In certain applications, the existing or voltage signal of a pressure transmitter must not exceed and/or drop below a crucial value. This is often ensured with the aid of so-called signal limiting.
Why is a signal clamping necessary to begin with?
If the pressure on a pressure transmitter lies within the nominal pressure range, then there will be a precise signal output (e.g. 4 ? 20 mA or 0 ? 10 V). However, in technical applications, it frequently happens that an originally planned pressure range is exceeded or is dropped below. Wanted can happen deliberately, for instance when cleaning, together with accidentally, for example through load variations or in case of a fault. In such cases, the sensor signal will also move outside the defined limits, so that, for example, a current signal in the number of 3.6 to 25 mA can occur.
If now, however, the evaluation electronics are set so that they recognise a signal outside of the defined limits as an error, in some situations, trouble-free operation of the complete system can’t be ensured anymore. In these cases, a sign limiting of the pressure transmitter is practical, so the output signal is maintained within the mandatory range (e.g. 3.8 ? 21 mA).
Note
A good example of a pressure transmitter with which the voltage signal plus the current signal can be limited may be the model S-20 (for general industrial applications) or the model MH-3 (for mobile working machines) from WIKA.