Convection thermocouple vacuum gauge

摘要

A thermocouple vacuum gauge includes a first thermocouple element spaced below a second thermocouple element. The two thermocouple elements are electrically connected in series in a back-to-back manner by connecting together their respective negative ends. A pulse generator supplies a pulsing on-off current only to the first thermocouple element. During the off intervals, a switch connects the positive ends of both thermocouple elements to a voltage measuring and comparing circuit which measures a thermally generated voltage signal between the positive ends of the thermocouple elements and compares the measured voltage signal to a reference signal. The result of the comparison is used to vary the output current of the pulse generator so as to supply an amount of current to the first thermocouple element sufficient to cause the measured voltage signal to approach the reference signal. The amount of current supplied sufficient to cause the measured voltage signal to approach the reference signal is proportional to the amount of pressure or vacuum in an enclosure in which the thermocouples of the vacuum gauge are placed. A method for measuring pressure at partial vacuum which employs these features is also described.