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7 Reasons for Multimeter Reading Wrong Voltage

By shafiq usama

7 Reasons for multimeter reading wrong voltage

As an electrical engineer, I love explaining how things like circuits and electronics work. I write on my blog to share simple explanations, reviews, and useful tips about the latest technology.

Have you ever been in a  situation where you're trying to take a multimeter reading, and the voltage just won't display correctly? If so, don't worry - you're not alone. This is a fairly common issue that can occur for various reasons. Let's look at some of the most common causes of inaccurate multimeter readings. Moreover, If you're multimeter reading wrong voltage, you're more prone to electrical shocks, so make sure you're always using caution.

multimeter reading wrong voltage

7 Reasons for multimeter reading wrong voltage: 

  1. Calibration Error
  2. Incorrect ranges:
  3. Don't know how to use it
  4. Probes are damaged
  5. Internal fuses are blown
  6. Environmental effects
  7. Short Circuit

Calibration Error

All electrical tools are subject to calibration errors, and multimeters are no different. This means that the reading you see on the multimeter may not be entirely accurate. While most multimeters are fairly accurate, it's always a good idea to double-check your readings with another multimeter or another type of electrical testing tool. In most multimeters, adjustments and trim pots can be used to calibrate the multimeter, but this is best left to a qualified technician.

Incorrect Ranges

Voltages are of two types AC & DC. These ac dc voltages range from millivolts to 1000V.  So multimeters have different ranges for measuring these voltages. While multimeters can measure a wide variety of voltage levels, they are not all-purpose devices. In order to get an accurate reading, you need to make sure that the multimeter is set to the correct range for the voltage you're trying to measure. For example, if you're trying to measure a voltage that's between 0 and 30 volts, you'll need to set the multimeter to the 50-volt range. You'll get an inaccurate reading if the multimeter is set to a higher range, like 1000V. Most DMMs nowadays have auto-ranging functions, so you don't need to worry about this.

Don't Know How to Use It

The usage of a multimeter without proper information can result in the multimeter reading the wrong voltage. You'll likely get inaccurate readings if you don't know how to use a multimeter. Make sure you understand how to use the multimeter before taking any readings.

I mean, where to insert the probes, which probe should be on phase, and which one should be on neutral for ac voltage measurement? Similarly, in the case of DC Voltage measurement, where to insert the probes for positive and negative measurement?

Probes Are Damaged

If the multimeter probes are damaged, they may not make a good connection with the multimeter leads. This can result in inaccurate multimeter readings. Inspect the multimeter probes to see if there is any carbon, ionization, or breakage; if yes, you must change the probes. Probes or test leads are classified as per CAT ratings so if you're using  a multimeter for industrial use, make sure you're using the correct probes.

Internal Fuses Are Blown results in multimeter reading wrong voltage

Every multimeter has safety fuses at the input side of test leads for our safety. These multimeters may result in the multimeter reading the wrong voltage if these fuses are blown. So, if your multimeter does not show any reading or OL, the fuses are blown. You can easily check these fuses with another multimeter; if they are blown, you'll need to replace them. You can also visit my Blog about How to test blown fuses with multimeter.

Environmental Effects

There are many environmental factors that can affect multimeters, like moisture, temperature, and dust. In such cases, your multimeter will show a lesser or higher reading than the actual one.

So, using multimeters in a clean and dry place is recommended. Moreover, the working environmental conditions are mentioned in the user manual, so make sure a multimeter is used.

Short Circuit  may also results in multimeter reading wrong voltage

A multimeter will also show the wrong reading if there is a short circuit. Short circuits can occur when the multimeter probes come in contact with each other or if there is a break in the multimeter's internal or external circuitry. You can also use a non-contact voltage detector pen to avoid these issues. Here is a complete guide on how to test voltages with a Non-Contact Voltage Detector Pen.

Tips to make your multimeter function properly

You can get more tips on multimeter reading here:

  • Use multimeters in a clean and dry place.
  • Use the multimeter only as specified in the user manual.
  • Do not use multimeters in an environment with excessive dust, moisture, or temperature.
  • Do not use multimeters near electrical noise sources.
  • Use the multimeter only with the correct type and rating of probe or test lead.
  • Inspect multimeter probes regularly for damage.
  • Do not use multimeters if the probes are damaged.
  • Use only multimeters with intact safety fuses.
  • Final Words:

    Voltages are like water pressures. The multimeter is like a pressure gauge. Likewise, to get an accurate multimeter reading, make sure the multimeter is set to the correct range, and you understand how to use the multimeter. Moreover, also check for damaged multimeter probes and blown fuses. And finally, be aware of environmental conditions that can affect multimeter readings.

    FAQS

    How do I test if my multimeter is accurate?

    To test the accuracy of your multimeter, you'll need a known good reference voltage source. You can use a resistor-capacitor (RC) circuit, a precision voltage reference, or a signal generator. Once you have your reference voltage source, follow these steps:
    1. Connect the positive lead of your multimeter to the positive lead of your reference voltage source.
    2. Connect the negative lead of your multimeter to the negative lead of your reference voltage source.
    3. Set your multimeter to the correct range and make sure it is in the correct mode for measuring voltage (DC or AC).
    4. Take a reading from your multimeter.
    5. Compare the reading from your multimeter to the known voltage of your reference voltage source. If the two readings are within the margin of error for your multimeter, then your multimeter is accurate.

    How often do I need to calibrate my multimeter?

    It is typically recommended that you calibrate your multimeter at least once per year. However, if you use your multimeter frequently or in critical applications, you may need to calibrate it more often. Check the user manual for your specific multimeter to see what the manufacturer recommends.

    What is the margin of error for a digital multimeter?

    The margin of error for a digital multimeter is typically ±0.5%. This means that if your multimeter reads 10 volts, the actual voltage could be anywhere between 9.95 volts and 10.05 volts. Analog multimeters have a larger margin of error, typically ±3%.