Megger mit300 insulation testers megger mit330 de the megger mit330 insulation tester features a comprehensive safety system which warns the operator or inhibits testing in unsafe conditions when connected to a live circuit gt25v acdc the instrument warns the users when connected to gt50v acdc the instrument will inhibit testing to avoid damage or injury it has a large clear backlit lcd which shows the digital reading plus a simulated analog pointer which is useful for watching dyn