National Instruments NI PXI-4070 User manual

©2003 National Instruments Corp. All rights reserved.
CVI™, FlexDMM™, LabVIEW™, National Instruments™, NI™, ni.com™, and NI-DMM™ are trademarks of
National Instruments Corporation. 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.
May 2003
370532B-01
NI PXI-4070 6½ Digit FlexDMM
Calibration Procedure
This document contains step-by-step instructions for writing an external
calibration procedure for the NI PXI-4070 6½ digit FlexDMM and
1.8 MS/s isolated digitizer (NI 4070).
Contents
Conventions ............................................................................................ 2
Calibration Overview.............................................................................. 3
What Is Calibration? ........................................................................ 3
Why Should You Calibrate? ............................................................ 3
How Often Should You Calibrate? .................................................. 4
What Calibration Options Are Available?....................................... 4
How Much Time Does Calibration Require? .................................. 4
Equipment and Other Test Requirements ............................................... 5
Required Test Equipment ................................................................ 5
Optional Test Equipment ................................................................. 5
Test Conditions ................................................................................ 5
Documentation................................................................................. 6
Software ........................................................................................... 7
Verification Procedures........................................................................... 10
Setting Up the Test Equipment........................................................ 10
Verifying DC Voltage...................................................................... 11
Verifying AC Voltage...................................................................... 19
Verifying 4-Wire Resistance ........................................................... 27
Verifying 2-Wire Resistance ........................................................... 29
Verifying DC Current ...................................................................... 34
Verifying AC Current ...................................................................... 36
Verifying Frequency ........................................................................ 38
Adjustment Procedures ........................................................................... 40
Setting Up the Test Equipment........................................................ 40
Adjusting DC Voltage and Resistance............................................. 41
Adjusting AC Voltage (AC- and DC-Coupled) Modes................... 47
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ni.com

NI PXI-4070 Calibration Procedure 2 ni.com
Adjusting Current Modes .................................................................54
Completing the Adjustment Procedures...........................................57
Verification Limits ..................................................................................58
DC Voltage.......................................................................................58
AC Voltage.......................................................................................58
4-Wire Resistance.............................................................................60
2-Wire Resistance.............................................................................61
DC Current .......................................................................................62
AC Current .......................................................................................62
Frequency .........................................................................................63
Calibration Function Reference...............................................................63
Technical Support Resources ..................................................................63
NI Web Support................................................................................63
Worldwide Support ..........................................................................64
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.
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, hardware labels,
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, and code excerpts.

©National Instruments Corporation 3 NI PXI-4070 Calibration Procedure
Calibration Overview
The complete calibration process for the NI 4070 consists of verifying
all modes with the test limits provided and adjusting the calibration
coefficients for all modes. Frequency is the only mode that does not require
adjustment. Reverifying all modes after adjustments ensures that the
adjustment procedures were performed correctly.
National Instruments can perform stringent in-house calibration of the
NI 4070 and can generate either a basic or a detailed calibration certificate
for you. Visit ni.com/calibration for more information on calibration
certificates. This document is provided for those who wish to perform the
calibration procedure themselves.
What Is Calibration?
Calibration is a set of operations that compares the values indicated by a
measuring instrument or measuring system to the corresponding values
realized by external standards. The result of a calibration can be used to
determine the measurement error and can correct for it in the adjustment
process.
The calibration process consists of verifying, adjusting, and reverifying a
device. During verification, you compare the measured performance to an
external standard of known measurement uncertainty to confirm that the
product meets or exceeds specifications. During adjustment, you correct
the measurement error of the device by adjusting the calibration constants
and storing the new calibration constants in the EEPROM.
Normally, the calibration sequence is as follows:
1. Verify the NI 4070 using the 2-year accuracy limits (or the 90-day
accuracy limits if it has been externally calibrated within that time).
2. Adjust the NI 4070.
3. Reverify the NI 4070 using the 24-hour accuracy limits (or the 2-year
accuracy limits when the 24-hour limits are not specified).
Why Should You Calibrate?
Properties of the electrical components responsible for gain and offset
errors may drift with time, temperature, and mechanical stress. Calibration
is required to compensate for this drift and ensure that you, as a user, are
confident that any measurements you make meet NI 4070 specifications.

