National Instruments NI PCI-5122 Manual

CALIBRATION PROCEDURE
NI PXI/PCI-5122
Contents
Conventions ............................................................................................ 2
Introduction............................................................................................. 3
What Is Calibration? ........................................................................ 3
Self-Calibration ........................................................................ 3
External Calibration.................................................................. 3
Why Should You Calibrate? ............................................................ 3
How Often Should You Calibrate?.................................................. 4
Software and Documentation Requirements........................................... 4
Software ........................................................................................... 4
Documentation................................................................................. 6
Self-Calibration Procedures .................................................................... 6
MAX ................................................................................................ 6
Scope SFP ........................................................................................ 7
NI-SCOPE ....................................................................................... 7
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 Specifications .................................................... 13
Vertical Offset and Vertical Gain Accuracy............................. 13
Programmable Vertical Offset Accuracy.................................. 19
Timing Accuracy ...................................................................... 21
Bandwidth and Flatness............................................................ 23
Trigger Sensitivity ........................................................................... 26
Adjusting the NI 5122...................................................................... 28
Calibration Utilities................................................................................. 30
MAX ................................................................................................ 30
NI-SCOPE ....................................................................................... 30

NI PXI/PCI-5122 Calibration Procedure 2 ni.com
Calibration Function References .............................................................31
Technical Support Resources ..................................................................31
NI Web Support................................................................................31
Worldwide Support ..........................................................................31
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.

©National Instruments Corporation 3 NI PXI/PCI-5122 Calibration Procedure
Introduction
This document contains instructions for calibrating the NI PXI/PCI-5122
digitizer (NI 5122). This calibration procedure is intended for metrology
labs. This document describes specific programming steps for writing an
external calibration procedure for the NI 5122.
What Is Calibration?
Calibration consists of verifying the measurement accuracy of a device
and correcting for any measurement error. Verification is measuring the
performance of a device and comparing the results to the specifications of
the device. NI calibrates every NI 5122 digitizer 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 digitizer.
The NI 5122 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. 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.
Why Should You Calibrate?
The accuracy of electronic components drifts with time and temperature,
which can affect measurement accuracy as a device ages. Calibration
verifies that the digitizer still meets its specified accuracy and NI standards.
If adjustments are necessary, calibration makes the adjustments to restore
the accuracy of the digitizer.

NI PXI/PCI-5122 Calibration Procedure 4 ni.com
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 5122
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. 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 requires installing NI-SCOPE version 2.6 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-SCOPE 2.6 or later includes all the functions and attributes necessary
for calibrating the NI 5122. 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.

©National Instruments Corporation 5 NI PXI/PCI-5122 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 2.6 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
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

NI PXI/PCI-5122 Calibration Procedure 6 ni.com
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
•NI-SCOPE Function Reference Help or NI-SCOPE VI Reference Help
These documents are installed when you install NI-SCOPE. You can also
download them from the NI Web site at ni.com/manuals.
Self-Calibration Procedures
The NI 5122 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.
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 device and select Self-Calibrate from the
drop-down menu.

©National Instruments Corporation 7 NI PXI/PCI-5122 Calibration Procedure
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 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)
•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 PXI/PCI-5122 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 8.
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 alternate
procedures that allow you to skip adjustment if the device already meets its
calibration test limits or published specifications.

©National Instruments Corporation 9 NI PXI/PCI-5122 Calibration Procedure
Complete Calibration
Performing a complete calibration is the recommended way to guarantee
that the NI 5122 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
Verify
Meets
Calibration
Test Limits?
Review Verification/
Adjustment Procedure
or Return Device

NI PXI/PCI-5122 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
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.