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How To Use A Multimeter To Test Wires

Updated on: July 10, 2019

Introduction

This tutorial will reveal you exactly how to make use of a digital multimeter (DMM), an indispensable tool that you can use to identify circuits, find out about other individuals’s digital layouts, and also even to test wires. Thus the ‘multi’-‘meter’ or multiple measurement name.

One of the most basic points we measure are voltage and current. A multimeter is also fantastic for some standard peace of mind checks as well as troubleshooting. Is your circuit not working? Does the button job? Put a meter on it! The multimeter is your initial protection when repairing a system. In this tutorial we will certainly cover measuring voltage, current, resistance and continuity.

Every fixer must know their way around a multimeter, which has just north of a zillion utilizes for screening electronic components and circuits.

In this tutorial we’re going to reveal you just how to utilize a multimeter. This tutorial is mainly attended to for novices that are starting out in electronic devices and have no suggestion exactly how to make use of a multimeter as well as how it can be valuable. We’ll explore the most common features on a multimeter and how to measure current, voltage, resistance as well as just how to check continuity.

What is a multimeter and also why do you need one?

A multimeter is a measurement device definitely essential in electronic devices. It combines 3 essential functions: a voltmeter, ohmeter, and also ammeter, and also sometimes continuity.

The tool permits you to understand what is going on in your circuits. Whenever something in your circuit isn’t functioning, it will aid you fixing. Right here’s some scenarios in electronics tasks that you’ll find the multimeter valuable:

  • is the button activate?
  • is this cord carrying out the electricity or is it damaged?
  • just how much current is streaming via this led?
  • exactly how much power do you have left on your batteries?

What could multimeters measure?

Mostly all multimeters can measure voltage, current, as well as resistance.

A few multimeters have a continuity check, leading to a loud beep if 2 things are electrically attached. This is useful if, as an example, you are developing a circuit and attaching cables or soldering; the beep suggests every little thing is linked and absolutely nothing has actually come loose. You can also use it to see to it 2 things are not connected, to help stop brief circuits.

A lot of multimeters additionally have a diode check feature. A diode is like a one-way shutoff that just allows electrical energy circulation in one instructions. The exact feature of the diode check can differ from one type to another. If you’re functioning with a diode and also can not inform which way it enters the circuit, or if you’re not sure the diode is working correctly, the check function can be rather handy. If your DMM has a diode check function, reviewed the guidebook to learn specifically how it functions.

Advanced models may have other features, such as the capacity to measure as well as identify various other electrical components, like transistors or capacitors. Given that not nearly all multimeters have these features, we will not cover them in this tutorial. You can review your multimeter’s guidebook if you need to use these attributes.

What Do Every One Of the Symbols Mean?

There’s a great deal going on when you look at the selection knob, however if you’re only mosting likely to be doing some basic things, you will not even utilize half of all the setups. In any type of instance, right here’s a review of what each symbol suggests:

Direct Current Voltage (DCV):In some cases it will be denoted with a V– instead. This setup is utilized to measure direct current (DC) voltage crazes like batteries.
Alternating Current Voltage (ACV): Sometimes it will certainly be represented with a V ~ instead. This setup is utilized to measure the voltage from alternating current resources, which is virtually anything that plugs right into an outlet, as well as the power coming from the outlet itself.
Resistance (Ω): This gauges just how much resistance there is in the circuit. The lower the number, the easier it is for the current to stream through, and vice versa.
Continuity: Usually represented by a wave or diode symbol. This simply checks whether a circuit is full by sending out a really small quantity of current through the circuit as well as seeing if it makes it out the other end. Otherwise, then there’s something along the circuit that’s causing an issue– locate it!
Direct Current Amperage (DCA): Similar to DCV, yet rather of offering you a voltage analysis, it will certainly inform you the amperage.
Straight Current Gain (hFE): This setting is to evaluate transistors and their DC gain, however it’s mostly pointless, considering that a lot of electrical contractors and hobbyists will certainly utilize the continuity check instead.

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

Once again, you possibly won’t even make use of half of the setups shown, so don’t obtain bewildered if you just recognize what a few of them do.

Just how to Use a Multimeter

For starters, allow’s go over several of the different parts of a multimeter. At the really fundamental degree you have the gadget itself, in addition to 2 probes, which are the black and red wires that have plugs on one end as well as metal tips on the various other.

