Manometers — devices for measurement of pressure of gases and liquids. Manometers are divided by a way of measurement of pressure on liquid, mechanical, electric and ionization.
Manometers differential and spring: 1 — a spiral spring; 2 — a tooth gearing; 3 — the closed end of a spring; 4 — the manometer tube which is reported with object in which pressure is measured; 5 — an arrow of the device.
The elementary liquid manometer is the open differential manometer (fig. , a). It represents U - shapedly curved glass tube with knees which ends have expansion in the top part. In a tube liquid is poured (mercury, water, alcohol, kerosene, etc. ) . One of knees of a tube connects to a cavity where pressure is measured. On a difference of levels of liquid in knees of a tube judge presence of pressure in the measured cavity. For convenience of measurement of pressure one of knees of a tube is graduated. Such manometers are widely used for research of a fabric exchange (the device of Warburg). Measurement of arterial pressure is performed by means of Reeve - Rochchi device (see Sfigmomanometriya) which basis the principle of the liquid manometer is. Liquid manometers are used to determination of pressure within 103 — 100 mm of mercury. In mechanical manometers (fig. , b) (membrane, spring) uses property of an elastic body to be deformed at change of the enclosed pressure. The barometer belongs to such devices (see) by means of which atmospheric pressure is measured. Measurement of pressure in the rarefied space is performed by means of the vacuum gage. Mechanical manometers apply to measurement of pressure within 106 — 100 mm hg.
In electric manometers the devices measuring fluctuations of tension, current, inductance, etc. depending on the enclosed pressure are used. They are used for measurement of pressure within 108 — 10 - 4 mm of mercury.
Pressure indicator ionization manometers is the ionic current proportional to gas density in the measured system. Ionization manometers are used to measurement of pressure of gases within 10 - 3 — 10 - 7 mm of mercury.
In hygienic practice manometers are used at determination of draft in air ducts and flues, in all works connected with measurement of pressure. In clinical trials manometers are used to measurement of pressure in vessels, cavities, etc.
