GB850737A - Improvements in or relating to circuits for determining the characteristics of pulsetrains - Google Patents

Abstract

850,737. Electric tests. RANK CINTEL Ltd. Jan. 31, 1958 [Feb. 1, 1957], No. 3543/57. Class 37 In a circuit for measuring the peak amplitude of pulses in a pulse train, the pulses are applied with positive polarity to the control grid of a cathode follower valve 2, Fig. 1, whose output is applied via a diode 5 to charge a capacitor 6, the potential at the cathode of diode 5 being arranged to be initially substantially the same as that at the cathode of valve 2. The potential on capacitor 6 rises to the peak value of the applied pulses and is applied to a cathode follower valve 7, the change in potential at the cathode of valve 7 being an indication of the peak potential of the pulses applied at terminal I and being measured at terminal 11. To discharge the capacitor a high resistance 8 is connected between the high potential terminal of the capacitor and the junction of resistors 9, 10, forming the cathode load of valve 7. The circuit may be modified to measure the number of pulses in an applied pulse train, Fig. 2, the grid resistor 4 being connected to the junction of resistors 9, 10, instead of to the earth line. As the first pulse is applied to the grid of valve 2 the capacitor 6 receives a charge dependent upon the pulse amplitude and valve 7 passes a current proportional to the pulse amplitude, the potential at the junction of resistors 9, 10, rising proportionately. The bias potential applied to the grid of valve 2 via resistor 4 is therefore increased and by suitable choice of values for resistors 8, 9 and 10, it may be arranged that the resultant rise in potential at the cathode of valve 2 is equal to the rise in potential on capacitor 6. When a succeeding pulse is applied to the grid of valve 2, the diode 5 conducts for the full duration of the pulse and adds a charge to the capacitor 6 which is substantially equal to that added by the first pulse, the process being repeated for each pulse in the train. The potential at the cathode of valve 7 therefore gives a measure of the number of pulses in a train and may be measured by a meter 11. A switch 14 is provided to discharge the capacitor 6 before each measurement, and may be an electronic switch arranged to operate automatically.