capacitance meter module

12-18 — elektor december 1981 capacitance meter module The block diagram in figure 1 shows the principle of operation of the capaci- tance meter module. Three separate signals are NANDed together to produce a usable input signal for the frequency counter. The pulse diagram shows the "waveforms" present at various parts of the circuit during the actual capaci- tance/frequency conversion. The circuit contains a 4 MHz crystal oscillator which is responsible for gener- ating the required clock pulses. Let us for a capacitor to charge to a specific value to the duration of the gate pulse, the frequency counter can be supplied with a proportionate amount of pulses—. to give a direct reading of the capacitor value. The actual capacitance-to-fre- quency converter consists, quite simply, of a monostable multivibrator (monoflop). The time duration of the monoflop is determined by the values of the resistors, R (preset potentio- meters), and the capacitor under test, capacitance meter mo...