CALIBRATION PROCEDURE NI PXI-5422 This document contains step-by-step instructions for writing a calibration procedure for the NI PXI-5422 arbitrary waveform generator. Contents Conventions ............................................................................................ 1 Introduction ............................................................................................. 2 What Is Calibration? ........................................................................ 2 Self-Calibration ...
Adjusting the Analog Output ....................................................35 Adjusting the Oscillator Frequency...........................................52 Adjusting the Calibration ADC.................................................55 Closing the External Adjustment Session .................................60 Calibration Utilities .................................................................................61 MAX...................................................................................
What Is Calibration? Calibration consists of verifying the output accuracy of a device and correcting for any output error. Verification is measuring the performance of a device and comparing the results to the specifications of the device. NI calibrates every NI PXI-5422 at the factory. During the factory calibration process, the calibration constants are stored in an onboard EEPROM. These values are loaded from this EEPROM and used as needed by the NI PXI-5422.
The output accuracy requirements of your application determine how often you should externally calibrate the NI PXI-5422. NI recommends that you perform a complete external calibration at least once every two years. You can shorten this interval based on the accuracy demands of your application. Refer to the External Calibration Options section for more information.
calling a 32-bit DLL. Many of the functions use constants defined in the niFgen.h file. To use these constants in C, you must include niFgen.h in your code when you write the calibration procedure. Refer to Table 1 for file locations. Table 1. Calibration File Locations File Name and Location Description IVI\Bin\niFgen_32.dll The NI-FGEN library, which provides the functionality for calibrating the NI PXI-5422. IVI\Lib\msc\niFgen.
Documentation For information about NI-FGEN and the NI PXI-5422, you may find the following documents helpful: • NI Signal Generators Getting Started Guide • NI Signal Generators Help • NI PXI-5422 Specifications • NI-FGEN Instrument Driver Quick Reference Guide The NI Signal Generators Getting Started Guide provides instructions for installing and configuring NI signal generators. The NI Signal Generators Help includes detailed information about the NI PXI-5422 and the NI-FGEN functions.
3. Select the device that you want to calibrate. 4. Initiate self-calibration in one of the following ways: • Click Self-Calibrate in the upper right corner. • Right-click the device name under Devices and Interfaces, and select Self-Calibrate from the drop-down menu. FGEN Soft Front Panel To initiate self-calibration from the FGEN SFP, complete the following steps: 1. Select the device that you want to calibrate using the Device Configuration dialog box (Edit»Device Configuration). 2.
External Calibration Options External calibration involves both verification and adjustment. Verification is the process of testing the device to ensure that the output accuracy is within certain specifications. You can use verification to ensure that the adjustment process was successful or to determine if the adjustment process needs to be performed. Adjustment is the process of measuring and compensating for device performance to improve the output accuracy.
Self-Calibrate Document Pre-Adjustment Results Verify Adjust (Cal Dates and Temperatures Updated) Document Post-Adjustment Results Verify Meets Calibration Test Limits? Yes No Review Verification/ Adjustment Procedure or Return Device Calibration/ Verification Complete Figure 1.
Optional Calibration You can choose to skip the adjustment steps of the calibration procedure if the output error is within the calibration test limits or the published specifications during the first verification. If all of the output errors determined during the first verification fall within the calibration test limits, the device is guaranteed to meet or exceed its published specifications for a full calibration interval.
Self-Calibrate Document Pre-Adjustment Results Verify Meets Calibration Test Limits? Yes No Meets Published Specifications? Yes No Results Within Published Specs (Adjustment Optional) Update Calibration Dates and Temperatures Without Adjusting No Adjust Anyway? Adjust (Cal Dates and Temperatures Updated) Yes Document Post-Adjustment Results Verify Calibration/ Verification Complete Yes Meets Calibration Test Limits? No Review Verification/ Adjustment Procedure or Return Device Figure 2.
External Calibration Requirements This section describes the test equipment and test conditions required for calibration. Test Equipment External calibration requires different equipment for each applicable specification. Refer to Table 2 for a list of equipment. Table 2.