NI PXI-4070 Calibration Procedure 4 ni.com
How Often Should You Calibrate?
The accuracy requirements of your measurement application determine
how often you should calibrate the NI 4070. NI recommends performing a
complete calibration at least once every two years. NI does not guarantee
the absolute accuracy of the NI 4070 beyond this two year calibration
interval. You can shorten the calibration interval based on the demands
of your application.
What Calibration Options Are Available?
Depending on your measurement and accuracy requirements, a complete
calibration of the NI 4070 may not be necessary. A number of options are
available that can shorten the time you spend on the calibration. The
following options are available:
• Complete calibration—Performing the entire calibration procedure
from beginning to end is the only way to guarantee that the
performance of the NI 4070 will meet or exceed the published
specifications for all modes and ranges.
• Complete calibration except AC voltage modes—If you do not use the
AC voltage modes for any measurements or the accuracy is irrelevant,
you have the option to skip these steps in the calibration procedure.
• Complete calibration except current modes—If you do not use the
current modes (neither DC nor AC) or the accuracy is insignificant for
your application, you have the option to skip the steps to calibrate both
current modes.
• Complete calibration except AC voltage and current modes—You can
choose to skip both the AC voltage modes calibration and the current
modes calibration if your application does not require them or the
accuracy is irrelevant.
How Much Time Does Calibration Require?
The amount of time required for calibrating varies depending on whether
you are running in automated mode or in manual mode. In automated
mode, the complete verification procedures for the NI 4070 take less than
30 minutes, and the complete adjustment procedures take approximately
50 minutes. If you choose to run the calibration in manual mode,
the process requires more time and is more prone to operator error.
NI recommends using an automated procedure, such as the procedures
available with National Instruments Calibration Executive software.
For more information on calibration, visit ni.com/calibration.

©National Instruments Corporation 5 NI PXI-4070 Calibration Procedure
Equipment and Other Test Requirements
This section describes the equipment, test conditions, documentation,
software, and connections required for calibration.
Required Test Equipment
The following equipment is required for calibrating the NI 4070:
• Fluke 5700A multifunction calibrator calibrated within the last
90 days or a Fluke 5720A multifunction calibrator calibrated within
the last year
• Pomona 5145 insulated double banana plug shorting bar (or another
means of creating a short with low thermal EMF (≤150 nV) across the
HI and LO input banana connectors on the NI 4070)
• Two Pomona B-4 banana-to-banana patch cords (cables) or similar
banana-to-banana cables with length not to exceed 4 in.
•Wire(≤22 AWG, ≤4 in.) for connecting the AUX CURRENT and
SENSE HI binding posts of the calibrator (alternatively, you can use
one of the Pomona B-4 cables instead of this wire)
• National Instruments PXI chassis and controller
• National Instruments calibration cable assembly for the NI 4070
(part number 161283A-01)
Optional Test Equipment
The following equipment is optional for calibrating the NI 4070 and is only
used for frequency verification:
• NI PXI-6608
• National Instruments SH68-68-D1 shielded cable
• National Instruments TB-2715 terminal block
• Pomona MDP 4892 double banana plug with strain relief
• Coaxial cable (for example, RG178)
Test Conditions
Follow these guidelines to optimize the connections and the environment
during calibration:
• Ensure that the PXI chassis fan speed is set to HI and that the fan filters
are clean.
• Plug the PXI chassis and the calibrator into the same power strip to
avoid ground loops.

NI PXI-4070 Calibration Procedure 6 ni.com
• Power on and warm up both the calibrator and the NI 4070 for at least
30 minutes before beginning this calibration procedure.
• Maintain an ambient temperature of 23 ±1 °C.
• Maintain an ambient relative humidity of less than 60%.
• Allow the calibrator to settle fully before taking any measurements.
Consult the Fluke 5700A/5720A user documentation for instructions.
• Allow the thermal EMF enough time to stabilize when you change
connections to the calibrator or the NI 4070. The suggested time
periods are stated where necessary throughout this document.
• Keep a shorting bar connected between the V GUARD and
GROUND binding posts of the calibrator at all times.
• Clean any oxidation from the spade lugs on the calibration cable
assembly before connecting them to the calibrator’s binding posts.
Oxidation is a discoloration that tarnishes the copper spade lugs so that
they appear dull rather than shiny.
• Leave the spade lugs on the calibration cable assembly that are labeled
SHD connected to the calibrator’s V GUARD binding post at all times.
• Prevent the cables from moving or vibrating by taping or strapping
them to a nonvibrating surface. Movement or vibration causes
triboelectric effects that can result in measurement errors.
Documentation
In addition to this calibration document, you may find the following
references helpful in writing your calibration utility:
•NI Digital Multimeters Help
•NI-DMM Instrument Driver Quick Reference Guide
•NI Digital Multimeters Getting Started Guide
•Specifications for the NI PXI-4070
All of these documents are installed on your computer when you install
NI-DMM. To locate them, select Start»Programs»National
Instruments»NI-DMM»Documentation.
If you are performing the optional frequency verification procedure,
you may need the following documents, which are available at ni.com/
manuals:
•TB-2715 Terminal Block Installation Guide
•About Your NI 6608 Device

