Reciprocal Frequency Counter - July 2023 - Silicon Chip Online
This design measures low-frequency signals accurately and quickly. A traditional frequency counter must sample over a long period to get an accurate result. This one instead measures the average period and calculates the inverse, so it only needs to monitor a few pulses to get a precise reading. It’s useful up to about 10MHz. by Charles Kosina
Source: siliconchip.com.au