An Infrared Gas Microflowmeter

Abstract

A new principle of measuring a gas flow rate from the emittance of the surface of the heat-sensitive element heated to a high (∼1270 K) temperature is described. It is shown that the transfer to the high-temperature region ensures independence of gas flowmeter readings on the temperature of both the incoming gas flow and external environment and that the use of a two-chamber design ensures independence of flowmeter readings on its orientation. The flowmeter does not include control and amplifying circuits. The relative error is ∼0.5% and does not exceed ∼0.2% at the flow orificing. The sensitivity of the flowmeter varies from 1.9 to 1.0 V/(mg s−1) in a 0-to 8-mg/s range. The time constant is not worse than ∼0.5–0.6 s at a 50% flow rate variation, and that of the orifice flowmeter is ∼0.2–0.3 s.