Multimeter measuring crystal oscillator

Multimeter measuring crystal oscillator

Tips: How to measure whether the crystal oscillator is oscillating without an oscilloscope?

You can use a multimeter to measure whether the voltage of the two pins of the crystal oscillator is half of the chip's operating voltage. For example, if the operating voltage is 5V, the measured voltage is about 2.5V. In addition, if you touch the other pin of the crystal with tweezers, the voltage changes significantly, which proves that it is oscillating.

Tips: Just connect a 1.5V battery to both ends of the crystal oscillator, put the crystal oscillator next to your ear and listen carefully. When you hear a clicking sound, it means it is oscillating, which means it is good!

Resistance method

Set the multimeter to the R×10K position, and the resistance between the two pins of the quartz crystal should be infinite. If the measured resistance is not infinite or even close to zero, it means that the crystal being tested is leaking or breaking down.

This method can only measure whether the crystal is leaking electricity. If there is a short circuit inside the crystal, the resistance method is powerless. At this time, the following method must be used

Homemade tester

According to the circuit shown in the figure, a simple quartz crystal tester can be welded to accurately test the quality of the crystal. The two test sockets XS1 and XS2 in the figure can be removed from the small seven-pin or small nine-pin electronic tube socket. It is better to choose a high-brightness LED light-emitting tube.

When testing a quartz crystal, insert the two pins of the quartz crystal into the two sockets XS1 and XS2, and press the switch SB. If the quartz crystal is good, the oscillation circuit composed of transistors VT1, C1, C2 and other components will oscillate, and the oscillation signal will be coupled to VD2 for detection through C3. The DC signal voltage after detection will turn on VT2, so the LED connected to the collector circuit of VT2 will light up, indicating that the quartz crystal being tested is good. If the LED is not on, it means that the quartz crystal being tested is bad. This tester has a wide frequency for testing quartz crystals, but the optimal operating frequency is from several hundred kilohertz to tens of megahertz.