IM 04L20A01-01E 11-3
11
Maintenance
Temperature Measurement When Using an RTD
Bb A
b
A
B
Measurement input terminals
Decade resistance box
(Model 2793-01 from Yokogawa M&C)
The resistance of three lead
wires must be equal.
Temperature Measurement When Using a thermocouple
+
−
b
A
B
0 °C standard temperature device
+−
Thermocouple wires or
TC extension wire
Copper wire
Copper wire
Thermocouple wire
DC voltage standard
Measurement
input terminals
Cold junction
Reference Junction Compensation of Thermocouple Input
As the measurement terminal of the FX100 is generally at room temperature, the
actual output of the thermocouple is different from the values given on the
thermoelectromotive force table based on 0 °C. The FX100 performs compensation
by measuring the temperature at the input terminal and adding the corresponding
thermoelectromotive force to the actual output of the thermocouple. Therefore, when
the measurement terminal is shorted (equivalent the detector tip being 0 °C), the
measured value indicates the temperature of the input terminal. When calibrating the
FX100, this compensation voltage (thermoelectromotive force of 0 °C reference
corresponding to the input terminal temperature) must be subtracted from the output
of the standard generator before application. As shown in the figure, by using the 0
°C standard temperature device to compensate the reference junction at 0 °C, you
can input the thermoelectromotive force of 0 °C reference from the DC voltage
standard and perform the calibration.
11.2 Calibration
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