The AC magnetic field indicator, sometimes called a pump spinner tool, is used to verify the presence of a magnetic field generated by alternating current. These indicators are useful to quickly check whether a solenoid valve or PSC pump (like those used in our flow centers) are energized. Wet rotor pumps are notoriously quiet and have very little vibration, so it can be difficult to tell if they are energized or running. Placing the AC magnetic field indicator close to the pump will cause the red and white disc to spin indicating that the pump is energized. This typically means the pump is circulating fluid, but not always. The pump may have a locked rotor or broken shaft and the magnetic field will still cause the disc to spin.