What is a voltmeter, and how is it used?

Short Answer:

A voltmeter is an instrument used to measure the voltage (also called potential difference) between two points in an electric circuit. The voltage tells us how much energy is available to move charges through the circuit, and it is measured in volts (V). Voltmeters are available in both analog and digital forms.

To use a voltmeter correctly, it must be connected in parallel across the component or part of the circuit where voltage is to be measured. Since it is connected across two points, it must have very high internal resistance so that it does not draw current and disturb the circuit.

Detailed Explanation:

Voltmeter

A voltmeter is a basic yet essential device in electrical and electronics engineering. Its main purpose is to measure the electrical potential difference between two points in a circuit. This helps users determine if a component is receiving the correct voltage or if there is a voltage drop due to faulty connections, damaged wires, or other problems.

Voltmeters are commonly found in laboratories, households, industries, and electronic service centers. Today, most voltmeters used are digital voltmeters (DVMs) because they give quick and accurate readings with minimal effort.

How a voltmeter works

A voltmeter operates by measuring the energy difference (voltage) between two points. It is based on Ohm’s Law and uses internal circuitry to display the measured voltage. To do this accurately, a voltmeter is connected in parallel with the component or section of the circuit where voltage needs to be checked.

A parallel connection means the voltmeter is connected across the circuit element without breaking the circuit. It samples the voltage at both points without drawing current. For this reason, the voltmeter must have very high internal resistance—ideally infinite—to minimize current draw and prevent affecting the actual voltage of the circuit.

Steps to use a voltmeter

  1. Turn OFF the circuit before connecting the voltmeter (for safety).
  2. Identify the two points where you want to measure voltage.
  3. Connect the probes: the red probe to the higher potential point and the black probe to the lower one.
  4. Set the voltmeter to the correct range (AC or DC, depending on the source).
  5. Turn ON the circuit and read the voltage on the display.
  6. If the reading is out of range, switch to a higher voltage setting.

Types of voltmeters

  • Analog voltmeter: Uses a moving needle and scale to show voltage.
  • Digital voltmeter (DVM): Shows numerical values on an LCD or LED screen.
  • AC/DC voltmeters: Designed to measure either alternating or direct voltage.
  • Multimeter in voltmeter mode: Commonly used device that includes a voltmeter as one of its functions.

Applications of voltmeters

  • Testing batteries and power supplies.
  • Troubleshooting voltage drops in circuits.
  • Monitoring input/output voltage of devices.
  • Checking wall outlets or electric panels.
  • Measuring voltage across components in electronic devices.
Conclusion:

A voltmeter is a useful device that measures the voltage between two points in an electric circuit. It is connected in parallel and has high resistance to ensure that it does not affect circuit operation. Voltmeters help ensure that electrical systems are working safely and within proper voltage limits. Understanding how to use a voltmeter is fundamental for anyone working with electric circuits.