National Instruments NI PXI-665 Series Manual

CALIBRATION PROCEDURE
NI PXI-665x
This document describes how to write a calibration procedure for the
10 MHz oscillator frequency of the NI PXI-6653 and NI PXI-6652 timing
and synchronization modules.
Contents
Conventions ............................................................................................ 1
Software .................................................................................................. 2
Documentation ........................................................................................ 2
Calibration Interval ................................................................................. 3
Password ................................................................................................. 3
Test Equipment ....................................................................................... 3
Test Conditions ....................................................................................... 3
Calibration Procedure ............................................................................. 4
Initial Setup...................................................................................... 4
Verification ...................................................................................... 4
Connecting the Clock Source ................................................... 4
Measuring the Frequency ......................................................... 6
Adjustment....................................................................................... 10
Reverification................................................................................... 13
Where to Go for Support......................................................................... 14
Conventions
The following conventions apply to this document:
»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.
When symbol is marked on a product, it denotes a warning advising you to
take precautions to avoid electrical shock.

NI PXI-665x Calibration Procedure 2 ni.com
When symbol is marked on a product, it denotes a component that may be
hot. Touching this component may result in bodily injury.
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. Italic text 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.
Software
This calibration procedure requires NI-Sync and NI-VISA. NI-Sync and
NI-VISA support a number of application development environments
(ADEs) and programming languages, including LabVIEW,
LabWindows™/CVI™, and Microsoft Visual C++. When you install the
drivers, you need to install support for only the ADE or programming
language you are using. The illustrations in this document show the
LabVIEW code for implementing calibration steps using NI-Sync and
NI-VISA.
Documentation
You need the NI-Sync User Manual to calibrate the NI PXI-665x.
The NI-Sync User Manual contains detailed information about using
the NI-Sync driver, including information about installing NI-Sync and
creating applications that use the NI-Sync driver. These sources, along with
this document, are your primary references for writing your calibration
utility. You also can refer to the documentation for the programming
language or application development environment you are using. For
further information about the device you are calibrating, refer to the
NI PXI-665x User Manual.

©National Instruments Corporation 3 NI PXI-665x Calibration Procedure
Calibration Interval
The measurement requirements of the application determine how often you
should calibrate the device to ensure its accuracy. National Instruments
recommends that you calibrate the NI PXI-6653 and NI PXI-6652 yearly.
You may want to shorten this interval based on the application demands.
Password
The default password for password-protected operations is NI.
Test Equipment
Calibrating the NI PXI-665xrequires the following equipment.
Test Conditions
Follow these guidelines to optimize connections and test conditions during
the calibration procedure:
• Install the NI PXI-665xin Slot 2 of the PXI chassis. The calibration
procedure requires features of PXI that are accessible only in slot 2.
Use of an NI PXI-1044 or NI PXI-1045 chassis is recommended to
reduce error associated in variance in the 5 V chassis supply.
• Maintain a temperature of approximately 25 °C.
• Keep relative humidity below 80 percent.
• Use shielded copper wire for all cable connections to the device.
• Allow a warm up time of at least 15 minutes for the NI PXI-6652 and
three hours for the NI PXI-6653 to ensure the measurement circuitry is
at a stable operating temperature.
• Keep PXI chassis filters clean and fan speed set to High.
Equipment Recommended Model Requirements
10 MHz clock source Symmetricom/Datum 8040 Accurate to within
0.75 parts-per-billion (ppb) for the
NI PXI-6653, or 150 ppb for the
NI PXI-6652.
BNC-SMB cable — —
SMB-SMB cable — —

NI PXI-665x Calibration Procedure 4 ni.com
Calibration Procedure
The steps used in the calibration procedure are as follows:
1. Initial setup.
2. Verification.
3. Adjustment.
4. Reverification.
Initial Setup
Complete the following steps to set up the NI PXI-665xfor calibration.
1. Make sure all components involved in the calibration procedure are
powered off.
2. Install the NI PXI-665xboard into slot 2 of your chassis.
Note The module must be installed in slot 2 of the chassis.
3. Power on the PXI chassis first, and then the external equipment.
4. Make sure that all the appropriate driver and application software is
installed on the host computer.
5. Configure the hardware properly with Measurement & Automation
Explorer (MAX). Refer to the NI PXI-665x Installation Guide for
details about configuring the PXI equipment.
Verification
The following steps outline the procedure for measuring the 10 MHz
oscillator frequency on the NI PXI-665xand determining whether the
device requires adjustment to meet the published specifications.
Connecting the Clock Source
1. Connect the accurate 10 MHz source to the ClkIn connector on the
NI PXI-665x.
2. Program the NI PXI-665xto route the ClkIn signal to PXI_Clk10In
without using its 10 MHz PLL by completing steps a–d.
Note Use the data in the C function call reference as inputs to your LabVIEW VI where
applicable.

©National Instruments Corporation 5 NI PXI-665x Calibration Procedure
a. Call niSync Initialize VI to set up a handle for the device.
b. Set a writable NI-Sync property node to pass FALSE to the
Use PLL? attribute.
c. Call niSync Connect Clock Terminals VI to connect ClkIn to
PXI_Clk10_In.
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_init with the following
parameters:
resourceName: Dev1
idQuery: NULL
resetDevice: VI_TRUE
vi: *SessionHandle
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_SetAttributeViBoolean
with the following parameters:
vi: “<SessionHandle>”
terminalName: “”
attributeID:
NISYNC_ATTR_CLKIN_USE_PLL
attributeValue: VI_FALSE
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_ConnectClkTerminals
with the following parameters:
vi: “<SessionHandle>”
sourceTerminal: NISYNC_VAL_CLKIN
destinationTerminal:
NISYNC_VAL_CLK10

