Capture La gt Processor Memory 4 gt Data Figure 2 1 NI 5911 Block Diagram Differential Programmable Gain Input Amplifier PGIA The NI 5911 has a differential programmable gain input amplifier PGIA at the analog input The purpose of the PGIA is to accurately interface to and scale the signal presented to the analog to digital converter ADC regardless of source impedance source amplitude DC biasing or common mode noise voltages National Instruments Corporation 2 1 NI 5911 User Manual Chapter 2 Hardware Overview Differential Input When measuring high dynamic range signals ground noise is often a problem The PGIA of the NI 5911 allows you to make noise free signal measurements The NI 5911 PGIA is a differential amplifier The PGIA differential amplifier efficiently rejects any noise which may be present on the ground signal Internal to the PGIA the signal presented at the negative input is subtracted from the signal presented at the positive input As shown in Figure 2 2 this subtraction removes ground noise from the signal2. Sampling Rate Resolution Bandwidth 12 5 MS s 12 bits 4 MHz 5 MS s 14 bits 2 MHz 2 5 MS s 16 bits 800 kHz 1 MS s 18 bits 400 kHz 500 kS s 18 bits 200 kHz 200 kS s 19 bits 80 kHz 100 kS s 19 bits 40 kHz 50 kS s 20 bits 20 kHz National Instruments Corporation 2 5 NI 5911 User Manual Chapter 2 Hardware Overview Calibration Table 2 2 Available Sampling Rates and Corresponding Bandwidth in Flexible Resolution Mode Continued Sampling Rate Resolution Bandwidth 20 kS s 20 bits 8 kHz 10 kS s 21 bits 4 kHz Like any other type of converter that uses noise shaping to enhance resolution the frequency response of the converter is only flat to its maximum useful bandwidth The NI 5911 has a bandwidth of 4 MHz Beyond this frequency there is a span where the converter acts resonant and where a signal is amplified before being converted These signals are attenuated in the subsequent digital filter to prevent aliasing However if the applied signal contains major signal components in this frequency range such as harmonics or noise the converter may overload and signal data will be invalid In this case you will receive a warning signaling overload You then need to either select a higher input range or attenuate the signal How Flexible Resolution Works The ADC can be sourced through a noise shaping circuit that moves quantization noise on the output of the ADC from lower
3. temperature on the critical circuitry used in flexible resolution mode If this circuit is unable to maintain the temperature within specification an error is generated This error indicates that the temperature of the ADC is out National Instruments Corporation 2 7 NI 5911 User Manual Chapter 2 Hardware Overview of range and should be recalibrated by performing an internal calibration During acquisition in flexible resolution mode an error will be generated if the input to the ADC goes out of range for the converter The fact that this condition has occurred may not be obvious by inspecting the acquired data due to the digital filtering that takes place on the acquired data Therefore an error occurs to let you know that the data includes some samples that were out of the range of the converter and may be inaccurate External Calibration External calibration calibrates the internal reference on the NI 5911 The NI 5911 is already calibrated when it is shipped from the factory Periodically the NI 5911 will need external calibration to remain within the specified accuracy For more information on calibration contact National Instruments or visit ni com calibration For actual intervals and accuracy refer to Appendix A Specifications Triggering and Arming There are several triggering methods for the NI 5911 The trigger can be an analog level that is compared to the input or any of several digital inputs You can also c
4. to the number of records you want to acquire before starting the acquisition The NI 5911 acquires an additional record each time a trigger is accepted until all the requested records are stored in memory This process does not require software intervention after the initial setup has been completed Between each record there is a dead time of approximately 5 us during which the trigger is not accepted During this time the memory controller is setting up for the next record There may also be additional dead time while the minimum number of pretrigger samples are being acquired Figure 2 9 shows a timing diagram of a multiple record acquisition National Instruments Corporation 2 13 NI 5911 User Manual Chapter 2 Hardware Overview x vV X v x Trigger Acquisition _ 4 SHS E In Progress Buffer 1 X 2 x Trigger Not Accepted Pretrigger Points Not Acquired X Trigger Not Accepted 5 us Dead Time X Trigger Not Accepted Acquisition in Progress vV Trigger Accepted Figure 2 9 Multiple Buffer Acquisition RTS Bus Trigger and Clock Lines PFI Lines NI 5911 User Manual The RTSI bus allows National Instruments boards to synchronize timing and triggering on multiple devices The RTSI bus has seven bidirectional trigger lines and one bidirectional clock signal You can program any of the seven trigger lines to provide or accept a synch
5. 0001 fs 5 to 40 C for all input ranges at 1 kHz excluding ripple from digital filters DC OH SGT creed eeregatecetiee cite aetieert 0 1 mV 0 01 fs 5 to 40 C for all input ranges Input Coupling 0 ee eee eee ee DC and AC software selectable AC coupling cut off frequency G3 dB i cessis sates iseseica tise neces 15 Hz 2 Input impedance sss sees eee 1 MQ 2 NI 5911 User Manual A 2 ni com Appendix A Specifications Max measurable input voltage 10 V DC peak AC Input protection sss se eee eee 42 VDC DC peak AC Input bias current sese eee eee ee eee eee ee 1 nA typical at 25 C Common Mode Characteristics Impedance to chassis ground Common mode rejection ratio Filtering Sampling Filter Alias Frequency Mode Bandwidth Ripple Attenuation 100 MHz n Oscilloscope 100 MHz 3 dB N A 12 5 MHz Flexible 3 75 MHz 0 2 dB 60 dB Resolution 5 MHz Flexible 2 MHz 0 1 dB 70 dB Resolution 2 5 MHz Flexible 1 MHz 0 05 dB 80 dB Resolution 1 MHz Flexible 400 kHz 0 005 dB 80 dB Resolution 500 kHz Flexible 200 kHz 0 005 dB 80 dB Resolution 200 kHz Flexible 80 kHz 0 005 dB 80 dB Resolution 100 kHz Flexible 40 kHz 0 005 dB 80 dB Resolution 50 kHz Flexible 20 kHz 0 005 dB 80 dB Resolution 20 kHz Flexible 8 kHz 0 005 dB 80 dB Resolution 10 kHz Flexible 4 kHz 0 005 dB 80 dB Resolution 1 lt n lt 2 2 in os
6. 6 memory 2 13 multiple record acquisition 2 13 to 2 14 oscilloscope mode 2 5 RTSI bus trigger and clock lines 2 14 to 2 15 trigger hold off 2 12 B 10 triggering and arming 2 8 to 2 12 analog trigger circuit 2 9 to 2 11 trigger sources figure 2 9 hysteresis value See analog trigger circuit ni com impedance formula for impedance divider 2 3 input and output impedance 2 3 source impedance B 9 input bias 2 4 input coupling B 10 input frequency B 9 input impedance 2 3 to 2 4 input protection circuits 2 4 input ranges 2 3 installing NI 5911 1 1 measurement accuracy for digitizers See digitizers measurement modes 2 4 to 2 6 flexible resolution mode 2 5 to 2 6 oscilloscope mode 2 5 memory description 2 13 triggering and memory usage 2 13 multiple record acquisition 2 13 to 2 14 dead time 2 13 multiple buffer acquisition figure 2 14 NI 5911 See also hardware overview block diagram 2 1 connectors BNC connector 1 1 DIN connector 1 1 location on front panel figure 1 2 SMB connector 1 1 front panel figure 1 2 installing 1 1 National Instruments Corporation l 3 Index specifications A 1 to A 8 acquisition characteristics A 2 to A 5 acquisition modes A 7 acquisition system A 1 to A 2 timebase system A 5 triggering systems A 6 VirtualBench Scope soft front panel 1 2 to 1 6 Acquire tab figure 1 4 acquiring data 1 4 to 1 5 features 1 5 to 1 6 front pa
7. MHz reference This reference frequency can be supplied by a crystal oscillator on the board or through an external frequency input through the RTSI bus clock line or a PFI input The NI 5911 may also output its 10 MHz reference on the RTSI bus clock line or a PFI line so that other NI 5911 boards or other equipment can be synchronized to the same reference While the reference clock input is sufficient to synchronize the 100 MHz sample clocks it is also necessary to synchronize clock dividers on each NI 5911 so that internal clock divisors are also synchronized on the different boards These lower frequencies are important because they are used to determine trigger times and sample position To synchronize the NI 5911 clock dividers you must connect the boards with a National Instruments RTSI bus cable One of the RTSI bus triggers must be designated as a synchronization line This line will be an output from the master board and an input on the slave boards To synchronize the boards a single pulse is sent from the master to the slaves which gives them a reference time to clear the clock dividers on the boards Hardware arming cannot be used during a multiple board acquisition National Instruments Corporation 2 15 NI 5911 User Manual Specifications This appendix lists the specifications of the NI 5911 These specifications are typical at 25 C unless otherwise specified Acquisition System Bandwidth sss Number of cha
