My answer to Where I should connect voltmeter?
Answer by Shaunak Agastya Vyas:
Whether it’s a DC voltage or a single phase AC Voltage, there are always two pins in between the voltage can be checked.
AC voltage doen’t require polarity to be taken into account. DC voltage has polarity aspect. But don’t worry. Even if you connect the pins inverted, the voltage will still be showed but the value will be inverted.