Measurement & Instrumentation

Figure 1: Hot-Cathode Ionization Gauge.

Working Principle of Ionization Gauge

The basic principle of an ionization gauge is the electrons emitted from a cathode strikes a gas molecule and knocks out an electron from it. Thus the gas molecule remains as a positively charged ion and carries a current called ion current. This current become a measure of the applied pressure when calibrated.

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Working Principle of Thermocouple Vacuum Gauge

The operating principle of thermocouple Vacuum Gauge is that the conducting ability of gas in vacuum or low pressure depends on the pressure i.e., it is a function of pressure. The measurement of vacuum using  thermocouple gauge is shown in figure 1.

Figure 1: Thermocouple Vacuum Gauge.

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Semiconductor Strain Gauge is also called piezo-resistive strain gauges. These are made up of doped silicon and germanium which have crystalline structure. When subjected to strain, resistivity of this material changes. This property is called piezo-resistive property.

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