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Connecting RTD Inputs
Each DT9872 and DT9874 contains pluggable screw terminals for connecting RTD inputs.
Internally, these signals are connected in differential mode.
Note: On the standard DT9874 instrument, channels 16 to 31 correspond to the RTD input
channels.
Figure 13
shows the numbering of the screw terminal blocks for RTD connections.
Figure 13: Screw Terminal Block Numbering for RTD Connections
The DT9872 supplies each RTD channel with 425 A of excitation current to prevent
self-heating. The resistance of the RTD circuit increases gradually, repeatably, and linearly
with temperature. As the resistance increases, the voltage drop across the RTD also increases.
4
3
2
Return
– Sense
+Sense
Current
Wiring Signals
RTD
Channels
1
47
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