National Instruments Marine Instruments NI 5911 User's Manual
Contents
1. 1 ji T i V 1 x WA x i d i i i 1 1 1 i 1 1 i 1 1 1 1 T L 1 1 i T i 1 1 1 1 1 1 1 1 1 i 1 i i L 1 I gt al 1 f T la gt lt aS re 1 j 1 ata 1 1 Pretrigger 1 Data 1 1 Hold Off Time in nanoseconds gt Adjustable between 40 ns and 171 8 s X Trigger Not Accepted V Trigger Accepted Memory NI 5911 User Manual Figure 2 8 Timing with Hold Off Enabled Samples are acquired into onboard memory on the NI 5911 before being transferred to the host computer The minimum size for a buffer 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 When specifying a smaller buffer size 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 on the size of each acquired sample 2 12 National Instruments Corporation Multiple Record Chapter 2 Hardware Overview 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 perfor2. Appendix A Specifications Dynamic Range Noise excluding input referred noise Total Sampling Frequency Bandwidth Noise Density Noise 100 MHz n 100 MHz 120 dBfs sqrt Hz 43 dBfs 12 5 MHz 3 75 MHz 135 dBfs sqrt Hz 64 dBfs 5 MHz 2 MHz 150 dBfs sqrt Hz 83 dBfs 2 5 MHz 1 MHz 155 dBfs sqrt Hz 91 dBfs 1 MHz 400 kHz 160 dBfs sqrt Hz 104 dBfs 500 kHz 200 kHz 160 dBfs sqrt Hz 107 dBfs 200 kHz 80 kHz 160 dBfs sqrt Hz 111 dBfs 100 kHz 40 kHz 160 dBfs sqrt Hz 114 dBfs 50 kHz 20 kHz 160 dBfs sqrt Hz 117 dBfs 20 kHz 8 kHz 160 dBfs sqrt Hz 121 dBfs 10 kHz 4 kHz 160 dBfs sqrt Hz 124 dBfs 1 lt n lt 2 in oscilloscope mode Distortion Sampling SFDR for input SFDR for input SFDR for input 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 20 kHz 100 dB 110 dB 160 dB 10 kHz 100 dB 110 dB 160 dB A 5 NI 5911 User Manual National Instruments Corporation Appendix A Specifications Timebase System Number of timebases Clock accuracy as Master Clock input tolerance as Slave Clock jitter Clock compatibility Interpolator resolution repetitive only Sampling clock frequen
3. 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 faster 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 sa
4. Measurements with the NI 5911 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 Acquiring Data When you launch VirtualBench Scope it operates in continuous run mode You can start acquiring signals with VirtualBench Scope by completing the following steps 1 Connect a signal to Channel 0 of your NI 5911 2 Configure VirtualBench Scope National Instruments Corporation Select General Settings from the Edit menu on the front panel Your NI 5911 is an IVI compliant device To configure VirtualBench SCOPE to use your NI 5911 click on the IVI Device Type Selector icon located in the Settings dialog box shown in Figure 1 3 Select NI 5911 as the device you want to use from the Device List located in the Settings dialog box shown in Figure 1 3 If the NI 5911 does not appear in the Device list make sure you have properly configured the device using the Measurement amp Automation Explorer Click on OK to use these settings 1 5 NI 5911 User Manual Chapter 1 Taking Measurements with the NI 5911 Device Type Selector ES VirtualBench Scope Settings List IVI Instru Device List Acquire Display Output 1 m lt Trigger Noise Rejection 0 0000 Trigger Holdoff mSec 1k v Buffer Size CF Note CF Note NI 5911 User Manual Figure 1 3 Ac
5. can be selected via software See Appendix B Digitizer Basics for more information on input coupling Measurement Modes NI 5911 User Manual The ADC samples at a constant rate of 100 MS s with a vertical resolution of 8 bits Using random interleaved sampling RIS the sample rate can be increased to 1 GS s In this conventional mode of operation called oscilloscope mode the analog bandwidth is 100 MHz For sampling signals with lower bandwidth the ADC can be sourced through a noise shaping circuit that moves quantization noise on the output of the ADC from lower 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 This mode called flexible resolution mode provides antialiasing protection due to the digital lowpass filter 2 4 National Instruments Corporation Chapter 2 Hardware Overview Oscilloscope Mode In the oscilloscope mode the NI 5911 works as a conventional desktop oscilloscope This mode is useful for displaying waveforms and for deriving waveform parameters such as slew rate rise time and settling time The sample resolution in oscilloscope mode is 8 bits 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
6. equipment used to monitor or safeguard human health and safety in medical or clinical treatment Conventions bold bold italic italic The following conventions are used in this manual The symbol leads you through nested menu items and dialog box options to a final action The sequence File Page Setup Options Substitute Fonts directs you to pull down the File menu select the Page Setup item select Options and finally select the Substitute Fonts options from the last dialog box This icon to the left of bold italicized text denotes a note which alerts you to important information This icon to the left of bold italicized text denotes a caution which advises you of precautions to take to avoid injury data loss or a system crash This icon to the left of bold italicized text denotes a warning which advises you of precautions to take to avoid being electrically shocked Bold text denotes the names of menus menu items parameters dialog boxes dialog box buttons or options icons windows Windows 95 tabs or LEDs Bold italic text denotes a note caution or warning Italic text denotes variables emphasis a cross reference or an introduction to akey concept This font also denotes text from which you supply the appropriate word or value as in Windows 3 x Contents Chapter 1 Taking Measurements with the NI 5911 Comme chins SiON Als T 1 1 Introduction to the VirtualBench Scope Soft Front Pane
7. 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 third parties or other events outside reasonable control Under
