National Instruments NI PXI-5422 User Manual

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.

Conventions ............................................................................................ 1

Introduction.............................................................................................2

What Is Calibration? ........................................................................ 2

Self-Calibration ........................................................................ 2

External Calibration.................................................................. 2

Why Should You Calibrate? ............................................................ 2

How Often Should You Calibrate? .................................................. 3

Software and Documentation Requirements...........................................3

Software ........................................................................................... 3

Documentation.................................................................................5

Self-Calibration Procedures .................................................................... 5

MAX ................................................................................................ 5

FGEN Soft Front Panel.................................................................... 6

NI-FGEN ......................................................................................... 6

External Calibration Options .................................................................. 7

Complete Calibration....................................................................... 7

Optional Calibration ........................................................................ 9

External Calibration Requirements ......................................................... 11

Test Equipment ................................................................................ 11

Test Conditions ................................................................................ 11

External Calibration Procedures ............................................................. 12

Writing Your Calibration Procedure................................................12

Calibration Procedures in LabVIEW........................................ 12

Calibration Procedures in LabWindows/CVI ...........................12

Calibration Procedures in C......................................................12

Verifying NI PXI-5422 Specifications ............................................13

Verifying the Oscillator Frequency Accuracy.......................... 15

Verifying the DC Gain and Offset Accuracy ...........................17

Adjusting the NI PXI-5422.............................................................. 31

Initializing the External Calibration Session ............................35

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.................................................................................................61

FGEN SFP........................................................................................61

NI-FGEN ..........................................................................................62

Where to Go for Support .........................................................................63

Conventions

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 directs you to pull down the File menu, select the Page Setup item, and select Options from the last dialog box.

This icon denotes a note, which alerts you to important information.

This icon denotes a caution, which advises you of precautions to take to avoid injury, data loss, or a system crash. When this symbol is marked on a product, refer to the Read Me First: Safety and Radio-Frequency Interference document for information about precautions to take.

bold Bold text denotes items that you must select or click in the software, such

as menu items and dialog box options. Bold text also denotes parameter names.

italic Italic text denotes variables, emphasis, a cross reference, or an introduction

to a key concept. This font also denotes text that is a placeholder for a word or value that you must supply.

monospace Text in this font denotes text or characters that you should enter from the

keyboard, sections of code, programming examples, and syntax examples. This font is also used for the proper names of disk drives, paths, directories, programs, subprograms, subroutines, device names, functions, operations, variables, filenames, and extensions.

Introduction

This document contains instructions for calibrating the NI PXI-5422 arbitrary waveform generator. This calibration procedure is intended for metrology labs. It describes specific programming steps for writing an external calibration procedure for the NI PXI-5422.

NI PXI-5422 Calibration Procedure 2 ni.com

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 NI PXI-5422 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 output accuracy by compensating for variables, such as temperature and time, that may have changed since the last external calibration. Self-calibration retains the traceability of the external calibration.

External Calibration

External calibration is generally performed at either NI or a metrology lab. This procedure replaces all calibration constants in the EEPROM and is equivalent to a factory calibration at NI. Because the external calibration procedure changes all EEPROM constants, it invalidates the original calibration certificate. If an external calibration is done with a traceable instrument, a new calibration certificate can be issued.

Why Should You Calibrate?

The accuracy of electronic components drifts with time and temperature, which can affect output accuracy as a device ages. Calibration verifies that the NI PXI-5422 still meets its specified accuracy and NI standards. If adjustments are necessary, calibration makes the adjustments to restore the accuracy.

How Often Should You Calibrate?

Self-calibration can be performed as necessary to compensate for environmental changes.

Caution Although you can use self-calibration repeatedly, self-calibrating the

NI PXI-5422 more than a few times a day may cause excessive wear on the relays over time.

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.

Software and Documentation Requirements

This section describes the software and documentation required for both self-calibration and external calibration.

