Elastic diaphragm gauges


#1

Elastic diaphragm gauge is a pressure measurement device, which works under the principle When an elastic transducer (diaphragm) is subjected to a pressure, it deviates. This deviation is proportional to the pressure applied when calibrating.

Construction of Elastic diaphragm gauges:

The main parts of the diaphragm, which is a thin circular plate (made of elastic metal), are firmly fixed around its edges. The diaphragm can be flat or corrugated.

A corrugated diaphragm has been shown in the diagram, where the displacement of the diaphragm is magnified by mechanical means. A flat diaphragm has been shown in the diagram where the displacement of the diaphragm is detected by a secondary transducer such as a parallel plate capacitor.

elastic%20trans

The upper part of the diaphragm is fixed with a protrusion of negligible weight. This projection is in turn connected to a link - sector - pinion arrangement in the case of a diaphragm indicator that uses mechanical means for the extension of the displacement.

A pointer is connected to the pinion that makes it sweep on a scale calibrated by pressure. If the displacement is detected by a secondary transducer, such as a parallel plate capacitor, its moving plate is connected to the protrusion.

Working of Elastic diaphragm gauges:

The lower side of the diaphragm is exposed to the pressure to be measured. Due to the applied pressure, the diaphragm is deformed. That’s the diaphragm that tends to move up. This deformation of the diaphragm is proportional to the applied pressure. In a mechanical system, this deformation is magnified by the arrangement of pinion link sector.

That is, the linear displacement of the diaphragm becomes a magnified rotational movement of the pinion. When the pinion rotates, it causes the pointer to adhere to it to assume a new position on the calibrated pressure scale that becomes a measure of the applied pressure.

In the case of the arrangement with the parallel plate capacitor, the movable plate moves upwards, thus reducing the space between the plates. This causes the capacitance of the capacitor to become a measure of the applied pressure.

Advantages of Elastic diaphragm gauges:

  • The best advantage is that they cost less

  • They have a linear scale for a wide range.

  • They can withstand the excess pressure and, therefore, are safe to use.

  • There is no permanent zero change.

  • They can measure both the absolute pressure and the gauge pressure, that is, the differential pressure.

Limitations of Elastic diaphragm gauges:

  • Shocks and vibrations affect their performance and, therefore, must be protected.

  • When used to measure high pressure, the diaphragm is damaged.

  • These meters are difficult to repair.