Pressure Gauge Working Principle
Pressure gauges are used for the measurement of relative pressures from 0.6 … 7,000 bar. They are classified as mechanical pressure measuring instruments, and thus operate without any electrical power.
Bourdon tubes are radially formed tubes with an oval cross-section. The pressure of the measuring medium acts on the inside of the tube and produces a motion in the non-clamped end of the tube. This motion is the measure of the pressure and is indicated via the movement.
The C-shaped Bourdon tubes, formed into an angle of approx. 250°, can be used for pressures up to 60 bar. For higher pressures, Bourdon tubes with several superimposed windings of the same angular diameter (helical tubes) or with a spiral coil in the one plane (spiral tubes) are used.
Parts of bourdon tube
Pointer, Dial Face, Window and Ring
Applications of pressure Gauge :Sensing elements for the measurements of medium to high pressures using atmo-spheric reference. For pressure gauges and switches using these elements.
Design Pressure:Up to 100,000 PSIG (690 MPa)
Design Temperature:Up to 600 ° F (316 ° C) with stainless steel Bourdon tube; lower with others; ± 1% zeroshift per 50 ° F (28 ° C) ambient variation
Materials of Construction:Phosphor bronze, alloy steel, 316 and 403 stainless steel, beryllium copper, Monel, Ni-Span C
Range of Pressure Gauge:Minimum span 15 PSI (100 kPa); maximum span 100,000 PSI (690 MPa)
Price of pressure Gauge:$50 to $300 for indicators and switches, $500 to $1,200 for direct recorders, and $750 to $1,800 for direct controllers and transmitters. Quartz helix units range for$2,500 for an electronic transmitter to $18,000 for an IEEE and RS-232 programmable, stable-alone station.
Bourdon pressure gauge advantage and disadvantage
Advantage of pressure gauge :-
- Bourdon tube is simple in construction.
- It is available in wide range.
- It has long life.
- It cost is low.
- Time tested application.
- Accuracy is high.
Disadvantage of pressure Gauge :-
- Susceptibility to hysteresis.
- Low spring gradient (below 50 psig)
- Susceptibility to shock and vibrations.