Software

Calibrating the NI PXI-5422 requires installing NI-FGEN version 2.2 or later on the calibration system. You can download NI-FGEN from the Instrument Driver Network at programming the Self-Calibration Procedures and the External

Calibration Procedures in the LabVIEW, LabWindows

application development environments (ADEs). When you install NI-FGEN, you only need to install support for the ADE that you intend to use.

NI-FGEN 2.2 or later includes all the functions and attributes necessary for calibrating the NI PXI-5422. For LabWindows/CVI, the NI-FGEN function panel ( LabVIEW support is in the appear in the function palette.

niFgen.fp) provides help about the functions available.

ni.com/idnet. NI-FGEN supports

niFgen.llb file, and all calibration functions

™

/CVI™, and C

Calibration functions are C function calls or LabVIEW VIs in NI-FGEN. In this document, the C function call is shown first, followed by the corresponding LabVIEW VI, or NI-FGEN LabVIEW property node, in parentheses. The C function calls are valid for any compiler capable of

NI PXI-5422 Calibration Procedure 4 ni.com

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.lib Allows you to create applications that call

functions in the

niFgen_32.dll:

• For Microsoft Visual C/C++, link to

msc\niFgen.lib.

• For LabWindows/CVI, link to the library appropriate to your current compatibility mode (

msc for Microsoft Visual C/C++).

IVI\Include\niFgen.h A header file for the accessible functions in

the

niFgen_32.dll. You must include this

file in any C code that you write to call these functions.

<LabVIEW>\instr.lib\niFgen\niFgen.llb

(LabVIEW)

IVI\Drivers\niFgen\niFgen.fp

(CVI)

The calibration process is described in the Self-Calibration Procedures and the External Calibration Procedures sections, including step-by-step instructions on calling the appropriate calibration functions.

Contains VIs that correspond to the functions in the

niFgen_32.dll.

Contains the function panels for the function in the

niFgen32.dll.

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. You can access this help file by selecting Start»Programs»National Instruments»NI-FGEN» Documentation»NI Signal Generators Help. For the latest versions of NI documentation, refer to

Self-Calibration Procedures

The NI PXI-5422 is capable of performing self-calibration, which adjusts the gain and offset of the main and direct analog paths. Self-calibration exclusively uses an onboard A/D converter (ADC) to measure the output voltage. You can implement self-calibration on the NI PXI-5422 by following procedures similar to the Verifying the DC Gain and Offset

Accuracy and the Adjusting the Analog Output procedures. However,

output impedance, oscillator frequency, and the calibration ADC cannot be adjusted during self-calibration.

ni.com/manuals.

You can initiate self-calibration interactively from Measurement & Automation Explorer (MAX) or from the FGEN Soft Front Panel (SFP). Alternately, you can initiate self-calibration programmatically using NI-FGEN.

MAX

To initiate self-calibration from MAX, complete the following steps:

1. Launch MAX.

2. Select My System»Devices and Interfaces»NI-DAQmx Devices.

NI PXI-5422 Calibration Procedure 6 ni.com

3. Select the device that you want to calibrate.

4. Initiate self-calibration in one of the following ways:

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

2. Open the Calibration dialog box (Utility»Calibration).

3. Click Perform self-calibration.

NI-FGEN

To self-calibrate the NI PXI-5422 programmatically using NI-FGEN, complete the following steps:

1. Call

2. Call

3. Call

•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.

Configuration dialog box (Edit»Device Configuration).

niFgen_init (niFgen Initialize VI) to open an NI-FGEN session

using the following parameters:

• resourceName: The name of the device that you want to calibrate.

You can find this name under Devices and Interfaces in MAX.

• IDQuery:

• 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.

niFgen_SelfCal (niFgen Self Cal VI) using the following

parameter:

• vi: The session handle returned from

niFgen_close (niFgen Close VI) to close the NI-FGEN session

using the following parameter:

• vi: The session handle returned from

VI_TRUE

niFgen_init

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. Performing an adjustment updates the calibration date, resetting the calibration interval. The device is guaranteed to meet or exceed its published specifications for the duration of the calibration interval.

