National Instruments 5124 Manuale

CALIBRATION PROCEDURE

NI 5122/5124

Contents

Conventions ............................................................................................ 2

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

Self-Calibration ........................................................................ 3

External Calibration.................................................................. 3

Calibration Interval................................................................... 3

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

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

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

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

MAX ................................................................................................ 6

Scope SFP ........................................................................................ 6

NI-SCOPE ....................................................................................... 6

External Calibration Options .................................................................. 8

Complete Calibration....................................................................... 9

Optional Calibration ........................................................................ 10

External Calibration Requirements......................................................... 12

Test Equipment ................................................................................ 12

Test Conditions ................................................................................ 12

External Calibration Procedures ............................................................. 13

Verifying NI 5122/5124 Specifications........................................... 13

Vertical Offset and Vertical Gain Accuracy............................. 13

Programmable Vertical Offset Accuracy.................................. 20

Timing Accuracy ...................................................................... 22

Bandwidth and Flatness............................................................ 24

Trigger Sensitivity ........................................................................... 29

Adjusting the NI 5122/5124 ............................................................ 31

Calibration Utilities................................................................................. 33

MAX ................................................................................................ 33

NI-SCOPE ....................................................................................... 34

Calibration Function References............................................................. 34

Where to Go for Support......................................................................... 34

NI 5122/5124 Calibration Procedure 2 ni.com

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.

♦The ♦symbol indicates that the following text applies only to a specific

product, a specific operating system, or a specific software version.

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.

monospace italic

Italic text in this font denotes text that is a placeholder for a word or value

that you must supply.

Introduction

This document contains instructions for calibrating NI PXI/PCI-5122 and

NI PXI/PCI-5124 digitizers. This calibration procedure is intended for

metrology labs. This document describes specific programming steps for

writing an external calibration procedure for the NI 5122/5124.

The NI 5122/5124 supports two types of calibration: self-calibration (or

internal calibration) and external calibration.

©National Instruments Corporation 3 NI 5122/5124 Calibration Procedure

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. Self-calibration

retains the traceability of the external calibration.

External Calibration

External calibration is generally performed with a high-precision

oscilloscope calibrator 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 signal

generator source, a new calibration certificate can be issued.

Calibration Interval

Self-calibration can be performed as necessary to compensate for

environmental changes.

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

NI 5122/5124 more than a few times a day may cause excessive wear on the relays over

time.

The measurement accuracy requirements of your application determine

how often you should externally calibrate the NI 5122/5124.

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 5122/5124 requires installing NI-SCOPE version 2.7 or

later on the calibration system. You can download NI-SCOPE from the

Instrument Driver Network at ni.com/idnet. NI-SCOPE supports

programming the Self-Calibration Procedures in a number of

programming languages. However, only LabVIEW and C are supported

for the External Calibration Procedures.

NI 5122/5124 Calibration Procedure 4 ni.com

NI-SCOPE 2.7 or later includes all the functions and attributes necessary

for calibrating the NI 5122/5124. For LabWindows™/CVI™, the

NI-SCOPE function panel niScopeCal.fp provides further help on the

functions available in CVI. LabVIEW support is installed in

niScopeCal.llb, and all calibration functions appear in the function

palette. Refer to Table 1 for file locations.

Calibration functions are C function calls or LabVIEW VIs in the

NI-SCOPE driver. In this document, the C function call is shown first,

followed by the corresponding LabVIEW VI in parentheses. The C

function calls are valid for any compiler capable of calling a 32-bit DLL.

Many of the functions use constants defined in the niScopeCal.h file.

To use these constants in C, you must include niScopeCal.h in your code

when you write the calibration procedure.

For more information on the calibration functions and VIs, refer to the

NI-SCOPE Function Reference Help or the NI-SCOPE VI Reference Help.

These references can be found in the NI High-Speed Digitizers Help.

To access this help file, go to Start»Programs»National Instruments»

NI-SCOPE»Documentation»NI High-Speed Digitizers Help.

Table 1. Calibration File Locations after Installing NI-SCOPE 2.7 or Later

File Name and Location Description

IVI\Bin\niscope_32.dll NI-SCOPE driver containing the entire

NI-SCOPE API, including calibration functions

IVI\Lib\msc\niscope.lib NI-SCOPE library for Microsoft C containing

the entire NI-SCOPE API, including calibration

functions

LabVIEW (

version

)\examples\instr\

niScope

Directory of LabVIEW NI-SCOPE example

VIs, including self-calibration; access the

calibration example from the LabVIEW

function palette

LabVIEW (

version

)\instr.lib\niScope

Calibrate\niScopeCal.llb

LabVIEW VI library containing VIs for calling

the NI-SCOPE calibration API; access

calibration functions from the NI-SCOPE

calibration section of the LabVIEW function

palette

IVI\Drivers\niScope\niScopeCal.fp CVI function panel file that includes external

calibration function prototypes and help on

using NI-SCOPE in the CVI environment

©National Instruments Corporation 5 NI 5122/5124 Calibration Procedure

Documentation

You may find the following documentation helpful as you write your

calibration procedure:

• NI High-Speed Digitizers Getting Started Guide

• NI High-Speed Digitizers Help

•NI PXI/PCI-5122 Specifications or NI PXI/PCI-5124 Specifications

•NI-SCOPE Function Reference Help or NI-SCOPE VI Reference Help

These documents are installed with NI-SCOPE. You can also download the

latest versions from the NI Web site at ni.com/manuals.