8. NI 5911 User Manual Appendix B Digitizer Basics Analog Bandwidth Analog bandwidth describes the frequency range in Hertz in which a signal can be digitized accurately This limitation is determined by the inherent frequency response of the input path which causes loss of amplitude and phase information Analog bandwidth is the frequency at which the measured amplitude is 3 dB below the actual amplitude of the signal This amplitude loss occurs at very low frequencies if the signal is AC coupled and at very high frequencies regardless of coupling When the signal is DC coupled the bandwidth of the amplifier will extend all the way to the DC voltage Figure B 2 illustrates the effect of analog bandwidth on a high frequency signal The result is a loss of high frequency components and amplitude in the original signal as the signal passes through the instrument Input Signal Bandwidth Instrument Measured Signal Sample Rate NI 5911 User Manual Figure B 2 Analog Bandwidth Sample rate is the rate at which a signal is sampled and digitized by an ADC According to the Nyquist theorem a higher sample rate produces accurate measurement of higher frequency signals if the analog bandwidth is wide enough to let the signal to pass through without attenuation A higher sample rate also captures more waveform details Figure B 3 illustrates a 1 MHz sine wave sampled by a 2 MS s ADC and a 20 MS s ADC The fa
9. NI 5911 User Manual Chapter 2 Hardware Overview Trigger Hold Off The trigger hold off is a length of time that the NI 5911 waits after a trigger is accepted before it accepts another trigger In other words when a trigger is received during acquisition the trigger counter is loaded with the desired hold off time Hardware then rejects all triggers until the counter has expired or the current acquisition completes whichever is longer 3 Note The time the acquisition takes to complete from the time a trigger occurs is posttrigger samples sample rate megahertz If this time is larger than the trigger hold off time the trigger hold off has no effect because triggers are always rejected during acquisition Trigger hold off is provided in hardware using a 32 bit counter clocked by a 25 MHz internal timebase With this configuration you can select a hardware hold off value of 40 ns to 171 8 s in increments of 40 ns Figure 2 8 shows a timing diagram of signals when hold off is enabled and the hold off time is longer than posttriggered acquisition iV x vV x Trigger _ Hold Off _ Acquisition L In Progress _ R Ka on E Pretrigger 1 1 1 Hold Off Time in nanoseconds gt Adjustable between 40 ns and 171 8 s Data X Trigger Not Accepted V Trigger Accepted Figure 2 8 Timing with Hold Off Enabled NI 5911 User Manual 2
10. The ADC converts at a constant rate of 100 MS s but you can choose to store only a fraction of these samples into memory at a lower rate This allows you to store waveforms using fewer data points and decreases the burden of storing analyzing and displaying the waveforms If you need faster sampling rates you can use Random Interleaved Sampling RIS to effectively increase the sampling rate to 1 GS s for repetitive waveforms In oscilloscope mode all signals up to 100 MHz are passed to the ADC You need to ensure that your signal is band limited to prevent aliasing Aliasing and other sampling terms are described more thoroughly in Appendix B Digitizer Basics Sampling Methods Real Time and RIS There are two sampling methods available in oscilloscope mode Real Time and RIS Using real time sampling you can acquire data at a rate of 100 MS n where n is a number from 1 to 4 3 million RIS sampling can be used on repetitive signals to effectively extend the sampling rate above 100 MS s In RIS mode you can sample at rates of 100 MS s n where n is anumber from 2 to 10 The available sampling rates resolutions and bandwidth for flexible resolution mode are shown in Table 2 2 Flexible Resolution Mode Table 2 2 shows the relationship between the available sampling rates and the corresponding bandwidth for flexible resolution mode Table 2 2 Available Sampling Rates and Corresponding Bandwidth in Flexible Resolution Mode
11. User Manual Index noise free signal measurement figure 2 2 digitizers B 1 to B 10 ADC resolution B 4 analog bandwidth B 2 making accurate measurements B 7 to B 10 dynamic range of 8 bit ADC figure B 8 general signal shape B 9 to B 10 input coupling B 10 input frequency B 9 peak to peak value B 7 to B 8 source impedance B 9 trigger hold off B 10 Nyquist theorem B 1 record length B 4 sample rate B 2 to B 3 triggering options B 4 to B 5 vertical sensitivity B 3 to B 4 DIN connector 1 1 to 1 2 distortion specifications A 4 to A 5 dynamic range specifications A 4 E EMC compliance A 7 Equivalent Time Sampling ETS B 5 errors during acquisition 2 7 to 2 8 F filtering specifications A 3 flexible resolution mode 2 5 to 2 6 available sampling rates table 2 5 to 2 6 definition 2 4 purpose and use 2 6 fuse self resetting note 1 3 NI 5911 User Manual l 2 G grounding considerations 2 2 H hardware overview 2 1 to 2 15 See also specifications acquisition system PFI lines 2 14 to 2 15 triggering and arming 2 8 to 2 12 block diagram of NI 5911 2 1 calibration 2 6 to 2 8 differential programmable gain input amplifier PGIA 2 2 to 2 4 AC coupling 2 4 differential input 2 2 grounding considerations 2 2 input bias 2 4 input impedance 2 3 to 2 4 input protection 2 4 input ranges 2 3 noise free signal measurement figure 2 2 flexible resolution mode 2 5 to 2
12. groups common mode rejection ratio a measure of an instrument s ability to reject interference from a common mode signal usually expressed in decibels dB a circuit that counts external pulses or clock pulses timing the manner in which a signal is connected from one location to another 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 a default parameter value recorded in the driver In many cases the default input of a control is a certain value often 0 that means use the current default setting a plug in data acquisition board card or pad The NI 5911 is an example of a device an analog input consisting of two terminals both of which are isolated from computer ground whose difference is measured a device that contains the necessary insulating structures to provide electric shock protection without the requirement of a safety ground connection software that controls a specific hardware instrument electrically erasable programmable read only memory ROM that can be erased with an electrical signal and reprogrammed any method used to sample signals in such a way that the apparent sampling rate is higher than the real sampling rate the condition or state of an analog or digital signal NI 5911 User Manual Glossary F filtering gain H hardware harmonics Hz UO in inductance input bias c
13. 11 Range Input Protection Threshold 10 V 10 V 5 V 5 V 2 V 5 V 1V 5 V 0 5 V 5 V 0 2 V 5 V 0 1 V 5 V Input Impedance The input impedance of the NI 5911 PGIA is 1 MQ between the positive and negative input The output impedance of the device connected to the NI 5911 and the input impedance of the NI 5911 form an impedance divider which attenuates the input signal according to the following formula where V is the measured voltage V is the source voltage R is the external source and R is the input impedance If the device you are measuring has a very large output impedance your measurements will be affected by this impedance divider For example if the device has 1 MQ output impedance your measured signal will be one half the actual signal value National Instruments Corporation 2 3 NI 5911 User Manual Chapter 2 Hardware Overview Input Protection AC Coupling Input Bias The inputs of the PGIA typically draw an input bias current of 1 nA at 25 C Attaching a device with a very high source impedance can cause an offset voltage to be added to the signal you measure according to the formula R x 1 nA where R is the external source impedance For example if the device you have attached to the NI 5911 has an output impedance of 10 KQ typically the offset voltage is 10 uV 10 KQ x1 nA The NI 5911 features input protection circuits that protect both
14. 12 ni com Memory Chapter 2 Hardware Overview The NI 5911 stores samples in onboard memory before transferring the samples to the host computer The minimum size for a buffer in the onboard memory is approximately 4 000 8 bit oscilloscope mode samples or 1 000 32 bit decimation mode samples Software allows you to specify buffers of less than these minimum sizes However the minimum number of points are still acquired into onboard memory but only the specified number of points are retrieved into the host computer s memory The total number of samples that can be stored depends on the size of the acquisition memory module installed on the NI 5911 and the size of each acquired sample Triggering and Memory Usage During the acquisition samples are stored in a circular buffer that is continually rewritten until a trigger is received After the trigger is received the NI 5911 continues to acquire posttrigger samples if you have specified a posttrigger sample count The acquired samples are placed into onboard memory The number of posttrigger or pretrigger samples is only limited by the amount of onboard memory Multiple Record Acquisitions After the trigger has been received and the posttrigger samples have been stored the NI 5911 can be configured to begin another acquisition that is stored in another memory record on the board This is a multiple record acquisition To perform multiple record acquisitions configure the NI5911
