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National Instruments Corporation
9
SCC-CO20 Isolated Current Output Module
Note
Normally you would adjust to 0
µ
A 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
µ
A.
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
V
AO
(
X
)
is the AO (
X
) voltage level.
I
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.
Specifications
These ratings are typical at 25
°
C unless otherwise stated.
Electrical
Number of output channels .................... 1
Output referencing ................................. Nonreferenced (floating)
Input range ............................................. 0 to 10 V
V
AO X
( )
500
----------------
I
CO
20
=