NI PXI-665x Calibration Procedure 6 ni.com
d. Call niSync Close VI to close the handle.
Measuring the Frequency
Complete the following procedure to measure the frequency of the onboard
clock source.
1. Connect the ClkOut terminal to the PFI 0 terminal by using an
SMB-to-SMB cable.
2. Complete steps a–d to program the board to connect the onboard
oscillator to ClkOut. Be sure to use the high-gain setting for clock out.
a. Call niSync Initialize VI to set up a handle for the device.
b. Set a writable NI-Sync property node to pass TRUE to the ClkOut
Gain Enable attribute.
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_close with the following
parameter:
vi: “<SessionHandle>”
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_init with the following
parameters:
resourceName: Dev1
idQuery: NULL (ignored)
resetDevice: VI_FALSE
vi: *SessionHandle
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_SetAttributeViBoolean
with the following parameters:
vi: “<SessionHandle>”
terminalName: “”
attributeID:
NISYNC_ATTR_CLKOUT_GAIN_ENABLE
attributeValue: VI_TRUE

©National Instruments Corporation 7 NI PXI-665x Calibration Procedure
c. Call niSync Connect Clock Terminals VI to connect the oscillator
to ClkOut.
d. Call niSync Close VI to close the session handle.
3. Complete steps a–c to measure the oscillator frequency through PFI 0.
To obtain an accurate measurement for calibration, the measurement
duration must be made sufficiently long. Refer to Table 1 for the
measurement duration to use.
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_ConnectClkTerminals
with the following parameters:
vi: “<SessionHandle>”
sourceTerminal:
NISYNC_VAL_OSCILLATOR
destinationTerminal:
NISYNC_VAL_CLKOUT
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_close with the following
parameter:
vi: “<SessionHandle>”
Table 1. Measurement Duration
Device Measure Accuracy
Required Measurement
Duration
NI PXI-6652 200 ppb 0.5 seconds
NI PXI-6653 1 ppb 100 seconds

NI PXI-665x Calibration Procedure 8 ni.com
a. Call niSync Initialize VI to set up a handle for the device.
b. Call niSync Measure Frequency VI to measure the frequency of
the oscillator.
c. Call niSync Close VI to close the session handle.
4. Compare the measured frequency to the device specifications.
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_init with the following
parameters:
resourceName: Dev1
idQuery: NULL
resetDevice: VI_FALSE
vi: *SessionHandle
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_MeasureFrequency with
the following parameters:
vi: “<SessionHandle>”
sourceTerminal:
NISYNC_VAL_OSCILLATOR
duration: 0.5 or 100
actualDuration: *actualDuration
measuredFrequency:
*measuredFrequency
error: *error
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_close with the following
parameter:
vi: “<SessionHandle>”

©National Instruments Corporation 9 NI PXI-665x Calibration Procedure
To determine if the device under test meets its specifications, you must
compare the measured frequency obtained in step 3 of Measuring the
Frequency with the specified accuracy. Table 2 shows the frequency range
that is acceptable according to the published specifications for the
NI PXI-665x.
If the measured value is within the low-limit and high-limit range listed
under the Acceptable Frequency Range—As Left in Table 3, the board is
meeting published specifications for the 24 hour period following a
calibration.
Table 2. One Year Test Limits
Device
Specified
Accuracy +
Aging
Acceptable Frequency Range—As Found
Low Limit High Limit
NI PXI-6652
(TCXO)
± 3.5 ppm 9,999,965 Hz 10,000,035 Hz
NI PXI-6653
(OCXO)
± 57.6 ppb 9,999,999.424 Hz 10,000,000.576 Hz
Table 3. 24 Hour Test Limits
Device
Specified Initial
Accuracy
Acceptable Frequency Range—As Left
Low Limit High Limit
NI PXI-6652
(TCXO)
± 2.5 ppm 9,999,975 Hz 10,000,025 Hz
NI PXI-6653
(OCXO)
± 6.1 ppb 9,999,999.939 Hz 10,000,000.061 Hz
Table 4. Calibration Target Frequency Ranges
Device
Calibration
Measurement
Accuracy
Calibration Measurement Target
Frequency Range
Low Limit High Limit
NI PXI-6652
(TCXO)
200 ppb 9,999,998 Hz 10,000,002 Hz
NI PXI-6653
(OCXO)
1 ppb 9,999,999.99 Hz 10,000,000.01 Hz

NI PXI-665x Calibration Procedure 10 ni.com
If the measured value is within the low-limit and high-limit range listed
under the Calibration Measurement Target Frequency Range in Table 4,
the board is considered to be calibrated and no adjustment is needed.
Adjustment
If the accuracy of the 10 MHz oscillator is outside the specified range
for the product, the device is out of calibration. A programmable voltage
controls the oscillator frequency. By varying this voltage and precisely
measuring the frequency, you can find a voltage that gives a frequency as
close as possible to 10 MHz.
1. Complete steps a–c to set the oscillator control voltage. The range of
acceptable voltage values is 0.0 V to 4.095 V with frequency
increasing as voltage increases. Use a control voltage of 2.0475 V,
which is in the middle of the valid range, as a starting point.
a. Call niSync Initialize VI to set up a handle for the device.
b. Set a writable NI-Sync property node to pass the constant 2.0475
to the Oscillator Voltage attribute.
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_init with the following
parameters:
resourceName: Dev1
idQuery: NULL
resetDevice: VI_FALSE
vi: *SessionHandle
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_SetAttributeViBoolean
with the following parameters:
vi: “<SessionHandle>”
terminalName: “”
attributeID:
NISYNC_ATTR_OSCILLATOR_VOLTAGE
attributeValue: 2.0475