15. A 7 acquisition system A 1 to A 2 NI 5911 User Manual l 4 calibration A 8 EMC compliance A 7 operating environment A 7 physical A 7 power requirements A 7 storage environment A 7 timebase system A 5 triggering systems A 6 storage environment specifications A 7 synchronization 2 15 system integration by National Instruments C 1 T TCD time to digital converter B 6 technical support resources C 1 to C 2 timebase system specifications A 5 time to digital converter TDC B 6 triggering and arming 2 8 to 2 12 analog trigger circuit 2 9 to 2 11 above level analog triggering mode figure 2 10 below level analog triggering mode figure 2 10 high hysteresis analog triggering mode figure 2 11 low hysteresis analog triggering mode figure 2 11 memory usage 2 13 specifications A 6 timing with hold off enabled figure 2 12 trigger hold off 2 12 B 10 trigger sources figure 2 9 triggering options digitizers B 4 to B 5 ni com Index V W vertical sensitivity Web support from National Instruments C 1 digitizers B 3 to B 4 Worldwide technical support C 2 specifications A 2 VirtualBench Scope soft front panel 1 2 to 1 6 Acquire tab figure 1 4 acquiring data 1 4 to 1 5 features 1 5 to 1 6 front panel figure 1 5 National Instruments Corporation l 5 NI 5911 User Manual
16. Computer Based Instruments NI 5911 User Manual Digital Oscilloscope for PCI Wy NATIONAL September 2000 Edition gt INSTRUMENTS Part Number 322150B 01 Worldwide Technical Support and Product Information ni com National Instruments Corporate Headquarters 11500 North Mopac Expressway Austin Texas 78759 3504 USA Tel 512 794 0100 Worldwide Offices Australia 03 9879 5166 Austria 0662 45 79 90 0 Belgium 02 757 00 20 Brazil 011 284 5011 Canada Calgary 403 274 9391 Canada Ontario 905 785 0085 Canada Qu bec 514 694 8521 China 0755 3904939 Denmark 45 76 26 00 Finland 09 725 725 11 France 01 48 14 24 24 Germany 089 741 31 30 Greece 30 1 42 96 427 Hong Kong 2645 3186 India 91805275406 Israel 03 6120092 Italy 02 413091 Japan 03 5472 2970 Korea 02 596 7456 Mexico D F 5 280 7625 Mexico Monterrey 8 357 7695 Netherlands 0348 433466 New Zealand 09 914 0488 Norway 32 27 73 00 Poland 0 22 528 94 06 Portugal 351 1 726 9011 Singapore 2265886 Spain 91 640 0085 Sweden 08 587 895 00 Switzerland 056 200 51 51 Taiwan 02 2528 7227 United Kingdom 01635 523545 For further support information see the Technical Support Resources appendix To comment on the documentation send e mail to techpubs ni com Copyright 1998 2000 National Instruments Corporation All rights reserved Important Information Warranty The NI 5911 is warranted against defects in materials and workmanship for a period of one year fr
17. L 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 WOULD CREATE A RISK OF HARM TO PROPERTY OR PERSONS INCLUDING THE RISK OF BODILY INJURY AND DEATH SHOULD NOT BE RELIANT SOLELY UPON ONE FORM OF ELECTRONIC SYSTEM DUE TO THE RISK OF SYSTEM FAILURE TO AVOID DAMAGE INJURY OR DEATH THE USER OR APPLICATION DESIGNER MUST TAKE REASONABLY PRUDENT STEPS TO PROTECT AGAINST SYSTEM FAILURES INCLUDING BUT NOT LIMITED TO BACK UP OR SHUT DOWN MECHANISMS BECAUSE EACH END USER SYSTEM IS CUSTOMIZED AND DIFFERS FROM NATIONAL INSTRUMENTS TESTING PLATFORMS AND BECAUSE A USER OR APPLICATION DESIGNER MAY USE NATIONAL INSTRUMENTS PRODUCTS IN COMBINATION WITH OTHER PRODUCTS IN A MANNER NOT EVALUATED OR CONTEMPLATED BY NATIONAL INSTRUMENTS THE USER OR APPLICATION DESIGNER IS ULTIMATELY RESPONSIBLE FOR VERIFYING AND VALIDATING THE SUITABILITY OF NATIONAL INSTRUMENTS PRODUCTS WHENEVER NATIONAL INSTRUMENTS PRODUCTS ARE INCORPORATED IN A SYSTEM OR APPLICATION INCLUDING WITHOUT LIMITATION THE APPROPRIATE DESIGN PROCESS AND SAFETY LEVEL OF SUCH SYSTEM OR APPLICATION Conventions 3 bold italic monospace The following conventions are used in this manual The symbol leads you through nested menu items and dial
18. Slider adjusts the voltage offset for each channel Use this slider to adjust multiple waveforms Trigger settings group controls the conditions required for signal acquisition For example you can command VirtualBench Scope to wait for a digital trigger or command it to acquire data without triggering in free run mode Main control bar buttons Runacquires data continuously Deselecting this button places the VirtualBench Scope in idle mode Single instructs VirtualBench Scope to perform a single sweep acquisition Auto Setup configures the scope for the best timebase volts per division and trigger setting for each channel currently selected with the channel selector Mode sets the mode of the scope to either volts versus time or X versus Y mode Select Cursor activates two cursors on the waveform display The zoom controls adjust the view of your display data Click the magnifying glass icon to zoom in on the displayed data Click the arrows to the right of the magnifying glass to zoom out to full scale 3 Note Refer to the VirtualBench Scope Online Help for additional help on the front panel items NI 5911 User Manual 1 6 ni com Hardware Overview This chapter includes an overview of the NI5911 explains the operation of each functional unit making up your NI 5911 and describes the signal connections Figure 2 1 shows a block diagram of the NI 5911
19. The inner conductor of the BNC is V the outer shell is V Input Signal V P Vout y _ Ground Noise Figure 2 2 Noise Free Measurements of Signal Grounding Considerations The path for the positive signal has been optimized for speed and linearity You should always apply signals to the positive input and ground to the negative input Reversing the inputs will result in higher distortion and lower bandwidth The negative input of the amplifier is grounded to PC ground through a 10 kQ resistor The PGIA is therefore referenced to ground so it is not necessary to make any external ground connections If the device you connect to the NI 5911 is already connected to ground ground loop noise voltages may be induced into your system Notice that in most of these situations the 10 kQ resistance to PC ground is normally much higher than the cable impedances you use As a result most of the noise voltage occurs at the negative input of the PGIA where it is rejected rather than in the positive input where it would be amplified NI 5911 User Manual 2 2 ni com Chapter 2 Hardware Overview Input Ranges To optimize the ADC resolution you can select different gains for the PGIA In this way you can scale your input signal to match the full input range of the converter The NI 5911 PGIA offers seven different input ranges from 0 1 V to 10 V as shown in Table 2 1 Table 2 1 Input Ranges for the NI 59
20. al to trigger the acquisition Random Interleaved Sampling Random Interleaved Sampling RIS is a form of Equivalent Time Sampling ETS that allows acquisition of pretriggered data ETS refers to any method used to sample signals in such a way that the apparent sampling rate is higher than the real sampling rate ETS is accomplished by sampling different points along the waveform for each occurrence of the trigger and then reconstructing the waveform from the data acquired over many cycles In RIS the arrival of the waveform trigger point occurs at some time randomly distributed between two sampling instants The time from the trigger to the next sampling instant is measured and this measurement allows the waveform to be reconstructed Figure B 5 shows three occurrences of a waveform In Frame 1 the dotted points are sampled and the trigger occurs time t before the next sample In Frame 2 the square points are sampled and the trigger occurs time t before the next sample In Frame 3 the triangular points are sampled and the trigger occurs time t3 before the next sample With knowledge of the three times t t2 and tz you can reconstruct the waveform as if it had been sampled at a higher rate as shown at the bottom of the figure National Instruments Corporation B 5 NI 5911 User Manual Appendix B Digitizer Basics Frame 1 Frame 2 Frame 3 Figure B 5 Waveform Reconstruction with RIS The time measurement is
