Numerical display control circuit for digital voltmeter - prevents too rapid display changes by monitoring input voltage change rate

摘要

A control circuit for digital mulivoltmeters, pH meters and the like, prevents the least significant digit displays changing tooraidly by monitoring the rate of change of the input voltage. An input voltage is monitored by a suitable digital voltmeter which drives, typically a four digit decimal display. The two least significant digits of this display may be inhibited by two transistors. These are driven by two sets of threshold circuits, appropriately scaled and consisting of linear amplifiers. These in turn are driven by a differentiating linear amplifier of which the output is the differential coefficient of the input voltage. If the input voltage changes more rapidly than the threshold voltages permit, the one or two least significant display digits, as appropriate, are then prevented from changing.