Frequency Comparator Draws 8 ?A: 03/03/97  EDN-Design Ideas 

Frequency Comparator has Status Output: 12/26/02 EDN-Design Ideas  / The original application for the circuit was to check the number of revolutions of an engine with only one LED as an indicator. The measurement of the number of revolutions usually involves sensors with a frequency output proportional to the number of revolutions.

Frequency Divider Adapts to I / O Conditions: 09/29/94 EDN-Design Ideas 

Frequency Window Comparator has hysteresis: 11/07/96  EDN-Design Ideas 

Low Flow Rate Thermal Flowmeter:

Make a Simple PCbased Frequency Meter: 04/29/99 EDN-Design Ideas  / PDF contains multiple circuits - scroll to find this circuit