8. fewer data points and decreases the burden of storing analyzing and displaying the waveforms If you need faster sampling rates you can use 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 Flexible Resolution Mode Flexible resolution mode 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 where high resolution is crucial Table 2 2 shows the relationship between the available sampling rates and the corresponding bandwidth for flexible resolution mode National Instruments Corporation 2 5 NI 5911 User Manual Chapter 2 Hardware Overview Table 2 2 Available Sampling Rates and Corresponding Bandwidth in Flexible Resolution Mode 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 MS s 18 bits 200 kHz 200 MS s 19 bits 80 kHz 100 MS s 19 bits 40 kHz 50 MS s 20 bits 20 kHz 20 MS s 20 bits 8 kHz 10 MS s 21 bits 4 kHz Like any other type
9. is generated Hysteresis _ Value Trigger Value Trigger 7 T Y Falling Edge Trigger i 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 value is less than trigger Value with the hysteresis specified by hysteresisValue The signal must cross back above the hysteresis Value before another trigger is generated Trigger Hold Off 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 National Instruments Corporation 2 11 NI 5911 User Manual Chapter 2 Hardware Overview 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 The time the acquisition takes to complete from the time a trigger occurs is posttrigger samples sample rate MHz 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 Figure 2 8 shows a timing diagram of signals when hold off is enabled and the hold off time is longer than posttriggered acquisition Trigger Hold Off Acquisition In Progress
10. of a difficult pulse train trigger Trigger Level V Hold off 1 and 3 Trigger Accepted 2 and 4 Trigger Ignored NI 5911 User Manual Figure B 6 Difficult Pulse Train Signal B 6 National Instruments Corporation Appendix B Digitizer Basics 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 6 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 National Instruments Corporation B 7 NI 5911 User Manual Customer Communication For your convenience th
11. 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 an error signaling overload You then need to either select a higher input range or attenuate the signal Acquisition System NI 5911 User Manual The NI5911 acquisition system controls the way samples are acquired and stored It is possible for the NI 5911 to acquire data at different rates and resolutions There are two sampling methods available in oscilloscope mode Real Time and Repetitive 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 a number from 2 to 10 The available 2 6 National Instruments Corporation Calibration Chapter 2 Hardware Overview sampling rates resolutions and bandwidth for flexible
12. resolution mode are shown in Table 2 2 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 The NI 5911 can be calibrated for very high accuracy and resolution due to an advanced calibration scheme There are two different calibration schemes depending on the type of calibration to be performed Internal calibration the more common of the two schemes is performed via a software command that compensates for drifts caused by environmental temperature changes Internal calibration can be executed without any external equipment connected External calibration which is performed much less frequently is used to recalibrate the board when the specified calibration interval has expired External calibration requires you to connect an external precision voltage reference to the board Internal Calibration To provide the maximum accuracy 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 ran
13. the time period that appears in the graphics display Each horizontal division represents one time period Graphics Display displays waveforms 1 3 NI 5911 User Manual Chapter 1 Taking Measurements with the NI 5911 iz Note NI 5911 User Manual e Vertical Slider adjusts the voltage offset for each channel Use this slider when you want to adjust multiple waveforms in the graphics display e Trigger Settings Group controls the conditions required for signal acquisition for example whether to wait for a digital trigger before acquiring data or whether to acquire data in free run mode no triggering s Main Control Bar Buttons Run acquires 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 e Zoom Controls adjusts the view of your display data Scroll Bar adjusts the zoom view Zoom In zooms in on displayed data Each zoom increases the view by a factor of two Zoom Out zooms out to full X scale Refer to the VirtualBench Scope Online Help for additional help on the front panel items 1 4 National Instruments Corporation Chapter 1 Taking
14. 100 MHz n Oscilloscope 4 MS 16 MS 12 5 MHz Flexible 1MS 4MS Resolution 5 MHz Flexible 1 MS 4MS Resolution 2 5 MHz Flexible 1MS 4MS Resolution 1 MHz Flexible 1MS 4MS Resolution 500 kHz Flexible 1MS 4MS Resolution National Instruments Corporation A 1 NI 5911 User Manual Appendix A Specifications Sampling Sample depth Sample depth Frequency Mode 4 MB option 16 MB option 200 kHz Flexible 1 MS 4MS Resolution 100 kHz Flexible 1 MS 4MS Resolution 50 kHz Flexible 1 MS 4MS Resolution 20 kHz Flexible 1MS 4MS Resolution 10 kHz Flexible 1MS 4MS Resolution 1 lt n lt 2 in oscilloscope mode Memory record sizes sees eee eee 2 000 samples to maximum sample depth determined by sample frequency Vertical sensitivity input ranges Noise Referred Input Range to Input 10 V 174 dBfs sqrt Hz 5 V 168 dBfs sqrt Hz 2 V 160 dBfs sqrt Hz V 154 dBfs sqrt Hz 0 5 V 148 dBfs sqrt Hz 0 2 V 140 dBfs sqrt Hz 0 1 V 134 dBfs sqrt Hz NI 5911 User Manual A 2 National Instruments Corporation Appendix A Specifications Acquisition Characteristics Accuracy Amplitude accuracy sese eee eee 0 05 signal 0 0001 fs 5 to 40 C for all input ranges at 1 kHz excluding ripple from digital filters DC OfTSEU Airesen ne en 0 1 mV 0 01 fs 5 C to 40 C for all input ranges Input Coupling oo eee eee ee
