Checking high voltage 120-240 Volts AC withcany device is dangerous! Electrical know how is a must. I've demonstrated how to check heater operation without the use of test equip. Simple observation of operations is the simplest method. I demonstrate the dificulty in measuring high voltages in cramp devices. Though the Cimbali heaters are readily accessed with cover removal. There is the potential to get shocked (electrocuted) from exposed wires while power is on.