Position can influence the accuracy of pressure transmitters

by STS Sensors on May 18, 2018
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Position can influence the accuracy of pressure transmitters

The accuracy of a pressure measurement can definitely be influenced by the position of the pressure transmitter. Particular attention to this should be paid in the low-pressure range.

When it comes to position dependence, inaccuracies can occur if the position of the pressure transmitter differs in practice from that used during the calibration process at the manufacturer. At STS, the norm is for pressure transmitters to be calibrated in a vertical position pointing downwards (see accompanying image above). If users now mount one of these calibrated pressure sensors in the opposite position, i.e. pointing vertically upwards, then inaccuracies may occur during the pressure measurement.

The reason for this is simple. In the latter position, the actual weight of the pressure transmitter will influence its precision. The membrane, filling body and transmission fluid act upon the actual sensor chip due to the gravitational force of the earth. This behavior is common to all piezoresistive pressure sensors, but it is only of importance in the low-pressure range.

Installation of pressure transmitters: Caution in the lower pressure ranges

The lower the pressure to be measured, the higher in this case the measurement error will be. With a 100 mbar sensor, the measurement error amounts to one percent. The higher the measuring range, the lower the effect becomes. Starting from a pressure of 1 bar, this error becomes practically negligible.

This measurement inaccuracy can be easily detected by users, especially when a relative pressure sensor is used. If users are working in the low-pressure range and it is not possible to mount the measuring instrument in the position in which it was factory calibrated, it should then be recalibrated in its actual position. Alternatively, users can also compensate for the measurement error themselves numerically on the control unit.

This additional effort can, of course, be easily avoided through competent application advice. Although STS pressure transmitters are calibrated vertically downwards as standard, it is easily possible to carry out the calibration in a different position. Our advice is to communicate the mounting position of your pressure transmitter with us in advance and you will then receive a measuring instrument perfectly matched to your application. We will be only too happy to advise you!

Topics: Piezorestive Measuring Cell, Piezoresistive Pressure Transmitter, Instructions For Mounting, Accuracy, Low Pressure

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