15. 2 2 to 2 4 AC coupling 2 4 differential input 2 2 to 2 4 grounding considerations 2 2 to 2 3 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 measurement modes 2 4 to 2 6 flexible resolution mode 2 5 to 2 6 oscilloscope mode 2 5 memory size 2 12 multiple record acquisition 2 13 to 2 14 dead time 2 13 multiple buffer acquisition figure 2 14 National Instruments Corporation l 3 Index 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 specifications A 1 to A 8 acquisition characteristics A 3 to A 5 acquisition modes A 7 to A 8 acquisition system A 1 to A 2 timebase system A 6 triggering systems A 6 to A 7 VirtualBench Scope soft front panel 1 2 to 1 6 Acquire tab figure 1 6 acquiring data 1 5 to 1 6 features 1 3 to 1 4 front panel figure 1 3 noise free measurements 2 2 Nyquist theorem B 1 0 operating environment specifications A 8 oscilloscope mode 2 5 output impedance 2 3 to 2 4 P peak to peak value B 4 to B 5 PFI lines as inputs 2 15 as outputs 2 15 PGIA noise free measurements 2 2 removing ground noise figure 2 2 physical specifications A 8 NI 5911 User Manual Index power requirement specifications A 7 pulse train signal difficult figure B
16. 6 R Real Time sampling 2 6 record length B 4 Repetitive RIS sampling 2 6 RTSI bus trigger and clock lines purpose and use 2 14 to 2 15 synchronization 2 16 S sample rate digitizers B 2 to B 3 flexible resolution mode sampling rates table 2 6 signal shape general 2 6 SMB connector 1 1 location on front panel figure 1 2 source impedance B 6 specifications A 1 to A 8 acquisition characteristics A 3 to A 5 accuracy A 3 common mode characteristics A 3 distortion A 5 dynamic range A 5 filtering A 4 acquisition modes A 7 to A 8 calibration A 8 EMC compliance A 8 operating environment A 8 physical A 8 power requirements A 7 storage environment A 8 acquisition system A 1 to A 2 timebase system A 6 triggering systems A 6 to A 7 storage environment specifications A 8 synchronization 2 15 to 2 16 NI 5911 User Manual l 4 T technical support C 1 to C 2 telephone and fax support numbers C 2 timebase system specifications A 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 specifications A 6 to A 7 timing with hold off enabled figure 2 12 trigger hold off 2 11 to 2 12 B 7 trigger sources figure 2 9 triggering options for digitizers B 4 V
17. Computer Based Instruments NI 5911 User Manual Digital Oscilloscope for PCI INSTRUMENTS October 1998 Edition Part Number 322150A 01 N NATIONAL Internet Support E mail support natinst com FTP Site ftp natinst com Web Address http www natinst com Bulletin Board Support BBS United States 512 794 5422 BBS United Kingdom 01635 551422 BBS France 01 48 65 15 59 Fax on Demand Support 512418 1111 Telephone Support USA Tel 512 795 8248 Fax 512 794 5678 International Offices Australia 03 9879 5166 Austria 0662 45 79 90 0 Belgium 02 757 00 20 Brazil 011 288 3336 Canada Ontario 905 785 0085 Canada Qu bec 514 694 8521 Denmark 45 76 26 00 Finland 09 725 725 11 France 01 48 14 24 24 Germany 089 741 31 30 Hong Kong 2645 3186 Israel 03 6120092 Italy 02 413091 Japan 03 5472 2970 Korea 02 596 7456 Mexico 5 520 2635 Netherlands 0348 433466 Norway 32 84 84 00 Singapore 2265886 Spain 91 640 0085 Sweden 08 730 49 70 Switzerland 056 200 51 51 Taiwan 02 377 1200 United Kingdom 01635 523545 National Instruments Corporate Headquarters 6504 Bridge Point Parkway Austin Texas 78730 5039 USA Tel 512 794 0100 Copyright 1998 National Instruments Corporation All rights reserved Important Information Warranty Copyright Trademarks The NI 5911 is warranted against defects in materials and workmanship for a period of one year from the date of shipment as evidenced by receipts or other do
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19. United Kingdom 01635 551422 Up to 9 600 baud 8 data bits 1 stop bit no parity France 01 48 65 15 59 Up to 9 600 baud 8 data bits 1 stop bit no parity FTP Support To access our FTP site log on to our Internet host ftp natinst com aS anonymous and use your Internet address such as joesmith anywhere com as your password The support files and documents are located in the support directories National Instruments Corporation C 1 NI 5911 User Manual Fax on Demand Support Fax on Demand is a 24 hour information retrieval system containing a library of documents on a wide range of technical information You can access Fax on Demand from a touch tone telephone at 512 418 1111 E Mail Support Currently USA Only You can submit technical support questions to the applications engineering team through e mail at the Internet address listed below Remember to include your name address and phone number so we can contact you with solutions and suggestions support natinst com Telephone and Fax Support National Instruments has branch offices all over the world Use the list below to find the technical support number for your country If there is no National Instruments office in your country contact the source from which you purchased your software to obtain support Country Australia Austria Belgium Brazil Canada Ontario Canada Qu bec Denmark Finland France Germany Hong Kong Israel Italy Japan Korea
20. 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 samples per second used to express the rate at which an instrument samples an analog signal 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 also thermal drift measurements that change as the temperature varies thermal electromotive forces voltages 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 G 6 National Instruments Corporation V v VAC VDC V error VI Vis 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 t
21. ain input amplifier PGIA at the analog input The purpose of the PGIA is to accurately interface to and scale the signal presented at the connector to the analog to digital converter ADC regardless of source impedance source amplitude DC biasing or common mode noise voltages When measuring high dynamic range signals ground noise is often a problem The PGIA of the NI 5911 allows you to make noise free measurements of the signal 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 signal The inner conductor of the BNC is V the outer shell is V Input Signal V gt 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 conne
