Note Normally you would adjust to 0 μA in order to calibrate the offset, but because the SCC-CO20 cannot source current, it is impossible to know when you have adjusted past 0 μA.
Using the SCC-CO20
The SCC-CO20 is a 0 to 20 mA programmable current sink. The current output is controlled by AO (X), a 0 to 10 V unipolar DAC output channel of an E/M Series DAQ device. The relationship between the AO (X) voltage level and the current output of the SCC-CO20 is linear and is described by the following equation:
VAO(X) I
-------------- = CO20 500
where
VAO (X) is the AO (X) voltage level.
ICO20 is the SCC-CO20 current output in amperes.
The current sink is an N-channel power MOSFET sink to an isolated ground reference. You can use the SCC-CO20 with industry-standard 0 to 20 or 4 to 20 mA current loops.
Note The current sink does not source current. If the input voltage is 0 V or less, the module sinks 0 mA.
Isolated Ground Reference
Each SCC-CO20 module is referenced to its own isolated ground. Each isolated ground can have up to 60 VDC of common-mode voltage between itself and any other channel ground or chassis ground. Refer to the Connecting the SCC-CO20 to a Load section for different ways to use the isolated ground in signal connections.
© National Instruments Corporation | 9 | SCC-CO20 Isolated Current Output Module User Guide |