A melt pressure transducer is used for measuring very high pressure at high temperatures near the tool at the end of an extruder. Because the temperatures are high the sensors diaphragm deflection is telegraphed, normally by liquid in a capillary tube, to a secondary diaphragm which is positioned away from the heat source. This secondary diaphragm has the strain gauge bridge bonded to it.

Because of the very high pressures and the critical measurements the melt pressure sensor provides, a calibration shunt resistor is fitted to output 80% of the full scale output when it is switched into the strain gauge circuit.

The Tracker 250 melt pressure indicators "Fast Cal" feature provides a fast and simple method of match calibrating to the transducer. The calibration sequence starts by measuring and storing the output signal value at zero pressure. The transducer's internal calibration resistor is then switched in by the Tracker 250 and measures and stores the signals (80% of Span) reading. The Tracker then calibrates to the stored zero and span signal values.

Re-calibration can be undertaken whenever the transducer is at ambient pressure (i.e. has no pressure applied to it). Should the transducer be faulty, or incorrectly wired, this will be indicated during the calibration procedure.