09/03/2026
For quick testing of quartz crystals I came up with this simple frequency meter. From the beginning the value was not so important to me, what is important is whether the crystal works or not. I was very surprised by the results, the frequency meter works perfectly with little deviations, which is great. Otherwise the crystal meter should work from 4Mhz to 45Mhz. At 4Mhz it has problems, but higher values work perfectly. For values lower than 4Mhz I will use a cmos xtal tester. I calibrated it with a 1mhz MCXO oscillator (0.1 ppm to 0.02 ppm), which is good.
I forced my cmos xtal tester to work at a very low crystal value of 32.768khz, the frequency meter showed 32.774khz, which is excellent. I will probably use it to select 32.768kHz crystals with the smallest error, to determine the most accurate value.
The frequency meter encouraged me to look for real advantages, depending on the crystal. For 32.768kHz, the data shows that watch crystals are real "spares" in the world of electronics. Their power consumption is extremely low, usually below 1 µW (microwatt). In the data sheets, this information is written as Drive Level. For 32 kHz crystals, a typical value is 0.1 µW to 0.5 µW, while MHz crystals can handle 100 µW or more. So I increased the resistance across the oscillator to 10Mohm and minimized the current through the crystal with a 1Mhz resistor, now it works great.