The principle of Force summing devices using suitable examples - Diaphragms ,Bellows ,Bourdon tubes

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Force summing devices serve as primary transducers and convert the pressure applied at the input into displacement, which then can be measured by means of secondary transducer. 

The   lists of most widely used force summing devices are:-

 -Diaphragms.

 -Bellows.

 -Bourdon tubes.

 Diaphragms:-

Any thin metal whose ends are fixed between two parallel plates is referred to as

diaphragm. It is one of the pressure measuring elements. 

The operating principle is the applied pressure is converted into proportional displacement. The materials used to make diaphragms are phosphor bronze, nickel, beryllium copper, stainless steel, etc. These can be available in flat or corrugated shapes.

When two corrugated diaphragms are joined together at their ends a capsule is formed.

When compared to flat diaphragms corrugated diaphragms produce greater displacements. Since the capsule is a combination of two diaphragms it generates more displacement which is twice that of the single corrugated diaphragm. This generated displacement is proportional to the applied pressure.

Bellows:-

Bellows, the pressure measuring elements are formed by the series combination of

capsules. The working principle of bellows is same as that of diaphragms i.e., the applied

displacement is converted into proportionate mechanical displacement. The materials used to

construct bellows are beryllium copper, brass, monel, stainless steel and nickel.

Whenever the pressure to be measured is applied

the sealed end of bellow suffers displacement. The generated displacement can be known by

attaching a pointer scale arrangement to the sealed end or by transmitting the displacement to the secondary transducer.

Bourdon Tubes:-

The bourdon tubes are available in different shapes such as spiral, helical, twisted

and C shaped. However all the tubes have non-circular cross-section. Also the materials used and working of all these types are same. The materials used in the construction of bourdon tubes are brass, steel and rubber.

The working principle of bourdon tube is same as that of diaphragms and

bellows i.e., the applied pressure is converted into mechanical displacement.

The displacement generated by the above force summing devices can be

converted into electrical form by transmitting it to LVDT. 

The output voltage generated by LVDT is proportional to displacement and hence applied pressure.

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