Current Output Circuit - National Instruments FIeldPoint FP-AO-200 Operating Manual

Current Output Circuit

The output circuit of the FP-AO-200 is a sourcing current output,
which means that it is designed to source current provided by an
external loop supply to a device or load capable of sinking this
current to the common voltage of the loop supply. The FP-AO-200
can operate with an external loop supply from 5 to 24 VDC;
however, this voltage dictates the maximum load impedance which
the FP-AO-200 can drive. With a 24 VDC loop supply, each output
can drive up to 1 kOhm of load impedance. With a 5 VDC loop
supply, each output can only drive up to 100 Ohms. The
FP-AO-200 detects and reports error conditions due to excessive
loads or insufficient loop supplies. For more information, refer to
the Open Loop Detection section in this document.
The FP-AO-200 updates the output channels as new values are sent
to it by the network module. The time it takes to respond to a
change on a single channel is between 3 and 6 ms. The response
time to changes on all eight channels is 24 to 27 ms.
Figure 3 shows a diagram of the current output circuit of a single
channel.
12-Bit
Isolated DAC
The FP-AO-200 has several unique features that promote reliable
operation, ease of use, and solid performance. These features are
described below.
V
C
Figure 3. FA-A0-200 Current Output Circuit
Open Loop
Indicator
Current
Sense
4
V
sup
I
out
COM
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