National Instruments PXI EXPRESS PXIe-1095 Manual

CALIBRATION PROCEDURE
PXIe-1095
PXI Chassis
This document contains the verification and adjustment procedures for the National
Instruments PXIe-1095 chassis. Refer to ni.com/calibration for more information about
calibration solutions.
Contents
Software.................................................................................................................................... 1
Documentation..........................................................................................................................1
Test Equipment......................................................................................................................... 2
Test Conditions......................................................................................................................... 2
Initial Setup...............................................................................................................................2
Verification................................................................................................................................3
Adjustment................................................................................................................................4
Reverification............................................................................................................................5
Where to Go for Support.......................................................................................................... 5
Software
Calibrating the PXIe-1095 requires the installation of the following software on the calibration
system:
• PXI Platform Services 18.1 or later
You can download PXI Platform Services from ni.com/downloads.
PXI Platform Services supports programming the calibration procedures using a number of
application development environments (ADEs), including LabVIEW, LabWindows™/CVI™,
and Microsoft Visual C++. When you install PXI Platform Services, you need to install
support only for the ADE that you intend to use.
Documentation
You might find the following documents helpful as you perform the calibration procedure:
• PXIe-1095 User Manual
• PXIe-1095 Specifications
The latest versions of these documents are available on http://www.ni.com/manuals.

Test Equipment
The following table lists the equipment NI recommends for the performance verification and
adjustment procedures. If the recommended equipment is not available, select a substitute
using the minimum requirements listed in the table.
Table 1. Recommended Test Equipment
Equipment Recommended Models Minimum Requirements
Frequency Reference Symmetricom 8040C
Output Frequency: 10 MHz
Accuracy: ≤ 1×10-10
Frequency Counter Keysight 53220A
Frequency Range: >10 MHz
Frequency Resolution: ≤0.001 Hz at 10
MHz
BNC-BNC Cable — —
BNC-SMA Cable — —
Test Conditions
The following setup and environmental conditions are required to ensure the PXIe-1095
chassis meets published specifications.
• Keep cabling as short as possible. Long cables and wires act as antennae, picking up
extra noise that can affect measurements.
• Verify that all connections, including front panel connections and screws, are secure.
• Maintain an ambient temperature of 23 °C ± 5 °C.
• Keep relative humidity below 80%.
• Ensure that the PXIe-1095 chassis has been continuously powered for at least 24 hours
prior to calibration to allow the 10 MHz oscillator frequency to stabilize.
• Ensure that the Frequency Reference has been continuously powered as specified by its
manual for its accuracy to meet the minimum requirements specified in Table 1. on page
2.
Initial Setup
Refer to the PXIe-1095 User Manual for information about how to install the software and
hardware and how to configure the device in Measurement & Automation Explorer (MAX).
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Verification
The performance verification procedure assumes that adequate traceable uncertainties are
available for the calibration references.
Complete the following procedure to determine the as-found status of the PXIe-1095 chassis.
Verifying OCXO Frequency Accuracy
1. Connect the 10 MHz Ref Out SMA on the rear of the PXIe-1095 chassis to Channel 1 of
the Frequency Counter.
2. Configure the Frequency Reference to output a 10 MHz sine wave on one of its output
channels. Connect this channel to the Ext Ref In port of the Frequency Counter.
3. Configure the Frequency Counter to use the Ext Ref In port as the reference oscillator
source and to use Channel 1 as its input source.
4. Measure the OCXO frequency using the Frequency Counter.
5. Compare the measured frequency to the device specifications.
To determine if the device under test meets its specifications, you must compare the measured
frequency with the published specifications. Table 2. on page 3 shows the frequency range
that is acceptable according to the published specifications of the PXIe-1095 chassis.
Table 2. One Year Test Limits
Device Specified Accuracy Within 1
Year of Calibration
Acceptable Frequency Range — As Found
Low Limit High Limit
PXIe-1095 ± 80×10-9 9,999,999.20 Hz 10,000,000.80 Hz
If the measured value is within the low-limit and high-limit range listed in Table 2. on page 3,
the chassis is operating in specification but requires adjustment to be considered calibrated. If
the measured value is outside the range listed in Table 2. on page 3, the chassis is operating
out of specification.
To determine if the device under test is already calibrated, you must compare the measured
frequency with the ranges listed in Table 3. on page 3.
Table 3. Adjustment Target Frequency Ranges (As-Left Limits)
Device Calibration Measurement
Accuracy
Acceptable Frequency Range — As Left
Low Limit High Limit
PXIe-1095 ±1×1099,999,999.99 Hz 10,000,000.01 Hz
PXIe-1095 Calibration Procedure | © National Instruments | 3

