This circuit has an accuracy of 1%. The components used must be precision as well. The input frequency range is 40 Hz to 10 kHz with the indicated components.
Other CMOS gates can be used in this sensor, which we found in the July 1995 Electronic Now...
This circuit is from the American magazine that no longer exists Science & Electronics,...
Using the 4046 PLL we found this circuit in the December 1989 Radio Electronics. The circuit...