©National Instruments Corporation 7 NI PXI-4070 Calibration Procedure
Software
The NI 4070 calibration procedure requires that NI-DMM version 2.1 or
later be installed on the calibration system. NI-DMM supports a number of
programming languages including LabVIEW, LabWindows™/CVI™,
Microsoft Visual C++, and Microsoft Visual Basic. When you install
NI-DMM, you only need to install support for the language you intend to
use to write your calibration utility.
Note NI-DMM versions earlier than version 2.1 do not support NI 4070 calibration.
The procedures in this document are described using C function calls.
You also can program in LabVIEW using the VIs that correspond to the
C function calls. Figure 1 shows the procedural flow for verification.
Figure 2 shows the procedural flow for adjustment.

NI PXI-4070 Calibration Procedure 8 ni.com
Figure 1. Verification Procedures Flowchart
Verify
DC Voltage
Modes?
Verify
4-Wire Resistance
Modes?
Verify
AC Voltage
Modes?
Verify
2-Wire Resistance
Modes?
Verify
DC Current
Modes?
Verify
AC Current
Modes?
Verify
Frequency
Mode?
Setting up
the Test
Equipment
Go to Verifying
DC Voltage
Go to Verifying
AC Voltage
Go to Verifying
4-Wire Resistance
Go to Verifying
2-Wire Resistance
Go to Verifying
DC Current
Go to Verifying
AC Current
Go to Verifying
Frequency
Ye s
Ye s
Ye s
Ye s
Ye s
Ye s
Ye s
No
No
No
No
No
No
No
Go to Adjustment
Procedures
Flowchart
Completing the
Adjustment
Procedures
Pre-Adjustment Post-Adjustment
Is this a
Pre-Adjustment or
Post-Adjustment
Verification?

©National Instruments Corporation 9 NI PXI-4070 Calibration Procedure
Figure 2. Adjustment Procedures Flowchart
Ye s Go to
Verification
Procedures Flowchart
Verification
Go to Adjusting
DC Voltage and
Resistance
Go to Adjusting
AC Voltage Modes
No
No
Ye s
Ye s
No
Completing the
Adjustment
Procedures
Adjust
AC Voltage
Modes?
Adjust
Current
Modes?
Go to Adjusting
Current Modes
Perform
Post-Adjustment
Verification?

NI PXI-4070 Calibration Procedure 10 ni.com
Verification Procedures
You can use the verification procedures described in this section for both
pre-adjustment and post-adjustment verification. The steps of each
verification procedure must be performed in the order listed; however, you
can omit entire sections (for example, the entire Verifying AC Current
section), if necessary.
The parameters Range, Resolution, and Sample Interval used in function
calls throughout this section have floating point values. For example, if
Range = 1, the floating point value is 1.0. The parameters Trigger Count,
Sample Count, Array Size, and ParamValue have integer values. Refer
to the NI Digital Multimeters Help for more information.
Note Many of the parameter values listed in this document are expressed in scientific
notation. Some programming languages do not support the direct entry of numbers in this
format. Care must be taken to properly enter these values with the appropriate number of
zeros. For example, the scientific notation number 10e–6 must be entered as 0.00001, and
the number 100e3 must be entered as 100000. If your programming language supports
numeric entries in scientific notation, NI recommends that you use this feature to minimize
possible data entry errors.
Setting Up the Test Equipment
NoteThe Setting Up the Test Equipment section is necessary for pre-adjustment
verifications only. If you are performing a post-adjustment verification, skip the setup and
go directly to the Verifying DC Voltage section.
To set up the test equipment, complete the following steps:
1. Remove all connections from the four input banana connectors on the
NI 4070.
2. Verify that the calibrator has been calibrated within the time limits
specified in the Required Test Equipment section, and that DC zeros
calibration has been performed within the last 30 days. Consult the
Fluke 5700A/5720A user documentation for instructions on
calibrating these devices.
Note Ensure that both the calibrator and the NI 4070 (installed in a powered-on PXI
chassis) are warmed up for at least 30 minutes before you begin this procedure.
3. Call niDMM_init with the resource name of the device to create a
Session.