External Calibration Procedures The complete external calibration procedure consists of self-calibrating, verifying the performance of the NI PXI-5422, adjusting the calibration constants, and verifying again after the adjustments. In some cases, the complete calibration procedure may not be required. Refer to the External Calibration Options section for more information. The external calibration procedure automatically stores the calibration date to allow traceability.
Verifying NI PXI-5422 Specifications Note Always self-calibrate the NI PXI-5422 before beginning a verification procedure. This section provides instructions for verifying the NI PXI-5422 specifications. This section also includes instructions for updating the calibration cycle. Verification determines whether the device is performing within its specifications prior to external adjustment. Verification and external adjustment together comprise a complete calibration.
NI PXI-5422 16-Bit 200 MS/s AWG ACCESS ACTIVE CH 0 CLK IN PFI 0 DIGITAL DATA & CONTROL PFI 1 Figure 3.
Verifying the Oscillator Frequency Accuracy This test verifies the frequency accuracy of the oscillator on the NI PXI-5422. The verification involves generating a 10 MHz sine wave with the NI PXI-5422 and measuring the sine wave frequency with one of the instruments from Table 2. To verify the frequency accuracy of the oscillator on the NI PXI-5422, complete the following steps: 1.
5. Note • vi: The session handle returned from niFgen_init • channelName: "0" • attributeID: NIFGEN_ATTR_ARB_OFFSET • value: 0 You can adjust this value based on which measuring device you use. 6. 7.
A frequency error of 45 Hz for a 10 MHz signal corresponds to an error of 4.5 ppm. This limit accounts for the initial accuracy and the frequency deviation caused by temperature and aging. Refer to Table 3 for frequency ranges. Table 3. Frequency Ranges Calibration Test Limit Published Specifications ±25 ppm Low High Low High 9,999,955 Hz 10,000,045 Hz 9,999,750 Hz 10,000,250 Hz 11.
3. 4. 5. 6. © National Instruments Corporation • IDQuery: VI_TRUE • resetDevice: VI_TRUE • vi: A pointer to a ViSession. The variable passed by reference through this parameter receives the value that identifies the session created by this function. This value acts as the session handle and is passed as the first parameter to all subsequent NI-FGEN functions.
7. Call niFgen_SetAttributeViBoolean to enable the analog output (niFgen property node: Basic Operation»Output Enabled) using the following parameters: • vi: The session handle returned from niFgen_init • channelName: "0" • attributeID: NIFGEN_ATTR_OUTPUT_ENABLED • value: VI_TRUE 8. Create an array of waveform samples for the positive full-scale DC waveform. This array should contain 500 samples with each sample having the value 1.0 (representation: double). 9.
12. Call niFgen_SetAttributeViReal64 to set the offset (niFgen property node: Arbitrary Waveform Output»Arbitrary Waveform Offset) using the following parameters: • vi: The session handle returned from niFgen_init • channelName: "0" • attributeID: NIFGEN_ATTR_ARB_OFFSET • value: 0 13. Repeat steps 14 through 24 for each of the 24 iterations listed in Table 4, changing the Gain value for each iteration. You can use Table 4 to record the results of these steps.
NI PXI-5422 Calibration Procedure 22 ni.com 0.150000 0.105000 0.075000 0.055000 0.037500 15 16 17 18 19 0.026000 0.205000 14 20 0.300000 13 1.650000 8 0.415000 2.000000 7 12 2.500000 6 0.600000 3.500000 5 11 5.000000 4 0.850000 7.000000 3 10 10.000000 2 1.250000 12.000000 1 9 Gain Iteration 0.026000 0.037500 0.055000 0.075000 0.105000 0.150000 0.205000 0.300000 0.415000 0.600000 0.850000 1.250000 1.650000 2.000000 2.500000 3.500000 5.000000 7.
© National Instruments Corporation 23 NI PXI-5422 Calibration Procedure 0.013000 0.009000 0.006500 22 23 24 2 0.006500 0.009000 0.013000 0.018500 – 0.006500 – 0.009000 – 0.013000 – 0.
