GB1200773A - Improvements in analogue to time-interval converters - Google Patents

Abstract

1,200,773. Analogue/digital converters. SOLARTRON ELECTRIC GROUP Ltd. 11 Oct., 1968 [25 Oct., 1967], No. 48587/67. Heading G4H. An analogue/digital converter includes an integrator integrating the unknown signal and a reference signal -V R , two comparators 12, 13 (Fig. 1), comparing the output V 0 of the integrator with signals V 1 , V 2 at least one of which V 2 is variable with time, and a bi-stable device 17 controlled by the comparators and switched to its first state when V 0 = V 1 and to its second state when V 0 = V 2 to apply the reference signal -V R to the integrator and to enable a gate 18 to pass clock pulses to a counter. The unknown signal V u is continuously applied to the integrator. The count may be displayed. In one embodiment (Fig. 2) the signal V 1 = 0 and the signal V 2 is a linearly increasing sawtooth signal of period T, the output V 0 of the integrator decreasing until V 0 = V 2 when the bi-stable is switched to enable the gate 18 and to apply the signal -V R to the integrator to cause the signal V 0 to increase until V 1 = 0 when the bi-stable is switched again. This process is repeated for one period T. In another embodiment V 1 is also a linearly increasing sawtooth signal of period T (Fig. 3, not shown), V 1 being of smaller amplitude then V 2 . In a third embodiment V 1 is fixed and V 2 is a linearly decreasing signal, the time interval when -V R is connected being then counted. The sawtooth waveforms could be replaced by staircase signals and the reference signal by a pulse train. To measure bi-polar inputs two sets of comparators 12, 13 are used each associated with a bi-stable, the bi-stables controlling a single counter and the polarity being indicated by that bi-stable which switches to its second state.