Homemade digital display capacitance table ----- Digital Capacitance Meter

Keywords: digital capacitance table circuit diagram, MC14511, NE556, MC14093 Author: 玉坤 This article describes a digital display capacitance meter having a measurement range of 10pF to 99.9μF. The drawings are the circuit diagrams of this capacitance table. The IC3 used in the timing circuit used in the figure is NE556, contains two 555 timers, and the five high-precision resistors connected to S1-B are constituted into a timing circuit in the capacitor to be measured. In this way, the capacity of the capacitor is converted into a time length of the timer. When the timer outputs high, the oscillating circuit consisting of NE556 remains, so that the capacitance is converted to the oscillation of the pulse number, and then utilizes the three-digit count circuit IC1 (MC14553) to convert to three decimal values, with MC14511B. Perform seven-segment LED display. Transistors VL ~ V3 (A1015) perform digital conversion so that the capacity of the capacitor can be used as a value of three digits. If the value is above three (999), the overflow signal is sent to a trigger circuit composed of two Schmidt and non-door (MC14093B), so that the overflow signal LED is bright. In the measurement control circuit, the R0 (15 kΩ) resistor and the C0 (0.0022μF) capacitor make the reset signal of the counter ICL slightly delayed, so that the effect of the circuit and wiring capacitance can be reduced. When debugging, connect a known capacity capacitor to the measured end, and the range switch is hit on the gear corresponding to the measured capacitance, and press the detection key. If there is a difference between the capacity of the capacitor and the display value, the fine-tuning resistor Rp is adjusted, and the adjustment is repeated until the capacity and the display value are consistent. The range switch SL is selected with a 2-knife 6-bit band switch, and the scope represents the relationship between the range and the three display. If the LED is on, the LED is on, at this time, it should be manually converted to a large number of ranges. When adjusting, the detection capacitance used is more accurate, the higher the accuracy of the unit.

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