GB1218464A - Improvements in or relating to digital readout apparatus - Google Patents

Abstract

1,218,464. A/D converters. ETHER Ltd. 9 May, 1969 [10 May, 1968], No. 22378/68. Heading G4H. In an analogue/digital converter of the type in which the analogue input is derived from a transducer with a known non-linear characteristic, the analogue signal at input 41 is compared with a reference signal from a voltage generator 25, clock pulses being accumulated in a counter 27, 28, 29, 30 until the signals are equal, the voltage generator 25 being controlled by the counter so that its output signal compensates for the non-linearity of the signal to be digitized. In the embodiment described, the unknown analogue signal is fed to an amplifier 44 via relay contacts 42a, 42b, 43a, 43b, positioned in accordance with the polarity of the input so that the input to comparator 40 is of constant polarity, the polarity bit being displayed (51). The binary coded decimal counter outputs are decoded into decimal form and displayed on number tubes. The two highest decades of the counter 29, 30, the latter only having two states, are connected to logic circuitry (Fig. 5) so that at predetermined counts transistors 76-80 are rendered conductive to connect associated resistances 51-75 to voltage generator 25. The voltage generator includes a capacitor 62 charged by pulses at input 58 applied to the base of a transistor 57, the resistors 71-75 being connected between the collector of the transistor 57 and earth to reduce the voltage change produced at the collector as the transistor is rendered conductive and non- conductive.