The original principle of pressure manometer is based on the tube edge displacement caused by elastic deformation of the Bourdon tube under action of pressure or vacuum. The C-shaped or spirally wound bourdon tube flexes when pressure is applied producing a rotational movement, which in turn causes the pointer to indicate the measured pressure. The construction is simple yet rugged and operation requires no additional power source.Nowadays, pressure gauges with digital display use an electronic pressure transmitter as sensing element and then transmit the output into digital display readout.In the past decades, pressure transmitters have been improved significantly through different technologies and approaches that result in lower power consumption, suitability for different material, smaller size and weight, and fast response with high reliability, sensitivity, accuracy and repeatability.Below pictures and graph show different possible pressure references to adjust the pressure transmitter based on them.
There are different approaches used to measure pressure. These approaches are mostly based on special requirement of customers and advantages of the technology executed.The most common sensing technologies used today are Force collector types, Piezo-resistive and Piezo-electric, Electromechanical Strain Gage, Variable Capacitance, Electromagnetic as well as optical fibre sensing.Force collector types are electronic pressure sensors using a force collector component, such as diaphragm, piston, bourdon tube, and/or bellows, to measure the strain caused by the applied force over an area, therefore, measure the pressure
In respect of Piezo-resistive effect, Piezo-resistive material such as silicon, molecularly diffused onto a metal or micro-machined diaphragm, is used to detect strain generated by the applied pressure. Similar to strain gauge-based pressure transmitters, Wheatstone bridge circuit is formed to maximize the output sensitivity of the sensor.
Piezoelectric materials are also used as sensing element due to their piezoelectric effect in response to applied mechanical stress.
Capacitive pressure sensor uses a diaphragm and pressure cavity to create a variable capacitor to detect strain due to applied pressure. Common technologies use metal, ceramic, and silicon diaphragms. Generally, these technologies are most applied to low pressures (Absolute, Differential and Gauge).