Improvements in and relating to digital voltmeters

1,095,695. Measuring voltages. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Nov. 1, 1965 [Nov. 4, 1964], No. 46061/65. Heading G4H. Apparatus for measuring an analogue input voltage U x comprises a comparator 1 into which is fed the voltage U x and a compensation voltage U c representative of the count in a counter 14, the output voltage from the comparator U v = U x - U c being fed via amplifiers 8, 9, 10 and threshold devices 11, 12, 13 to control the counter 14. In the form shown the difference voltage U v is fed to gate 11 having a threshold value 111 mV to pass a pulse to the most significant decade 15 of counter 14 if the voltage exceeds the threshold value. Similarly the difference voltage after an amplification by 10 at amplifier 9 is fed to gate 12 having a threshold value 110 to pass the pulse to the second decade 16 of the counter if this value is exceeded. After a further amplification by 10 the voltage is fed to gate 13 having a threshold value 50 mV to control the least significant decade 17 of the counter 14. The counter 14 controls a voltage divider 18 which feeds back to the comparator 1 the compensation voltage U c corresponding to the count attained in the counter for the process to be repeated.