22. arge output impedance your measurements will be affected by this impedance divider For example if the device has 1MQ output impedance your measured signal will be 1 2 the actual signal value National Instruments Corporation 2 3 NI 5911 User Manual Chapter 2 Hardware Overview 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 x 1 nA Input Protection The NI 5911 features input protection circuits that protect both the positive and negative analog input from damage from AC and DC signals up to 42V 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
23. ary 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 specifications 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 PCI eXtensions for Instrumentation PXI is an open specification that builds off the CompactPCI specification by adding instrumentation specific features resistor random access memory 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 root 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 National Instruments Corporation G 5 NI 5911 User Manual Glossary sense settling time S s system noise T temperature coefficient thermal drift thermal EMFs thermoelecotric potentials transfer rate NI 5911 User Manual seconds samples in four wire resistance the sense measures the voltage
24. cale 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 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 NI 5911 User Manual Appendix A Specifications Physical Dimensions ss sese 33 8 x 9 9 cm 13 3 x 3 9 in T O connectors Analog input CHO eee BNC female Digital triggers eee SMB female 9 pin DIN Operating Environment Ambient temperature ses sees eee eee 5 to 40 C Relative humidity sees sees ee eee eee 10 to 90 noncondensing Storage Environment Ambient temperature esse eee 20 to 65 C EMC Compliance CE97 FCC Calibration Internal aage dotiar edog 2y 4 RR Internal calibration is done upon software command The calibration involves gain offset and linearity correction for all input ranges and input modes Interval an aza TTT 30 a week or any time temperature changes beyond 5 C Hardware detects temperature variations beyond calibration limits which can also be queried by software Extemal 2020 3 Gcni ieee eins Internal reference requires recalibration Interval ices asser cnez ct cT rha heva 3 years Warm up time eee eee eee eee 1 minute NI 5911 User Manual A 8 National Instruments Corporation Digitizer Basics This app
25. cies Oscilloscope mode sss sese eee Flexible Resolution mode Synchronization Phase difference Triggering Systems NI 5911 User Manual A 6 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 Siba zs dede Ha nEi iez lt 75 pSrms independent of reference clock source TTL for both input and output 1 ns 100 MHz n where 1 lt n lt 2 2 100 MHz n where n 8 20 50 100 200 500 1000 2000 5000 10000 Via RTSI trigger lines Between multiple instruments lt 5 ns at any input frequency lt 100 MHz from input connector to input connector Above threshold below threshold between thresholds outside thresholds CHO RTSI lt 0 6 gt PFI 1 2 Rising falling National Instruments Corporation Hysteresis Coupling Pretrigger depth Posttrigger depth Holdoff by time Sensitivity TRIG input range esse eects TRIG input impedance TRIG input protection ee Acquisition Modes RIS accuracy Single shot Power Requirements National Instruments Corporation A 7 Appendix A Specifications 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 million samples 1 to 16 million samples 40 ns 171 85 in increments of 40 ns 170 steps in full s
26. ct to the NI 5911 is already connected to ground ground loop noise voltages may be induced into your system Note that in most of these situations the 10 KQ resistance to PC ground is normally much higher than 2 2 National Instruments Corporation Chapter 2 Hardware Overview 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 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 inputs to 10 V inputs as shown in Table 2 1 Table 2 1 Input Ranges for the NI 5911 Range Input Protection Threshold 10V 10 V 5V 5 V 2V 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 VR Vin Sin R R 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 l
27. cumentation 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 manual is accurate The document has been carefully reviewed for technical accuracy In the event that technical or typographical errors exist National Instruments reserves the right to make changes to subsequent editions of this document without prior notice to holders of this edition The reader should consult National Instruments if errors are suspected In no
28. e with flexible resolution The NI 5911 offers unsurpassed flexibility for performing measurements from DC to 100 MHz Using the NI 5911 flexible resolution feature you can choose the sampling rate and resolution best suited to your application Detailed specifications for the NI 5911 are in Appendix A Specifications 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 The BNC connector is for attaching the analog input signal you wish to measure The BNC connector is analog input channel 0 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 Introduction to the VirtualBench Scope Soft Front Panel 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 2 To launch the soft fr
29. e eee ee DC and AC software selectable AC coupling cut off frequency S38 dB vss cocss essen ne ees 15 Hz 2 Input impedance sss sese ereer eee 1 MQ 2 Max measurable input voltage 10 V DC peak AC Input protection sees eee ee eee 42 VDC DC peak AC Input bias current sese eee eee eee ee ee 1 nA typical at 25 C Common Mode Characteristics Impedance to chassis ground 10 kQ Common mode rejection ratio CMRR gt 70 dB Fin lt 1 kHz National Instruments Corporation A 3 NI 5911 User Manual Specifications 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 in oscilloscope mode A 4 National Instruments Corporation NI 5911 User Manual
