This circuit uses a heated filament as a sensor. With the air current it changes resistance, and the circuit detects it. The circuit is from a 1969 EEE.
This low drift or offset circuit is from an 80's documentation. The configuration can be made with...
This is a commercial circuit from a Japanese publication from 1972. The circuit uses a FET that...
This instrumentation amplifier was obtained from Popular Electronics in 1993. The operational...