As shown in the figure, this circuit uses a 31/2 voltmeter DVM to display the measurement results. K1 is the power switch and K2 is the range selector switch. IC1a constitutes a narrow pulse oscillator, and the oscillation frequency is fixed at about 100 Hz. IC1b constitutes a one-shot trigger delay, the trigger pulse is a fixed-cycle pulse provided by IC1a, and the one-shot delay is determined by the resistance value R selected by Cx and K2. The DVM can be either 7107 or 7106 or 14433 with CB14433. It is a three-and-a-half digit voltmeter. The full-scale input voltage can be set arbitrarily within 2V.
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