Pressure Measuring Instruments

McLeod Vacuum Gauge

A known volume gas is compressed to a smaller volume whose final value provides an indication of the applied pressure. I have given a brief post on the equations used with good construction diagram of McLeod Vacuum Gauge

Strain Gauge Pressure Cell

When a closed container is subjected to the appilied pressure, it is strained (that is, its dimension changes). Measurement of this strain with a secondary transducer like a strain gauge ( metallic conductor) becomes a measure of the appilied pressure.

The Two types of Strain Gauge Pressure Cell, Flattened tube pressure cell and Cylindrical type pressure cell are discussed.

Elastic diaphragm gauges

When an elastic transducer (diaphragm is this case) is subjected to a pressure, it deflects. This deflection is proportional to the appilied pressure when calibrated.

Bourdon tube Pressure Gauge

when an elastic transducer ( bourdon tube in this case ) is subjected to a pressure, it defects. This deflection is proportional to the applied pressure when calibrated.

Manometer with equal unequal limb types

This is the most simple and precise device used for the measurement od pressure. It consists of a transparent tube constructed in the form of an elongated ā€˜Uā€™, and partially filled with the manometeric fliud such as mercury. The purpose of using mercury as the manometeric fluid is that their specific gravity at various temperatures are known exactly and they dont stick to the tube. The two common types of manometers are the equal limb type and unequal limb type.

Dead Weight Tester

The dead weight tester apparatus consists of a chamber which is filled with oil free impurities and a piston ā€“ cylinder combination is fitted above the chamber as shown in diagram. The top portion of the piston is attached with a platform to carry weights. A plunger with a handle has been provided to vary the pressure of oil in the chamber. The pressure gauge to be tested is fitted at an appropriate plate.

Pressure Measurement using U-tube Manometer

A well known very simple device used to measure the pressure is the U-tube manometer. The name U-tube is derived from its shape. U-tube manometer is shown below.

Terms related to pressure

All the important terms related to Pressure measurement like Atmospheric pressure, Absoulte pressure, Gauge Pressure, Vacuum pressure, Static Pressure, Total or Stagnation pressure, Dynamic ā€“ or ā€“ Impact ā€“ or ā€“ Velocity pressure and more are discussed.

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