Continuous sinusoidal wave modulation of the three-grid Bayard–Alpert gauge

Abstract

A continuous sinusoidal wave (10 Hz) potential was supplied to the intermediate grid (G2) of a special three-grid Bayard–Alpert (BA) gauge. The ion collector current corresponding to the instant maximum potential of G2 was regarded as Ion and that corresponding to the instant minimum potential was regarded as Ioff. It was confirmed that this peak-to-peak value, Ion−Ioff, was equal to the difference between the two dc currents, ΔI, which was obtained by manual switching modulation. In order to reduce the effect of noise, a low-pass filter was used. Although the waveform of the signal current was deformed by the filter, the error by this deformation was negligible. Corresponding to the modulation, a considerably strong induced current flowed in the collector circuit, and to avoid the effect of this current, two methods were used in conjunction. One was phase-sensitive detection and the other was compensation. The theoretical concept and electronic circuits are shown with some experimental data.