21. all a software function to trigger the board Figure 2 3 shows the different trigger sources When you use a digital signal that signal must be at a high TTL level for at least 40 ns before any triggers will be accepted 3 Note The NI 5911 does not support delayed triggering NI 5911 User Manual 2 8 ni com Chapter 2 Hardware Overview COME Analog Trigger Circuit Low __ COMP Level a Analog Trigger Circuit Software ATC_OUT RTSI lt 0 6 gt lt Trigger PFI1 PFl2 D 2 Arm b Trigger and Arm Sources ATC_OUT Figure 2 3 Trigger Sources Analog Trigger Circuit The analog trigger on the NI 5911 operates by comparing the current analog input to an onboard threshold voltage This threshold voltage the trigger value can be set within the current input range in 170 steps This means that for a 10 V input range the trigger can be set in increments of 20 V 170 118 mV There may also be a hysteresis value associated with the trigger that can be set in the same size increments The hysteresis value creates a trigger window the signal must pass through before the trigger is accepted You can generate triggers on a rising or falling edge condition as illustrated in the following figures The four different modes of operation for the analog trigger are shown in Figures 2 4 to 2 7 National Instruments Corporation 2 9 NI 5911 User Manual Chapter 2 Hardware Ove
22. alue This parameter in units of volts reflects the maximum change in signal voltage If V is the signal voltage at any given time then V pk to pk V max V min The peak to peak value affects the vertical sensitivity or gain of the input amplifier If you do not know the peak to peak value start with the smallest gain maximum input range and increase it until the waveform is digitized using the maximum dynamic range without clipping the signal Refer to Appendix A Specifications for the maximum input voltage for your NI 5911 device Figure B 7 shows that a gain of 5 is the best setting to digitize a 300 mV 1 MHz sine wave without clipping the signal National Instruments Corporation B 7 NI 5911 User Manual Appendix B Digitizer Basics 127 LSB 47 LSB po lt 0 LSB 8 LSB A n H nai a coe eee ee Pa T eZ a oS 128 LSB a Gain 1 Input Range 5 V Number of LSBs 15 127 LSB 128 LSB b Gain 5 Input Range 1 V Number of LSBs 77 153 LSB 127 LSB 0 LSB Acquired Signal 128 LSB 154 LSB c Gain 20 Input Range 250 mV Number of LSBs 307 2 Figure B 7 Dynamic Range of an 8 Bit ADC with Three Different Gain Settings NI 5911 User Manual B 8 ni com National Instruments Corporation Appendix B Digitizer Basics Source impedance Mocst digitizers and digital storage oscilloscopes DSOs have a 1 MQ input resistance in the passband If the sour
23. ce impedance is large the signal will be attenuated at the amplifier input and the measurement will be inaccurate If the source impedance is unknown but suspected to be high change the attenuation ratio on your probe and acquire data In addition to the input resistance all digitizers DSOs and probes present some input capacitance in parallel with the resistance This capacitance can interfere with your measurement in much the same way as the resistance does Input frequency If your sample rate is less than twice the highest frequency component at the input the frequency components above half your sample rate will alias in the passband at lower frequencies indistinguishable from other frequencies in the passband If the signal s highest frequency is unknown you should start with the digitizer s maximum sample rate to prevent aliasing and reduce the digitizer s sample rate until the display shows either enough cycles of the waveform or the information you need General signal shape Some signals are easy to capture by ordinary triggering methods A few iterations on the trigger level finally render a steady display This method works for sinusoidal triangular square and saw tooth waves Some of the more elusive waveforms such as irregular pulse trains runt pulses and transients may be more difficult to capture Figure B 8 shows an example of a difficult pulse train trigger B 9 NI 5911 User Manual Appendix B Digitizer Ba
24. cilloscope mode National Instruments Corporation A 3 NI 5911 User Manual Appendix A Specifications Dynamic Range Noise excluding input referred noise Sampling Frequency Bandwidth Noise Density Total Noise 100 MHz n 100 MHz 120 dBfs Hz 43 dBfs 12 5 MHz 3 75 MHz 135 dBfs Hz 64 dBfs 5 MHz 2 MHz 150 dBfs Hz 83 dBfs 2 5 MHz 1 MHz 155 dBfs Hz 91 dBfs 1 MHz 400 kHz 160 dBfs Hz 104 dBfs 500 kHz 200 kHz 160 dBfs Hz 107 dBfs 200 kHz 80 kHz 160 dBfs Hz 111 dBfs 100 kHz 40 kHz 160 dBfs Hz 114 dBfs 50 kHz 20 kHz 160 dBfs Hz 117 dBfs 20 kHz 8 kHz 160 dBfs Hz 121 dBfs 10 kHz 4 kHz 160 dBfs Hz 124 dBfs 1 lt n lt 2 2 in oscilloscope mode Distortion SFDR for input SFDR for input SFDR for input Sampling Frequency 0 dBfs 20 dBfs 60 dBfs typical 100 MHz n 50 dB 50 dB N A 12 5 MHz 65 dB 85 dB 125 dB 5 MHz 70 dB 90 dB 130 dB 2 MHz 75 dB 95 dB 135 dB 1 MHz 85 dB 105 dB 145 dB 500 kHz 90 dB 110 dB 150 dB 200 kHz 100 dB 110 dB 160 dB 100 kHz 100 dB 110 dB 160 dB 50 kHz 100 dB 110 dB 160 dB NI 5911 User Manual A 4 ni com Appendix A Specifications SFDR for input SFDR for input SFDR for input Sampling Frequency 0 dBfs 20 dBfs 60 dBfs typical 20 kHz 100 dB 110 dB 160 dB 10 kHz 100 dB 110 dB 160 dB Timebase System National Instruments Corpo
25. ct a signal to Channel 0 of your NI 5911 2 Configure VirtualBench Scope From the Edit menu on the front panel select General Settings b Select NI 5911 from the instrument list as shown in Figure 1 3 If the NI 5911 is not in the device list make sure you have properly configured the device using Measurement amp Automation Explorer MAX For more information on how to configure your NI 5911 in MAX refer to the Where to Start with Your Oscilloscope Digitizer document that shipped with your NI 5911 c Click OK to use these settings E VirtualBench Scope Settings List IVI Instruments IW Baa 1 NI 5911 lt Acquire Display Output 1 m B Trigger Noise Rejection 0 0000 Trigger Holdoff mSec 1k w Buffer Size IZ Use Equivalent Time Sampling BF Loe SELENE Cancel Apply 1 Device Type Selector 2 Device List Figure 1 3 Acquire Tab of VirtualBench Scope Settings Dialog Box NI 5911 User Manual 1 4 ni com Chapter 1 Taking Measurements with the NI 5911 B Note When you launch VirtualBench Scope it automatically uses the settings of your previous VirtualBench Scope session 3 Enable the Ch 0 button in the channel selector area Disable all other channels Disabled channels have a gray frame around them Click Auto Setup on the main control bar 5 Click Run to start the acquisition 3 Note Refer to the VirtualBench Scope Online Help for additional help configur
26. fix for 1 000 or 10 used with units of measure such as volts hertz and meters 1 000 samples laboratory virtual instrument engineering workbench a graphical programming ADE developed by National Instruments least significant bit meters megabytes of memory see buffer million samples most significant bit National Instruments Corporation G 5 NI 5911 User Manual Glossary noise Nyquist frequency Nyquist Sampling Theorem 0 Ohm s Law overrange oversampling P passband PCI peak value posttriggering NI 5911 User Manual an undesirable electrical signal Noise comes from external sources such as the AC power line motors generators transformers fluorescent lights soldering irons CRT displays computers electrical storms welders radio transmitters and internal sources such as semiconductors resistors and capacitors Noise corrupts signals you are trying to send or receive a frequency that is one half the sampling rate See Nyquist Sampling Theorem the theorem states that if a continuous bandwidth limited analog signal contains no frequency components higher than half the frequency at which it is sampled then the original signal can be recovered without distortion R V I the relationship of voltage to current in a resistance a segment of the input range of an instrument outside of the normal measuring range Measurements can still be made usually with a degradation in s
27. frequencies to higher frequencies A digital lowpass filter applied to the data removes all but a fraction of the original shaped quantization noise The signal is then resampled to a lower sampling frequency and a higher resolution Flexible resolution provides antialiasing protection due to the digital lowpass filter NI 5911 User Manual The NI 5911 can be calibrated for very high accuracy and resolution due to an advanced calibration scheme There are two different types of calibration Internal or self calibration and external calibration Internal calibration is performed via a software command that compensates for drifts caused by environmental temperature changes You can internally calibrate your NI 5911 without any external equipment connected External calibration recalibrates the device when the specified calibration interval has expired See Appendix A Specifications for the calibration interval External calibration requires you to connect an external precision voltage reference to the device 2 6 ni com Chapter 2 Hardware Overview Internally Calibrating the NI 5911 Internally calibrate your NI 5911 with a software function or a LabVIEW VI Read more about the function niScope_ CalSelfCalibrate in your NI SCOPE Function Reference Help file LabVIEW users see the context sensitive help Help Show Context Help forniscope Cal Self Calibrate vi When Internal Calibration Is Needed To provide the maximum accuracy
