Manometers - devices for measurement of pressure of gases and liquids. By the method of measurement of pressure gauges are divided into liquid, mechanical, electrical and ionization.

Pressure differential (a) and spring (b): 1 - coiled spring; 2 - gear; 3 - the closed end of the spring; 4 - tube manometer, soamsawali with the object in which the measured pressure; 5 - arrow of the device.

The simplest liquid manometer is an open differential pressure gauge (Fig., a). It is a U-shaped bent glass tube with the knees, the ends of which have the extension in the upper part. Inside the tube is filled with a liquid (mercury, water, alcohol, kerosene and other). One of the tribes of the tube is connected with the cavity where the measured pressure. On a difference of liquid levels in the knees tube judge available pressure measured in the cavity. For the convenience of pressure measurement one of the tribes of the tube can be graded. Such gauges is widely used for the investigation of tissue exchange (Warburg). Blood pressure measurement is made by means of apparatus Riva rocci (see Sphygmomanometry), based on the principle of liquid manometer. Liquid pressure gauges are used to determine the pressure within 103-100 mm RT. senior In mechanical gauges (Fig., b) (diaphragm, spring) used the property of elastic bodies deformed at change of pressure being applied. These devices include barometer (see), which is measured atmospheric pressure. Pressure measurement in the rarefied space is performed with the help of vacuum gauge. Mechanical pressure gauges are used to measure the pressure within 106-100 mm RT. Art.
Electrical gauges are used device that measures voltage, current, inductance, etc. depending on the applied pressure. They are used to measure the pressure within 108-10-4 mm RT. Art.
An indicator of the pressure ionization gauges ion current is proportional to the density of the gas in the measuring system. Ionization gauges are used for pressure measurement of gases within 10-3-10-7 mm RT. Art.
In practice gauges used in determining the thrust in the air ducts and chimneys, all work related to pressure measurement. In clinical studies pressure gauges are used for measuring the pressure in blood vessels, cavities and other