Pressure Indicator

an instrument for measuring and recording pressure changes in pneumatic automatic devices and in the cylinders of piston engines. Pressure indicators usually have a sensing element (sensor) and transmitting and recording devices.

In a pneumatic pressure indicator, the pressure on the piston or diaphragm (the sensing element) is transmitted by means of a rod to the arm of a recording instrument, which registers the changes in the position of the piston or diaphragm (that is, changes in pressure). In electric pressure recorders, the pressure fluctuations are transformed by the sensor into electric signals that are indicated by an oscillograph or electric meters.