National-instruments Isolated Current Output Module SCC-CO20 Manuale Utente Scaricare il pdf (Pagina 9)

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:

where

AO (X)

is the AO (X) voltage level.

CO20

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.

AO X()

500

--------------- I

CO2

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National-instruments Isolated Current Output Module SCC-CO20 Manuale Utente Pagina 9