If the measured value is within the low-limit and high-limit range listed in Table 3. on page 3,
no adjustment is needed.
Note Test limits in Table 2. on page 3 are based on the PXIe-1095 specifications.
Refer to the most recent PXIe-1095 specifications online at ni.com/manuals.
Adjustment
Adjusting OCXO Frequency Accuracy
If the OCXO frequency accuracy is outside the specified range for the product, then the device
is out of calibration.
A programmable voltage controls the OCXO frequency. By using the NI System
Configuration API to vary this voltage and precisely measure the frequency, you can find a
voltage that gives a frequency as close as possible to 10 MHz.
Note You can use a binary search algorithm to find the optimal oscillator control
voltage. The PXIe-1095 uses a 16-bit digital-to-analog convertor (DAC) to create
the oscillator control voltage; therefore, you need 16 (at most) iterations of
adjustment and measurement to calibrate the 10 MHz oscillator.
Complete the following procedure to adjust the OCXO frequency accuracy of the PXIe-1095
chassis:
1. Get a resource handle for the PXIe-1095 to calibrate using the System Configuration API.
a. Call Initialize Session to set up a new session.
b. Call Create Filter to create a new filter for searching for devices. Set the IsChassis
and IsNI attributes of the filter to TRUE.
c. Find the chassis resource name of the PXIe-1095 to calibrate using Measurement &
Automation Explorer (MAX) and set the Alias attribute of the filter to match the
chassis resource name.
d. Call Find Hardware using the filter created in the previous steps. Set the Experts
parameter of this function to ni-pxi. This function returns an array with exactly
one element: the resource handle to the chassis. Check your filter settings if the
resource handle only is not returned.
2. Initialize the calibration process.
a. Using the resource handle obtained with Find Hardware, set the CalPasswd
property to the current calibration password for the chassis.
Note NI is the default calibration password.
b. Using the same resource handle, set the CalExtAction property to Start.
c. Call Save Changes to commit these changes to hardware.
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3. Write a new value for the oscillator DAC value. The range of oscillator control voltage
values is 0 to 65535, with frequency increasing as the value increases. Use a DAC value
of 32768, which is in the middle of the valid range, as a starting point.
a. Using the same resource handle, set the DacValue property to the new DAC value.
b. Call Save Changes to commit these changes to hardware.
4. Measure the OCXO frequency following the steps in Verifying the OCXO Frequency
Accuracy.
5. Compare the measured frequency to the target frequency and repeat steps 3 and 4,
adjusting the oscillator DAC value up to increase the frequency and down to decrease the
frequency.
Note NI recommends that you implement a binary search to determine the
optimal DAC value. This requires going through 16 iterations, with
confirmation that the final DAC value measured crosses over the target
frequency when the DAC value is changed by 1 bit.
6. Compare the final measured frequency to the specified limits in Table 3. on page 3 to
confirm adjustment completed successfully.
7. If adjustment was successful, commit the calibration values to device memory. If
adjustment was unsuccessful, cancel the external adjustment action; the chassis may be in
need of repair.
a. Using the resource handle obtained in step 1c, set the CalExtAction property to
Commit (or Cancel if adjustment was unsuccessful).
b. Call Save Changes to commit these changes to hardware.
Reverification
Repeat the Verification section to determine the as-left status of the device. If the measured
value is within the low-limit and high-limit range listed in Table 3. on page 3, the chassis is
considered to be calibrated and no further adjustment is needed.
Note If any test fails reverification after performing an adjustment, verify that you
have met the Test Conditions before returning your device to NI. Refer to Where to
Go for Support for information about support resources or service requests.
Where to Go for Support
The National Instruments website is your complete resource for technical support. At ni.com/
support you have access to everything from troubleshooting and application development self-
help resources to email and phone assistance from NI Application Engineers.
National Instruments corporate headquarters is located at 11500 North Mopac Expressway,
Austin, Texas, 78759-3504. National Instruments also has offices located around the world to
help address your support needs. For telephone support in the United States, create your
service request at ni.com/support and follow the calling instructions or dial 512 795 8248. For
PXIe-1095 Calibration Procedure | © National Instruments | 5

telephone support outside the United States, visit the Worldwide Offices section of ni.com/
niglobal to access the branch office websites, which provide up-to-date contact information,
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377631A-01 December 13, 2018