With Low Price Rotation Tester And Ac Detector For Circulating Pumps Etc By Geonordic

It can also be used to detect the magnetic field produced by AC. The red and white disc spins on its axle when the tester is placed close to a sufficiently strong AC field. When placed close to a pump that is turning the disc will also rotate. Quickly indicates rotation direction Detects AC fields Detects solenoid valves