National Instruments NI 5922 Calibration Procedure
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CALIBRATION PROCEDURE
NI 5922
Contents
This document describes specific programming steps for writing
a calibration utility for the National Instruments PXI-5922
flexible-resolution digitizer. This calibration procedure is intended
for metrology labs.
Introduction ............................................................................................. 2
Self-Calibration................................................................................ 2
External Calibration ......................................................................... 2
Calibration Intervals ........................................................................ 2
Software and Documentation........................................................... 2
Self-Calibration Procedures .................................................................... 4
MAX ................................................................................................ 5
Scope SFP ........................................................................................ 5
NI-SCOPE ....................................................................................... 5
External Calibration Options .................................................................. 6
Complete Calibration ....................................................................... 7
Optional Calibration ........................................................................ 8
External Calibration Requirements......................................................... 10
Test Equipment ................................................................................ 10
Test Conditions ................................................................................ 10
External Calibration Procedures ............................................................. 11
Verifying NI 5922 Specifications .................................................... 11
Vertical Offset Accuracy .......................................................... 12
Noise ......................................................................................... 13
Input Bias Current .................................................................... 15
Vertical Gain Accuracy ............................................................ 17
Timing Accuracy ...................................................................... 19
Flatness ..................................................................................... 20
Trigger Sensitivity .................................................................... 24
Adjusting the NI 5922...................................................................... 25
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Summary of Contents for National Instruments NI 5922
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Page 1: Table Of Contents
CALIBRATION PROCEDURE NI 5922 This document describes specific programming steps for writing a calibration utility for the National Instruments PXI-5922 flexible-resolution digitizer. This calibration procedure is intended for metrology labs. Contents Introduction ..................... 2 Self-Calibration................2 External Calibration ................. 2 Calibration Intervals ................ -
Page 2: Introduction
MAX....................27 NI-SCOPE ..................27 Where to Go for Support .................28 Introduction The NI 5922 supports two types of calibration: self-calibration (or internal calibration) and external calibration. Self-Calibration Self-calibration, also known as internal calibration, uses a software command and requires no external connections. Self-calibration improves measurement accuracy by compensating for variables such as temperature that may have changed since the last external calibration. -
Page 3: Software And Documentation
Software and Documentation Calibrating the NI 5922 requires installing NI-SCOPE version 2.8 or later on the calibration system. You can download NI-SCOPE from . NI-SCOPE supports programming the ni.com/downloads self-calibration procedures in a number of programming languages. However, only LabVIEW and C are supported for the external calibration procedures. -
Page 4: Self-Calibration Procedures
Self-Calibration Procedures The NI 5922 includes precise internal circuits and references used during self-calibration to adjust for time and temperature drift. The digitizer gain, offset, and flatness are all corrected in self-calibration. Measuring the accuracy of these internal calibration circuits with another instrument during external calibration provides traceability for the verification procedure. -
Page 5: Max
Launch the Calibration dialog box by selecting Utility» Self Calibration. Click OK to begin self-calibration. NI-SCOPE To self-calibrate the NI 5922 programmatically using NI-SCOPE, complete the following steps: Disconnect or disable any AC inputs to the digitizer. Call (niScope Initialize VI) to obtain an instrument niScope_init session handle. -
Page 6: External Calibration Options
In this case, you can perform an adjustment if you want to further improve the measurement accuracy or reset the calibration interval. If some measurement errors determined during verification do not fall within the published NI 5922 Calibration Procedure ni.com... -
Page 7: Complete Calibration
Complete Calibration Performing a complete calibration is the recommended way to guarantee that the NI 5922 meets or exceeds its published specifications for a two-year calibration interval. At the end of the complete calibration procedure, you verify that the measurement error falls within the calibration test limits. -
Page 8: Optional Calibration
In this case, you can update the calibration date, effectively resetting the calibration interval, without actually performing an adjustment. Refer to the Adjusting the NI 5922 section for more information. If all of the measurement errors determined during the first verification fall within the published specifications, but not within the calibration test limits, adjustment is also optional. - Page 9 Adjust Adjust (Cal Dates and Anyway? Temperatures Updated) Verify Document Post-Adjustment Results Meets Calibration/ Calibration Verification Test Limits? Complete Review Verification/ Adjustment Procedure or Return Device Figure 2. Optional Calibration Programming Flow © National Instruments Corporation NI 5922 Calibration Procedure...
