The crystal oscillator has complex structure and design, and it is a very fragile component. When it does not work properly, it will affect the whole circuit. It is particularly important to learn how to test the crystal oscillator. Next, let's understand it~

  Three simple methods for testing crystal oscillator
  1. Oscilloscope detection method

 The crystal oscillator will generate sine wave during excitation. It is appropriate to check the waveform representing sine wave on the clock pin. If the clock does not work properly, replace the crystal oscillator.

   When the display came in, there was no high-voltage symptom. It was found that the waveform was very unstable by checking the crystal with an oscilloscope. Replacing the microprocessor solved the problem of no high-voltage, and the crystal oscillator waveform showed a perfect sine wave.

 2. Frequency counter detection method

  The measurement must be carried out when the equipment power is "on". Place the probe of the instrument or frequency counter on the crystal oscillator pin and read the measured value. Ensure that the range of the frequency counter table used is higher than the crystal oscillator frequency being checked.

   If the crystal oscillator is 8 MHz, the instrument used should have a range capable of checking this frequency. Assuming that the reading of the crystal oscillator is 2.5 MHz, it can be known that the crystal oscillator cannot work normally and needs to be replaced. Ordinary digital multimeter usually has a small inspection frequency range.

   3. Test circuit detection method

   Display devices can display characters and symbols, and are widely used in electronic equipment. LED (light emitting diode) nixie tube and liquid crystal display are the most widely used display devices.   
Typically, the crystal oscillator is placed in the feedback network of the transistor. If it oscillates and the LED lights up, it means that the crystal oscillator is running. If the crystal oscillator does not work, the LED will go out. Other expensive crystal oscillator testers do not use LEDs as indicators, but use panel instruments to indicate whether the crystal oscillator is working normally.

    Testing crystal oscillators is not an easy task. There are many ways to check. Only practical and effective methods can achieve twice the result with half the effort.