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Commissioning
5.4.3
Temperature coefficient tK [ppm/K]
An electronic circuit is usually temperature dependent to a greater or lesser degree. In analog measurement
technology this means that when a measured value is determined by means of an electronic circuit, its
deviation from the "true" value is reproducibly dependent on the ambient/operating temperature.
A manufacturer can alleviate this by using components of a higher quality or by software means.
The temperature coefficient, when indicated, specified by Beckhoff allows the user to calculate the expected
measuring error outside the basic accuracy. The basic accuracy is usually specified for 23 °C ambient
temperature, in special cases also at other temperature.
Due to the extensive uncertainty considerations that are incorporated in the determination of the basic
accuracy, Beckhoff recommends a quadratic summation.
Example: Let the basic accuracy be ±0.01% typ. (full scale value), tK = 20 ppm/K typ at 23 °C.; the accuracy
A35 at 35 °C is wanted, hence ΔT = 12 K:
-6
-2
Remarks:
ppm ≙ 10
% ≙ 10
EL3681
Version: 3.0
127
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