How To Use A Multimeter To Test Voltage Of Live Wires

Updated on: December 12, 2018



This tutorial will certainly show you exactly how to make use of a digital multimeter (DMM), an essential device that you can use to identify circuits, discover other individuals’s electronic layouts, and also even test voltage of live wires. For this reason the ‘multi’-‘meter’ or numerous measurement name.

One of the most standard things we measure are voltage and current. A multimeter is additionally fantastic for some standard peace of mind checks and troubleshooting. Is your circuit not functioning? Does the switch job? Place a meter on it! The multimeter is your very first defence when fixing a system. In this tutorial we will cover measuring voltage, current, resistance and also continuity.

Every fixer ought to recognize their way around a multimeter, which has simply north of a zillion uses for testing digital elements as well as circuits.

In this tutorial we’re going to reveal you exactly how to use a multimeter. This tutorial is mainly addressed for beginners that are beginning out in electronics and also have no suggestion exactly how to use a multimeter and just how it can be beneficial. We’ll explore the most usual attributes on a multimeter and just how to measure current, voltage, resistance and how to examine continuity.

What is a multimeter as well as why do you require one?

A multimeter is a measurement device definitely required in electronics. It incorporates 3 essential functions: a voltmeter, ohmeter, as well as ammeter, as well as in some instances continuity.

The tool permits you to comprehend what is going on in your circuits. Whenever something in your circuit isn’t working, it will certainly assist you fixing. Below’s some circumstances in electronics tasks that you’ll locate the multimeter helpful:

  • is the button turn on?
  • is this cord performing the electricity or is it broken?
  • just how much current is moving via this led?
  • just how much power do you have left on your batteries?

What should multimeters measure?

Mostly all multimeters can measure voltage, current, and resistance.

A handful of multimeters have a continuity check, leading to a loud beep if two things are electrically attached. This is helpful if, as an example, you are constructing a circuit and attaching cables or soldering; the beep suggests everything is linked and absolutely nothing has actually come loose. You can also use it to make certain two things are not attached, to assist prevent brief circuits.

Various other multimeters also have a diode check function. A diode resembles a one-way valve that just allows electrical energy circulation in one direction. The precise feature of the diode check can vary from one type to another. If you’re functioning with a diode and also can not inform which method it goes in the circuit, or if you’re uncertain the diode is working effectively, the check attribute can be fairly helpful. If your DMM has a diode check function, read the guidebook to discover exactly just how it works.

Advanced models may have various other functions, such as the ability to measure as well as determine various other electrical components, like transistors or capacitors. Since not just about all multimeters have these features, we will certainly not cover them in this tutorial. You can review your multimeter’s handbook if you require to make use of these attributes.

What Do Each Of the Symbols Mean?

There’s a great deal taking place when you check out the selection knob, but if you’re only going to be doing some standard things, you won’t also utilize fifty percent of all the setups. Regardless, here’s a run-through of what each sign suggests:

Direct Current Voltage (DCV):Sometimes it will certainly be signified with a V– rather. This setting is made use of to measure straight current (DC) voltage crazes like batteries.
Alternating Current Voltage (ACV): Sometimes it will certainly be signified with a V ~ instead. This setup is used to measure the voltage from alternating current sources, which is practically anything that connects into an outlet, in addition to the power coming from the outlet itself.
Resistance (Ω): This determines just how much resistance there is in the circuit. The lower the number, the simpler it is for the current to move with, and also vice versa.
Continuity: Usually denoted by a wave or diode symbol. This just examines whether or not a circuit is total by sending out a really small quantity of current with the circuit and also seeing if it makes it out the other end. Otherwise, then there’s something along the circuit that’s causing a trouble– locate it!
Direct Current Amperage (DCA): Similar to DCV, however rather than giving you a voltage reading, it will inform you the amperage.
Straight Current Gain (hFE): This setup is to evaluate transistors and also their DC gain, yet it’s mostly worthless, since most electrical experts as well as hobbyists will certainly make use of the continuity check instead.

Your multimeter might likewise have a committed setup for examining the amperage of AA, AAA, as well as 9V batteries. This setting is generally denoted with the battery symbol.

Once more, you possibly will not even utilize half of the settings revealed, so do not get overwhelmed if you just recognize what a few of them do.

How to Use a Multimeter

For beginners, let’s discuss a few of the various parts of a multimeter. At the very fundamental degree you have the gadget itself, along with two probes, which are the black as well as red cable televisions that have plugs on one end and metal pointers on the other.

The tool itself has a display screen on top, which provides you your readout, and there’s a large selection knob that you can rotate around to pick a specific setup. Each setup might also have different number worths, which exist to measure various strengths of voltages, resistances, as well as amps. So if you have your multimeter collection to 20 in the DCV area, it will measure voltages as much as 20 volts.

