Siemens SITRANS T Series Operating Instructions Manual page 54

Functions
9.15 Special characteristic curve
Example
The transmitter is used for measuring a customer-specific thermocouple. The thermocouple
supplies the following mV signals in this case:
● At the start of scale value: - 10 mV (equals -100 °C)
● At full scale value: 40 mV (equals +400 °C)
Proceed as follows
Note
It may be necessary to perform a sensor calibration at the start of scale value (-10 mV) and
full scale value (40 mV) before the sensor characteristic is recorded and the correction
values have been entered.
1. The mV transmitter sensor class is selected using the parameter assignment software
SIPROM T or SIMATIC PDM.
2. Characteristic curve correction of the thermocouple should be performed across 6 pairs of
values. The type of cold junction compensation is a fixed value = 0 °C.
3. Parameter entries
Sensor signal at transmit-
ter input
-10 mV
-5 mV
0 mV
15 mV
35 mV
40 mV
Example for a parameter
Determining the pairs of values X[i] and Y[i] using, as an example, the pair of values i = 3 is
explained below.
Calculation X[i=3]
The characteristic curve parameter X[3] = 0 mV corresponds with 20 % as a percentage in
relation to
start of scale value = - 10 mV and full scale value = 40 mV.
Calculation Y[i=3]
54
Characteristic curve pair
Pair of values X[i]
i = 1 0 %
i = 2 10 %
i = 3 20 %
i = 4 50 %
i = 5 90 %
i = 6 100 %
Measured value [i] after
characteristic curve cor-
rection
Y[i]
0 % -100 °C
15 % -25 °C
20 % 0 °C
55 % 175 °C
95 % 375 °C
100 % 400 °C
SITRANS TH200/TH300
Operating Instructions, 08/2015, A5E00393069-04