2.
Set the niDCPower Output Function property or NIDCPOWER_OUTPUT_FUNCTION
attribute to DC Current for the NI 4138.
3.
Set the first specified level range, limit range, and limit on the NI 4138.
4.
Measure the internal device temperature and perform self-calibration if necessary.
a)
If the internal device temperature exceeds T
cal
± 1 °C, wait up to 5 minutes for the
temperature to stabilize to within T
cal
± 1 °C.
b)
If after 5 minutes the stable temperature still exceeds T
cal
± 1 °C, call the self-
calibration VI or function.
5.
Set the level on the NI 4138 to the first specified test point.
6.
Calculate the current through the shunt by completing the following steps.
a)
Take a voltage measurement across the shunt using the DMM.
b)
Divide the voltage measurement by the calibrated value of the shunt.
c)
Record the calculated value as
DMM Measured Current
.
7.
Calculate the lower and upper current measurement test limits using the following
formula: Current Measurement Test Limits = Test Point ± (|Test Point| * % of C
Offset ).
8.
Verify that the recorded DMM value falls within the test limits.
9.
Repeat the previous steps, from setting the level to the test point on the NI 4138 up to this
step, for each specified test point in the level range.
10. If more than one level range is specified, repeat the previous steps using the values
specified in each level range.
Adjustment
This section describes the steps needed to adjust the device to meet published specifications.
Following the adjustment procedure automatically updates the calibration date and
temperature on the device.
Adjusted Specifications
Adjustment corrects the following specifications for the device:
•
Voltage programming accuracy
•
Current programming accuracy
•
Voltage measurement accuracy
•
Current measurement accuracy
Note
You do not need to separately verify or adjust both measurement and output.
The architecture of the NI 4138 ensures that if measurement is accurate, then output
is as well, and vice versa.
Initiating the Adjustment Session
1.
After completing verification, wait a minimum of 5 minutes for the internal device
temperature to stabilize.
NI PXIe-4138 Calibration Procedure
|
© National Instruments
|
15