Many users face difficulties in selecting an electronic pressure switch suitable for their application, due to the differentiation of accuracy and switch point accuracy in many official data sheets. Nevertheless, there is a significant difference between the switch point accuracy and the pressure-reading accuracy of an electronic pressure switch that should be considered when looking at the overall accuracy of a pressure switch.
Accuracy of pressure switches
The general accuracy of an electronic pressure switch is the accuracy of the pressure measurement itself. This accuracy depends to a great extent on the pressure sensor used within the electronic switch. The maximum measured error of the pressure signal is derived from the non-linearity, zero offset, span tolerance, hysteresis and repeatability of the sensor – resulting from the electronics evaluating the sensor signal and the sensor itself. Thus, the general accuracy only determines how accurate the current media pressure can be measured, but doesn’t give you any indication on the accuracy of your switch point signal.
Switch point accuracy
The switch point signal is an output signal provided by internal electronics within the electronic pressure switch, using PNP or NPN transistors. These electronics analyse the pressure reading from the pressure sensor and activate the switch output signal whenever a set pressure reading has been exceeded. However, these electronics are in addition to those of the standard pressure sensor and therefore add an additional error on top of the standard accuracy of the sensor. Thus, the switch point accuracy is a cumulative accuracy rating of the standard accuracy and the accuracy of the switch point electronics.
It is therefore important to understand, when looking at the accuracy of a switch point, that there can be a difference between the actual pressure and the activated switch point.
Thus, the switch point accuracy, which is closer to a total accuracy rating, should primarily be used to select an electronic pressure switch suitable for your needs. This differentiation between the general accuracy and the switch point signal accuracy also applies to temperature, level and flow switches.
If you need any help in selecting an appropriate switching solution for your pressure, temperature, level or flow measurement, your contact person will gladly be of assistance.
Please find information about our pressure switch PSD-30 here.
