Explanation Of The Parameters - Siemens SIMATIC ET 200AL Manual

Parameters/address space

4.3 Explanation of the parameters

4.3 Explanation of the parameters
Temperature unit
You use this parameter to set the temperature unit with which you want to measure the
temperature.
Type/range of measurement
You use this parameter to set the measurement type or the measuring range for acquiring
the measured values.
Note
Unused channels
"Deactivate" unused channels in the parameter assignment to improve the cycle time of the
module.
A deactivated channel always returns the value 7FFF
Temperature coefficient (for RTD)
The temperature coefficient depends on the chemical composition of the material. In Europe,
only one value is used per sensor type (default value).
The correction factor for the temperature coefficient (α value) specifies how much the
resistance of a certain material changes when the temperature is raised by 1 °C.
The further values facilitate sensor-specific setting of the temperature coefficient and
enhance accuracy.
Reference junction
If the measuring point is subjected to a different temperature than the reference junction
(free ends of the thermocouple at the connection point), a thermal voltage arises between
the free ends. The level of the thermal voltage depends:
• On the temperature difference between the measuring point and the free ends
• On the type of material combination of the thermocouple
Since a temperature difference is always detected with a thermocouple, the temperature of
the reference junction has to be determined in order to determine the temperature of the
measuring point.
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Analog input module AI 4xRTD/TC 4xM12 (6ES7144-5KD50-0BA0)
Equipment Manual, 08/2020, A5E48753535-AA