| 摘要 |
974,499. Analogue to digital converters. TELEFONAKTIEBOLAGET L.M. ERICSSON. Aug. 23, 1961 [Aug. 23, 1960] No. 30473/61. Heading G4H. [Also in Division H3] A plurality of bi-stable circuits (see Division H3) are used in a digital voltmeter. The voltage EA to be measured is applied to one input of a voltage comparator DD together with a reference voltage ER having a value equal to half the maximum value measurable by the circuit. In the presence of a start voltage applied at terminal A of stage A 1 a synchronising pulse applied at the terminal B of stage A 1 will open the gate G1 and switch over a bi-stable circuit V1. In the absence of a further input to the circuit this will change the previously zero voltage at point Y to a value such that the voltage to be measured is increased by an amount equal to the reference voltage. If however the reference voltage was less than the voltage to be measured the comparator DD will apply a voltage to the bi-stable circuit V2 coincident with the synchronizing pulse so that the latter bi-stable circuit also changes over and the voltage applied at terminal Y is such that the reference voltage is subtracted from the voltage to be measured. The operation of bi-stable circuit V1 applies an enabling voltage to gate G1 of stage A 2 so that the next synchronizing pulse at B, in response to a comparison of the reference voltage with the modified voltage to be measured, applies at terminal Y of stage A 2 a voltage such that at the output of network N the voltage to be measured is effectively increased or decreased by an amount equal to half the reference voltage The process of comparison and addition or subtraction from the value to be measured continues along the stages. The circuit can be arranged to give a serial or parallel indication of the digital value of the analogue voltage. Fig. 1 (not shown) illustrates a circuit suitable for unit A 1 A 2 etc. in which bistable circuit V 1 comprises cross coupled similar transistors and bi-stable circuit V 2 comprises two complementary transistors. |