Your DMM will certainly likewise feature two or 3 ports for connecting in the probes:

  • the COM port mean “Common”, as well as the black probe will certainly always connect into this port.
  • VΩmA port (in some cases signified as mAVΩ) is simply a phrase for voltage, resistance, as well as current (in milliamps). This is where the red probe will certainly link into if you’re measuring voltage, resistance, continuity, and also current less than 200mA.
  • the 10ADC port (often signified as just 10A) is made use of whenever you’re measuring current that’s more than 200mA. If you’re uncertain of the current draw, start with this port. On the other hand, you would not utilize this port at all if you’re measuring anything other than current.

Warning: Make sure that if you’re measuring anything with a current greater than 200mA, you connect the red probe right into the 10A port, rather than the 200mA port. Or else you could blow the fuse that’s within the multimeters. Moreover, measuring anything over 10 amps could blow a fuse or damage the multimeter as well.

Your measurement tool may have completely separate ports for measuring amps, while the other port is especially simply for voltage, resistance, and continuity, however many cheaper multimeters will certainly share ports.

Anyway, allow’s begin in fact utilizing a multimeter. We’ll be measuring the voltage of a AA battery, the current draw of a wall surface clock, and also the continuity of a simple wire as some examples to obtain you started and also knowledgeable about utilizing a multimeter.

Components of Multimeters

Multimeters are made up by 4 essential sections:

  • Display: this particular is exactly where the measurements are shown
  • Selection Knob: this picks what you intend to measure
  • Ports: this is where you plug in the probes
  • Probes: a multimeter comes with 2 probes. Usually, one is red and also the other is black.


  • “COM” or “–” port is where the black probe should be connected. The COM probe is traditionally black.
  • 10A is made use of when measuring big currents, greater than 200mA.
  • µAmA is made use of to measure current.
  • allows you to measure voltage and also resistance and test continuity.


COM stands for typical and is generally connected to Ground or ‘-‘ of a circuit.The COM probe is traditionally black but there is no distinction in between the red probe and black probe other than color.


10A is the unique port used when measuring large currents (better than 200mA).

Selection Knob

The selection knob enables the customer to set the tool to check out different things such as milliamps (mA) of current, voltage (V) as well as resistance (Ω).


2 probes are connected into 2 of the ports on the front of the device. The probes have a banana type adapter on completion that connects into the multimeter. Any kind of probe with a banana plug will certainly function with this meter. This enables various types of probes to be made use of.

Probe Types

There are several sorts of probes readily available. Here are a few of our favorites:

  • Banana to Alligator Clips: These are terrific cable televisions for attaching to big wires or pins on a breadboard. Great for performing longer term examinations where you don’t have to have to hold the probes in location while you manipulate a circuit.
  • Banana to IC Hook: IC hooks function well on smaller ICs and also legs of ICs.
  • Banana to Tweezers: Tweezers come in handy if you are requiring to test SMD parts.
  • Banana to Test Probes: If you ever before break a probe, they are inexpensive to replace!

Measuring Voltage

To begin, let’s measure voltage on a AA battery: Plug the black probe into COM as well as the red probe right into mAVΩ. Establish to “2V” in the DC (direct current) variety. Nearly all portable electronic devices make use of direct current), not alternating current. Link the black probe to the battery’s ground or ‘-‘ as well as the red probe to power or ‘+’. Squeeze the probes with a little stress against the positive as well as adverse terminals of the AA battery. If you’ve obtained a fresh battery, you should see around 1.5 V on the display screen (this battery is new, so its voltage is somewhat higher than 1.5 V).

You can measure DC voltage or AC voltage. The V with a straight line indicates DC voltage. The V with the wavy line indicates AC voltage.

To be able to measure voltage follow all of these steps:

  1. Set the setting to V with a curly line if you’re measuring AC voltage or to the V with a straight line if you’re measuring DC voltage.
  2. See to it the red probe is connected to the port with a V beside it.
  3. Connect the red probe to the silver lining of your component, which is where the current is originating from.
  4. Connect the COM probe to the opposite of your component.
  5. Read the value on the screen.

Pointer: to measure voltage you need to attach your multimeter in parallel with the component you desire to measure the voltage. Putting the multimeter in parallel is positioning each probe along the leads of the component you wish to measure the voltage.

Measuring a battery’s voltage

In this example we’re mosting likely to measure the voltage of a 1.5 V battery. You understand that you’ll have around 1.5 V. So, you need to select a variety with the selection knob that can read the 1.5 V. So you ought to choose 2V when it comes to this multimeter. If you take an autorange one, you do not have to bother with the variety you require to pick.