This document provides two sets of test limits for most verification stages, the calibration test limits and the published specifications. The calibration test limits are more restrictive than the published specifications. If all of the output errors determined during verification fall within the calibration test limits, the device is guaranteed to meet or exceed its published specifications for a full calibration interval (two years). For this reason, you must verify against the calibration test limits when performing verification after adjustment.

If all of the output errors determined during verification fall within the published specifications, but not within the calibration test limits, the device meets its published specifications. However, the device may not remain within these specifications for another two years. The device will meet published specifications for the rest of the current calibration interval.

In this case, you can perform an adjustment if you want to improve the output accuracy or reset the calibration interval. If some output errors determined during verification do not fall within the published specifications, you must perform an adjustment to restore the device operation to its published specifications.

The Complete Calibration section describes the recommended calibration procedure. The Optional Calibration section describes alternate procedures that allow you to skip adjustment if the device already meets its calibration test limits or published specifications.

Complete Calibration

Performing a complete calibration is the recommended way to guarantee that the NI PXI-5422 meets or exceeds its published specifications for a two-year calibration interval. At the end of the complete calibration procedure, you verify that the output error falls within the calibration test limits. Figure 1 shows the programming flow for complete calibration.

NI PXI-5422 Calibration Procedure 8 ni.com

Self-Calibrate

Verify

Adjust

(Cal Dates and

Temperatures

Updated)

Verify

Document

Pre-Adjustment

Results

Document

Post-Adjustment

Results

Calibration/ Verification

Complete

Ye s N o

Meets

Calibration

Test Limits?

Review Verification/ Adjustment

Procedure or

Return Device

Figure 1. Complete Calibration Programming Flow

Optional Calibration

Note Regardless of the results of the first verification, if you choose to perform an

adjustment you must verify that the output error falls within the calibration test limits at the end of the calibration procedure.

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. 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 PXI-5422 section for more information.

If all of the output errors determined during the first verification fall within the published specifications, but not within the calibration test limits, adjustment is also optional. However, you cannot update the calibration date because the device will not necessarily operate within the published specifications for an additional two years.

Figure 2 shows the programming flow for the optional calibration.

NI PXI-5422 Calibration Procedure 10 ni.com

Self-Calibrate

Verify

Document

Pre-Adjustment

Results

Update Calibration

Dates and

Temperatures

Without Adjusting

Calibration/ Verification

Ye s N o

Complete

Meets

Calibration

Test Limits?

Ye s No

Results

Within

Published Specs

(Adjustment

Optional)

Adjust

Anyway?

Specifications?

Ye sNo

Meets

Published

Ye s

Adjust

(Cal Dates and

Temperatures

Updated)

Verify

Meets

Calibration

Test Limits?

Document

Post-Adjustment

Results

Review Verification/ Adjustment

Procedure or

Return Device

Figure 2. Optional Calibration Programming Flow

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. Equipment Required for Calibrating the NI PXI-5422

Instrument

Digital multimeter (DMM)

Male banana to female BNC adapter

Male BNC to female SMB cable

Spectrum analyzer or frequency meter

Male BNC to female SMB cable

Test Conditions

Applicable

Specification

DC gain and offset DC accuracy ≤ ±50 ppm

Frequency accuracy Ability to measure

Follow these guidelines to optimize the connections and the environment during calibration:

• Keep connections to the NI PXI-5422 short.

• Keep relative humidity below 80%.

• Maintain a temperature between 18 °C and 28 °C.

• Observe the 15-minute warm-up time.

Minimum

Specifications

Resolution ≤1 µV

— —

50 Ω, RG-223 —

10 MHz or higher sine waves

Frequency accuracy to ±500 ppb

50 Ω, RG-223 —

Recommended

Instrument

NI PXI-4070

Agilent HP 34401A

Keithley 2000

NI PXI-5660

Agilent HP 8560E

Agilent HP 53131A or HP 53132A with timebase option 001, 010, or 012

NI PXI-5422 Calibration Procedure 12 ni.com

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.

