How to measure the quality of quartz crystal

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How to measure the quality of quartz crystal [Copy link]

How to measure the quality of quartz crystal

In appearance, it is neat, without cracks, the pins are firm and reliable, and the resistance value is infinite. If the resistance measured by a multimeter is very small or even close to zero, it means that the crystal being tested is leaking or breaking down and is damaged. If the measured resistance is infinite, it cannot be determined whether the crystal is damaged. The inspection method at this time is: use a test pen, insert its blade into the live wire hole of the mains, hold one leg of the transistor with your fingers, and touch the top of the test pen with the other leg. If the neon bulb is red, it generally means that the crystal is good. If the neon tube is not bright, it means that the crystal is broken.

The general method is to make an oscillation circuit, connect the crystal to be tested, and see if it can oscillate. If it can oscillate, it means the crystal is good, otherwise it is bad. A commonly used detection circuit is shown in the figure: the crystal to be tested and the field effect tube VT form an oscillator. If the crystal oscillator is good, the oscillator starts oscillating, the signal is coupled to VD1 through C1, rectified by VD2, filtered by C2, and amplified by the composite amplifier circuit to drive the LED to emit light. If the transistor is damaged, the oscillator cannot oscillate and the LED cannot emit light. The inductor L is used to prevent the oscillation signal from passing through, and can only pass direct current. Among them, LL represents the crystal to be tested.

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