GB1367586A - Analogue digital converter - Google Patents

Abstract

1367586 A/D converter W KRAUT [trading as BIZERBA-WERKE WILHELM KRAUT KG] E SCHULTE and O PICHL [trading as DATRON - ELECTRONIC PICHL & SCHULTE KG] 21 Dec 1972 [23 Dec 1971] 59035/72 Heading G4H A digital voltmeter comprises a constant negative voltage source 5 supplying an integrator 1, a reference voltage source 4, and a comparator 3 for comparing the output voltage of the integrator at point C with a voltage at point A which may either be the reference voltage or an unknown voltage U x , the output of the comparator being input to a control unit 8 which controls a counter 5 and a store 7 and the several switches shown. In operation, the output of the integrator is first pushed to a positive maximum by closure of switch S5 and the counter is set at +n max . Switch S4 is then closed together with S2, and switch S5 is opened and the voltage at C is compared at 3 with a voltage (- U ref ), and when the voltage at point B equals zero the controller 8 causes pulses from a generator 6 to decrement counter 5 and also closes switch S3 and opens S2 whereby the unknown voltage U x is compared with the ramp output of the integrator. If U x is <0, equality at point B occurs when the voltage at point C is >0, and this equality causes the controller 8 to cause the count at 5 to be stored at 7, which count is a measure of the voltage U x . If U x > 0 the integrator voltage falls to zero as does the count at 5, and at this point the controller causes, by means of a switch S8, the counter to count upwards. The integrator output at C continues to increase in a negative sense and when the voltage at B is equal to zero the stored 7 is activated as above, the position of the switch 8 being indicative of the sign of U x . The counter is counted up to + n max again and the voltage at C is allowed to fall to a minimum which should be equal to +U ref . At this point the switch S1 is closed and the comparison made. If any deviation is detected the constant voltage value at 2 is amended via switches S6, S7 to correct this.