30. e of the ADC is out 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 National Instruments Corporation 2 13 NI 5911 User Manual Chapter 2 Hardware Overview 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 will occur to let you know that the data includes some samples that were out of the range of the converter and may be inaccurate RTSI 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 synchronous 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 NI5911 has two digital lines that can be used to accept a trigger accept or generate a reference clock or output a square wave of programmable frequency The function of each PFI line is inde
31. endix explains basic information you need to understand about making measurements with digitizers including important terminology Understanding Digitizers Nyquist Theorem 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 a5 MHz sine wave digitized by a 6 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 MHz sine wave To prevent aliasing in the passband a lowpass filter limits the frequency content of the input signal above the Nyquist rate National Instruments Corporation B 1 NI 5911 User Manual Appendix B Digitizer Basics Analog Bandwidth Analog bandwidth describes the frequency range in Hertz in which a
32. ge the heater will no longer be able to stabilize the temperature and signal data will no longer be accurate When the temperature range has been exceeded you will receive a warning and you will need to perform an internal calibration By executing a software command you can internally calibrate the NI 5911 without connecting any external equipment 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 National Instruments Corporation 2 7 NI 5911 User Manual Chapter 2 Hardware Overview Note 3 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 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 External Calibration External calibration is used to calibrate 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
33. hat should be applied to a product in normal use normally well under the breakdown voltage for safety margin National Instruments Corporation G 7 NI 5911 User Manual Index A AC coupling 2 4 accuracy characteristics A 3 acquisition multiple record 2 13 to 2 14 acquisition characteristics specifications A 3 to A 5 accuracy A 3 common mode characteristics A 3 distortion A 5 dynamic range A 5 filtering A 4 acquisition modes specifications A 7 to A 8 calibration A 8 EMC compliance A 8 operating environment A 8 power requirements A 7 storage environment A 8 acquisition system 2 6 to 2 16 calibration 2 7 to 2 8 external calibration 2 8 internal calibration 2 7 to 2 8 errors during acquisition 2 14 memory 2 12 multiple record 2 13 to 2 14 PFI lines 2 15 RTSI bus trigger and clock lines 2 14 to 2 15 specifications A 1 to A 2 synchronization 2 15 to 2 16 triggering and arming 2 8 to 2 12 above level analog triggering mode figure 2 10 analog trigger circuit 2 9 to 2 11 below level analog triggering mode figure 2 10 high hysteresis analog triggering mode figure 2 11 National Instruments Corporation low hysteresis analog triggering mode figure 2 11 trigger hold off 2 11 to 2 12 VirtualBench Scope soft front panel 1 5 to 1 6 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 trigger
34. ideration helps you to choose the correct settings Such characteristics include e Peak to peak value 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 B 4 National Instruments Corporation Appendix B Digitizer Basics to Appendix A Specifications for the maximum input voltage for your NI 5911 device Figure B 5 shows that a gain of 5 is the best setting to digitize a 300 mV 1 MHz sine wave without clipping the signal 127 LSB 7 LSB po e lt 0 LSB 8 LSB gt e lt Xe XNe 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 5 Dynamic Range of an 8 Bit ADC with Three Different Gain Settings National Instruments Corporation B 5 NI 5911 User Manual Appendix B Digitizer Basics Source impedance Most digitizers and digi
35. ie rnat e e E E R uote 1 2 Figure 1 2 VirtualBench Scope Soft Front Panel esse sese 1 3 Figure 1 3 Acquire Tab of VirtualBench Scope Settings Dialog Box 1 6 Figure 2 1 NLS9II Block Di taM siae 2 1 Figure 2 2 Noise Free Measurements of Signal sese eee 2 2 Figure 2 3 Tripper SONCE Sareo reo E fond doce a o E ONER OH ARAE ERESSE eee 2 9 Figure 2 4 Below Level Analog Triggering Mode sees sees sees 2 10 Figure 2 5 Above Level Analog Triggering Mode sss sees 2 10 Figure 2 6 High Hysteresis Analog Triggering Mode sss eee eee 2 11 Figure 2 7 Low Hysteresis Analog Triggering Mode sese 2 11 Figure 2 8 Timing with Hold Off Enabled 2 12 Figure 2 9 Multiple Buffer Acquisition eee eee 2 13 Figure B 1 Sine Wave Demonstrating the Nyquist Frequency sss sees eee B 1 Figure B 2 Analog Bandwidth sss sees B 2 Figure B 3 1 MHz Sine Wave Sample eee ee eee B 3 Figure B 4 Transfer Function of a 3 Bit ADC B 3 Figure B 5 Dynamic Range of an 8 Bit ADC with Three Different Gain Settings B 5 Figure B 6 Difficult Pulse Train Signal sese ee eee eee B 6 Tables Table 2 1 Input Ranges for the NI 5911 ee eee ceseceseeeseeeeeeeeeeeeeneceeecnseeeneeeeee 2 3 Table 2 2 Available Sampling Rates and Corresponding Bandwidth in Flexible Resolution Mode 2 6 NI 5911 User Manual vi National Instruments Corporation Taking Measurements with the NI 5911 Thank you for buying a National Instruments 5911 digital oscilloscop