The tool itself has a display at the top, which gives you your readout, as well as there’s a huge selection knob that you can rotate around to choose a particular setting. Each setup might likewise have different number worths, which are there to measure different strengths of voltages, resistances, and also amps. So if you have your multimeter collection to 20 in the DCV section, it will certainly measure voltages as much as 20 volts.

Your DMM will certainly likewise feature 2 or 3 ports for plugging in the probes:

  • COM port stands for “Common”, as well as the black probe will certainly constantly link into this port.
  • VΩmA port (occasionally denoted as mAVΩ) is simply a phrase for voltage, resistance, and also current (in milliamps). This is where the red probe will plug right into if you’re measuring voltage, resistance, continuity, and current less than 200mA.
  • the 10ADC port (in some cases represented as simply 10A) is utilized whenever you’re measuring current that’s greater than 200mA. If you’re unsure of the current draw, start with this port. On the various other hand, you would certainly not utilize this port in all if you’re measuring anything aside from current.

Warning: Make sure that if you’re measuring anything with a current more than 200mA, you plug the red probe into the 10A port, instead of the 200mA port. Otherwise you can blow the fuse that’s within the multimeters. Moreover, measuring anything over 10 amps might blow a fuse or damage the multimeters also.

Your measurement tool could have entirely different ports for measuring amps, while the other port is especially just for voltage, resistance, and also continuity, however a lot of less expensive multimeters will certainly share ports.

Anyhow, let’s start in fact making use of a multimeter. We’ll be measuring the voltage of a AA battery, the current draw of a wall clock, as well as the continuity of a straightforward wire as some instances to get you started and also knowledgeable about using a multimeter.

Parts of Multimeters

A multimeter is made up by 4 important sections:

  • Display: this specific is exactly where the measurements are shown
  • Selection Knob: this chooses what you want to measure
  • Ports: this is where you plug in the probes
  • Probes: a multimeter includes 2 probes. Usually, one is red as well as the various other is black.

Ports

  • “COM” or “–” port is where the black probe must be linked. The COM probe is conventionally black.
  • 10A is utilized when measuring large currents, better than 200mA.
  • µAmA is utilized to measure current.
  • enables you to measure voltage as well as resistance as well as examination continuity.

COM

COM represent common and is almost always linked to Ground or ‘-‘ of a circuit.The COM probe is conventionally black yet there is no difference in between the red probe and black probe aside from shade.

10A

10A is the special port used when measuring big currents (greater than 200mA).

Selection Knob

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

Probes

Two probes are connected into 2 of the ports on the front of the unit. The probes have a banana kind adapter on the end that connects into the multimeter. Any kind of probe with a banana plug will work with this meter. This permits various kinds of probes to be utilized.

Probe Types

There are several kinds of probes offered. Right here are a few of our faves:

  • Banana to Alligator Clips: These are excellent wires for attaching to big wires or pins on a breadboard. Helpful for executing longer term examinations where you don’t need to need to hold the probes in location while you manipulate a circuit.
  • Banana to IC Hook: IC hooks function well on smaller ICs as well as legs of ICs.
  • Banana to Tweezers: Tweezers are handy if you are needing to check SMD components.
  • Banana to Test Probes: If you ever before damage a probe, they are economical to change!

Measuring Voltage

To begin, let’s measure voltage on a AA battery: Plug the black probe right into COM and the red probe into mAVΩ. Set to “2V” in the DC (straight current) range. Almost all portable electronics use straight current), not alternating current. Connect the black probe to the battery’s ground or ‘-‘ and also the red probe to power or ‘+’. Press the probes with a little stress versus the favorable and negative terminals of the AA battery. If you’ve obtained a fresh battery, you must see around 1.5 V on the screen (this battery is brand brand-new, so its voltage is somewhat more than 1.5 V).

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

Measuring voltage

  1. Set the mode to V with a bumpy line if you’re measuring AC voltage or to the V with a straight line if you’re measuring DC voltage.
  2. Make sure the red probe is linked to the port with a V next to it.
  3. Attach the red probe to the silver lining of your component, which is where the current is coming from.
  4. Link the COM probe to the various other side of your component.
  5. Read the value on the display screen.

Suggestion: to measure voltage you have to attach your multimeter in parallel with the component you desire to measure the voltage. Positioning the multimeter in parallel is putting each probe along the leads of the component you intend 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 recognize that you’ll have roughly 1.5 V. So, you must select a range with the selection knob that can read the 1.5 V. So you must choose 2V when it comes to this multimeter. If you take an autorange one, you don’t need to bother with the range you require to select.