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Page 10: External Calibration Requirements
External Calibration Requirements Test Equipment Table 2 lists the equipment required for externally calibrating the NI 5922. If you do not have the recommended instruments, use these specifications to select a substitute calibration standard. Table 2. Required Equipment for NI 5922 External Calibration... -
Page 11: External Calibration Procedures
Allow a warm-up time of at least 15 minutes after NI-SCOPE loads. Unless manually disabled, NI-SCOPE automatically loads with the operating system and enables the device. The warm-up time ensures that the measurement circuitry of the NI 5922 is at a stable operating temperature. •... -
Page 12: Vertical Offset Accuracy
NI 5922. You must verify both channels and each iteration listed in Table 3. Disconnect all cabling from the BNC inputs of the NI 5922. No input signal is needed because the NI 5922 internal 50 Ω resistor connects the input to ground. -
Page 13: Noise
Complete the following steps to verify noise performance of the NI 5922. You must verify both channels and each iteration listed in Table 4. Disconnect all cabling from the BNC inputs of the NI 5922. No input signal is needed because the NI 5922 internal 50 Ω resistor connects the input to ground. - Page 14 Repeat steps 1 through 7 for each iteration in Table 4. Repeat steps 1 through 8 for channel 1, changing the value of the channelList parameter from "0" "1" Table 4. NI 5922 Noise Performance Sample Rate Calibration Published Iteration...
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Page 15: Input Bias Current
384 µV 401 µV 15 M Input Bias Current Complete the following steps to verify input bias current of the NI 5922. You must verify both channels. Disconnect all cabling from the BNC inputs of the NI 5922. Call niScope_ConfigureChanCharacteristics... - Page 16 = the voltage measured in step 6 b = the voltage measured in step 9 1,000,000 is the NI 5922 impedance in ohms Compare the resulting bias current to the value listed in the Calibration Test Limits column or the Published Specifications column in Table 5.
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Page 17: Vertical Gain Accuracy
Published Specification ±350 nA ±500 nA Vertical Gain Accuracy Complete the following steps to verify vertical gain accuracy of the NI 5922. You must verify both channels and each iteration listed in Table 6. Call (niScope niScope_ConfigureChanCharacteristics Configure Chan Characteristics VI) with the following parameters: •... - Page 18 Range, Positive Input, and Negative Input values accordingly. 15. Move the calibrator to the digitizer input channel 1 and repeat steps 1 through 14, changing the value of the channelList parameter from "0" "1" NI 5922 Calibration Procedure ni.com...
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Page 19: Timing Accuracy
±0.0293% ±0.05% Timing Accuracy Complete the following steps to verify the timing accuracy for the NI 5922. The same time source is used for both channel 0 and channel 1, so you only need to Note verify the timing accuracy on one channel. -
Page 20: Flatness
Calibration Test Limi Published Specification ±5.3 ppm ±50 ppm Flatness Complete the following steps to verify the flatness of the NI 5922. You must verify both channels and each iteration listed in Table 8. Call (niScope niScope_ConfigureChanCharacteristics Configure Chan Characteristics VI) with the following parameters: •... - Page 21 Set the peak-to-peak voltage amplitude to one tenth of the vertical range used in step 2. Set the load impedance of the calibrator to 50 Ω . Wait 1,000 ms for the impedance matching of the calibrator to settle. © National Instruments Corporation NI 5922 Calibration Procedure...
- Page 22 The vector X4 has 81 elements. Index this vector from i = 0 to 80. Calculate a new complex vector X5 by calculating on all the elements within X4: X4 i [ ] ⁄ X5 i [ ] --------------------------------------- - sin π × ⁄ NI 5922 Calibration Procedure ni.com...
- Page 23 0.15 dB 0.15 dB 15 M 0.3 dB 0.3 dB Note The –3 dB bandwidth of the NI 5922 is set by its digital filters and does not need to be verified. © National Instruments Corporation NI 5922 Calibration Procedure...
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Page 24: Trigger Sensitivity
Trigger Sensitivity Complete the following steps to verify trigger sensitivity for the external trigger channel of the NI 5922. Call (niScope niScope_ConfigureChanCharacteristics Configure Chan Characteristics VI) with the following parameters: • channelList: "0" • inputImpedance: NISCOPE_VAL_1_MEG_OHM • maxInputFrequency: Call (niScope Configure Vertical... -
Page 25: Adjusting The Ni 5922
"NISCOPE_VAL_POSITIVE" "NISCOPE_VAL_NEGATIVE" Note The NI 5922 uses the digitized data from the input channel ADC when performing an analog trigger on CH 0 or CH 1. Verifying the trigger sensitivity for the input channels is not necessary. Adjusting the NI 5922... - Page 26 Complete all of the following steps to externally adjust the NI 5922. Connect the scope calibrator to the channel 0 input of the digitizer. Configure the calibrator to output an exact 1 MHz sine wave with 1 V peak-to-peak amplitude and 1 MΩ load impedance.
- Page 27 NISCOPE_VAL_ACTION_STORE calibration You have finished adjusting the NI 5922. It is not necessary to adjust each channel individually. However, you should repeat the entire verification procedure to verify a successful adjustment. Calibration Utilities...
- Page 28 Instruments trademarks. Other product and company names mentioned herein are trademarks or trade names of their respective companies. For patents covering National Instruments products, refer to the appropriate location: Help»Patents in your software, the patents.txt file on your CD, or ni.com/patents.