F
3-
-0
8T
H
M
--n
8C
h.
T
he
rm
oc
ou
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e
In
.
9--6
F3--08THM--n 8-Channel Thermocouple Input
Module Operation
Before you begin writing the control program, it is important to take a few minutes to
understand how the module processes and represents the analog signals.
The F3--08THM--n module supplies1 channel of data per each CPU scan. Since
there are eight channels, it can take up to eight scans to get data for all channels.
Once all channels have been scanned the process starts over with channel 1.
Channel 1
Scan N
Read the data
Store data
I/O Update
Execute Application Program
Channel 2
Scan N+1
Channel 8
Scan N+7
Channel 1
Scan N+8
Scan
.
.
.
.
.
.
Even though the channel updates to the CPU are synchronous with the CPU scan,
the module asynchronously monitors the thermocouple signal and converts the
signal to a temperature (or 12-bit binary) representation. This enables the module to
continuously provide accurate measurements without slowing down the discrete
control logic in the RLL program.
Channel Scanning
Sequence
