The step-by-step potentiometer as a digitizer

A digital potentiometer-type millivolt recorder is described in which resistances are successively paralleled by relays to modify the current in a standard resistor and hence the p.d. across it. This process progresses automatically until balance is detected, when the relay state is transferred into a store. Three separate digitizing channels are employed in series-parallel to give a speed of 25 characters per second at a tape punch, or 10 characters per second with a simultaneous typed record. Alternatively, single chosen channels can be brought out on a visual figure display. The equipment can be provided with inputs as multiples of 72 channels with a maximum sensitivity corresponding to 15 mV full scale at 200 ohms source impedance. The resolution is 1 part in 1000 of full scale. The instrument is of bench-top size and is suitable for measurements in multiple installations of resistance strain gauges, thermocouples and other transducers of similar output.