Temperature compensated Pirani type apparatus for heat loss gas pressure measurement

摘要

A heat loss gauge 60 for measuring gas pressure (vacuum pressure) in an environment includes a resistive sensing element 12 and a resistive compensating element 14. The resistive compensating element 14 is in circuit with the sensing element and has temperature response and physical characteristics substantially matching those of the sensing element and is exposed to a substantially matching environment. An electrical source 61 is connected to the sensing and compensating elements for applying current through the elements. The currents have a defined ratio with the current through the sensing element being substantially greater than the current through the compensating element. Measuring circuitry is connected to the sensing element and the compensating element for determining gas pressure in the environments to which the elements are exposed based on the electrical response of the sensing element and the compensating element.