Self-Calibration Procedures

The NI 5122/5124 includes precise internal circuits and references used

during self-calibration to adjust for time and temperature drift. The

digitizer gain, offset, flatness, and trigger timing 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. Absolute accuracy is ensured by

compensating for any error measured in the internal references.

Note Self-calibrate the digitizer before you perform verification. NI-SCOPE includes

self-calibration example programs for LabVIEW, CVI, and Microsoft Visual C.

You can initiate self-calibration using Measurement & Automation

Explorer (MAX), using the Scope Soft Front Panel (SFP), or

programmatically using NI-SCOPE.

IVI\Include\niScopeCal.h Calibration header file, which you must include

in any C program accessing calibration

functions. This file automatically includes

niScope.h, which defines the rest of the

NI-SCOPE interface

IVI\Drivers\niScope\Examples\ Directory of NI-SCOPE examples for CVI, C,

Visual C++, and Visual Basic

Table 1. Calibration File Locations after Installing NI-SCOPE 2.7 or Later (Continued)

File Name and Location Description

NI 5122/5124 Calibration Procedure 6 ni.com

MAX

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

1. Disconnect or disable any AC inputs to the digitizer.

2. Launch MAX.

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

4. Select the device that you want to calibrate.

5. Initiate self-calibration using one of the following methods:

•ClickSelf-Calibrate in the upper right corner of MAX.

• Right-click the name of the device in the MAX configuration tree

and select Self-Calibrate from the drop-down menu.

Scope SFP

To initiate self-calibration from the Scope SFP, complete the following

steps:

1. Disconnect or disable any AC inputs to the digitizer.

2. Launch the Scope SFP (Start»Programs»National Instruments»

NI-SCOPE»Scope Soft Front Panel).

3. Select the device you want to calibrate using the Device Configuration

dialog box (Edit»Device Configuration).

4. Launch the Calibration dialog box (Utility»Self Calibration).

5. Click OK to begin self-calibration.

NI-SCOPE

To self-calibrate the NI 5122/5124 programmatically using NI-SCOPE,

complete the following steps:

1. Disconnect or disable any AC inputs to the digitizer.

2. Call niScope_init (niScope Initialize VI) to obtain an instrument

session handle. Set the following parameters:

•resourceName: The device name assigned by MAX

•IDQuery: NISCOPE_VAL_VI_FALSE

•resetDevice: NISCOPE_VAL_VI_FALSE

•vi: The returned session handle that you use to identify the

instrument in all subsequent instrument driver function calls

3. Call niScope_calSelfCalibrate (niScope Cal Self Calibrate VI)

with the following parameters:

•sessionHandle: The instrument handle that you obtain from

niScope_init (niScope Initialize VI)

©National Instruments Corporation 7 NI 5122/5124 Calibration Procedure

•channelList: VI_NULL

•option: VI_NULL

Because the session is a standard session rather than an external

calibration session, the new calibration constants are immediately

stored in the EEPROM. Therefore, you can include this procedure in

any application that uses the digitizer.

4. Call niScope_close (niScope Close VI) to close the session handle.

Set the following parameter:

•vi: The instrument handle you obtained from niScope_init

NI 5122/5124 Calibration Procedure 8 ni.com

External Calibration Options

External calibration involves both adjustment and verification. Adjustment

is the process of measuring and compensating for device performance to

improve the measurement accuracy. Performing an adjustment updates the

calibration date, effectively resetting the calibration interval. The device is

guaranteed to meet or exceed its published specifications for the duration

of the calibration interval. Verification is the process of testing the device

to ensure that the measurement accuracy is within certain specifications.

Verification can be used to ensure that the adjustment process was

successful, or to determine if the adjustment process needs to be performed

at all. During verification, you must compare the measurement error to

limits given in Tables 3 through 12.

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 measurement 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 measurement errors determined

during verification fall within the published specifications, but not within

the calibration test limits, the device is meeting its published specifications.

However, the device will not necessarily remain within these specifications

for an additional two years. The device will meet published specifications

for the remainder of the current calibration interval. 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

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 alternative

procedures that allow you to skip adjustment if the device already meets its

calibration test limits or published specifications.

©National Instruments Corporation 9 NI 5122/5124 Calibration Procedure

Complete Calibration

Performing a complete calibration is the recommended way to guarantee

that the NI 5122/5124 will meet or exceed 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. Figure 1 shows the programming flow for complete

calibration.

Figure 1. Complete Calibration Programming Flow

Adjust (Cal Dates and

Temperatures Updated)

Document

Post-Adjustment

Results

Document

Pre-Adjustment

Results

Calibration/

Verification

Complete

Ye s N o

Self-Calibrate

Verify

Meets

Calibration

Test Limits?

Review Verification/

Adjustment Procedure

or Return Device

NI 5122/5124 Calibration Procedure 10 ni.com

Optional Calibration

You can choose to skip the adjustment steps of the calibration procedure if

the measurement error is within the calibration test limits or the published

specifications during the first verification. If all of the measurement 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 5122/5124

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. However, you cannot update the

calibration date, because the device will not necessarily operate within the

published specifications for an additional two years.

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

adjustment, you must verify that the measurement error falls within the calibration test

limits at the end of the calibration procedure.

Figure 2 shows the programming flow for the optional calibration.

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