a helium spannungsversorgungschaltung halide leak detector (see 6.4)

摘要

The invention relates to a control circuit for a leak detector embodying a 180 DEG mass spectrometer and incorporating the following circuit assemblies: a first measurement circuit for measuring and indicating the helium partial pressure; a second measurement circuit for measuring and indicating the total pressure of the gas in the pipeline and/or container system to be investigated for leaks; a transformer unit; a mains supply section for generating the supply voltages needed in the control circuit; an emission-current generating circuit for generating and controlling the emission current for the incandescent cathode of the mass spectrometer; and a circuit for generating and controlling the ion-accelerating voltages, which comprises a rectifier circuit and a voltage division circuit for generating an electron-accelerating voltage (Ie-, Ie+) to accelerate the electrons emitted from the incandescent cathode and an ion voltage for accelerating the helium ions ionised by the emitted electrons from the secondary voltage transmitted by the transformer unit. It is characterised in that the voltage-division circuit incorporates a chain of Zener diodes containing three groups (96V, 264V, 144V) which are supplied from the rectifier circuit via a constant current controller (Q4), in that the first group of Zener diodes (96V) is shunted by a first potentiometer (P1), and in that the tapping point of the first potentiometer (P1) forms the connection point for a further voltage divider formed from a second and third potentiometer (P2; P3). IMAGE