What are voltmeters used for?

A voltmeter is an instrument which is used to measure the voltage across two terminals in a circuit. It is measured commonly in volts, millivolts, or kilovolts.

A voltmeter is used to check the input and output voltage of various equipment such as motors, batteries, medical equipment, electrical panel boards, plastic machinery, electronic devices, etc. It is connected in parallel to the circuit for which voltage is to be measured.