The installation of a sensor element or a corresponding assembly has the advantage that very compact dimensions are possible. However, some points need to be taken into account, which are an additional effort for the customer compared to using a fully adjusted sensor with an amplified output signal.
For example, for each sensor, the zero point and span error must be measured and compensated through the customer’s electronics. For this purpose, a measurement of the sensor signal, both in the unpressurised state and at nominal pressure/working pressure, is needed.
In both cases there will be a signal deviation from the expected value (= offset). However, these measuring errors can be eliminated via the evaluation electronics. Especially when setting the working pressure, one should take care that a sufficiently accurate reference is used (standard value: the reference, in accordance with the specification of the EN 837 standard, should have an at least 4 times smaller measuring error than the sensor to be adjusted).
For illustration, a numerical example of a metal thin-film sensor (e.g. WIKA model TTF-1): The zero point offset can be up to 25 %; the span error, depending on the pressure range, 15-25 %. In the worst case with the same sign, so that the measured value makes no sense if the above-described adjustment is not made.
After adjustment of the zero point and span errors, attention must be paid to the specifications from the corresponding data sheet of the sensor elements and their components to determine the accuracy at room temperature (non-linearity, hysteresis, non-repeatability).
Further information on metal thin-film sensors Model TTF-1 can be found on the WIKA website.
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