Begin by turning on it, plugging the probes right into their corresponding ports and after that setting the selection knob to the highest possible number worth in the DCV area, which in my situation is 500 volts. If you don’t recognize at least the voltage variety of the thing you’re measuring, it’s constantly an excellent suggestion to begin with the greatest value first and after that function your method down until you obtain a precise reading.

In this instance, we recognize the AA battery has a really low voltage, however we’ll start at 200 volts just for the sake of example. Next off, position the black probe on the adverse end of the battery and the red probe on the favorable end. Take a look at the reading on the screen. Considering that we have the multimeter set to a high 200 volts, it shows “1.6” on the display, indicating 1.6 volts.

However, I desire an even more accurate analysis, so I’ll move the selection knob reduced to 20 volts. Right here, you can see that we have an even more exact reading that hovers in between 1.60 and 1.61 volts. If you were to ever set the selection knob to a number worth lower than the voltage of the point you’re examining, the multimeter would certainly simply check out “1”, representing that it’s strained. So if I were to set the handle to 200 millivolts (0.2 volts), the 1.6 volts of the AA battery is excessive for the multimeter to take care of at that setup.

All the same, you could be asking why you would require to check the voltage of something in the first place. Well, in this situation 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 read 1.2 volts, it’s close to being unusable.
In an extra sensible scenario, you can do this sort of measuring on an automobile battery to see if it could be passing away or if the generator (which is what charges the battery) is spoiling. A reading between 12.4-12.7 volts implies that the battery is in good condition. Anything lower which’s proof of a passing away battery. In addition, start your car up as well as rev it up a little bit. If the voltage does not increase to about 14 volts or two, after that it’s likely that the generator is having issues.

Overload

What occurs if you select a voltage setting that is too low for the voltage you’re attempting to measure? Nothing poor. The meter will just present a 1. This is the meter attempting to inform you that it is overloaded or out-of-range. Whatever you’re trying to check out is way too much for that specific setting. Try changing the multimeter knob to a the next highest setup.

Selection Knob

As to why does the meter knob read 20V and not 10V? If you’re wanting to measure a voltage less than 20V, you count on the 20V setting. This will certainly permit you to read from 2.00 to 19.99. The first number on numerous multimeters is only able to present a ‘1’ so the arrays are limited to 19.99 instead of 99.99. Hence the 20V max array rather than 99V max variety.

Measuring Resistance

Connect the red probe right into the best port and turn the selection knob to the resistance area. Then, link the probes to the resistor leads. The way you link the leads doesn’t matter, the result coincides.

Normal resistors have color codes on them. If you don’t know what they indicate, that’s ok! There are lots of online calculators that are simple to use. However, if you ever find yourself without web accessibility, a multimeter is really useful at measuring resistance.

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

The meter will check out among three things, 0.00, 1, or the actual resistor value.

In this instance, the meter reviews 0.97, implying this resistor has a worth of 970Ω, or regarding 1kΩ (remember you remain in the 20kΩ or 20,000 Ohm mode so you require to move the decimal 3 locations to the right or 970 Ohms).

If the multimeter reads 1 or displays OL, it’s overwhelmed. You will require to try a greater mode such as 200kΩ setting or 2MΩ (megaohm) mode. There is no injury if this take place, it simply implies the variety knob requires to be readjusted.

If perhaps the multimeter reads 0.00 or virtually absolutely no, after that you require to decrease the mode to 2kΩ or 200Ω.

Bear in mind that numerous resistors have a 5% tolerance. This implies that the shade codes may suggest 10,000 Ohms (10kΩ), yet due to disparities in the production procedure a 10kΩ resistor can be as low as 9.5 kΩ or as high as 10.5 kΩ. Don’t worry, it’ll work just fine as a pull-up or general resistor.

Generally of thumb, it’s unusual to see a resistor less than 1 Ohm. Keep in mind that measuring resistance is not best. Temperature can affect the reviewing a great deal. Likewise, measuring resistance of a device while it is literally set up in a circuit can be really complicated. The bordering parts on a motherboard can significantly influence the analysis.

