GB820244A - Improvements in or relating to pulse filter circuits - Google Patents

Abstract

820,244. Electric tests. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. May 28, 1958 [June 13, 1957], No. 18694/57. Class 37. [Also in Group XL (c)] In a derivative type pulse polaragraph the slowly changing D.C. level is removed from the pulse waveform by a circuit comprising a D.C. amplifier having a feed-back loop which is rendered inoperative during the pulses but maintains the D.C. voltage fed back substantially the same as that which would have been fed back in the absence of the pulse. A polaragraph cell PC having a dropping mercury electrode 2 is connected to the input of the amplifier and supplied with a polarizing voltage of the form shown in Fig. 1 (a). The resulting current through the cell comprises a desired component which occurs during the pulse and an undesired varying component which periodically returns to zero when a drop occurs. The cell is connected to an amplifier circuit V1, V2, V3 which provides an output at the cathode of V3 and also feeds a negative feedback path comprising amplifier valves V4 and V5, a switch V6, V7, V8, V9, a capacitor C1 and a Miller integrator circuit V11 which is connected to the input of valve V2. This feedback path which stabilizes the D.C. level is interrupted during the presence of the desired input pulses by applying positive and negative pulses A and B to the diode circuit. The capacitor C1 and the integrating circuit causes the current fed back to continue to change during the pulse at the same rate as immediately before the start of the pulse. It is stated that two circuits such as that shown may be cascaded if further stabilization of the D.C. component is required. The invention is applicable both to derivative type polaragraph and the normal type. The sharp current pulses occurring at the commencement of the desired pulse are eliminated if only the second half of the.pulse is utilized.