METHOD OF DETERMINATION OF GAS PRESSURE AND DEVICE FOR ITS IMPLEMENTATION Russian patent published in 1996 - IPC

FIELD: method is intended for determination of pressure of rarefied gases with the help of thermocouples. SUBSTANCE: thermojunction is placed into gas atmosphere, constant current is passed through it, emf is measured and is used to find pressure. In this case first electrodes of thermocouple are deenergized, compensating voltage of opposite polarity is input in series with thermocouple, compensated voltage is adjusted till zero difference of compared voltages is obtained. Constant current is passed through electrodes of thermocouple in direction which causes cooling of thermojunction. Current is smoothly increased to obtain maximum value of difference voltage and first value of difference voltage is measured. Then direction of current is changed to opposite one. Device for implementation of method incorporates measurement bottle joined to space of gas volume where two electrodes made of different materials, their midparts being in electric contact and forming common junction, source of constant voltage, millivoltmeter, two slide-wires, low resistance resistor, operational amplifier and two two-pole switches are located. Like inputs of switches are connected to outputs of first slide-wire via mobile contact, unlike inputs are interconnected. Outputs of switches are connected to input terminals of electrodes which output terminals are linked via low-resistance resistor to forward and inverse inputs of operational amplifier to which output millivoltmeter is connected. Terminals of low-resistance resistor are coupled to output of second slide-wire via mobile contact. Inputs of first and second slide-wires are connected to output of source of constant voltage. EFFECT: provision for increased accuracy due to exclusion of influence of instability of current passed through junction and of instability of temperature of junction and free ends of thermocouple. 2 cl, 1 dwg