Voltcraft ms 410 magnetic field tester voltcraft ms 410 p the voltcraft ms 410 magnetic field tester is intended for detecting constant and alternating magnetic fields the tester is ideal for testing the functioning of inductors carrying currents such as relays magnetic valves etc p p the tester works with any contacts and therefore it is normally not necessary to open the casing when a magnetic field is detected the test tip starts to flash a permanent test magnet to test the