Bourdon tube pressure gauge

Bourdon tubes are circular-shaped tubes with oval cross sections The pressure of the medium acts on the inside of the tube. The outward pressure on the oval cross section forces it to become rounded. Because of the curvature of the tube ring, the bourdon tube then bends as indicated in the direction of the arrow

Due to their robust construction, bourdon are often used in harsh environments and high pressures, but can also be used for very low pressures; the response time however, is slower than the bellows or diaphragm.

Spiral Pressure Elements pressure Gauge

The free-end travel and force of the C-tube are insufficient to operate many motion balance devices. Motion balance describes the means by which the motion of the pressure element moves the sector, mechanically transmitting a rotary motion to the pinion assembly and indicator. The spiral element shown in can be considered to function as a series of C-tubes connected end to end. When pressure is applied, the element tends to uncoil and, by producing greater movement without amplification, yields greater accuracy and sensitivity.Less hysteresis and friction result because of the reduced need for additional links and levers. In general, the same types of materials are used for spiral element construction as for C-tubes. Spiral pressure transducers produce more tip travel and higher torque capability at the free end than C-tubes. They are thus more capable of use as direct-drive readout devices. Instruments that utilize these types of transducers can respond to lower pressure and thus are more sensitive, partly because of the reduced friction involved in the movement. The operating range of spiral and helical elements is from a few inches of water to a few hundred pounds per square inch. These transducers are used primarily in pressure transmitters, pneumatic controllers and receiver instruments. Their use in pressure gages is limited.

Helical bourdon tube pressure Gauge

The helical elements produce more free-end travel and torque than spiral elements. Other advantages include a high errange of operating pressure with sufficient over range protection. The operating range is affected by coil diameter, wall thickness, the number of coils used, and the material of construction, which is the same as may be used in C-tube elements Applications of helical elements include direct reading for the following: indicators, recorders, controllers, switches, transmitters, and differential instruments when pressures are applied to both sides of the elements.

Diaphragm type pressure Gauge sensor

A diaphragm is a circular-shaped convoluted membrane that is attached to the pressure fixture around the circumference (refer to Figure ). The pressure medium is on one side and the indication medium is on the other. The deflection that is created by pressure in the vessel would be in the direction of the arrow indicated.

Diaphragms provide fast acting and accurate pressure indication. However, the movement or stroke is not as large as the bellows

Bellows pressure gauge

Bellows type elements are constructed of tubular membranes that are convoluted around the circumference (see Figure ). The membrane is attached at one end to the source and at the other end to an indicating device or instrument. The bellows element can provide a long range of motion (stroke) in the direction of the arrow when input pressure is applied.