14. Call niFgen_SetAttributeViReal64 to set the gain (niFgen property node: Arbitrary Waveform Output»Arbitrary Waveform Gain) using the following parameters: • vi: The session handle returned from niFgen_init • channelName: "0" • attributeID: NIFGEN_ATTR_ARB_GAIN • value: The Gain value listed in Table 4 for the current iteration 15.
23. Subtract the Ideal Negative Full-Scale value from the Measured Negative Full-Scale value and record the result under Error Negative Full-Scale. The Error Negative Full-Scale value should be less than or equal to the limit you are using. 24. Call niFgen_AbortGeneration (niFgen Abort Generation VI) to abort the waveform generation using the following parameter: • vi: The session handle returned from niFgen_init 25. Return to step 14 until iterations are completed. 26.
NI PXI-5422 Calibration Procedure 26 ni.com 0.150000 0.105000 0.075000 0.055000 0.037500 15 16 17 18 19 0.026000 0.205000 14 20 0.300000 13 1.650000 8 0.415000 2.000000 7 12 2.500000 6 0.600000 3.500000 5 11 5.000000 4 0.850000 7.000000 3 10 10.000000 2 1.250000 12.000000 1 9 Gain Iteration 0.013000 0.018750 0.027500 0.037500 0.052500 0.075000 0.102500 0.150000 0.207500 0.300000 0.425000 0.625000 0.825000 1.000000 1.250000 1.750000 2.500000 3.
© National Instruments Corporation 27 NI PXI-5422 Calibration Procedure 2 1 0.018500 0.013000 0.009000 0.006500 21 22 23 24 0.003250 0.004500 0.006500 0.009250 – 0.003250 – 0.004500 – 0.006500 – 0.
5. 6. 7.
13. Measure the negative DC voltage out of the NI PXI-5422. Record negative DC voltage out measurement in the Measured Negative Offset column of Table 5. 14. Subtract the Ideal Negative Offset from the Measured Negative Offset and record the result under Error Negative Offset. The Error Negative Offset should be less than or equal to the limit you are using. 15.
NI PXI-5422 Calibration Procedure 30 ni.com 1.000000 0.950000 0.900000 0.850000 0.800000 0.750000 0.710000 1 2 3 4 5 6 7 0.710000 0.750000 0.800000 0.850000 0.900000 0.950000 1.000000 – 0.710000 – 0.750000 – 0.800000 – 0.850000 – 0.900000 – 0.950000 –1.000000 Ideal Negative Full-Scale (Volts) Measured Positive Full-Scale (Volts) Measured Negative Full-Scale (Volts) Offset (Volts)1 ±0.025000 ±0.025000 ±0.025000 ±0.025000 ±0.025000 ±0.025000 ±0.
4. 5. 6.
11. Measure the negative DC voltage out of the NI PXI-5422. Record the negative DC voltage out measurement in the Measured Negative Full-Scale Value column of Table 6. 12. Call niFgen_AbortGeneration (niFgen Abort Generation VI) to abort the waveform generation using the following parameter: • vi: The session handle returned from niFgen_init 13. Average the Measured Positive Full-Scale Value and Measured Negative Full-Scale Value to calculate the Offset. 14.
1. 2. Call niFgen_InitExtCal (niFgen Init Ext Cal VI) to open an NI-FGEN external calibration session using the following parameters: • resourceName: The name of the device you want to calibrate. This name can be found under Devices and Interfaces in MAX. • password: The password required to open an external calibration session. If this password has not been changed since manufacturing, the password is NI. • vi: A pointer to a ViSession.
Initialize Ext Cal Session Initialize Analog Output Calibration Adjust Main Path Pre-Amp Offset Adjust Main Path Pre-Amp Gain Adjust Main Path Post-Amp Gain and Offset Adjust Direct Path Gain Initialize Oscillator Frequency Calibration Adjust Oscillator Frequency Initialize Calibration ADC Calibration Adjust Calibration ADC Close Ext Cal Session Figure 4. NI PXI-5422 External Calibration Procedure NI PXI-5422 Calibration Procedure 34 ni.
