Emerson Rosemount MCL-220 Reference Manual page 83

Reference Manual
00809-0100-3414
To check the accuracy of the temperature measurement, set the resistor simulating the
resistance temperature device to the values indicated in the table and note the
temperature readings. The measured temperature might not agree with the value in the
table. During sensor calibration, an offset might have been applied to make the measured
temperature agree with a standard thermometer. The offset is also applied to the
simulated resistance. The transmitter is measuring temperature correctly if the difference
between measured temperatures equals the difference between the values in the table to
within ±0.1 °C.
For example, start with a simulated resistance of 103.9 Ω, which corresponds to 10.0 °C.
Assume the offset from the sensor calibration was -0.3 Ω. Because of the offset, the
transmitter calculates temperature using 103.6 Ω. The result is 9.2 °C. Now change the
resistance to 107.8 Ω, which corresponds to 20.0 °C. The transmitter uses 107.5 Ω to
calculate the temperature, so the display reads 19.2 °C. Because the difference between
the displayed temperatures (10.0 °C) is the same as the difference between the simulated
temperatures, the transmitter is working correctly.
Temp. (°C)
0
10
20
25
30
40
50
60
70
80
85
90
100
Rosemount MCL
Pt 100 (Ω)
100.0
103.9
107.8
109.7
111.7
115.5
119.4
123.2
127.1
130.9
132.8
134.7
138.5
Troubleshoot
May 2019
83