Abstract: A piezoelectric transducer for use as an accelerometer has a polarized piezoelectric element sandwiched between a spigot and a sleeve. The element is hollow and conical, or frusto-conical so that the sandwiching effect can be achieved by means of axial clamping, as by a screw. This avoids the use of solders or adhesives and thus allows high temperature operation.

Abstract: A transducer generates a signal whose amplitude corresponds to the vibration amplitude of a machine under test. The output of the transducer is passed to a comparator which gives a logic 1 output when the transducer output signal lies outside an acceptable range, and a logic 0 output when it falls within the range. If a logic 1 output occurs, the length of time for which it persists is measured and, if it persists for greater than a preset time, an alarm is actuated.

Abstract: The transducer comprises a diaphragm to which the pressure to be measured or monitored is applied to cause deflection. An electrode is formed on one surface of the diaphragm and this electrode forms a differential capacitor in conjunction with a further pair of electrodes mounted on a fixed support plate adjacent the diaphragm. Deflection of the diaphragm causes imbalance of the capacitor to a degree dependent on the deflection.