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.
4
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ni.com
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PXIe-1095 Calibration Procedure
