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    08 Jun, 2023
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    Understanding Voltmeters: A Beginner’s Guide to Measuring Electrical Potential


    When it comes to understanding electricity, one of the fundamental tools that you’ll encounter is the voltmeter. This seemingly simple device is crucial for anyone working with or learning about electronics. In this comprehensive guide, we’ll demystify the voltmeter, providing novices with an easy-to-understand yet rich explanation of its working principles, safety precautions, installation methods, and selection guide. Whether you’re a budding electrician or a curious hobbyist, you’ll find everything you need to start measuring electrical potential like a pro.

    What is a Voltmeter?

    A voltmeter is a measuring instrument used to measure the DC or AC voltage value in a circuit. In use, in order to ensure that the measured parameters are valuable, the voltmeter needs to have a very high resistance in the internal structure, and the voltmeter should be connected in parallel with the circuit to prevent the reading of the voltmeter from being disturbed.

    A din rail voltmeter is a special voltmeter designed to be mounted on a rail, which can provide accurate voltage measurement for various circuit systems, and can be widely used in industrial, commercial, and residential applications.

    Din Rail Single Phase Digital Voltmeter - TOVME-1 60-450VAC
    Din Rail Single Phase Digital Voltmeter - TOVME-1
    Din Rail Three Phase Digital Voltmeter - TOVME-3 60-450VAC
    Din Rail Three Phase Digital Voltmeter - TOVME-3

    The products in the picture above are single-phase and three-phase DIN-rail AC digital voltmeters. This style of voltmeter is very compact and easy to install. It is an ideal solution.

    The Basics of How Voltmeters Work

    Electric potential difference, also known as voltage, is a key concept in the field of electricity. It’s what drives the flow of current through a circuit, and it’s what a voltmeter measures with precision. But how does a voltmeter do this?

    Voltmeters, in essence, are designed to measure the difference in electrical potential between two points in an electric circuit without significantly altering the voltage of the circuit itself.

    Analog voltmeters use a needle to indicate voltage levels, while digital voltmeters provide numerical readings on a display. Both types play a pivotal role in diagnosing and troubleshooting electrical systems.

    Understanding how voltmeters are integrated into circuits is crucial for their effective use. They must be connected in parallel with the circuit component whose voltage you wish to measure. This ensures that the voltmeter measures the voltage across the component without affecting the current flowing through it.

    Voltmeter Symbol

    Voltmeter Symbol - Letter V
    Voltmeter Symbol - Letter V

    What are the types of voltmeters?

    There are many styles of voltmeters. For example, portable multimeters carried by electricians are used to detect current, resistance, and voltage. There are also battery-powered voltmeter devices. Some voltmeters are installed together with the device under test for long-term detection, such as installed Rail voltmeters on the rail.

    There are mainly two main types of voltmeters as follows, namely digital voltmeters, and analog voltmeters.

    Digital voltmeter. The digital voltmeter will display the measured voltage value in digital form, unlike the pointer of other voltmeters, which can reduce the mistakes of observers. In practical applications, digital voltmeters are versatile, inexpensive, and capable of accurate and fast readings.

    Analog voltmeter. The analog voltmeter will move the pointer on the dial to the corresponding scale position according to the voltage value in the circuit. Voltmeters are usually designed to consume the least amount of current in order to minimize the impact on the circuit under test. Due to the use of the pointer, when observing the value of the analog voltmeter, it is necessary to observe whether the analog voltmeter is in a horizontal orientation, and also pay attention to whether there is any other magnetic field interference nearby.

    Digital Voltmeters and Their Advantages

    Digital voltmeters (DVMs) have revolutionized the way we measure voltage. Unlike their analog counterparts, DVMs provide a digital readout that is often easier to read and more accurate. Here are the advantages and features that make digital voltmeters a preferred choice for many professionals:

    Precision and Accuracy: Digital voltmeters are known for their high level of accuracy. They minimize reading errors and provide precise measurements, critical for sensitive electronic devices and systems.