Begin by activating it, connecting the probes right into their respective ports and after that setting the selection knob to the highest number worth in the DCV area, which in my instance is 500 volts. If you don’t understand at the very least the voltage array of the point you’re measuring, it’s constantly a great suggestion to begin with the highest value first and after that function your way down until you get an accurate analysis.

In this situation, we recognize the AA battery has an extremely reduced voltage, however we’ll begin at 200 volts just for the benefit of example. Next, place the black probe on the adverse end of the battery and also the red probe on the positive end. Have a look at the reading on the screen. Considering that we have the multimeter collection to a high 200 volts, it shows “1.6” on the screen, meaning 1.6 volts.

However, I desire an even more precise analysis, so I’ll relocate the selection knob reduced down to 20 volts. Right here, you can see that we have an even more accurate reading that floats between 1.60 and also 1.61 volts. If you were to ever before set the selection knob to a number worth less than the voltage of the important things you’re examining, the multimeter would just review “1”, signifying that it’s overloaded. So if I were to establish the knob to 200 millivolts (0.2 volts), the 1.6 volts of the AA battery is too much for the multimeter to take care of at that setup.

All the same, you might be asking why you would certainly need to examine the voltage of something to begin with. Well, in this case with the AA battery, we’re checking to see if it has any type of juice left. At 1.6 volts, that’s a fully-loaded battery. However, if it were to check out 1.2 volts, it’s close to being unusable.
In an extra practical circumstance, you could do this sort of measuring on an auto battery to see if it might be passing away or if the generator (which is what charges the battery) is spoiling. A reading between 12.4-12.7 volts means that the battery remains in good condition. Anything reduced as well as that’s evidence of a passing away battery. Moreover, start your auto up and also rev it up a little bit. If the voltage doesn’t boost to around 14 volts or two, then it’s most likely that the generator is having concerns.


What happens if you pick a voltage setup that is too reduced for the voltage you’re attempting to measure? Absolutely nothing negative. The meter will just show a 1. This is the meter trying to inform you that it is overloaded or out-of-range. Whatever you’re trying to read is excessive for that certain setting. Try transforming the multimeter knob to a the next greatest setting.

Selection Knob

Precisely why does the meter knob reviewed 20V as well as not 10V? If you’re seeking to measure a voltage much less than 20V, you transform to the 20V setup. This will certainly allow you to check out from 2.00 to 19.99. The very first figure on lots of multimeters is just able to show a ‘1’ so the arrays are restricted to 19.99 instead of 99.99. Therefore the 20V max array as opposed to 99V max variety.

Measuring Resistance

Connect the red probe right into the ideal port as well as turn the selection knob to the resistance area. After that, connect the probes to the resistor leads. The way you link the leads does not matter, the result coincides.

Normal resistors have shade codes on them. If you do not understand what they imply, that’s ok! There are plenty of on-line calculators that are simple to utilize. However, if you ever before discover yourself without internet access, a multimeter is extremely useful at measuring resistance.

Select an arbitrary resistor and set the multimeter to the 20kΩ setting. Then hold the probes against the resistor legs with the very same quantity of pressure you when pressing a key on a key-board.

The meter will certainly check out among three points, 0.00, 1, or the real resistor worth.

In this situation, the meter checks out 0.97, meaning this resistor has a worth of 970Ω, or concerning 1kΩ (remember you are in the 20kΩ or 20,000 Ohm setting so you need to move the decimal 3 places to the right or 970 Ohms).

If the multimeter reviews 1 or displays OL, it’s overwhelmed. You will certainly need to attempt a higher mode such as 200kΩ setting or 2MΩ (megaohm) mode. There is no damage if this occur, it simply implies the variety knob needs to be readjusted.

Whenever the multimeter reads 0.00 or almost absolutely no, after that you require to decrease the setting to 2kΩ or 200Ω.

Keep in mind that several resistors have a 5% tolerance. This means that the shade codes may suggest 10,000 Ohms (10kΩ), however because of disparities in the manufacturing process a 10kΩ resistor might be as low as 9.5 kΩ or as high as 10.5 kΩ. Do not worry, it’ll work simply great as a pull-up or general resistor.

As a guideline of thumb, it’s uncommon to see a resistor less than 1 Ohm. Keep in mind that measuring resistance is not best. Temperature can affect the reviewing a whole lot. Additionally, measuring resistance of a device while it is literally set up in a circuit can be extremely tricky. The bordering elements on a motherboard can greatly impact the reading.

