Introduction: For professional manufacturers, the factory testing of the crystal oscillator is to use the 250B test system of S&A Company of the United States to detect a series of parameters of the crystal oscillator. We are discussing here how the end user can use a simple instrument they own to detect a series of parameters. The crystal is good or bad:
1. It is best to use the oscilloscope or frequency meter to test whether the crystal oscillator starts. The simplest method is to use a multimeter to measure (the frequency is usually measured using a π-type network analyzer). When the general crystal oscillation occurs, the voltage of its pin is measured with the DC voltage of the multimeter. Different circuit voltages are different, generally from a few tenths of a volt to two tenths of a few volts. The voltage difference between the two legs of the crystal is 0.03V. If the difference between the two pins is too large, it may not start. In addition, if you use a tweezers to touch another foot of the crystal, this voltage changes significantly and proves to be a vibration.
2. A good quartz crystal, the appearance should be very clean, no cracks, the pin is solid and reliable, the pin resistance should be infinite. If you use a multimeter to measure the resistance is very small or zero, you can conclude that the crystal is bad, but the resistance Infinity does not completely confirm that the crystal is good. At this time, a test pencil can be inserted into the hot wire hole of the mains socket, pinching any pin of the crystal with your finger, and touching the other pin of the crystal to the top of the test pencil. In the metal part, if the electric pen is blistering, the crystal is generally good, and if it is not bright, the crystal is bad.
3. Measured with digital multimeter's capacitance block: Under normal circumstances, a good crystal has dozens of Pf's capacitance. If there are no or few measurements, it indicates that the crystal is not good.
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