User`s guide

34 •• Utility/Calibration
6.2.3 Voltage Output Calibration
Because there is internal reference voltage for every DA channels, the
calibration for every channels are independent. In the following procedure,
VRn-1 and VRn-2 is used to represent the full range and offset of the nth
channels. The following is the calibration procedure of the DA output.
Step 1. Connect the n th DA output (Vn) to VDM(+) of the digital multi-
meter. Connect the AGND signal to VDM (-).
Step 2. Send digital value ‘0’ to DA. Roughly adjust the offset (trim VR n-
2) until the VDM value equal to zero.
Step 3. Send digital value ‘32767’ to DA. Record VDM value as V1. Send
digital value ‘-32767’ to DA. Record VDM value as V2. Adjust the
full range (trim VR n-1) until V1-V2 value equal to +20V.
Step 4. Send digital value ‘0’ to DA. Precisely adjust the offset (trim VR n-
2) until the VDM value equal to zero.
6.2.4 Current Output Calibration
The current output calibration is used only on cPCI/PCI-6208A. Because the
current output channel n is controlled by the voltage of channel n, the VR n-1
and VR n-2 is also used for calibrating the n-th current output channel.
Step 1. Connect the n-th current output (An) to VDM(A+) of the digital multi-
meter. Connect the both junction of the current load (typical 250
ohm) to the VDM (A-) and ground (AGND) respectively.
Step 2. Select the current range by S/W program. For example, to set the
current range as 4~20 mA.
Step 3. Send digital value ‘0’ to DA. Adjust the offset (trim VR n-2) until the
current value equal to the minimum value of the current range. For
example, adjust to 4mA if the current range is 4~20mA.
Step 4. Send digital value ‘32767’ to DA. Adjust the full range (trim VR n-1)
until the current value equal to the maximum value of the full range.
For example , to adjust to 20 mA if the current range is 4~20mA.
Step 5. Repeat step 3 and step 4 until the accuracy is in user application‘s
specifications.