Battery Powered Frequency Meter (0 to 20kHz)

https://www.electronics-lab.com/battery-powered-frequency-meter-0-to-20khz/

The circuit is a simple digital frequency meter that is made of a frequency-to-voltage converter and an analog-to-digital display converter that can be operatedfrom a single 9-volt battery. The TC7126 ADC generates the voltage required by the TC9400 FVC with internal regulators. The TC7126 is designed to directly drive a 3-1/2 digit, non-multiplexed LCD display […]