36. ing 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 B bias input 2 4 block diagram of NI 5911 2 1 BNC connector 1 1 location on front panel figure 1 2 bulletin board support C 1 C calibration 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 NI 5911 User Manual Index SMB connector 1 1 conventions used in manual v customer communication C 1 to C 2 D dead time in multiple record acquisition 2 13 differential input 2 2 to 2 4 grounding considerations 2 2 to 2 3 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 digitizers B 1 to B 7 ADC resolution B 4 analog bandwidth B 2 making accurate measurements B 4 to B 7 dynamic range of 8 bit ADC figure B 5 general signal shape B 6 to B 7 input coupling B 7 input frequency B 6 peak to peak value B 4 to B 5 source impedance B 6 trigger hold off B 7 Nyquist theorem B 1 record length B 4 sample rate B 2 to B 3 triggering options B 4 vertical sensitivity B 3 DIN connector 1 1 location on front panel figure 1 2 distortion specifications A 5 dynamic range specificati
37. is appendix contains forms to help you gather the information necessary to help us solve your technical problems and a form you can use to comment on the product documentation When you contact us we need the information on the Technical Support Form and the configuration form if your manual contains one about your system configuration to answer your questions as quickly as possible National Instruments has technical assistance through electronic fax and telephone systems to quickly provide the information you need Our electronic services include a bulletin board service an FTP site a fax on demand system and e mail support If you have a hardware or software problem first try the electronic support systems If the information available on these systems does not answer your questions we offer fax and telephone support through our technical support centers which are staffed by applications engineers Electronic Services Bulletin Board Support National Instruments has BBS and FTP sites dedicated for 24 hour support with a collection of files and documents to answer most common customer questions From these sites you can also download the latest instrument drivers updates and example programs For recorded instructions on how to use the bulletin board and FTP services and for BBS automated information call 512 795 6990 You can access these services at United States 512 794 5422 Up to 14 400 baud 8 data bits 1 stop bit no parity
38. ls sees 1 2 Soft Front Panel TTT 1 3 Using the VirtualBench SCOPE Soft Front Panel esse sese 1 5 AC QUIPIN GD ata T 1 5 Chapter 2 Hardware Overview Measurement Fundamentals sese esse eee eee 2 2 Differential Input TTT 2 2 Grounding Considerations sss sese ee eee ee eee 2 2 ET G Ee ia lee EEE EEE EE EE N EE EEE 2 3 Input Impedance eee eee a a e a i i i 2 3 Tnp t Bias aciionou EE E EE E 905 2 4 Input Protechon nenien el e E eed oh aes 2 4 AC COUPN TT 2 4 Measurement Modes T 2 4 Oscilloscope lS TTT 2 5 Flexible Resolution Mode sese sese 2 5 ACQUISILON Syste TT 2 6 Calibrations 02053 seein seins ete He ee es 2 7 Internal Cali bratiott s cc sccs cecen tos E E ESEE 2 7 External Calibrations sinne eee teesis eies 2 8 Tigrerns and ST 2 8 Analog Trigger COU 2 9 THs Ser Hold Off TTT 2 11 MEM Ory 93 erie asters Ce Arcee Ge ea A ee ES 2 12 Multiple Recorder osn Jesus encode sstevscendsevteaeedis ches oiae i E E Sy 2 13 Errors During Acquisition sss sese eee eee eee 2 13 RTSI Bus Trigger and Clock Lines sss sese 2 14 PELE ines tea b ait cide teste Sos Ree a AA ee AS 2 14 PRET S AS NPU Sa e a E ceevcuvtesesesceveescnevoubeestyoveeneuvtadvees 2 14 PFI Lines as Outputs oo eee e a E N 2 14 elel T 2 15 National Instruments Corporation V NI 5911 User Manual Contents Appendix A Specifications Appendix B Digitizer Basics Appendix C Customer Communication Glossary Index Figures Figure l l NES9U Connectors
39. m multiple record acquisitions the NI 5911 is configured to the number of records to be acquired before starting the acquisition The NI 5911 acquires an additional record each time a trigger is accepted until all the requested records have been 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 Trigger Acquisition In Progress Buffer 5uS 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 Errors During Acqu Figure 2 9 Multiple Buffer Acquisition isition 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 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 temperatur
40. measure of the ratio of two signal levels dB 20log10 V1 V2 for signals in volts G 2 National Instruments Corporation DC default setting differential input double insulated drivers E EEPROM F filtering gain H hardware harmonics Hz National Instruments Corporation G 3 Glossary 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 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 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 NI 5911 User Manual Glossary in ind
41. mple rate more accurately captures the waveform shape as well as frequency B 2 National Instruments Corporation Appendix B Digitizer Basics 1 La E 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 A Range 0 5 V 110 10 100 01 010 00 000 k 0 X 5V Voltage Fluctuations in This Region Will Be Unnoticed Figure B 4 Transfer Function of a 3 Bit ADC National Instruments Corporation B 3 NI 5911 User Manual Appendix B Digitizer Basics ADC Resolution Record Length Triggering Options ADC resolution limits the accuracy of a measurement The higher the resolution number of bits the more accurate the measurement An 8 bit ADC divides the vertical range of the input amplifier into 256 discrete levels With a vertical range of 10 V the 8 bit ADC cannot resolve vol
42. o necessary to synchronize clock dividers on each NI 5911 board 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 NI 5911 Acquisition System Bandwidth ccccsssccecesssseceeceessneceeees Number of channels sss sees eee Number of flexible resolution ADC Max sample rate eee eee 100 MHz maximum at all input ranges 1 for PCI 2 for VXI 1 for PCI 2 for VXI 1 GS s repetitive 100 MS s single shot Sample onboard memory sse eee sees e 4 MB or 16 MB Memory sample depth Sampling Sample depth Sample depth Frequency Mode 4 MB option 16 MB option
