National Instruments NI 6738, Calibration Procedure, Page: 9 / 28

8 | ni.com | NI 6738/6739 Calibration Procedure
Self-Calibration
Complete the following steps to self-calibrate the device.
Note Disconnect all external signals before beginning self-calibration.
1. Wait for the device to warm-up for at least 15 minutes.
2. Launch MAX.
3. Select My System»Devices and Interfaces» your device .
4. Click Self-Calibrate .
Checking Device Temperature Changes
Device temperature changes greater than those described in the Test Conditions section will
require action to ensure that your calibration is successful. Complete the following steps to check
for device temperature changes:
1. Self-calibrate your device as described in the Self-Calibration section.
2. Call
DAQmxGetCalDevTemp
with the following parameter:
• deviceName :
Dev_name
3. Call
DAQmxGetSelfCalLastTemp
with the following parameter:
• deviceName :
Dev_name
If the current device temperature differs by more than 1 °C from the last self-calibration
temperature, or you cannot maintain a device temperature within 1 °C of the last
self-calibration temperature throughout the verification process, the calibration limits for
the devices that support self-calibration are not valid.
In order to successfully calibrate your device in this case:
• Allow the device temperature to settle and self-calibrate your device again.
• Change the test limits to include the additional error due to temperature drift. Refer to
your device specifications document for more information.
4. Call
DAQmxGetExtCalLastTemp
with the following parameter:
• deviceName :
Dev_name
If the current device temperature differs by more than 10 °C from the last external
calibration temperature, or you cannot maintain a device temperature within 10 °C of the
last external calibration temperature throughout the verification process, the calibration
limits are not valid.
In order to successfully calibrate your device in this case:
• Change the system so that the temperature is within ±10 °C of the temperature
recorded during the last external calibration.
• Change the test limits to include the additional error due to temperature drift. Refer to
your device specifications document for more information.