INM831B Rev 4
4
4.1.2
4-wire RTDs (see figure 7)
Wiring 4-wire RTDs requires additional terminal blocks. The ENC83
and ENC83-SS enclosures provide such terminals, as well as earth
terminals for all cable screens.
1)
Connect the ‘sense’ leads of up to fifteen 4-wire RTDs to the
terminal pairs
I1
to
I15
, making sure that the polarity is
correct.
2)
Connect the ‘source’ leads of the RTDs to the corresponding
terminal block pair of the ENC83 enclosure.
3)
Connect any RTD cable screens to the enclosure’s earthing bar.
4)
Connect a link wire between the +ve source lead of each RTD
(except the last) and the –ve source lead of the next RTD.
5)
Connect the –ve source lead of the first RTD to the –ve end of the
current loop (terminal 7).
6)
Connect the +ve source lead of the last RTD to the +ve end of the
current loop (terminal 38).
7)
To monitor the RTD excitation current, connect terminal 39 to 41
and connect terminal 40 to 42. The unit can then calculate the
current from the voltage developed across the built-in 100 ohm
resistor.
4-wire RTD
terminal bar
4-wire RTD
terminal bar
Earth
bar
Earth
bar
Enclosure
ground
Figure 7
- Typical 4-wire RTD installation in an ENC83 enclosure
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H2
Spare
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M
TL
8
31
B
An
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