This circuit is from an article that teaches how to assemble it in the magazine Electronics Now from July 1993. It uses a liquid crystal display module from the time with 3 and a half digits.
This circuit converts an AC signal into a voltage of the same peak value with precision and is...
This application is not modern since few computers have parallel ports. But you can use this...
Found in National Semiconductor documentation from the 90's this circuit uses a piezoelectric sensor....