    Ease of Use: With a clear digital display, there’s no need to interpret where the needle points on a scale, as you would with an analog voltmeter. This makes DVMs more user-friendly, especially for novices.

    Advanced Features: Many digital voltmeters come with additional functionalities such as auto-ranging, which automatically selects the correct measurement range, and data hold, which keeps the reading on the display even after the probes are removed.

    Durability and Reliability: Digital voltmeters are generally more resistant to shock and vibration than analog meters, making them more durable and reliable in various environments.

    By understanding the advantages of digital voltmeters, users can make more informed decisions when performing electrical measurements and choosing the right equipment for their needs.

    Unit of measure for a voltmeter

    The unit of voltage is volts (V), and in a circuit, it represents the potential difference between two points. Different voltmeters can measure voltage values in different size ranges, for example, millivolts (mV), volts (V), and kilovolts (kV).

    The accuracy of the measured data depends on the quality and maintenance calibration of the voltmeter product. Generally speaking, a high-quality voltmeter can have better accuracy, and regular maintenance and calibration can also bring reliable measurement data.

    Deciphering Symbols and Readings on Voltmeters

    Voltmeters are marked with various symbols and scales that can be confusing for beginners. Understanding these symbols is critical for taking accurate measurements and ensuring safe use of the device. Here’s a breakdown of common symbols and readings you’ll encounter:

    Common Symbols: The ‘V’ symbol is used to denote voltage. You’ll also find ‘AC’ and ‘DC’ symbols, indicating alternating current and direct current measurements, respectively. A wavy line (~) represents AC, and a straight or dashed line (- or …) represents DC.

    Reading Scales: For analog voltmeters, you’ll typically see a series of numbered lines. The value you read corresponds to the voltage level. For digital voltmeters, the reading is presented in digits, simplifying the process.

    Understanding Ranges: Voltmeters can measure different ranges of voltages. It’s important to select the correct range to avoid damaging the device and to get an accurate reading. If in doubt, start with the highest range and work downwards.

    By familiarizing yourself with the symbols and scales on your voltmeter, you can ensure that you’re interpreting your measurements correctly and getting the most out of your device.

    Common application scenarios of voltmeters

    The voltmeter is connected in parallel to the circuit under test and is often used to detect the DC or AC voltage value in various equipment circuits such as electronic equipment, medical equipment, and low-power mechanical equipment. In practical applications, for example:

    1. Detect whether a circuit is energized, such as wall sockets and sockets.
    2. Measure the voltage on the known resistance circuit to calculate the current.
    3. Detect the voltage of the battery to determine whether the battery needs to be charged or replaced.
    4. Monitor the voltage and other information of the device under test to calculate the power consumption of the device under test.

    In the practical application of voltmeters, safety is very important. Voltmeters should be used by professionals who are familiar with how to use them safely, wear appropriate personal protective equipment, and ensure that the rated voltage range of the voltmeter used is suitable for the voltage to be measured.

    How to buy a suitable voltmeter according to your actual needs?

    Considering the type of circuit applied, the voltage range to be measured, and other additional product features, the following factors need to be considered when selecting a voltmeter:

    Circuit Type: Consider the type of circuit the voltmeter will be used in. There are also different options for voltmeters for high-voltage circuits and low-voltage circuits.

    Voltage range: Make sure that the required voltage range is within the voltage range of the selected voltmeter. Note that some voltmeters have a fixed voltage measurement range, while others have multiple selectable voltage measurement ranges.

    Measurement Accuracy: Ensure that the selected voltmeter provides accurate and reliable measurement data. Generally speaking, high-quality voltmeters have more perfect data accuracy.

    Numerical display: Digital voltmeters and analog voltmeters have different numerical display methods. Digital voltmeters use a digital display to show voltage values, while analog voltmeters use scales and needles to show them.

    Other additional functions: additional needs for additional functions, such as data logging, network connection, etc., functions that can provide more convenience.

    It is very important to choose a suitable voltmeter according to your actual needs. This type of voltmeter needs to provide accurate and reliable values and meet specific requirements.

