While there are still rather general indications and rules for the device-specific criteria as to whether absolute or relative pressure sensors should be used, it is hardly possible to make general recommendations for the application-specific criteria. The following examples therefore show, rather by way of example, some potential criteria that need to be taken into account.
Closed systems: In closed systems such as cooling circuits, the pressure of the medium reacts independently of the ambient pressure. Therefore, sometimes the absolute pressure is measured. However, due to cost reasons, relative pressure transmitters are used. For if all relative pressure sensors measure against the same atmospheric pressure, the atmospheric influence is equalised if only the differences between the individual measuring points are used and not the absolute level of the pressure.
Process parameters: Since the ratio of air to fuel is decisive in many combustion processes, these calculations are usually based on absolute pressure values for the ideal ratio. Therefore, in numerous cases, the absolute pressure is measured when investigating combustion processes. An alternative is to use relative pressure sensors and reference them against a barometric sensor that accurately measures the atmospheric pressure. The disadvantage of this method is that the errors of the relative pressure sensor and the barometric sensor add up to the total measurement error.