When you are looking to measure pretty much anything to do with electricity – the only tool that is going to be up to the task is a multimeter. A multimeter is used to test the current (amps), voltage (volts) and/or resistance (ohms) of a range of different circuits. We will explain the different of these below, but if you are wanting to save money and time in waiting for an electrician to come to your house to get the bottom of a problem – then a multimeter is definitely the tool for you.
All multimeters are going to have different accuracy, strengths and features, which is what we have compared in this article, but most work to around 2% higher or lower in their readings – close enough for you to get a good idea of what is going wrong (or right) in your electrical products at home.
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You might still be thinking that such a multifunctional device is intended only for professional use but you couldn’t be more wrong! If you’re a keen do-it-yourselfer, a multimeter will prove to be a relatively inexpensive yet indispensable addition to your DIY toolkit! Whether it’s determining wiring capacity or checking your car battery, a multimeter will obtain the information you need quickly, accurately and safely.
Not only that, but they’re incredibly versatile – measuring current, voltage and resistance are just the basic functions you can expect from a multimeter; there are more sophisticated models available which offer advanced options capable of measuring microamps, decibels, rotations per minute, even temperature and humidity!!
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Analogue Vs Digital
There are two main types of multimeter available: analogue and digital.
Digital: the most popular and readily-available type of multimeter; digital models have a digital screen which displays the desired measurement reading; digital multimeters are regarded as being more accurate and reliable than their predecessor – the needle analogue multimeter – however they can take time to stabilise when obtaining a reading.
Analogue: the original style of multimeter; analogue models display measurements via a needle (think of your old kitchen scales!). Reading and logging data can be difficult with analogue models but they are preferred by some professionals when working with particularly sensitive measurements.
Multimeter Uses
- Can detect electrical faults and faulty connections in appliances, circuits, power supplies and wiring systems
- To debug a circuit
- To test how well current is travelling through a circuit
- To determine the level of resistance present within a circuit
- To check the inductance of coils
- To measure line voltage, DC and AC current
- To check the health of your car battery
- To check a car’s 12V socket
- To test circuits to check they’re powered at the correct voltage
Regardless of what you’re using your multimeter for, it’s vital that you check the multimeter maximum voltage and current ratings to be sure they’re greater than the voltage range you intend on measuring.
Multimeter models & cost
| Model | Cost | Pros & Cons |
| Pen | Around £20 – £30 | Compact, pen-shaped low-budget multimeters Handheld Have a single test probe for non-contact AC voltage detection Limited functions Low-priced |
| Handheld | Ranging from around £8 – £150 | Most common type of multimeter Cuboid in shape Easy to use Large selection dial 3 ports |
| Bench or Box | Ranging from £220 – £1000+ | High-end models Suitable for professional use Capacity to test a wide range of circuitry 4+ ports Large setting selection Costly Robust digital/LCD display |
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Multimeter checklist
Regardless of your budget, you need to invest in a multimeter which offers at least the following three fundamental functions:
- The capability to select voltage ranges
- Ohm (resistance) measurement
- The option to switch between AC and DC voltages
Voltage range
Also known as the ‘tolerance range’. It’s important you establish how much current you’ll typically be reading so you’re able to set your multimeter to that range e.g. if you’re testing the 12V socket in your car, you’d need to set your multimeter to the 20V setting. Whatever the expected reading, the multimeter should be set to slightly above that tolerance to allow for any small margins of error.
Resistance measurement
Any decent multimeter should have the option to measure resistance, which is particularly useful when identifying breaks or faults in a circuit; the lower the ohm reading, the less resistance there is present in the circuit.
AC/DC options
Again, any decent multimeter, even budget models, will have the option to select both AC and DC ranges typical of UK electrical goods. When deciding on the best multimeter for you, it’s always worth checking that it has the ranges you need e.g. if you intend on using your multimeter primarily for computers and technology, then investing in a multimeter with a decent DC range is what you’ll need.