    Why are voltmeters connected in parallel and ammeters in series?

    An ammeter is a measuring device that measures the magnitude of the current in a circuit. Since the resistance of the ammeter is low, the ammeter is basically connected in series with the circuit.

    The voltmeter has high resistance, so the voltmeter is basically connected in parallel to the circuit. Because if the voltmeter is connected in series on the circuit, the high resistance will greatly affect the current on the circuit, resulting in inaccurate measurement data.

    Why is the resistance of the voltmeter high?

    When the voltmeter measures the voltage value, in order to ensure that the current of the device under test is not changed as much as possible, the voltmeter needs to be designed in a high-resistance style. In this way, the current will not flow to the line with the voltmeter, and the accuracy of the measured data can be guaranteed.

    Testing a Circuit Breaker with a Voltmeter

    Using a voltmeter to test a circuit breaker is a practical skill that can help diagnose electrical issues in your home or workplace. Here’s how to safely perform this test:

    Preparation: Ensure that all safety precautions are in place. Turn off the device or circuit you’re testing, and make sure you have easy access to the circuit breaker.

    Setting the Voltmeter: Set your voltmeter to measure AC voltage in a range appropriate for your home’s electrical system – this is usually 120 volts or 240 volts in most residential settings.

    Testing: With the circuit breaker in the ‘ON’ position, place the voltmeter probes on the terminal screws of the breaker. A properly functioning breaker should show a voltage reading close to what your electrical system is rated for (120V/240V). If the reading is significantly lower or there is no reading, the breaker may be faulty.

    Safety Check: After testing, remove the probes, turn off the voltmeter, and restore power only after you’ve confirmed that it’s safe to do so.

    This simple test can be invaluable in troubleshooting electrical problems and ensuring the safety and functionality of your electrical system.

    Precautions and Tips for Using Voltmeters Effectively

    While voltmeters are incredibly useful tools, improper use can lead to inaccurate readings or even damage the voltmeter. Here are some precautions and tips to help you use your voltmeter effectively:

    Never Exceed the Maximum Rating: Always check the maximum voltage that your voltmeter can measure and never attempt to measure beyond this limit. This can protect the device from damage and prevent potential accidents.

    Use the Right Probe Inputs: Many digital voltmeters have multiple inputs for probes. Ensure you’re using the correct inputs for the type of measurement you’re taking to avoid any damage to the voltmeter or inaccurate readings.

    Regular Calibration: To ensure that your voltmeter gives accurate readings over time, it’s important to have it calibrated regularly according to the manufacturer’s instructions.

    Avoid Parallax Errors: When using an analog voltmeter, ensure that you view the needle straight on rather than from an angle to avoid parallax errors, which can make the needle appear to point to a different value than it actually is.

    Understand the Limitations: Know that voltmeters are designed to measure voltage only. For other measurements like current and resistance, you will need to use other tools like ammeters and ohmmeters, respectively.

    By following these tips, you can ensure that you’re using your voltmeter safely and getting the most accurate readings possible.


    All in all, a voltmeter is an important tool for measuring voltage in a circuit. Voltmeters mainly include analog voltmeters and digital voltmeters, which can measure direct current and alternating current and are widely used in industry, commerce, and residences.

    In this guide, we’ve explored the versatile world of voltmeters, from their basic operation to tips for accurate use and a selection guide for purchasing the right one. With this knowledge, novices and seasoned professionals alike can approach electrical measurements with confidence and precision.

    Remember, a voltmeter is more than just a tool; it’s your gateway to understanding and harnessing the power of electricity safely and effectively. By choosing the appropriate voltmeter and using it correctly, you can perform a wide range of electrical diagnostics and tasks with ease.

    Whether you’re testing a circuit breaker, diagnosing an electrical appliance, or simply indulging in a hobby, the right voltmeter can make all the difference. Take the time to learn and practice, and you’ll find that a voltmeter is an indispensable ally in all your electrical projects.

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