28. generated at the junctions of dissimilar metals that are functions of temperature Also called thermoelectric potentials See thermal EMFs the rate measured in bytes s at which data is moved from source to destination after software initialization and set up operations the maximum rate at which the hardware can operate any event that causes or starts some form of data capture sampling at a rate lower than the Nyquist frequency can cause aliasing the number of output updates per second G 8 ni com VAC VDC error VI Vims W waveform shape working voltage Glossary volts volts alternating current volts direct current voltage error virtual instrument 1 a combination of hardware and or software elements typically used with a PC that has the functionality of a classic stand alone instrument 2 a LabVIEW software module VI which consists of a front panel user interface and a block diagram program volts root mean square value the shape the magnitude of a signal creates over time the highest voltage that should be applied to a product in normal use normally well under the breakdown voltage for safety margin National Instruments Corporation G 9 NI 5911 User Manual Index Numbers 5 V signal limitation on current note 1 3 self resetting fuse note 1 3 A AC coupling 2 4 accuracy characteristics A 2 to A 3 accurate measurements for digitizers See digitizers acquisitio
29. hould 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 Instruments installation operation or maintenance instructions owner s modification of the product owner s abuse misuse or negligent acts and power failure or surges fire flood accident actions of
30. independent of temperature changes the NI 5911 contains a heater that stabilizes the temperature of the most sensitive circuitries on the board However the heater can accommodate for temperature changes over a fixed range of 5 C When temperatures exceed this range the heater no longer is able to stabilize the temperature and signal data becomes inaccurate When the temperature range has been exceeded you receive a warning and you need to perform an internal calibration What Internal Calibration Does Internal calibration performs the following operations 1 The heater is set to regulate over a range of temperatures centered at the current environmental temperature The circuit components require a certain amount of time to stabilize at the new temperature This temperature stabilization accounts for the majority of the calibration time 2 Gain and offset are calibrated for each individual input range The linearity of the ADC is calibrated using an internal sinewave generator as reference 4 The time to digital converter used for RIS measurements is calibrated le Note Do not apply high amplitude or high frequency signals to the NI 5911 during internal calibration For optimal calibration performance disconnect the input signal from the NI 5911 Why Errors Occur During Acquisition The NI 5911 has circuitry to detect error conditions that may affect the acquired data The NI 5911 uses a heater circuit to maintain constant
31. ing VirtualBench Scope for your specific application Soft Front Panel Features The following figure shows the VirtualBench Scope soft front panel rtualBench Scope Scopel File Edit Controls Measure Help Channels mm Chi Math1 Volts div R Refi m Ref2 pe oe f Coupling DC SZ lt Timebase V Position Trigger lt Q Mode Worm gt thi 21 chi chi G D 2 Slope s Run wj Single a fr Pe Mode X Select a Kiga Set50 m 1 Channels Selector 4 Vertical Slider 6 Zoom Controls 2 Channel Settings Group 5 Main Control Bar 7 Graphics Display 3 Trigger Settings Group Figure 1 4 VirtualBench Scope Soft Front Panel National Instruments Corporation 1 5 NI 5911 User Manual Chapter 1 Taking Measurements with the NI 5911 The VirtualBench Scope soft front panel has the following features Channels selector picks a channel or math functions that display waveforms Channel settings group Channel settings selector selects the channel whose settings will be modified Coupling toggles between DC and AC coupling Volts div adjusts the vertical resolution of the channel you select V Position controls the displayed voltage offset Timebase controls the length of the time period that is displayed Turn the knob clockwise to reduce the time period Each horizontal division represents one time period Vertical
32. line problem solving and diagnostic resources include frequently asked questions knowledge bases product specific troubleshooting wizards manuals drivers software updates and more Web support is available through the Technical Support section of ni com NI Developer Zone The NI Developer Zone at ni com zone is the essential resource for building measurement and automation systems At the NI Developer Zone you can easily access the latest example programs system configurators tutorials technical news as well as a community of developers ready to share their own techniques Customer Education National Instruments provides a number of alternatives to satisfy your training needs from self paced tutorials videos and interactive CDs to instructor led hands on courses at locations around the world Visit the Customer Education section of ni com for online course schedules syllabi training centers and class registration System Integration If you have time constraints limited in house technical resources or other dilemmas you may prefer to employ consulting or system integration services You can rely on the expertise available through our worldwide network of Alliance Program members To find out more about our Alliance system integration solutions visit the System Integration section of ni com National Instruments Corporation C 1 NI 5911 User Manual Appendix C Technical Support Resources Worldwide Supp
33. made with a time to digital converter TDC The resolution of the TDC is the number of physical bins to which the TDC can quantize the trigger arrival time This resolution should be several times higher than the maximum desired interpolation factor which is the maximum number of logical bins to which you want the trigger arrival time quantized The higher resolution ensures that when the TDC output is requantized to the desired interpolation factor all output values have a roughly equal probability of occurrence that is all logical bins will contain approximately the same number of physical bins NI 5911 User Manual B 6 ni com Appendix B Digitizer Basics For example consider the maximum interpolation factor to be 5 If the TDC could output values from 0 to 15 then each logical bin will contain three physical bins as shown in Figure B 6 Logical Bin pop tp a S S S a S S S eile ali es e e ise ile ee a a ie Sample i i i i Clock l 3 Physical Bins 1 Logical Bin Physical Bin Desired Interpolation Factor 5 Max Interpolation Factor 15 Figure B 6 Relationship between Interpolation Factor Logical Bins and Physical Bins Making Accurate Measurements For accurate measurements you should use the right settings when acquiring data with your NI 5911 Knowing the characteristics of the signal in consideration helps you to choose the correct settings Such characteristics include e Peak to peak v
34. mmable Gain Input Amplifier PGIA sese 2 1 Differential Input i 755 sr zr a es Neda hides ute aT Ta E 359775 2 2 Grounding Considerations sss ses sss esse sees eee 2 2 Input Ranges T 2 3 Input Impedance ii o alee id uit disease Namie 2 3 INputsBias ssc cise t araa as dle taki tea aati ha hase iinet 2 4 Input N ae TTT 2 4 AC ase 2 4 Oscilloscope and Flexible Resolution Modes sss sese 2 4 Oscilloscope Moden ssrin zera enaa RTT OH RTT 2 5 Sampling Methods Real Time and RIS sese 2 5 Flexible Resolution Mode ss sserssscs saree nanna ecn arrn 2 5 How Flexible Resolution Works 0 sees eee 2 6 Cali Drath On oers secu ceeca E EI PO EET E EE said eeesa raves stpseens Seevetectenn eect 2 6 Internally Calibrating the NI 5911 sese 2 7 When Internal Calibration Is Needed sss 2 7 What Internal Calibration Does sees eee 2 7 Why Errors Occur During Acquisition sees sees sese ee eee 2 7 Extermal Calibration 3c visti ketio dates oleate oc ance teste ee ee oh 2 8 Teas Serine and T 2 8 Analog Trigger Circuits sno oaro ae a ea a eR AE A EA REEE 2 9 Pris eer Te 61 a E aleve E EAE ES EESE 2 12 Mem Ory sts tiie et E RENA ans A ee E eS 2 13 Triggering and Memory Usage sees eee 2 13 Multiple Record Acquisitions sss sees 2 13 National Instruments Corporation v NI 5911 User Manual Contents RTSI Bus Trigger and Clock Lines sss sss esse eee 2 14 STREET 2 14 PFL Linesas Inputs mereni E EAA 2 14 PFI Lines as OUfPUtS iorsin i seani
35. n multiple record 2 13 to 2 14 VirtualBench Scope soft front panel 1 4 to 1 5 acquisition characteristics specifications A 2 to A 5 accuracy A 2 to A 3 common mode characteristics A 3 distortion A 4 to A 5 dynamic range A 4 filtering A 3 acquisition modes specifications A 7 ADC resolution B 4 analog bandwidth B 2 analog trigger circuit 2 9 to 2 11 above level analog triggering mode figure 2 10 below level analog triggering mode figure 2 10 high hysteresis analog triggering mode figure 2 11 low hysteresis analog triggering mode figure 2 11 arming See triggering and arming National Instruments Corporation B bias input 2 4 block diagram of NI 5911 2 1 BNC connector 1 1 to 1 2 C calibration errors occurring during acquisition 2 7 to 2 8 external calibration 2 8 internal calibration 2 7 to 2 8 specifications A 8 clock lines 2 14 to 2 15 common mode characteristics A 3 connectors BNC connector 1 1 DIN connector 1 1 location on front panel figure 1 2 SMB connector 1 1 conventions used in manual iv customer education C 1 D dead time in multiple record acquisition 2 13 differential input grounding considerations 2 2 noise free signal measurement figure 2 2 differential programmable gain input amplifier PGIA 2 1 to 2 4 AC coupling 2 4 differential input 2 2 input bias 2 4 input impedance 2 3 to 2 4 input protection 2 4 input ranges 2 3 NI 5911
