How to judge the quality of a crystal oscillator?

Crystal oscillator (referred to as "crystal oscillator") is a frequency component that uses the piezoelectric effect of quartz crystal to generate high-precision frequency, providing a reference frequency signal for the system. It is mainly used for wireless data transmission and clock. Crystal oscillator damage can cause clock failure, and the quality of the crystal oscillator directly affects the performance of the entire circuit. Let's learn how to judge the quality of a crystal oscillator.

1. Appearance inspection: Use a magnifying glass to examine the appearance of the crystal oscillator and observe for cracks or other physical damage signs. If the surface of the crystal oscillator is damaged, it may indicate that the crystal oscillator has been damaged or failed.

2. Gently shake the crystal oscillator close to the ear. If you can hear the sound, it usually means that the crystal oscillator is damaged. Even if it can still vibrate, the frequency may change, which may affect the normal operation of the device.

3. Measure with a multimeter (using the Hz range of the multimeter), connect the probes to the lead angles of the crystal oscillator, and observe whether there are readings. A normal working crystal oscillator should display a stable frequency value. If there is no reading or the reading is unstable, it may indicate that there is a problem with the crystal oscillator.

4. Measure with an oscilloscope, connect the probe of the oscilloscope to the pin of the crystal oscillator, observe the display of the oscilloscope. A normal working crystal oscillator should display a stable waveform, and the frequency should match the nominal frequency of the crystal oscillator. If the oscilloscope displays an unstable waveform or the frequency deviates from the nominal value, then the crystal oscillator may have a fault.

5. Measurement of resistance method: Use a multimeter (R × 10k range) to measure the forward and reverse resistance values of the active crystal oscillator. Under normal circumstances, they should be ∞ (infinity), indicating that the crystal oscillator has no short circuit or leakage. If the active crystal oscillator has a certain resistance value or is 0, it indicates that the active crystal oscillator has leaked or been damaged due to breakdown.

6. Measurement capacitance method: Use a digital capacitance meter (or the capacitance range of a digital multimeter) to measure the capacitance of an active crystal oscillator, which can roughly determine whether the active crystal oscillator has changed value. If the measured capacity of the active crystal oscillator is greater than the approximate value or has no capacity, it can be determined that the active crystal oscillator has changed value or is open circuit damaged.

7. Testing circuit: A testing circuit composed of transistors and related external components can also be used to check whether the active crystal oscillator is intact. If the active crystal oscillator is connected to the circuit and the circuit can start oscillating and the LED indicator light flashes, it indicates that the active crystal oscillator has good performance; If the circuit does not vibrate and the LED indicator light does not light up, it indicates that the active crystal oscillator is damaged.

8. Testing with a frequency meter: Connect the frequency meter to both ends of the crystal oscillator and observe the frequency value output by the frequency meter. If the frequency value is the same as the rated frequency of the crystal oscillator, the crystal oscillator is working normally. If the frequency value is different from the rated frequency, there may be a fault in the crystal oscillator.

9. Check the voltage of the crystal oscillator: Determine the quality of the crystal oscillator by checking its voltage. Generally speaking, the voltage of the crystal oscillator should be within the nominal voltage range and have minimal voltage fluctuations. If the voltage of the crystal oscillator exceeds the nominal voltage range or fluctuates greatly, it indicates that there may be a problem with the crystal oscillator.

10. Using replacement method: You can replace the faulty crystal oscillator with a new one and observe the performance of the circuit board. If the circuit board is working properly, the original crystal oscillator may have a malfunction.

It should be noted that the above methods can only preliminarily determine the quality of the crystal oscillator, and cannot guarantee the quality of the crystal oscillator 100%. If you suspect that there is a problem with the crystal oscillator, you can choose a higher precision instrument or consult a professional for testing.

That's all for today's sharing, thank you for reading! The next episode will be even more exciting!