The mockup generally looks like with a basic clock running of a AA battery. On the silver lining, the cord going from the battery to the clock is separated. We simply position our 2 probes in between that break to finish the circuit once again (with the red probe connected to the source of power), just this moment our multimeter will certainly review out the amps that the clock is pulling, which in this case is around 0.08 mA.

While a lot of multimeters can additionally measure alternating current (AC), it’s not truly a good idea (especially if its live power), given that AC can be dangerous if you wind up making a mistake. If you require to see whether an electrical outlet is working, use a non-contact tester rather.

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

TIP: to position the multimeter in series, 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 cable in your circuit. If you disconnect the multimeter, your circuit won’t function.

Before measuring the current, be certain that you’ve connected at a loss probe in the appropriate port, in this instance µAmA. In the example listed below, the very same circuit of the previous instance is used. The multimeter belongs to the circuit.

Test Continuity

If there is very low resistance in between two points, which is much less than a couple of ohms, the 2 factors are electrically attached and also you’ll listen to a continual sound. If the audio isn’t constant or if you don’t listen to any sound in any way, it suggests that what you’re testing has a damaged link or isn’t linked in any way.

WARNING: In order to examine continuity you should shut off the system! Turn off the power supply!

Touch the 2 probes together and also, as they are attached, you’ll hear a continual sound.To test the continuity of a wire, you simply need to connect each probe to the cord pointers.

Continuity is a terrific means to examine if 2 SMD pins are touching. If your eyes can not see it, the multimeter is normally a terrific 2nd testing source. When a system is not functioning, continuity is another thing to help fix the system.

  • Set your multimeter to the continuity setting making use of the selection knob.
  • The readout on the display will promptly read “1”, which implies that there isn’t any kind of continuity. This would certainly be right given that we have not linked the probes to anything yet.
  • Next off, make certain the circuit is unplugged and also has no power. After that attach one probe to one end of the wire and the various other probe to the other end– it matters not which probe takes place which end. If there is a full circuit, your multimeter will certainly either beep, reveal a “0”, or something apart from a “1”. If it still reveals a “1”, after that there’s a trouble and also your circuit isn’t total.
  • You can likewise evaluate that the continuity attribute functions on your multimeter by touching both probes to each other. This completes the circuit and your multimeter need to let you recognize that.

A continuity examination informs us whether two things are electrically linked: if something is continuous, an electric current can move openly from one end to the various other.

If there’s no continuity, it suggests there is a break somewhere in the circuit. This might show anything from a blown fuse or bad solder joint to an inaccurately wired circuit.

Altering the Fuse

Among the most typical mistakes with a new multimeter is to measure current on a bread board by penetrating from VCC to GND. This will immediately brief power to ground via the multimeter causing the bread board power supply to brown out. As the current rushes through the multimeter, the internal fuse will certainly warm up and afterwards melt out as 200mA streams with it. It will occur in a fraction of a second and also without any type of actual audible or physical sign that something is wrong.

Keep in mind that measuring current is performed in collection (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’ and that the system does not activate like it ought to when you attach the multimeter. This is because the interior fuse is damaged and also functions as a busted wire or open.

To change the fuse, discover your helpful dandy mini screw motorist, and also begin obtaining screws. The elements and also PCB traces inside the multimeter are developed to take different amounts of current. You will damage and perhaps wreck your multimeter if you accidentally press 5A with the 200mA port.

There are times where you need to measure high current tools like an electric motor or home heating component. Do you see the two places to put the red probe on the front of the multimeter? 10A left wing as well as mAVΩ on the right? If you attempt to measure greater than 200mA on the mAVΩ port you run the risk of blowing the fuse. However if you utilize the 10A port to measure current, you run a much reduced risk of blowing the fuse. The compromise is sensitivity. As we discussed above, by utilizing the 10A port and also handle setting, you will just have the ability to read to 0.01 A or 10mA. A lot of systems use greater than 10mA so the 10A setup as well as port works all right. If you’re attempting to measure extremely reduced power (mini or nano amps) the 200mA port with the 2mA, 200uA, or 20uA could be what you need.

Final thought

You’re currently prepared to use your digital multimeter to start measuring the world around you. Feel free to start using it to respond to many questions. A digital multimeter will certainly address lots of questions about electronics.

A multimeter is a necessary tool in any electronics laboratory. In this overview, we’ve revealed you How To Use a Multimeter. You’ve found out how to measure voltage, current and also resistance, and just how to inspect continuity.