Writing Your Calibration Procedure

Before you begin to write your calibration program, review the programming flows in Figures 1 and 2.

Calibration Procedures in LabVIEW

To write calibration procedures in LabVIEW, you must use the VIs included in the appear within the NI-FGEN Calibration palette under Functions» Instrument I/O»Instruments Drivers»NI-FGEN»Calibration.

Calibration Procedures in LabWindows/CVI

To write calibration procedures in LabWindows/CVI, you must use the functions included in the the calibration functions under the Calibration class node.

niFgen.llb file. After installation, these VIs

niFgen.fp file. After installation, you can locate

Calibration Procedures in C

To write calibration procedures in C, you must include the niFgen.h file in the code that calls the calibration functions, and you must link the

niFgen.lib file into the build of your executable.

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. To verify that the NI PXI-5422 still meets its specifications, you must use NI-FGEN to control the NI PXI-5422.

The steps in the verification procedures describe the code that you use to generate the appropriate signals, as well as the NI-FGEN function calls that you make to verify specifications.

You can verify the following specifications for the NI PXI-5422:

• Oscillator frequency accuracy

• DC gain and offset accuracy

The verification procedure for each of these specifications includes setting up, programming, and cleaning up.

Note If any of these tests fail immediately after you perform an external adjustment, verify

that you have met the required test conditions before you return the NI PXI-5422 to NI for repair.

Refer to Table 2 for information about which instrument to use for verifying each specification. Refer to Figure 3 for the names and locations of the NI PXI-5422 front panel connectors.

NI PXI-5422 Calibration Procedure 14 ni.com

NI PXI-5422

16-Bit 200 MS/s AWG

ACCESS ACTIVE

CH 0

CLK

PFI 0

PFI 1

DIGITAL DATA & CONTROL

Figure 3. NI PXI-5422 Front Panel Connectors

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. Connect the NI PXI-5422 CH 0 front panel connector to the instrument measuring the frequency accuracy with a male BNC to female SMB cable.

2. Call

3. Call

4. Call niFgen_SetAttributeViReal64 to set the gain (niFgen

niFgen_init (niFgen Initialize VI) using the following

parameters:

• resourceName: The name of the device that you want to verify.

You can find this name under Devices and Interfaces in MAX.

• IDQuery:

VI_TRUE

• resetDevice: VI_TRUE

• vi: A pointer to a ViSession. The variable passed by reference

niFgen_SetAttributeViReal64 to set the sample rate

(niFgen property node: Arbitrary Waveform Output»Sample Rate) using the following parameters:

• vi: The session handle returned from

niFgen_init

• channelName: "0"

• attributeID: NIFGEN_ATTR_ARB_SAMPLE_RATE

• value: 200000000

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: 1

Note You can adjust this value based on which measuring device you use.

NI PXI-5422 Calibration Procedure 16 ni.com

5. 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

Note You can adjust this value based on which measuring device you use.

6. 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_init

• channelName: "0"

• attributeID: NIFGEN_ATTR_ANALOG_FILTER_ENABLED

• value: VI_TRUE

7. Generate an array of waveform samples. The waveform should have 20 samples per cycle with a total of 500 samples. This configuration results in 25 sine wave cycles. Because you set the sample rate to 200 MS/s and because you are using 20 samples per cycle, the resulting waveform is a 10 MHz sine wave.

Note The sample values of this waveform must fall between –1.0 and 1.0.

8. Call

niFgen_CreateArbWaveform (niFgen Create Arbitrary

Waveform VI) using the following parameters:

• vi: The session handle returned from

• wfmSize: The size in samples (

niFgen_init

500) of the waveform you created

in step 7

• wfmData: The array of waveform samples that you created in

step 7

• wfmHandle: The variable passed by reference through this

parameter receives the value (waveform handle) that identifies the waveform created by this function.

