GB632378A - Electron multiplier tube circuits - Google Patents

Abstract

632,378. Current and voltage measurements by vacuum or low-pressure discharge apparatus. GENERAL ANILINE & FILM CORPORATION. Dec. 6, 1946, No. 36166. Convention date, Feb. 15. [Class 37] [Also in Groups XL (b) and XL (c)] An electronic measuring circuit comprising an electron multiplier tube including an anode, a cathode, and intermediate multiplier electrodes on which potentials are impressed is provided with voltage stabilizing means in circuit with the multiplier anode and the next adjacent multiplier electrode in order to maintain the potential between them substantially constant irrespective of variations in the anode current. In the arrangement shown a light source 15 is arranged to direct light upon the cathode 16 of a photomultiplier tube 20, which also includes an anode 25, an adjacent intermediate electrode 30, and eight other intermediate electrodes 17. The operating potentials applied to the cathode 16, anode 25, and intermediate electrodes 17, 30 are obtained from a voltage dividing resistor 35 having one end 21 connected to the negative terminal 22 of a constant potential source. The anode 25 is connected to the positive terminal 24 of the potentiometer 35 through the input circuit' of a pentode amplifier 40. The intermediate electrode 30 is connected directly to the terminal 24, the intermediate electrodes 17 being connected to tappings on the potentiometer 35. The anode 25 is connected to the control grid 27 of the pentode 40, a grid biassing resistor 28 being connected to the positive terminal 32 of a battery 33. The screen grid 34 also is connected to the terminal 32, and the anode 36 of the pentode 40 is connected to the positive terminal 23 of the constant potential source. The potential between the anode 25 and electrode 30 is controlled by constant potential means comprising a gaseous discharge tube 45 in series with a resistor 38, the voltage drop across the tube being about 55 volts and independent of the current through the tube. An indicating meter 50 is connected across the resistor 38 and is also supplied with a bucking current from a portion of the battery 33 through a resistor 42. The density of a sample 13 may be measured by placing it in the path of the light from the source 15, the density being a logarithmic function of the light transmitted. With the arrangement shown, the meter 50 provides direct readings of density on a uniformly graduated scale. The discharge tube 45 may be replaced by a constant potential battery. Specification 624,313 is referred to.