GB1435774A - Circuit arrangement for registeri - Google Patents

Abstract

1435774 Measuring voltage drops STICHTING REACTOR CENTRUM NEDERLAND 31 Aug 1973 [5 Sept 1972] 41170/73 Heading H3H A circuit for measuring the magnitude of a voltage drop of an alternating voltage comprises a plurality of threshold circuits and means for storing the states of the threshold circuits when the voltage drops below a predetermined level. The A.C. voltage is applied at 102 to bridge rectifier 3 and the full wave rectified voltage is smoothed and applied to threshold circuits 4-10 and 20, which comprise comparators with reference voltages set by potential dividers 11 set to 90, 80, 70, 60, 50, 40, 30 and 20% respectively of the nominal voltage. The outputs of comparators 4-10 are applied to circuit 15 which has an output a BCD representation of the comparator output and hence the applied voltage. The BCD values are applied to shift registers 19, 20, 21. Zero crossing of the input signal are detected by circuit 23 which triggers monostable 24 and which, after a given period triggers monostable 25 producing a lmSc. clock pulse at the pripert signal peaks. When the A.C. input is less than 90% of its nominal value, AND gate 31 is enabled and the clock pulses pass via AND gate 31, AND gate 30 and OR gate 29 to the shift input of register 19-21, thus storing the value of input voltage at successive clock intervals. If the input drops below 20% of nominal input, AND gate 26 is enabled and a clock pulse sets bi-stable 27 and shuts gate 30. Thus gates 31 and 26 only permit shift pulses to reach the register when the input is between 20 and 90% of its nominal value. When threshold circuit 4 responds to the input rising to over 90% of nominal, bi-stable 28 is set and an extra shift pulse steps the register, so that a zero is displayed. The register contents may be indicated by lamps and a separate shift register may count the number of times that the input voltage drops below its nominal value.