FP-TC-120 and cFP-TC-120 4 ni.com
Note On the FP-TB-3 terminal base and the cFP-CB-3
connector block, use the C terminals for COM
connections.
The COM terminals of all the channels are internally connected
and are connected to the terminals labeled C on the terminal base.
You do not need to connect a power source to the V or C terminals
of the terminal base or connector block. The C and COM terminals
are internally connected to the isolated ground reference of the
module and to any shield connections you make, so connecting a
power supply to one of these terminals may create a ground loop
and cause measurements to be misreferenced. Connecting the C
and COM terminals of the [c]FP-TC-120 to the V, C, or COM
terminals of another FieldPoint module defeats the isolation
barriers between the two modules.
Taking Measurements
with the [c]FP-TC-120
The [c]FP-TC-120 has eight differential input channels. All eight
channels share a common ground reference that is isolated from
other modules in the FieldPoint system. Each of the input channels
has a bias resistor to this isolated ground reference on the negative
terminal, IN(–), and a pull-up resistor on the positive terminal,
IN(+), to detect open thermocouples. Each channel has a COM
terminal that connects to the isolated ground reference. Each
channel is filtered, then sampled by a 16-bit analog-to-digital
Table 1. Terminal Assignments
Channel
Terminal Numbers
IN(+)
IN(–)
COM
0 1 2 18
1 3 4 20
2 5 6 22
3 7 8 24
4 9 10 26
5 11 12 28
6 13 14 30
7 15 16 32
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