This circuit with a bargraph scale was found in a 90s Popular Electronics. The circuit measures the intensity of a sound in three scales. R14 works as a sensitivity adjustment.
This circuit is from a publication from the 70s, but it can be assembled with any diac and a Triac...
This circuit was obtained in a 1983 publication. It is a 1-transistor voltmeter, capable of...
This circuit from Radio Electronics magazine, March 1994 edition uses two LM388 bridged, providing a 4...