Transistor megohmmeter works - Solutions - Huaqiang

Crystal oscillator

Crystal resonator 2.5*2.0mm 2520 16MHZ (16.000MH

The transistor megger is a meter that is powered directly from a DC power source without a hand-cranked generator. The alternating voltage generated by the transistor oscillator is rectified by a transformer and voltage doubled to output a DC voltage as shown. The oscillator is a magnetically coupled multi-resonant circuit. The DC voltage Ec is divided by the resistors R1, R2 to supply the base bias voltages of the transistors V1 and V2. After Ec is turned on by S, there is always some imbalance in the symmetrical wiring. If the current of the V1 collector current, that is, the current in the transformer winding N3 is slightly larger than the current in N4, the magnetic flux is generated in the transformer core, and the magnetic flux is in N1 and N2. The induced induced electromotive force direction is such that the V1 base further becomes negative, the V2 base further becomes positive, and strong positive feedback causes V1 to turn on quickly and V2 to turn off quickly. It can be considered that Ec is added to the equivalent and N4 is equivalent to the non-pass, and the iron core is gradually magnetized. When the iron core is gradually magnetized to saturation, the magnetic flux no longer increases, the induced electromotive force disappears, the V1 base current decreases, and the core flux decreases, thus generating an induced electromotive force in the opposite direction, and strong positive feedback causes the V2 guide. Pass, V1 cutoff. As a result of this cycle, a pulse oscillation is generated to induce a high-voltage square wave AC voltage at the output of the transformer. Through the transformer boost and voltage doubler rectifier, it can generate 5000V DC high voltage with a range of up to 0-1000MΩ.