The mockup usually resembles with a basic clock running of a AA battery. On the silver lining, the cord going from the battery to the clock is damaged up. We merely position our two probes in between that break to finish the circuit once again (with the red probe attached to the source of power), just this time our multimeter will certainly review out the amps that the clock is pulling, which in this situation is around 0.08 mA.

While most multimeters can additionally measure rotating current (AC), it’s not really a good idea (particularly if its real-time power), because AC can be dangerous if you wind up slipping up. If you need to see whether or not an outlet is functioning, make use of a non-contact tester rather.

To measure current you require to remember that parts in collection share a current. So, you need to link your multimeter in collection with your circuit.

TIP: to position the multimeter in collection, you need to position the red probe on the lead of a component and the black probe on the following component lead. The multimeter acts as if it was a cord in your circuit. If you detach the multimeter, your circuit will not function.

Prior to measuring the current, be certain that you’ve plugged in the red probe in the appropriate port, in this situation µAmA. In the instance listed below, the exact same circuit of the previous example is used. The multimeter becomes part of the circuit.

Test for Continuity

If there is really reduced resistance between two factors, which is much less than a couple of ohms, both points are electrically linked and you’ll hear a continual sound. If the audio isn’t constant or if you do not hear any audio in any way, it suggests that what you’re testing has a damaged connection or isn’t attached in all.

WARNING: To be able to check continuity you ought to switch off the system! Shut off the power source.

Touch the two probes with each other and, as they are attached, you’ll hear a continual sound.To examination the continuity of a wire, you just need to attach each probe to the wire ideas.

Continuity is an excellent method to evaluate if two SMD pins are touching. If your eyes can not see it, the multimeter is typically a great second testing source. When a system is not functioning, continuity is one even more point to help troubleshoot the system.

  • Establish your multimeter to the continuity setup utilizing the selection knob.
  • The readout on the display will quickly check out “1”, which means that there isn’t any kind of continuity. This would be appropriate because we have not connected the probes to anything yet.
  • Next off, ensure the circuit is unplugged and has no power. After that connect one probe to one end of the cord and also the other probe to the various other end– it matters not which probe takes place which end. If there is a total circuit, your multimeter will certainly either beep, show a “0”, or something besides a “1”. If it still reveals a “1”, after that there’s an issue and your circuit isn’t total.
  • You can also check that the continuity attribute services your multimeter by touching both probes to every other. This completes the circuit as well as your multimeter ought to allow you know that.

A continuity examination informs us whether 2 points are electrically linked: if something is continuous, an electric current can stream freely from one end to the various other.

If there’s no continuity, it implies there is a break someplace in the circuit. This can suggest anything from a blown fuse or negative solder joint to an inaccurately wired circuit.

Altering the Fuse

Among the most usual errors with a brand-new multimeter is to measure current on a bread board by probing from VCC to GND. This will right away short power to ground via the multimeter causing the bread board power supply to brown out. As the current rushes via the multimeter, the internal fuse will warm up and afterwards melt out as 200mA streams through it. It will certainly happen in a flash and without any type of genuine audible or physical indication that something is incorrect.

Remember that measuring current is carried out in series (interrupt the VCC line to the breadboard or microcontroller to measure current). If you try to measure the current with a blown fuse, you’ll most likely observe that the meter reviews ‘0.00’ which the system doesn’t activate like it needs to when you connect the multimeter. This is due to the fact that the interior fuse is broken and functions as a busted cable or open.

To alter the fuse, discover your handy dandy mini screw vehicle driver, and also begin taking out screws. The parts and also PCB traces inside the multimeter are created to take different amounts of current. You will certainly damage and also possibly spoil your multimeter if you unintentionally push 5A with the 200mA port.

There are times where you need to measure high current devices like a motor or home heating aspect. Do you see the 2 places to put the red probe on the front of the multimeter? 10A on the left and mAVΩ on the right? If you try to measure more than 200mA on the mAVΩ port you run the danger of blowing the fuse. But if you make use of the 10A port to measure current, you run a much reduced threat of blowing the fuse. The compromise is level of sensitivity. As we spoke about above, by using the 10A port and knob setting, you will just be able to read down to 0.01 A or 10mA. Most of systems utilize greater than 10mA so the 10A setup and also port functions all right. If you’re attempting to measure really low power (micro or nano amps) the 200mA port with the 2mA, 200uA, or 20uA could be what you need.

Final thought

You’re now all set to utilize your digital multimeter to start measuring the globe around you. Really feel cost-free to start using it to answer several concerns. A digital multimeter will answer numerous concerns about electronic devices.

A multimeter is a necessary tool in any electronic devices lab. In this guide, we’ve revealed you how to utilize a multimeter to test voltage of live wires. You’ve found out how to measure voltage, current and also resistance, and also just how to check continuity.