Gauge aneroid

Aneroid gauge A gauge used for the measurement of static, velocity, or total pressure with a pitot tube. 

Aneroid gauge, electronic An aneroid gauge with the advantage of being able to integrate the velocity pressure directly into velocity. 

Bourdon gauges are used on gas cylinders and are also considered a type of aneroid gauge. These devices have a coiled tube (shown in Figure 3.5) and are used to measure the pressure difference between the pressure exerted by the gas in a cylinder and the atmospheric pressure. The coiled tube is mechanically coupled to a pointer (shown in red). As a gas at a pressure above atmospheric pressure enters the coiled tube, it causes it to slightly uncoil, kind of like those New Year s Eve paper noisemakers. This causes the pointer to move over a numerical scale, thereby indicating the gauge pressure in the tank. 

A precision aneroid manometer is used for measurements in the 760— 1 torr range. Thermocouple gauges are used in the 1 — 1 x 10 3 range. A cold cathode ionization gauge is used in the high vacuum range down to 10-6 torr. 

The best-known design of a diaphragm vacuum gauge is a barometer with an aneroid capsule as the measuring system. It contains a hermetically sealed, evacuated, thin-walled diaphragm capsule made of a copper-beryllium alloy. As the pressure drops, the capsule diaphragm expands. 

The standard in sphygmomanometers uses a column of mercury, exactly as a mercury barometer does. It requires a separate stethoscope and a trained ear for proper operation. Another type of device is called an aneroid sphygmomanometer, which uses an analog gauge that is calibrated against a mercury column. 

In many cases a Fortin-type barometer (Fig. M-13) is suitable. In this case the merexuy in the well is exposed to the atmosphere with the other end evacuated and sealed. All barometer readings shotdd be corrected for temperature, local gravity, and capiUary effect. Atmospheric pressure can also be measured by an aneroid barometer, which is a special type of elastic gauge. It is sometimes used in place of a manometer-type barometer because of the ease of transportation. 

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