43. ons A 5 E electronic support services C 1 to C 2 NI 5911 User Manual l 2 e mail support C 2 EMC compliance A 8 errors during acquisition 2 14 F fax and telephone support numbers C 2 Fax on Demand support C 2 filtering specifications A 4 flexible resolution mode 2 5 to 2 6 available sampling rates table 2 6 FTP support C 1 G grounding considerations 2 2 to 2 3 H hardware overview 2 1 to 2 16 See also specifications AC coupling 2 4 acquisition system 2 6 to 2 16 calibration 2 7 to 2 8 errors during acquisition 2 14 memory 2 12 multiple record 2 13 to 2 14 PFI lines 2 15 RTSI bus trigger and clock lines 2 14 to 2 15 synchronization 2 15 to 2 16 triggering and arming 2 8 to 2 12 block diagram of NI 5911 2 1 differential input 2 2 to 2 4 grounding considerations 2 2 to 2 3 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 National Instruments Corporation measurement fundamentals 2 2 to 2 4 measurement modes 2 4 to 2 6 flexible resolution mode 2 5 to 2 6 oscilloscope mode 2 5 hysteresis value See analog trigger circuit impedance formula for impedance divider 2 3 input and output impedance 2 3 to 2 4 source impedance B 6 input bias 2 4 input coupling B 7 input frequency B 6 input impedance 2 3 to 2 4 input protection circuits 2 4 input ranges 2 3 measurement fundamentals
44. ont panel select Start Programs National Instruments Scope VirtualBench Scope NI 5911 User Manual 1 2 National Instruments Corporation Chapter 1 Taking Measurements with the NI 5911 ip VirtualBench Scope Scopel oix File Edit Controls Measure Help Run w Single Ar o Channels OO Chl Chi Math 1 Volts div m Refl b l Ref 2 A be S d 4 Coupling 3 DC SZ Timebase Y Position ie G lase Tigger 4 Mode Worm gt C1 Ch1 C2 Ch1 sell C1 H SS A HZD Set50 m alr Ch Ch1 4 alr alr Alun uto sz ae Setup 7 Mode gt Select ca 1 Channel Display Selector 2 Channel Settings Selector 3 Channel Settings 4 Trigger Setting Group 7 Zoom Controls 5 Vertical Slider 8 Graphics Display 6 Main Control Bar Figure 1 2 VirtualBench Scope Soft Front Panel Soft Front Panel Features The VirtualBench Scope soft front panel has the following features National Instruments Corporation Channel Display Selector selects a waveform for display on the graphics display Channel Settings Channel Settings Selector selects the channel whose settings will be modified Volts div adjusts the vertical sensitivity of the channel you select V Position controls the DC offset of the displayed waveform Timebase controls the timebase setting Turning the knob clockwise reduces
45. pendent however only one trigger source can be accepted during acquisition PFI Lines as Inputs You can select PFI1 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 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 NI5911 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 2 14 National Instruments Corporation Synchronization Chapter 2 Hardware Overview The NI 5911 uses a digital phase lock loop to synchronize the 100 MHz sample clock to a 10 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 NI5911 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 als
46. quire Tab of VirtualBench Scope Settings Dialog Box 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 group Disable all other channels Click on AutoSetup on the main control bar Click on Run to start the acquisition Refer to the VirtualBench Scope Online Help for additional help on configuring VirtualBench Scope for your specific application 1 6 National Instruments Corporation Hardware Overview This chapter includes an overview of the NI 5911 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 Analog Input AC DC Coupling Connector Protect Calibration 4 MOhm PGA Mux A D Converter 100 MHz 8 bit 4 Noise Shaper gt p Calibration Generator P Timing IO Reference Digital IO Memory Control Clock Connector 7 k Digital Signal Capture La gt Processor Memory a gt pata Figure 2 1 NI 5911 Block Diagram National Instruments Corporation 2 1 NI 5911 User Manual Chapter 2 Hardware Overview Measurement Fundamentals Differential Input NI 5911 User Manual The NI5911 has a differential programmable g
47. rating system version Operating system mode Programming language Programming language version Other boards in system Base I O address of other boards DMA channels of other boards Interrupt level of other boards Documentation Comment Form National Instruments encourages you to comment on the documentation supplied with our products This information helps us provide quality products to meet your needs Title NI 5911 User Manual Edition Date October 1998 Part Number 322150A 01 Please comment on the completeness clarity and organization of the manual If you find errors in the manual please record the page numbers and describe the errors Thank you for your help Name Title Company Address E Mail Address Phone Fax Mail to Technical Publications Fax to Technical Publications National Instruments Corporation National Instruments Corporation 6504 Bridge Point Parkway 512 794 5678 Austin Texas 78730 5039 Glossary Prefix Meanings Value p pico 10 2 n nano 10 9 u micro 10 6 m milli 10 3 k kilo 103 M mega 10 G giga 10 Numbers Symbols percent positive of or plus negative of or minus per S degree plus or minus Q ohm A amperes AC alternating current AC coupled the passing of a signal through a filter network that removes
48. ress Fax Phone Computer brand Model Processor Operating system include version number Clock speed MHz RAM MB Display adapter Mouse ___ yes ___no___ Other adapters installed Hard disk capacity MB Brand Instruments used National Instruments hardware product model Revision Configuration National Instruments software product Version Configuration The problem is List any error messages The following steps reproduce the problem NI 5911 Hardware and Software Configuration Form Record the settings and revisions of your hardware and software on the line to the right of each item Complete a new copy of this form each time you revise your software or hardware configuration and use this form as a reference for your current configuration Completing this form accurately before contacting National Instruments for technical support helps our applications engineers answer your questions more efficiently National Instruments Products Hardware revision Interrupt level of hardware Base I O address of hardware Programming choice National Instruments software Other boards in system Base I O address of other boards DMA channels of other boards Interrupt level of other boards Other Products Computer make and model Microprocessor Clock frequency or speed Type of video board installed Ope