9. Call

niFgen_InitiateGeneration (niFgen Initiate Generation VI)

to initiate the waveform generation using the following parameter:

• vi: The session handle returned from

niFgen_init

10. Measure the frequency out of the NI PXI-5422.

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. Call

niFgen_AbortGeneration (niFgen Abort Generation VI) to

abort the waveform generation using the following parameter:

• vi: The session handle returned from

niFgen_init

12. Call niFgen_close (niFgen Close VI) to close the instrument driver session, to destroy the instrument driver session and all of its properties, and to release any memory resources NI-FGEN uses. Use the following parameter:

• vi: The session handle returned from

niFgen_init

Verifying the DC Gain and Offset Accuracy

This test verifies the DC gain and offset accuracy of the NI PXI-5422 into a high-impedance load by generating a number of DC voltages and offsets, measuring the voltage with a DMM, and comparing the NI PXI-5422 to the error limits.

The DC gain and offset accuracy verification procedure has three sub-procedures that verify the following:

• Main analog path gain

• Main analog path offset

• Direct path gain

Verifying the Main Analog Path Gain

To verify the gain of the NI PXI-5422 main analog path, complete the following steps:

1. Connect the NI PXI-5422 CH 0 front panel connector to the DMM for measuring DC gain and offset accuracy.

2. Call

niFgen_init (niFgen Initialize VI) using the following

parameters:

• resourceName: The name of the device that you want to verify.

You can find this name under Devices and Interfaces in MAX.

NI PXI-5422 Calibration Procedure 18 ni.com

• IDQuery: VI_TRUE

• resetDevice: VI_TRUE

• vi: A pointer to a ViSession. The variable passed by reference

3. 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_init

• channelName: "0"

• attributeID: NIFGEN_ATTR_ANALOG_FILTER_ENABLED

• value: VI_FALSE

4. Call niFgen_SetAttributeViReal64 to set the load impedance

(niFgen property node: Output Attributes»Load Impedance) using the following parameters:

• vi: The session handle returned from

niFgen_init

• channelName: "0"

• attributeID:

NIFGEN_ATTR_LOAD_IMPEDANCE

• value: 10000000000

5. Call niFgen_SetAttributeViInt32 to set the analog path (niFgen

property node: Output Attributes»Analog Path) using the following parameters:

• vi: The session handle returned from

niFgen_init

• channelName: "0"

• attributeID: NIFGEN_ATTR_ANALOG_PATH

• value: NIFGEN_VAL_MAIN_ANALOG_PATH

6. Call niFgen_SetAttributeViReal64 to set the output impedance

(niFgen property node: Basic Operation»Output Impedance) using the following parameters:

• vi: The session handle returned from

niFgen_init

• channelName: "0"

• attributeID: NIFGEN_ATTR_OUTPUT_IMPEDANCE

• value: 50

+ 44 hidden pages

National Instruments NI PXI-5422 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Contents

Conventions

Introduction

What Is Calibration?

Self-Calibration

External Calibration

Why Should You Calibrate?

How Often Should You Calibrate?

Software and Documentation Requirements

Software

Table 1. Calibration File Locations

Documentation

Self-Calibration Procedures

FGEN Soft Front Panel

NI-FGEN

External Calibration Options

Complete Calibration

Figure 1. Complete Calibration Programming Flow

Optional Calibration

Figure 2. Optional Calibration Programming Flow

External Calibration Requirements

Test Equipment

Table 2. Equipment Required for Calibrating the NI PXI-5422

Test Conditions

External Calibration Procedures

Writing Your Calibration Procedure

Calibration Procedures in LabVIEW

Calibration Procedures in LabWindows/CVI

Calibration Procedures in C

Verifying NI PXI-5422 Specifications

Figure 3. NI PXI-5422 Front Panel Connectors

Verifying the Oscillator Frequency Accuracy

Table 3. Frequency Ranges

Verifying the DC Gain and Offset Accuracy