555 capacitance tester circuit diagram
Posted on Nov 10, 2015 12160
The tester consists of an dual time base circuit 556 and a number of RC components and other components. Illustrated by the right half of the
circuit 556 (556 1/2) and R2, R3, C2, C3 and other components astable multivibrator, the oscillation frequency f = 1.44 / (R2 + 2R3) C2. Parameters correspond icon the frequency of about 60Hz or so. The left half of 556 (556 1/2) and C4, range resistors R4 ~ R8 and measured capacitance Cx constitute one-shot trigger circuit, 5 feet at the low level period of the square wave output of the right half, monostable flip, one-shot pulse width depends on the range resistors R4 ~ R8 and Cx, ie, t = 1.1 (R4 ~ R8) Cx. According to the measured capacitance Cx select a different size range. Cx different capacities, the 556 9-pin output level correspondingly different, after potentiometer RP1 connected mA current file table or multimeter. RP1 potentiometer for the correction, for full-scale calibration with standard capacitance. 556 feet of each waveform diagram shown in Fig. B. This circuit can be measured capacitance of 10pF ~ 1uF within range. Range divided 10p ~ 100p ~ 1000p ~ 0.01u ~ 0.1u ~ 1u, corresponding to the current range of 100uA ~ 0.5mA.