Initializing the External Calibration Session Call niFgen_InitExtCal (niFgen Init Ext Cal VI) to open an NI-FGEN external calibration session using the following parameters: • resourceName: The name of the device you want to calibrate. This name can be found under Devices and Interfaces in MAX. • password: The password required to open an external calibration session. If this password has not been changed since manufacturing, the password is NI. • vi: A pointer to a ViSession.
3. 4. 5. 6. 7.
8. 9.
2. 3. 4.
5. 6. 7. Call niFgen_SetAttributeViBoolean to set the analog filter state (niFgen property node: Output Attributes»Analog Filter Enabled) using the following parameters: • vi: The session handle returned from niFgen_InitExtCal • channelName: "0" • attributeID: NIFGEN_ATTR_ANALOG_FILTER_ENABLED • value: The Analog Filter Enable value for the current iteration from Table 7.
f. g. Call niFgen_SetAttributeViInt32 to set the gain DAC value (niFgen property node: Calibration»Gain DAC Value) using the following parameters: • vi: The session handle returned from niFgen_InitExtCal • channelName: "0" • attributeID: NIFGEN_ATTR_GAIN_DAC_VALUE • value: 1000 Call niFgen_Commit (niFgen Commit VI) to commit the attribute values to the device using the following parameter: • vi: The session handle returned from niFgen_InitExtCal h. Wait 500 ms for the output to settle. i.
8. Call niFgen_CalAdjustMainPathPreAmpOffset (niFgen Cal Adjust Main Path Pre Amp Offset VI) using the following parameters: • vi: The session handle returned from niFgen_InitExtCal • channelName: "0" • configuration: The Current Configuration value for the current iteration from Table 7. • gainDACValues: An array containing two elements—the two values (2000, 1000) that you set as the gain DAC in the order that you measured them.
3. 4. Call niFgen_SetAttributeViInt32 to set the offset DAC value (niFgen property node: Calibration»Offset DAC Value) using the following parameters: • vi: The session handle returned from niFgen_InitExtCal • channelName: "0" • attributeID: NIFGEN_ATTR_OFFSET_DAC_VALUE • value: 32000 Repeat steps 5 through 8 for each of the 10 iterations listed in Table 8, changing the Analog Filter Enable, Pre-Amplifier Attenuation, and Current Configuration values for each iteration. Table 8.
6. 7. Call niFgen_SetAttributeViReal64 to set the pre-amplifier attenuation (niFgen property node: Calibration»Pre-Amplifier Attenuation) using the following parameters: • vi: The session handle returned from niFgen_InitExtCal • channelName: "0" • attributeID: NIFGEN_ATTR_PRE_AMPLIFIER_ATTENUATION • value: The Pre-Amplifier Attenuation value for the current iteration from Table 8. Take the following voltage measurements at the NI PXI-5422 CH 0 front panel connector into a high-impedance load: a.
g. h. Call niFgen_WriteBinary16AnalogStaticValue (niFgen Write Binary 16 Analog Static Value VI) to set the main DAC value using the following parameters: • vi: The session handle returned from niFgen_InitExtCal • channelName: "0" • value: –29232 Call niFgen_Commit (niFgen Commit VI) to commit the attribute values to the device using the following parameter: • 8. NI PXI-5422 Calibration Procedure vi: The session handle returned from niFgen_InitExtCal i. Wait 500 ms for the output to settle. j.
Adjusting the Main Path Post-Amplifier Gain and Offset 1. 2. 3. 4. 5.
Table 9.
8. Take the following voltage measurements at the NI PXI-5422 CH 0 front panel connector into a high-impedance load: a. b.
9.
4. 5. 6. 7. 8.
