Checking inputs
CNT-SVN01C-EN 29
Checking resistance temperature detector (RTD) inputs
To check RTD inputs for proper operation:
1. Make sure that the sensor is connected.
2. Set the multi-meter to measure Vac, then measure the voltage across
the input at the signal and common screw terminals.
The measured voltage should be less than 0.1 Vac. If the voltage is
greater than this, temperature readings may change erratically.
3. Set the multi-meter to measure Vdc, then measure the voltage across
the input at the signal and common screw terminals.
The measured voltage should be less than 0.1 Vdc. If the voltage is
greater than this, temperature readings may be offset.
CAUTION
Equipment damage!
Continue to step 4 only if you completed steps 2 and 3 successfully.
Measuring resistance may damage the meter if the voltage is too high.
4. Set the multi-meter to measure resistance. If you completed steps 2
and 3 successfully, measure the resistance across the input at the sig-
nal and common screw terminals.
For a 375 platinum RTD, the resistance should be between 868 Ω and
1350 Ω
, which translates to temperatures of –30°F and 200°F (–34°C
and 93°C). Table 6 on page 28 shows appropriate ranges for other
types of RTDs.
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