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The Transducer Block
3.8 AI_TRANSDUCER Block (PA Slot 3) Parameter List
SITRANS TH400 PROFIBUS® PA
34
Configuration Manual, 02/2007, A5E01039143-01
3.8.8
Sensor calibration, Description
Sensor calibration is a very useful function when the transmitter output needs to be adjusted
to the sensor signal, e.g. when the temperature sensor does not correspond to the ideal
values for the selected temperature range. The results depend on the accuracy of the
calibrator or reference equipment. In the following a temperature sensor calibration is
described, however the principle can be used for all input types.
SENSOR_CAL_METHOD_1 / 2 defines the use of either “Factory trim Standard” (the factory
defined values calculated according to the valid norms) or “User Trim Standard” (the sensor
calibrated values) in the transmitter for sensor 1 and 2 respectively. During sensor calibration
SENSOR_CAL_METHOD_1 / 2 must be set to “Factory trim Standard” = 103.
The sensor calibration function in SITRANS TH400 will change the slope of the linarisation
curve so the curve is adjusted to the connected sensor. To obtain accurate temperature
measurement in the range e.g. 0...100 °C apply to the sensor a temperature e.g. of 5 °C as
the low temperature and e.g. 95 °C as the high temperature through a precise temperature
calibrator.
At sensor calibration the succeeding procedure must be followed precisely
(Example: sensor 1):
1.
SENSOR_CAL_METHOD_1 = 103
2.
Apply the low temperature of the calibrator to the sensor
3.
CAL_POINT_LO_1 = 5.00 (type in the low temperature of the calibrator)
4.
CAL_ACTUAL_LO_1 = 1.00 (The measurement of the deviation starts by typing in a
random value)
5.
Apply the high temperature of the calibrator to the sensor
6.
CAL_POINT_HI_1 = 95.00 (type in the high temperature of the calibrator)
7.
CAL_ACTUAL_HI_1 = 1.00 (The measurement of the deviation starts by typing in a
random value and SITRANS TH400 calculates the curve
slope according to the measured deviations.)
8.
SENSOR_CAL_METHOD_1 = 104 (the sensor calibration just carried out is used)