GAS METER — the device for measurement of volume of the gas passed through it.
In G.'s medicine of page apply generally to a respiration volumetry at an anesthesia (see. Inhalation anesthesia ) and artificial ventilation of the lungs (see. Artificial respiration , artificial ventilation of the lungs), is more rare at functional researches of lungs in the course of the independent breath inspected for measurement vital capacity of lungs (see) or separately each of the volumes making it (respiratory and reserve), and also the volume of the exhaled air for a certain time term. G.'s testimonies are usually expressed to page in units volume. By the principle of action of G. of page divide on volume and high-speed.
Volume gas counter and. Volume G.'s action by the village is based on summing of separate doses, equal on volume, of the gas passing through it, to-rye serially fill tight cameras (camera) of the counter and are forced out from them owing to a difference of pressure before passing via the counter. Pages in turn share volume G. on drum and with bellows.
Drum G. of page (a water, or «wet», wet gas meter — fig.) consists of the case, the reel with blades and the calculating mechanism. The drum is placed in the case on a horizontal axis. The case is filled in with water to a certain level (higher than an axis). Blades of a drum, wall of the case and a water surface (liquid seal) form measuring (measured) cameras. At the provision of a drum shown in the drawing, gas comes to cameras A and B, and the camera G is connected to an output pipe (union). As pressure of gas on an entrance to the counter and in cameras A and B is more, than at the exit and in the camera G, the drum is rotated clockwise. When the cut and is blocked by water, the cut and' acts from it, the camera G is filled with water, and gas is forced out via the union. Further the camera B is filled with gas, and from the camera A gas is forced out. Cameras have identical volume, and at a fixed level of water quantity of turns of a drum in direct ratio to the volume of the page of gas which passed through G. The Otschetny device of drum G. of page represents a scale with an arrow and the roller index or several scales with shooters. Counters are supplied with thermometers for measurement of water temperature and incoming gas, the manometer for measurement of excessive pressure in front of the counter, devices providing the set water line in the counter. According to measurement of temperature of gas and water, and also pressure the amendment to G.'s testimonies of page is entered. Drum G. are expected by page a gas rate of 5 — 100 l/min; resistance to an air flow (resistance to an exhalation) at lung ventilation of 8 l/min — 5 — 6 mm w.g.; relative error no more than +1%. Drum G. page have the increased accuracy, but are inconvenient in operation (demand constant overseeing by the water line, frequent change it, have rather big sizes and weight) therefore they are used by hl. obr. in vitro.
Of page with bellows (a dry wet gas meter) are less exact in comparison with drum (relative error of ±2%), but are more easy-to-work. One or two furs placed in the case form with its walls and partitions measuring cameras (respectively two or four). Distribution of gas is made by zolotniks or valves, to-rye are put in action by mobile walls of bellows. G. of page with two measuring bellows and zolotnik distribution of gas are more eurysynusic. To one cycle of operation of the counter, i.e. a certain volume of the gas which passed through the counter there corresponds one turn of a shaft of the zolotnik device. The calculating mechanism connected with shaft sums up volumes. The Otschetny device represents the roller index or a scale with an arrow or several scales with shooters. A gas rate for G. of page with bellows in the same limits, as for drum G. of page. Resistance to an air flow at lung ventilation of 8 l/min — 7 — 8 mm w.g. Counters are supplied with the thermometer and the manometer for measurement of temperature and pressure of the gas coming to them for the purpose of amending indications.
Of page with bellows are used both in the narcotic and respiratory equipment, and at functional researches of lungs in the course of the independent breath inspected. In the latter case G. of page joins to inspected via the valve of an exhalation, a respiratory hose and a mask. Pages apply volume G. also to measurement of the air volume exhaled previously in the rubberized bag. Inspected during the certain time term measured by a stop watch exhales air in a bag through a mask with a respiratory hose and the valve of an exhalation. Then air is passed through G. by pages. The received results use for calculation of minute ventilation of the lungs (see. Lung ventilation); if in the course of exhalation of air in a bag the respiration rate is defined, then on the exhaled volume of gas and a respiration rate calculate respiratory volume.
High-speed gas meters (rotor and vane). The rotor or krylchatka are installed in the case with a gap and connected with the calculating mechanism. With a constant speed of a flow each turn of a rotor (krylchatka) corresponds to a certain volume of the gas which passed through the counter. The calculating mechanism sums up quantity of turns, and the otschetny device shows the bulk volume of gas. The Otschetny device of high-speed G. of page represents one or several scales with shooters. These counters are, as a rule, expected a gas rate from 6 to 30 l/min. Resistance to an air flow at ventilation of 8 l/min — no more than 3 — 5 mm w.g.
High-speed G. of page are less exact in comparison with volume owing to an overflowing of gas in a gap and influences of change of rate of volume flow of gas in the course of breath on the speed of rotation of a rotor (krylchatka). However they have the smaller sizes and weight, simpler and are more reliable and therefore are applied both in the narcotic and respiratory equipment, and at a research of function of external respiration. For measurement of vital capacity of lungs the vane counter LTDP (lung-tester dry portable) released by the domestic industry is used. Relative error of the counter no more than ±8%, weight is 0,15 kg. High-speed G. apply the pages added with the converter of range of speeds of a rotor (krylchatka) in an electric signal or a radio signal in systems of remote (telemetric) measurement of lung ventilation.
Bibliogr. Pavlovsky A. N. Measurement of an expense and amount of liquids, gas and steam. M, 1967, bibliogr.
N. S. Mironova, L. I. Nemerovsky.