This is a design circuit for measure inductance of the inductor labeled LX which is the inductance to be measured. The o/p of the circuit is a TTL square wave whose frequency relates to the inductance being measured. The inductance meter adapter output is connected to a frequency meter and the inductance is calculated from the frequency. This is the figure of the circuit;
The center operate of the circuit is the buffer colpitts oscillator(the first stage) which resonates with the unknown inductance to give a Sine wave of a particular frequency . The frequency of the sine wave is a function of the unknown inductance and the four 1000pF capacitors. The output sine wave is amplified by the second transistor and is then rectified by the capacitor and diode combination that follows. The rectified sine wave now having only positive excursions is buffered by the third transistor and is then fed to the 74ls393. Counter IC which is configured as a divide by 256 counter. The output of the IC pin 6 and ground is connected to the frequency meter.
The parts:
The 7805 regulator powers the IC and the last 2 transistors
The circuit operates from a 9V battery which also feeds the regulator
The Ic consists of two counters in one package of 14 pins hence you need just one.
PIN 14 is VCC and PIN 7 is ground
The ic is TTl IC
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