This circuit was found in a Popular Electronics of the 1990s. The sensor is a rotating mechanical system with a propeller-driven magnet to count pulses with a reedswitch.
We found the configuration below, with unit gain, in the National Semiconductor Linear...
This circuit is from an Electronic Design from the 90's. The main integrated circuit is uncommon...
This circuit appears on this site from different sources. This is from documentation from the...