What is the device used to measure a potential difference in a circuit called?

Hint :The voltage or the electric potential difference or the electric pressure or the electric tension of the charge is measured in the volts. It is well-defined as the work done per unit of charge to move the charge between the two points.

Complete Step By Step Answer:
In the international system and standards of units, the derived unit for the voltage or the potential difference is named as the volt and it is denoted by v. The unit for the electric potential difference is named as the volt in the honor of the Italian physicist Alessandro Volta, who invented the voltaic pile.
In other simple words, the electric potential of the charge is well-defined as the work required for moving the unit positive charges from infinity to the given point.
$V = \dfrac{W}{Q}$
One volt can be demarcated as the energy consumption of one joule per electric charge of the one coulomb.
The voltmeter is the device used to measure the potential difference in the circuit.
A voltmeter is an instrument used for measuring the electric potential and is denoted by the letter “V” in the circle.

Note :
Remember that voltmeter does not always give an accurate reading but it is generally suitable for the approximate calculations. The inaccurate readings are due to the high internal resistance of the instrument which causes error in the measurement. Know the difference between the voltmeter and ammeter symbols and apply it accordingly. Ammeter is signified by the letter A in the circle and they are used to measure either direct or the alternating current.