In certain applications, the current or voltage signal of a pressure transmitter must not exceed and/or drop below a crucial value. This could be 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 defined signal output (e.g. 4 ? 20 mA or 0 ? 10 V). However, in technical applications, it frequently happens an originally planned pressure range is exceeded or is dropped below. This may happen deliberately, for example when cleaning, along with accidentally, for instance through load variations or in the event of a fault. In such cases, the sensor signal may also move beyond your defined limits, in order that, for example, a current signal in the range of 3.6 to 25 mA can occur.
If now, however, the evaluation electronics are set so they recognise a signal outside the defined limits being an error, in a few situations, trouble-free operation of the complete system cannot be ensured anymore. In such cases, a sign limiting of the pressure transmitter is practical, in order that the output signal is maintained within the mandatory range (e.g. 3.8 ? 21 mA).
Note
Copy of a pressure transmitter with which the voltage signal plus the current signal can be limited is the model S-20 (for general industrial applications) or the model MH-3 (for mobile working machines) from WIKA.