National Instruments Isolated Current Output Module SCC-CO20 - Manual (Page 8)

SCC-CO20 Isolated Current Output Module User Guide 8 ni.com
Figure 5. Connecting the SCC-CO20 to a Grounded External Loop Supply
and a Grounded Load
For information about how to configure the SCC-CO20 module using
NI-DAQmx, refer to the SCC Quick Start Guide.
Calibrating Gain and Offset Errors
The SCC-CO20 is calibrated at the factory before shipment. If you want
to adjust the gain and offset of the SCC-CO20 in your system using an
E/M Series DAQ device, you need a current meter (ammeter) with an
accuracy of at least ±2
μA.
To adjust the gain and offset of the SCC-CO20, complete the following
steps:
1. Disconnect the load from the SCC-CO20 you want to calibrate.
2. Set an output range of 0 to 10 V for AO (X), the E/M Series DAQ
device channel connected to the SCC-CO20.
3. Connect the negative lead of the ammeter to the current sink (pin 2)
and the positive lead to the current supply (pin 3) of the SCC-CO20.
4. Using your software, have AO (X) output 10 mVDC.
5. Adjust the offset potentiometer on the top of the SCC-CO20 until the
ammeter reads 20
μA. The offset is now calibrated.
6. Using your software, have AO (X) output 9 VDC.
7. Adjust the gain potentiometer on the top of the SCC-CO20 until the
ammeter reads 18 mA. The gain is now calibrated.
1
2
Load
0–20 mA
SINK
SCC-CO20
ISO GND
+
–
I