National Instruments Network Adapter NI PXIe-6672 Manual

CALIBRATION PROCEDURE
NI PXIe-6672
This document describes how to write a calibration procedure for the
10 MHz oscillator frequency of the NI PXIe-6672 timing and
synchronization module.
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
Measuring the Frequency ......................................................... 6
Adjustment....................................................................................... 9
Reverification................................................................................... 13
Conventions
The following conventions apply to this document:
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NI PXIe-6672 Calibration Procedure 2 ni.com
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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 PXIe-6672.
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 PXIe-6672 User Manual.

©National Instruments Corporation 3 NI PXIe-6672 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 PXIe-6672 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 PXIe-6672 requires the following equipment.
Test Conditions
Follow these guidelines to optimize connections and test conditions during
the calibration procedure:
• Install the NI PXIe-6672 in the system timing slot of the PXI Express
chassis. The calibration procedure requires features of PXI that are
accessible only in the system timing slot.
• 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 PXIe-6672 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
150 parts-per-billion (ppb)
BNC-SMB cable — —
SMB-SMB cable — —

NI PXIe-6672 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 PXIe-6672 for calibration.
1. Make sure all components involved in the calibration procedure are
powered off.
2. Install the NI PXIe-6672 board into the system timing slot of your
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 with Measurement & Automation Explorer
(MAX). Refer to the NI PXIe-6672 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 PXIe-6672 and 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 PXIe-6672.
2. Program the NI PXIe-6672 to 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 PXIe-6672 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 PXIe-6672 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 PXIe-6672 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.
a. Call niSync Initialize VI to set up a handle for the device.
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 >”
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_init with the following
parameters:
resourceName: Dev1
idQuery: NULL
resetDevice: VI_FALSE
vi: *SessionHandle

NI PXIe-6672 Calibration Procedure 8 ni.com
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.
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 1 shows the frequency range
that is acceptable according to the published specifications for the
NI PXIe-6672.
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_MeasureFrequency with
the following parameters:
vi: “<
SessionHandle >”
sourceTerminal:
NISYNC_VAL_OSCILLATOR
duration: 0.5
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 PXIe-6672 Calibration Procedure
If the measured value is within the low-limit and high-limit range listed
under the Acceptable Frequency Range, the board is calibrated correctly.
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.
Table 1. Acceptable Frequency Ranges
Device
Specified
Accuracy
Acceptable Frequency Range
Low Limit High Limit
NI PXIe-6672
(TCXO)
±2.5 ppm 9,999,975 Hz 10,000,025 Hz
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_init with the following
parameters:
resourceName: Dev1
idQuery: NULL
resetDevice: VI_FALSE
vi: *SessionHandle

NI PXIe-6672 Calibration Procedure 10 ni.com
b. Set a writable NI-Sync property node to pass the constant 2.0475
to the Oscillator Voltage attribute.
c. Call niSync Close VI to close the session handle.
Proceed with the following steps to find the correct oscillator control
voltage.
2. After setting the control voltage, measure the frequency again with the
NI-Sync Measure Frequency VI to measure PFI 0, as shown in Step 3
of the Measuring the Frequency section.
Complete steps a–c to measure PFI 0.
a. Call niSync Initialize VI to set up a handle for the device.
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
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
resetDevice: VI_FALSE
vi: *SessionHandle

©National Instruments Corporation 11 NI PXIe-6672 Calibration Procedure
b. Call niSync Measure Frequency VI to measure the frequency of
the oscillator.
c. Call niSync Close VI to close the session handle.
3. Compare the measured frequency to the device specifications.
4. If the measured frequency is still outside of the specified limit, repeat
steps 1–3 of the Adjustment section until the measured value falls
within the acceptable frequency range for your module, as shown in
Table 1, Acceptable Frequency Ranges.
5. Commit the calibration values to the Calibration EEPROM using the
following procedure.
a. Call niSync Initialize External Calibration VI to initialize the
process.
Note NI is the default user password. If you have changed the calibration password, use
your user-selected calibration password in place of NI.
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_MeasureFrequency with
the following parameters:
vi: “<
SessionHandle >”
sourceTerminal:
NISYNC_VAL_OSCILLATOR
duration: 0.5
actualDuration: *actualDuration
measuredFrequency:
*measuredFrequency
error: *error
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_close with the following
parameter:
vi: “<
SessionHandle >”

NI PXIe-6672 Calibration Procedure 12 ni.com
b. Call niSync Adjust Oscillator Voltage VI to adjust the voltage of
the oscillator.
c. Call niSync Close External Calibration VI to commit the settings
and close the session.
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_InitExtCal with the
following parameters:
resourceName: “<MAX ID>“
password: NI
calibrationInstrumentHandle:
*SessionHandle
LabVIEW Block Diagram NI-SYNC C Function Call
Call
niSync_CalAdjustOscillatorVoltage
with the following parameters:
vi: “<
SessionHandle >”
newVoltage: <new control voltage>
oldVoltage: *oldVoltage
LabVIEW Block Diagram NI-SYNC C Function Call
Call niSync_CloseExtCal with the
following parameter:
vi: “<
SessionHandle >”
action:NISYNC_VAL_EXT_CAL_COMMIT

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Reverification
After completing the adjustments to the NI PXIe-6672, it is important that
you verify the oscillator frequency operation by repeating the steps listed
in the Verification section. Re-verifying after making the adjustments
ensures that the NI PXIe-6672 is operating within its test limits.