Multimeter digital components
The face of a digital multimeter typically includes the following components:
| Component | Description |
| Display | A digital/LCD display on the front of the device where measurement readings can be viewed. |
| Selection dial/ Rotary switch | A large switch or knob, usually located centrally, where the type of measurement/unit of measurement is selected. |
| Ports | Also referred to as connection points; usually located at the front of the multimeter, where one end of the multimeter’s probes are attached. |
| Input jacks | The point where the test leads are inserted. |
| Wires | Your multimeter will come with at least two wires – one red and one black; one end of each wire will have a connector which is inserted into the ports. |
| Probes | On the other end of each multimeter wire, you will find a probe; there are different types of probe available but the most common is alligator clips or test probes. More sophisticated multimeter models will come with multiple probe types. |
| Buttons | Used to select the various functions; button layout and configuration will vary according to brand and model. |
Voltage, current and resistance
Voltage, current, and resistance are all measurable quantities relating to the flow of electricity and a multimeter will allow you to obtain readings for any one of these.
Voltage
- Measured in volts (V)
- The driving force (electrical pressure) behind the flow of a current
- How ‘hard’ electricity is being ‘pushed’ through a circuit
- Also referred to as ‘potential difference’ or ‘electromotive force’
Current
- Measured in amps (A)
- How much electricity is flowing through the circuit
- The higher the current, the more electricity is flowing
- If the current is low, then it is measured in milli-amps (mA)
- 1000 mA = 1A
Resistance
- Measured in ohms (Ω)
- How difficult it is for electricity to flow through something
- The higher the resistance, the more difficult it is for electricity to flow
- The property of a material that limits current flow
- Resistance to alternating current is referred to as ‘impedance’
Additional features
All multimeters should have voltage, current and resistance measuring capability otherwise they wouldn’t be worthy of the ‘multi’ in ‘multimeter’!!
If you have a decent budget, you may well be considering a more sophisticated multimeter model – the more you’re willing to spend, the more likely it is you’ll find a multimeter with plenty of ‘extra’ features:
- Various types of probes included with the multimeter e.g. alligator clips, IC hooks and test probes
- Autoranging capability – a handy, clever feature which automatically changes the multimeter’s range to the setting that best matches the circuit it’s taking its readings from
- Temperature probe – allows the user to measure the temperature of electronic devices which can be useful when diagnosing particularly elusive circuit problems
- Durable, hard-wearing casing, usually rubber, to protect the multimeter from the weather; from water; any sudden impact such as dropping; and any prolonged exposure to extreme cold or heat
- A high-contrast, backlit LED screen offering bold, clear readings on digital multimeters enables readings to still be obtained in conditions where lighting and visibility conditions are poor
- An integrated, non-contact AV detector allows the user to obtain accurate AC voltage readings without any physical contact, minimising any potential safety risks
- A ‘data hold’ and/or ‘maximum value hold’ function gives you the option to store current/voltage/resistance readings for future reference, without the hassle of having to manually record the data elsewhere
- Integrated optional kick-stand for quick and easy hands-free operation
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Frequently Asked Questions
Which is the best multimeter to buy?
In order to find the best multimeter, you’ll need to be clear on the voltage range you intend on using it for. The multimeter you choose will need to have a higher voltage/current rating than what you’re intending to measure, otherwise, you run the risk of damaging the multimeter or, worse still, finding yourself on the receiving end of a nasty electric shock!
What do the multimeter symbols mean?
The three most common symbols you’re likely to see on the front of a multimeter are V, A, and Ω. ‘V’ stands for ‘volts’, which is the unit of measurement for voltage; ‘A’ stands for ‘amps’, which is the unit of measurement for current; and ‘Ω’ stands for ‘ohms’, which is used to measure resistance.
What is auto-ranging and manual ranging?
Auto-ranging multimeters automatically select the most appropriate measurement range for the circuit it’s connected to, whereas manual ranging multimeters require you to select the desired measurement range yourself. When using a manual ranging multimeter, it’s always better to go slightly above the typical range, rather than below.
How do multimeters work?
Multimeters work by measuring resistance. They inject a small current into the circuit and then measure the drop in voltage across various points in the circuit. This then allows the multimeter to give readings linked to the voltage and current in the circuit.
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