Study on New Method for Measurement of Internal Pressure of Vacuum Interrupters

In this paper a new method is presented for measuring internal pressure of vacuum tubes, without using magnetic fields but using decay velocity of emission current. Firstly, 500muA emission current is used to bombard the surfaces of contacts, which removes superfluous adsorbed layers of molecules from contacts surfaces. Secondly, 35muA emission current is used to ionize the residual gas, which yields ion current. The ion current strikes the surfaces of contacts, adsorbs and then becomes new added layers of molecules, which enlarges the work function of contacts material and reduces the emission current. The decay velocity (=Deltaj_thetas/Deltat, where Deltaj_thetas decay amount, Deltat decay time) of emission current is varied with internal pressure of vacuum tubes. So with certain Deltaj_thetas, internal pressure can be determined by measuring Deltat. The relationship of internal pressure with Deltat is deduced in theory and validated by experiment