36. n samples 1 to 16 million samples 40 ns 171 85 s in increments of 40 ns 170 steps in full scale voltage range 5 V without external attenuation 1 MQ 1 in parallel with 30 pF 15 pF 42 V DC peak AC lt 10 kHz without external attenuation ni com Acquisition Modes RIS Single shot Power Requirements Physical accuracy IS eT T T O connectors Analog input CHO Digital triggers Operating Environment Ambient temperature ceeeeeeseeeeees Relative humidity Storage Environment Ambient temperature ceeeeeeeeeeeees EMC Compliance CE97 FCC National Instruments Corporation A 7 Appendix A Specifications 1 GS s down to 200 MS s effective sample rate repetitive signals only Data is interleaved in software lt 0 5 ns 100 MS s down to 10 kS s sample rate for transient and repetitive signals 4A 100 mA 100 mA 33 8 by 9 9 cm 13 3 by 3 9 in BNC female SMB female 9 pin mini DIN 5 to 40 C 10 to 90 noncondensing 20 to 65 C NI 5911 User Manual Appendix A Specifications Calibration neral aca ted Laa oca Tneryal el eee ee NI 5911 User Manual A 8 Internal calibration is done upon software command The calibration involves gain offset and linearity correction for all input ranges and input modes 1 week or any time temperature changes beyond 5 C Hardware detects temperature variations beyond calibra
37. na 2 15 SYMCHLOMIZAUON ssscs sees cess cetaessesadscagead cceubdusegaleusheted sua EARE E EEA codes ewessdueeds 2 15 Appendix A Specifications Appendix B Digitizer Basics Appendix C Technical Support Resources Glossary Index NI 5911 User Manual vi ni com Taking Measurements with the NI 5911 Thank you for buying a National Instruments 5911 digital oscilloscope with flexible resolution This chapter provides information on installing connecting signals to and acquiring data from your NI 5911 Installing the NI 5911 There are two main steps involved in installation 1 Install the NI SCOPE driver software You use this driver to write programs to control your NI 5911 in different application development environments ADEs NI SCOPE also allows you to interactively control your NI 5911 with VirtualBench Scope 2 Install your NI 5911 For step by step instructions for installing NI SCOPE and the NI 5911 see the Where to Start with Your National Instruments Oscilloscope Digitizer Connecting Signals Figure 1 1 shows the front panel for the NI 5911 The front panel contains three connectors a BNC connector an SMB connector and a 9 pin mini circular DIN connector see Figure 1 2 The BNC connector is for attaching the analog input signal you wish to measure The BNC connector is analog input channel 0 To minimize noise do not allow the shell of the BNC cable to touch or lie near the metal of the computer chassi
38. nel figure 1 5 NI Developer Zone C 1 NI SCOPE driver software examples 1 3 installing 1 1 programmatically controlling NI 5911 1 3 noise free measurements 2 2 Nyquist theorem B 1 0 operating environment specifications A 7 oscilloscope mode definition 2 4 purpose and use 2 5 Real Time and RIS sampling methods 2 5 output impedance 2 3 P peak to peak value B 7 to B 8 PFI lines as inputs 2 14 as outputs 2 15 PGIA See differential programmable gain input amplifier PGIA physical specifications A 7 NI 5911 User Manual Index power requirement specifications A 7 programmatically controlling NI 5911 1 3 pulse train signal difficult figure B 10 R Random Interleaved Sampling RIS interpolation factor figure B 7 purpose and use 2 5 specifications A 7 theory of B 5 to B 7 waveform reconstruction figure B 6 Real Time sampling 2 5 record length B 4 RIS See Random Interleaved Sampling RIS RTSI bus trigger and clock lines PFI lines 2 14 to 2 15 purpose and use 2 14 to 2 15 synchronization 2 15 S sample rate digitizers B 2 to B 3 flexible resolution mode sampling rates table 2 5 to 2 6 signal shape general B 9 to B 10 SMB connector 1 1 to 1 2 source impedance B 9 specifications A 1 to A 8 acquisition characteristics A 2 to A 5 accuracy A 2 to A 3 common mode characteristics A 3 distortion A 4 to A 5 dynamic range A 4 filtering A 3 acquisition modes
39. nnels Number of flexible resolution ADC Max sample rate 1 GS s repetitive 100 MS s single shot 100 MHz maximum at all input ranges 1 for PCI 2 for VXI 1 for PCI 2 for VXI Sample onboard memory sss sees ee 4 MB or 16 MB Memory sample depth Sampling Sample Depth Sample Depth Frequency Mode 4 MB 16 MB 100 MHz n Oscilloscope 4MS 16 MS 12 5 MHz Flexible Resolution 1 MS 4MS 5 MHz Flexible Resolution 1 MS 4MS 2 5 MHz Flexible Resolution 1 MS 4MS 1 MHz Flexible Resolution 1MS 4MS 500 kHz Flexible Resolution 1 MS 4MS 200 kHz Flexible Resolution 1MS 4MS 100 kHz Flexible Resolution 1 MS 4MS 50 kHz Flexible Resolution 1 MS 4MS National Instruments Corporation A 1 NI 5911 User Manual Appendix A Specifications Sampling Sample Depth Sample Depth Frequency Mode 4 MB 16 MB 20 kHz Flexible Resolution 1 MS 4MS 10 kHz Flexible Resolution 1 MS 4MS 1 lt n lt 22 in oscilloscope mode Memory record sizes sese eee eee 2 000 samples to maximum sample depth determined by sample frequency Vertical sensitivity input ranges Input Range Noise Referred to Input 10 V 174 dBfs Hz 5 V 168 dBfs Hz 2 V 160 dBfs Hz 1 V 154 dBfs Hz 0 5 V 148 dBfs Hz 0 2 V 140 dBfs Hz 0 1 V 134 dBfs Hz Acquisition Characteristics Accuracy Amplitude accuracy sese sees eee ee eee 0 05 signal 0
40. og 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 Bold text denotes items that you must select or click on 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 This font 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 Text in this font is also used for proper names of functions or variables Contents Chapter 1 Taking Measurements with the NI 5911 Tnistallang the NU S91 eas bae e dhata oboegdesdecutey tiguecssaiysscedstas Mave sesdbeveteseeettesd tty 1 1 E STT ETT i sbepes testa ieth tthe Saves sath wi aeases E A 1 1 Acquiring Data with Your NI 5911 occ cee aea greaat receve Eeden 1 3 Programmatically Controlling Your NI 591 sss 1 3 Interactively Controlling Your NI 5911 with VirtualBench Scope 1 3 Using the VirtualBench Scope Soft Front Panel eee 1 3 Soft Front Panel Features 000 ese eseescesseseceeessnesscsseessesseeesseevensens 1 5 Chapter 2 Hardware Overview Differential Progra
41. om 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 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 s
42. oot mean square a measure of signal amplitude the square root of the average value of the square of the instantaneous signal amplitude read only memory real time system integration bus the National Instruments timing bus that connects devices directly by means of connectors on top of the boards for precise synchronization of functions seconds samples samples per second used to express the rate at which an instrument samples an analog signal 100 MS s would equal 100 million samples each second NI 5911 User Manual Glossary sense settling time source impedance system noise T temperature coefficient thermal drift thermal EMFs thermoelectric potentials transfer rate trigger U undersampling update rate NI 5911 User Manual in four wire resistance the sense measures the voltage across the resistor being excited by the excitation current the amount of time required for a voltage to reach its final value within specified limits 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 a measure of the amount of noise seen by an analog circuit or an ADC when the analog inputs are grounded the percentage that a measurement will vary according to temperature See thermal drift measurements that change as the temperature varies thermal electromotive forces voltages
43. ort National Instruments has offices located around the world to help address your support needs You can access our branch office Web sites from the Worldwide Offices section of ni com Branch office Web sites provide up to date contact information support phone numbers e mail addresses and current events If you have searched the technical support resources on our Web site and still cannot find the answers you need contact your local office or National Instruments corporate Phone numbers for our worldwide offices are listed at the front of this manual NI 5911 User Manual C 2 ni com Glossary Prefix Meanings Value p pico 10 7 n nano 10 9 u micro 10 6 m milli 10 3 k kilo 103 M mega 106 G giga 10 Symbols percent positive of or plus negative of or minus per degree plus or minus Q ohm A A amperes A D analog to digital AC alternating current National Instruments Corporation G 1 NI 5911 User Manual Glossary AC coupled ADC ADC resolution alias amplification amplitude flatness attenuate bandwidth buffer bus C C channel NI 5911 User Manual the passing of a signal through a filter network that removes the DC component of the signal analog to digital converter an electronic device often an integrated circuit that converts an analog voltage to a digital number the resolution of
