GB842924A - Improvements relating to electronic analogue digital converters - Google Patents

Abstract

842,924. Analogue-to-digital converters. METROPOLITAN-VICKERS ELECTRICAL CO. Ltd. June 20, 1958 [June 26, 1957], No. 20188/57. Class 40 (1). A voltage analogue is converted into a digital equivalent by apparatus comprising four dekatrons adapted to count incoming pulses, the cathodes being so connected to successive tappings on a resistance chain that the current through each tube produces a potential drop along the resistance chain of a value dependent on the cathode which is operative, the total drop being representative of the total count of pulses, means being provided for comparing this potential drop with the input voltage and means for stepping the tubes to achieve a balance. The four dekatrons T1, T2, T3 and T4 count in units, tens, hundreds and thousands, respectively and are connected to tapped resistors R1, R2, R3 and R4, themselves connected in series through adjustable resistors R5, R6, R7. The potential across the resistor chain appears at A and is dependent upon which of the cathodes is conducting in each dekatron, i.e. upon the count registered by the dekatrons. The voltage at A is compared in a detector amplifier with the unknown voltage which energizes an " up " or a " down " terminal according as to whether the unknown voltage exceeds or not the voltage at A. If the " up " terminal is energized " stepup " gates C are opened to allow pulses from a generator to be applied to the guides of dekatron T1 so as to step-up the value registered. Carry pulses between the dekatrons pass through the gates C to increase the value in succeeding dekatrons. If the " down " terminal is energized step-down gates AC are opened to cause the pulses from the generator to subtract from the value in the counter. In either case the addition or subtraction continues until the potential at A balances the unknown voltage and neither the " up " or " down " terminal is energized. The value registered then represents the unknown voltage. Serial mode outputs are taken from gates SU1 and SD1. The apparatus may be adapted to measure a resistance, by determining the voltage produced by passing a standard current or a current may be measured by passing it through a standard resistance.