GB1222142A - An analogue-digital converter with automatic correction of its recoding factor - Google Patents

Abstract

1,222,142. Selective signalling. LICENTIA PATENT - VERWALTUNGS G.m.b.H. 21 June, 1968 [23 June, 1967; 8 Sept., 1967], No.29811/68. Heading G4H. In a circuit in which a voltage, for example from a temperature sensitive resistor RÁ Fig. 2, is digitized by amplifying 7 the voltage, converting 8 into a corresponding frequency, and counting 12 the cycles thereof for a known period, the counting period is determined by a " zero point " number 11 and "time " number 16, whereby the final count can be made to be zero for 0 degrees and 10,000 for 100 degrees, for example, and means 4, 5 are provided for periodically entering reference voltages corresponding to 0 degrees and to 100 degrees during periodic calibrating intervals whereby the stored numbers can be checked and corrected. In normal operation, initially the complements of the stored " zero point " and " time " numbers are transferred into zero point 10 and time 15 counters respectively. A gate 9 is then opened and cycles of the unknown frequency pass to the zero point counter 10. When this counter becomes full, cycles then pass to the main measuring counter 12, and this continues until the time counter 15 has become full of clock-pulses. During a calibrating period first the 100 degrees voltage is entered, and a cycle, as outlined above commences. If the stored numbers are correct then the main counter and the time counter should become full simultaneously. If one becomes full before the other, one of two gates 13, 14 is opened allowing low frequency clock pulses to increase or decrease the stored " time " number 16, until both have become full. The " time " number having been corrected, the 0 degree voltage is applied and the " zero point " number is corrected. To effect this, cycles of the corresponding frequency are counted in the zero point counter 10 for the entire period determined by the time counter 15, and the result is taken as the new zero point number.