44. pecifications sampling at a rate greater than the Nyquist frequency the frequency range that a filter passes without attenuation Peripheral Component Interconnect a high performance expansion bus architecture originally developed by Intel to replace ISA and EISA it is achieving widespread acceptance as a standard for PCs and workstations and offers a theoretical maximum transfer rate of 132 Mbytes s the absolute maximum or minimum amplitude of a signal AC DC the technique to acquire a programmed number of samples after trigger conditions are met G 6 ni com pretriggering PXI R R RAM real time sampling random interleaved sampling resolution rms ROM RTSI bus S s National Instruments Corporation G 7 Glossary the technique used on a device to keep a buffer filled with data so that when the trigger conditions are met the sample includes the data leading up to the trigger condition PCI eXtensions for Instrumentation PXI is an open specification that builds off the CompactPCI specification by adding instrumentation specific features resistor random access memory sampling that occurs immediately method of increasing the sample rate by repetitively sampling a repeated waveform the smallest signal increment that can be detected by a measurement system Resolution can be expressed in bits or in digits The number of bits in a system is roughly equal to 3 3 times the number of digits r
45. ration Number of timebases Clock accuracy as Master Clock input tolerance as Slave Clock T T eee Clock compatibility Interpolator resolution repetitive only eee Sampling clock frequencies Oscilloscope mode Flexible Resolution mode Synchronization Phase difference between multiple instruments A 5 2 RTSI clock configured as a 10 MHz clock output Master or RTSI clock configured as a 10 MHz reference clock input Slave 10 MHz 50 ppm 10 MHz 100 ppm lt 75 pSrms independent of reference clock source TTL for both input and output 1 ns 100 MHz n where 1 lt n lt 232 100 MHz n where n 8 20 50 100 200 500 1000 2000 5000 10000 Via RTSI trigger lines lt 5 ns at any input frequency lt 100 MHz from input connector to input connector NI 5911 User Manual Appendix A Specifications Triggering Systems COUpIING Fis ncnct vn dive teteeteietteet Pretrigger depth T Posttrigger depth eee Holdoff by time sss eee SONSILVILY mosies TRIG input range eee TRIG input impedance sss ee TRIG input protection sese ee NI 5911 User Manual A 6 Above threshold below threshold between thresholds outside thresholds CHO RTSI lt 0 6 gt PFI 1 2 Rising falling Full scale voltage n where n is between 1 and 170 full scale voltage on TRIG is fixed to 5 V without external attenuation AC DC on CHO TRIG 1 to 16 millio
46. ronous trigger signal You can also use any of the RTSI trigger lines to provide a synchronization pulse from a master board if you are synchronizing multiple NI 5911 boards You can use the RTSI bus clock line to provide or accept a 10 MHz reference clock to synchronize multiple NI 5911 boards The NI 5911 has two digital lines that can accept a trigger accept or generate a reference clock or output a square wave of programmable frequency The function of each PFI line is independent However only one trigger source can be accepted during acquisition PFI Lines as Inputs You can select PFI or PFI2 as inputs for a trigger or a reference clock Please see the section Synchronization for more information about the use of reference clocks in the NI 5911 2 14 ni com Chapter 2 Hardware Overview PFI Lines as Outputs You can select PFI1 or PFI2 to output several digital signals Reference Clock is a 10 MHz clock that is synchronous to the 100 MHz sample clock on the NI 5911 You can use the reference clock to synchronize to another NI 5911 configured as a slave device or to other equipment that can accept a 10 MHz reference Frequency Output is a 1 kHz digital pulse train signal with a 50 duty cycle The most common application of Frequency Output for the NI 5911 is to provide a signal for compensating a passive probe Synchronization The NI 5911 uses a digital phase locked loop to synchronize the 100 MHz sample clock to a 10
47. rview Y Falling Edge Trigger A Rising Edge Trigger Figure 2 4 Below Level Analog Triggering Mode In below level analog triggering mode the trigger is generated when the signal value is less than the trigger value Trigger Value Y Falling Edge Trigger A Rising Edge Trigger Figure 2 5 Above Level Analog Triggering Mode In above level analog triggering mode the trigger is generated when the signal value is greater than trigger value NI 5911 User Manual 2 10 ni com Chapter 2 Hardware Overview Trigger Value Hysteresis Value i Trigger A K A 1 Y Faning Edge Trigger Rising Edge Trigger Figure 2 6 High Hysteresis Analog Triggering Mode In high hysteresis analog triggering mode the trigger is generated when a signal crosses above the hysteresis value and then crosses above the trigger value The signal must cross back below the hysteresis value before another trigger is generated Hysteresis _ Value Trigger Value Trigger Y Falling Edge Trigger A Rising Edge Trigger Figure 2 7 Low Hysteresis Analog Triggering Mode In low hysteresis analog triggering mode the trigger is generated when the signal crosses below the hysteresis value and then crosses the trigger value The signal must cross back above the hysteresis value before another trigger is generated National Instruments Corporation 2 11
48. s The SMB connector is for external triggers and for generating a probe compensation signal The SMB connector is PFI1 The DIN connector gives you access to an additional external trigger line The DIN connector can be used to access PFI2 National Instruments Corporation 1 1 NI 5911 User Manual Chapter 1 Taking Measurements with the NI 5911 Figure 1 1 NI 5911 Connectors 0 OO 2 GND 3 Reserved 1 5 Volts Fused 4 Reserved 7 Reserved 5 Reserved 8 Reserved 6 PFI2 9 Reserved NI 5911 User Manual Figure 1 2 9 Pin Mini Circular DIN Connector ni com Chapter 1 Taking Measurements with the NI 5911 B Note The 5 V signal is fused at 1 1 A However National Instruments recommends limiting the current from this pin to 30 mA The fuse is self resetting Acquiring Data with Your NI 5911 You can acquire data either programmatically by writing an application for your NI 591 1 or interactively with the VirtualBench Scope soft front panel Programmatically Controlling Your NI 5911 To help you get started programming your NI 5911 NI SCOPE comes with examples that you can use or modify You can find LabVIEW examples by going to Program Files National Instruments LabVIEW Examples Instr niScopeExamples 11b Examples for CVI C and Visual Basic programmers using Windows 98 95 are located in vxipnp win95 Niscope Example
49. s and examples for CVI C and Visual Basic programmers using Windows 2000 NT are available at vxipnp winnt Niscope Examples Other resources include the NI SCOPE Instrument Driver Quick Reference Guide It contains abbreviated information on the most commonly used functions and LabVIEW VIs For more detailed function reference help see the NI SCOPE Function Reference Help file located at Start Programs National Instruments SCOPE For more detailed VI help use LabVIEW context sensitive help Help Show Context Help Interactively Controlling Your NI 5911 with VirtualBench Scope The VirtualBench Scope soft front panel allows you to interactively control your NI 5911 as you would a desktop oscilloscope The following sections explain how to make connections to your NI 5911 and take simple measurements using the VirtualBench Scope soft front panel as shown in Figure 1 4 To launch the soft front panel select Start Programs National Instruments SCOPE VirtualBench Scope Using the VirtualBench Scope Soft Front Panel The following sections describe how to perform simple analog input measurements using the VirtualBench Scope soft front panel National Instruments Corporation 1 3 NI 5911 User Manual Chapter 1 Taking Measurements with the NI 5911 Acquiring Data When you launch VirtualBench Scope it operates in continuous run mode To start acquiring signals with VirtualBench Scope complete the following steps 1 Conne
50. sics V SVF Trigger Level Hold off Hold off 1 and 3 Trigger Accepted 2 and 4 Trigger Ignored Figure B 8 Difficult Pulse Train Signal Ideally the trigger event should occur at condition one but sometimes the instrument may trigger on condition two because the signal crosses the trigger level You can solve this problem without using complicated signal processing techniques by using trigger hold off which lets you specify a time from the trigger event to ignore additional triggers that fall within that time With an appropriate hold off value the waveform in Figure B 8 can be properly captured by discarding conditions two and four e Input coupling You can configure the input channels on your NI 5911 to be DC coupled or AC coupled DC coupling allows DC and low frequency components of a signal to pass through without attenuation In contrast AC coupling removes DC offsets and attenuates low frequency components of a signal This feature can be exploited to zoom in on AC signals with large DC offsets such as switching noise on a 12 V power supply Refer to Appendix A Specifications for input limits that must be observed regardless of coupling NI 5911 User Manual B 10 ni com Technical Support Resources Web Support National Instruments Web support is your first stop for help in solving installation configuration and application problems and questions On
