What is a solenoid voltage tester?

 (Solenoid voltage tester) 

   Also known in the trade by the nickname "wiggies," are also multi-function testers, but they are somewhat simpler and easier to use than the battery-operated multimeters. Both analog and digital models are available. Solenoid volt meters are capable of testing for both voltage and polarity. Electricians use them frequently because they can test both AC voltage and DC voltage in a range from 100 to 600 volts. Pros often prefer this tool over the multimeter for many applications, since it is very rugged and has no batteries to monitor. It is not, however, quite as accurate as a multimeter for providing a numerical measurement of how much voltage is present. 

Solenoid testers have two wires, each with a probe, extending out of the bottom of the tester. Solenoid testers do not use batteries to power them, so they are always ready to check voltage. The announce the presence of voltage by clicking or vibrating—the louder the clicking or more pronounced the vibration, the higher the voltage level. They have a low impedance and often will trip ground-fault circuit-interrupter

devices or circuit breakers during testing.