METHOD OF AND APPARATUS FOR GAS PRESSURE MEASUREMENT BY THE GAS-FRICTION PRINCIPLE

摘要

For measurement of gas pressure a gas-friction vacuum meter is used in whose measuring head a rotating body is suspended in a magnetic field contact-free between electromagnetic drive coils. The rotating body is set in motion with the aid of the drive coils and maintained at a rotational speed above a preset minimum rotational speed. The speed reduction of the rotating body occurring on account of gas friction is continually or intermittently balanced with current flows from a three-phase generator to the drive coils. In the measuring head rotational speed sensors are arranged and positioned, which detect and respond to the rotational frequency of the rotating body, and further transmit output signals to an electronic analyzer unit, which determines the pressure from the timely change of the rotation frequency. In order to increase the pressure range for which the apparatus may be accurately used further, the analyzer unit receives a temperature signal, which correlates with the temperature of the gas surrounding the rotational body, in such a way, that the pressure measurement is corrected for the influence of heat transferred to the gas during operation of the rotating body.