9. Call niFgen_SetAttributeViInt32 to set the analog path value (niFgen property node: Output Attributes»Analog Path) using the following parameters: • vi: The session handle returned from niFgen_InitExtCal • channelName: "0" • attributeID: NIFGEN_ATTR_ANALOG_PATH • value: NIFGEN_VAL_DIRECT_ANALOG_PATH 10. Call niFgen_Commit (niFgen Commit VI) to commit the attribute values to the device using the following parameter: • vi: The session handle returned from niFgen_InitExtCal 11.
g. Call niFgen_Commit (niFgen Commit VI) to commit the attribute values to the device using the following parameter: • vi: The session handle returned from niFgen_InitExtCal h. Wait 500 ms for the output to settle. i. Use the DMM to measure the voltage output by the device. This measurement is measurement 1, which is used in step 12. j. Call niFgen_WriteBinary16AnalogStaticValue (niFgen Write Binary 16 Analog Static Value VI) to set the main DAC value using the following parameters: k. l.
12.
4. Note Call niFgen_SetAttributeViReal64 to set the offset (niFgen property node: Arbitrary Waveform Output»Arbitrary Waveform Offset) using the following parameters: • vi: The session handle returned from niFgen_InitExtCal • channelName: "0" • attributeID: NIFGEN_ATTR_ARB_OFFSET • value: 0 You can adjust this value based on which measuring device you use. 5. 6. 7. 8.
9. Call niFgen_CreateArbWaveform (niFgen Create Arbitrary Waveform VI) using the following parameters: • vi: The session handle returned from niFgen_InitExtCal • wfmSize: The size in samples (500) of the waveform you created in step 8 • wfmData: The array of waveform samples that you created in step 8 • wfmHandle: The variable passed by reference through this parameter receives the value (waveform handle) that identifies the waveform created by this function. 10.
c. Call niFgen_InitiateGeneration (niFgen Initiate Generation VI) to initiate the waveform generation using the following parameter: • d. vi: The session handle returned from niFgen_InitExtCal Measure the frequency of the generated waveform. This value is the measured frequency. 14.
5. 6. 7. 8. 9.
• vi: The session handle returned from niFgen_InitExtCal • channelName: "0" • attributeID: NIFGEN_ATTR_OUTPUT_ENABLED • value: VI_TRUE 11. Call niFgen_Commit (niFgen Commit VI) to commit the attribute values to the device using the following parameter: • vi: The session handle returned from niFgen_InitExtCal 12. Wait 500 ms for the output to settle. 13.
• returnCalibratedValue: VI_FALSE • calADCValue: A ViReal64 variable. The variable passed by reference through this parameter receives the voltage measured by the onboard ADC. This value is cal ADC measurement 0, which is used in step 32. 19.
27. Call niFgen_ReadCalADC (niFgen Read CAL ADC VI) to measure the analog output voltage with the onboard calibration ADC using the following parameters: • vi: The session handle returned from niFgen_InitExtCal • numberOfReadsToAverage: 3 • returnCalibratedValue: VI_FALSE • calADCValue: A ViReal64 variable. The variable passed by reference through this parameter receives the voltage measured by the onboard calibration ADC. This value is cal ADC measurement 1, which is used in step 32. 28.
33. Call niFgen_SetAttributeViBoolean to disable the analog output (niFgen property node: Basic Operation»Output Enabled) using the following parameters: • vi: The session handle returned from niFgen_InitExtCal • channelName: "0" • attributeID: NIFGEN_ATTR_OUTPUT_ENABLED • value: VI_FALSE 34.
Calibration Utilities NI-FGEN supports several calibration utilities that allow you to retrieve information about adjustments performed on the NI PXI-5422, restore an external calibration, change the external calibration password, and store small amounts of information in the onboard EEPROM. You can retrieve some data using MAX or the FGEN SFP; however, you can retrieve all the data using NI-FGEN. MAX To retrieve data using MAX, complete the following steps: 1. Launch MAX. 2.
NI-FGEN NI-FGEN provides a full complement of calibration utility functions and VIs. Refer to the NI Signal Generators Help for the complete function reference.
Where to Go for Support The National Instruments Web site is your complete resource for technical support. At ni.com/support you have access to everything from troubleshooting and application development self-help resources to email and phone assistance from NI Application Engineers. A Declaration of Conformity (DoC) is our claim of compliance with the Council of the European Communities using the manufacturer’s declaration of conformity.