51. ster ADC digitizes 20 points per cycle of the input signal compared with 2 points per cycle with the slower ADC In this example the higher sample rate more accurately captures the waveform shape as well as frequency B 2 ni com Appendix B Digitizer Basics T U La K m Sample Rate 2 MS s e Sample Rate 20 MS s Figure B 3 1 MHz Sine Wave Sample Vertical Sensitivity Vertical sensitivity describes the smallest input voltage change the digitizer can capture This limitation is because one distinct digital voltage encompasses a range of analog voltages Therefore it is possible that a minute change in voltage at the input is not noticeable at the output of the ADC This parameter depends on the input range gain of the input amplifier and ADC resolution It is specified in volts per LSB Figure B 4 shows the transfer function of a 3 bit ADC with a vertical range of 5 V having a vertical sensitivity of 5 8 V LSB National Instruments Corporation B 3 NI 5911 User Manual Appendix B Digitizer Basics A Range 0 5 V 111 B 110 101 100 011 T E 010 H i 001 i i 000 i i t a 0 s 5 V Voltage Fluctuations in This Region Will Be Unnoticed Figure B 4 Transfer Function of a 3 Bit ADC ADC Resolution ADC resolution limits the accuracy of a measurement The higher the resolution number of bits the more accurate the measurement An 8 bit ADC di
52. the ADC which is measured in bits An ADC with16 bits has a higher resolution and thus a higher degree of accuracy than a 12 bit ADC a false lower frequency component that appears in sampled data acquired at too low a sampling rate a type of signal conditioning that improves accuracy in the resulting digitized signal and reduces noise a measure of how close to constant the gain of a circuit remains over a range of frequencies to reduce in magnitude bit one binary digit either 0 or 1 byte eight related bits of data an eight bit binary number Also used to denote the amount of memory required to store one byte of data the range of frequencies present in a signal or the range of frequencies to which a measuring device can respond temporary storage for acquired or generated data software the group of 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 and ISA bus Celsius pin or wire lead to which you apply or from which you read the analog or digital signal G 2 ni com clock CMRR counter timer coupling D dB DC default setting device differential input double insulated drivers E EEPROM equivalent time sampling event National Instruments Corporation G 3 Glossary hardware component that controls timing for reading from or writing to
53. the positive and negative analog input from damage from AC and DC signals up to 42 V If the voltage at one of these inputs exceeds a threshold voltage V the input clamps to V and a resistance of 100 KQ is inserted in the path to minimize input currents to a nonharmful level The protection voltage V is input range dependent as shown in Table 2 1 When you need to measure a small AC signal on top of a large DC component you can use AC coupling AC coupling rejects any DC component in your signal before it enters into the PGIA Activating AC coupling inserts a capacitor in series with the input impedance Input coupling can be selected via software See Appendix B Digitizer Basics for more information on input coupling Oscilloscope and Flexible Resolution Modes NI 5911 User Manual In oscilloscope mode the NI 5911 works as a conventional desktop oscilloscope acquiring data at 100 MS s with a vertical resolution of 8 bits This mode is useful for displaying waveforms and for deriving waveform parameters such as slew rate rise time and settling time Flexible resolution differs from oscilloscope mode in two ways it has higher resolution sampling rate dependent and the signal bandwidth is limited to provide antialiasing protection This mode is useful for spectral analysis distortion analysis and other measurements for which high resolution is crucial 2 4 ni com Chapter 2 Hardware Overview Oscilloscope Mode
54. 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 Trademarks CVI LabVIEW National Instruments ni com and VirtualBench are trademarks of National Instruments Corporation Product and company names mentioned herein are trademarks or trade names of their respective companies 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 CONTRO
55. tion limits which can also be queried by software Internal reference requires recalibration ni com Digitizer Basics This appendix explains basic information you need to understand about making measurements with digitizers including important terminology Understanding Digitizers Nyquist Theorem National Instruments Corporation B 1 To understand how digitizers work you should be familiar with the Nyquist theorem and how it affects analog bandwidth and sample rate You should also understand terms including vertical sensitivity analog to digital converter ADC resolution record length and triggering options The Nyquist theorem states that a signal must be sampled at least twice as fast as the bandwidth of the signal to accurately reconstruct the waveform otherwise the high frequency content will alias at a frequency inside the spectrum of interest passband An alias is a false lower frequency component that appears in sampled data acquired at too low a sampling rate Figure B 1 shows a 5 MHz sine wave digitized by a6 MS s ADC The dotted line indicates the aliased signal recorded by the ADC at that sample rate Figure B 1 Sine Wave Demonstrating the Nyquist Frequency The 5 MHz frequency aliases back in the passband falsely appearing as if it were a 1 MHz sine wave To prevent aliasing in the passband a lowpass filter limits the frequency content of the input signal above the Nyquist rate
56. urrent input impedance instrument driver interrupt NI 5911 User Manual a type of signal conditioning that allows you to filter unwanted signals from the signal you are trying to measure the factor by which a signal is amplified sometimes expressed in decibels the physical components of a computer system such as the circuit boards plug in boards chassis enclosures peripherals cables and so on multiples of the fundamental frequency of a signal hertz per second as in cycles per second or samples per second input output the transfer of data to from a computer system involving communications channels operator interface devices and or data acquisition and control interfaces inches the relationship of induced voltage to current the current that flows into the inputs of a circuit the measured resistance and capacitance between the input terminals of a circuit a set of high level software functions that controls a specific plug in DAQ board Instrument drivers are available in several forms ranging from a function callable language to a virtual instrument VI in LabVIEW a computer signal indicating that the CPU should suspend its current task to service a designated activity G 4 ni com interrupt level ISA K kS L LabVIEW LSB m MB memory buffer MS MSB Glossary the relative priority at which a device can interrupt industry standard architecture kilo the standard metric pre
57. vides the vertical range of the input amplifier into 256 discrete levels With a vertical range of 10 V the 8 bit ADC cannot resolve voltage differences smaller than 39 mV In comparison a 12 bit ADC with 4 096 discrete levels can resolve voltage differences as small as 2 4 mV Record Length Record length refers to the amount of memory dedicated to storing digitized samples for postprocessing or display In a digitizer record length limits the maximum duration of a single shot acquisition For example with a 1 000 sample buffer and a sample rate of 20 MHz the duration of acquisition is 50 us the number of points multiplied by the acquisition time point or 1 000 x 50 ns With a 100 000 sample buffer and a sample rate of 20 MHz the duration of acquisition is 5 ms 100 000 x 50 ns Triggering Options One of the biggest challenges of making a measurement is to successfully trigger the signal acquisition at the point of interest Since most high speed digitizers actually record the signal for a fraction of the total time they can easily miss a signal anomaly if the trigger point is set incorrectly The NI 5911 is equipped with sophisticated triggering options such as trigger NI 5911 User Manual B 4 ni com Appendix B Digitizer Basics thresholds programmable hysteresis values and trigger hold off The NI 5911 also has two digital triggers that give you more flexibility in triggering by allowing you to connect a TTL CMOS digital sign
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