49. sValue is used to create a trigger window the signal must pass through before the trigger is accepted Triggers can be generated 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 Overview Trigger Value Y Falling Edge Trigger 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 triggerValue hysteresis Value is unused 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 triggerValue hysteresis Value is unused NI 5911 User Manual 2 10 National Instruments Corporation Chapter 2 Hardware Overview Trigger Y ff it a ZL Hysteresis Value Trigger i Y Faing Edge Trigger Rising Edge Trigger Figure 2 6 High Hysteresis Analog Triggering Mode In high hysteresis analog triggering mode the trigger is generated when the signal value is greater than triggerValue with the hysteresis specified by hysteresisValue The signal must cross back below the hysteresisValue before another trigger
50. tage 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 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 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 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 signal to trigger the acquisition Making Accurate Measurements NI 5911 User Manual For accurate measurements you should use the right settings when acquiring data with your NI 5911 Knowing the characteristics of the signal in cons
51. tal storage oscilloscopes DSOs have a 1 MQ input resistance in the passband If the source 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 6 shows an example
52. the DC component of the signal National Instruments Corporation G 1 NI 5911 User Manual Glossary A D ADC ADC resolution amplification amplitude flatness attenuate bus CMRR coupling D dB NI 5911 User Manual analog to digital analog to digital converter an electronic device often an integrated circuit that converts an analog voltage to a digital number the resolution of 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 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 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 common mode rejection ratio a measure of an instrument s ability to reject interference from a common mode signal usually expressed in decibels dB the manner in which a signal is connected from one location to another decibel the unit for expressing a logarithmic
53. 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 CVI LabVIEW and VirtualBench are trademarks of National Instruments Corporation Product and company names listed are trademarks or trade names of their respective companies WARNING REGARDING MEDICAL AND CLINICAL USE OF NATIONAL INSTRUMENTS PRODUCTS National Instruments products are not designed with components and testing intended to ensure a level of reliability suitable for use in treatment and diagnosis of humans Applications of National Instruments products involving medical or clinical treatment can create a potential for accidental injury caused by product failure or by errors on the part of the user or application designer Any use or application of National Instruments products for or involving medical or clinical treatment must be performed by properly trained and qualified medical personnel and all traditional medical safeguards equipment and procedures that are appropriate in the particular situation to prevent serious injury or death should always continue to be used when National Instruments products are being used National Instruments products are NOT intended to be a substitute for any form of established process procedure or
54. uctance input bias current input impedance instrument driver interrupt interrupt level UO ISA MB noise NI 5911 User Manual 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 the relative priority at which a device can interrupt input output the transfer of data to from a computer system involving communications channels operator interface devices and or data acquisition and control interfaces industry standard architecture meters megabytes of memory 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 G 4 National Instruments Corporation 0 Ohm s Law overrange PCI peak value PXI resolution rms ROM Gloss
55. vertical sensitivity digitizers B 3 specifications A 2 VirtualBench Scope soft front panel 1 2 to 1 6 Acquire tab figure 1 6 acquiring data 1 5 to 1 6 features 1 3 to 1 4 front panel figure 1 3 National Instruments Corporation
56. within the specified accuracy For more information on calibration contact National Instruments using the support information in Appendix C Customer Communication For actual intervals and accuracy refer to Appendix A Specifications Triggering and Arming NI 5911 User Manual There are several triggering methods for the NI5911 The trigger can be an analog level that is compared to the input or any of several digital inputs You can also call a software function to trigger the board Figure 2 3 shows the different trigger sources When a digital signal is used that signal must be ata high TTL level for at least 40 ns before any triggers will be accepted 2 8 National Instruments Corporation Chapter 2 Hardware Overview COMB Analog Trigger ATC_OUT Circuit Low __ COMP Level a Analog Trigger Circuit Software ATC_OUT RTSI lt 0 6 gt EN Trigger PFI1 PFI2 2 m Arm b Trigger and Arm Sources 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 triggerValue 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 hysteresisValue associated with the trigger that can be set in the same size increments The hysteresi
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