Martindale tek200 non contact voltage and magnetic field detector martindale martek200 p the martindale tel200 detects the presence and polarity of magnetic fields produced by indicators relays solenoids and transformers br the integral self test activates the sensor in the tip of the tester at 50hz as well as checking the battery and led this proves that the unit is fully functional and avoids the need for a separate proving unit p p in addition this unit incorporates all the capa