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How to Use a Digital Multimeter to Test Continuity

Updated on: December 11, 2018

The Introduction

These recommendations will show you exactly how to use a digital multimeter (DMM), a crucial device that you can use to identify circuits, learn more about various other people’s digital designs, and also test continuity. For this reason the ‘multi’-‘meter’ or several measurement name.

The most fundamental things we measure are voltage and also current. A multimeter is additionally great for some fundamental sanity checks and also troubleshooting. Is your circuit not functioning? Does the switch work? Place a meter on it! The multimeter is your very first protection when fixing a system. In this tutorial we will cover measuring voltage, current, resistance as well as continuity.

Every fixer ought to know their means around a multimeter, which has just north of a zillion uses for screening digital components and also circuits.

In this tutorial we’re going to reveal you how to utilize a multimeter. This tutorial is mainly dealt with for newbies who are starting out in electronics and have no idea just how to use a multimeter and also how it can be beneficial. We’ll check out one of the most typical functions on a multimeter and how to measure current, voltage, resistance and how to inspect continuity.

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

A multimeter is a measurement tool absolutely necessary in electronic devices. It combines three crucial attributes: a voltmeter, ohmeter, and ammeter, as well as in many cases continuity.

The tool enables you to comprehend what is taking place in your circuits. Whenever something in your circuit isn’t working, it will help you troubleshooting. Below’s some circumstances in electronics projects that you’ll discover the multimeter beneficial:

  • is the switch activate?
  • is this cable performing the electrical energy or is it broken?
  • just how much current is flowing via this led?
  • how much power do you have left on your batteries?

What could multimeters measure?

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

Various multimeters have a continuity check, causing a loud beep if two points are electrically attached. This is helpful if, as an example, you are building a circuit as well as connecting cables or soldering; the beep suggests whatever is connected and also absolutely nothing has come loose. You can also use it to see to it 2 things are not linked, to help prevent brief circuits.

A number of multimeters additionally have a diode check function. A diode is like a one-way shutoff that just lets electrical power flow in one instructions. The specific function of the diode check can differ from one type to another. If you’re collaborating with a diode and also can’t tell which means it enters the circuit, or if you’re not sure the diode is working properly, the check attribute can be quite helpful. If your DMM has a diode check function, reviewed the guidebook to learn exactly how it works.

Advanced models might have other features, such as the capacity to measure and determine various other electric components, like transistors or capacitors. Because not almost all multimeters have these functions, we will certainly not cover them in this tutorial. You can read your multimeter’s guidebook if you need to use these features.

What Do All Of the Symbols Mean?

There’s a whole lot taking place when you take a look at the selection knob, yet if you’re just going to be doing some fundamental stuff, you won’t even make use of half of all the setups. All the same, below’s a rundown of what each sign indicates:

Direct Current Voltage (DCV):Occasionally it will certainly be represented with a V– rather. This setup is utilized to measure direct current (DC) voltage crazes like batteries.
Alternating Current Voltage (ACV): Sometimes it will certainly be signified with a V ~ rather. This setup is utilized to measure the voltage from alternating current resources, which is practically anything that connects into an outlet, along with the power coming from the electrical outlet itself.
Resistance (Ω): This determines exactly how much resistance there is in the circuit. The reduced the number, the much easier it is for the current to flow through, and also the other way around.
Continuity: Usually signified by a wave or diode symbol. This just checks whether a circuit is complete by sending a really small amount 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– discover it!
Direct Current Amperage (DCA): Similar to DCV, however rather than giving you a voltage reading, it will tell you the amperage.
Straight Current Gain (hFE): This setup is to evaluate transistors as well as their DC gain, however it’s primarily useless, since a lot of electrical contractors and also hobbyists will certainly use the continuity check instead.

Your multimeter may additionally have a devoted setting for testing the amperage of AA, AAA, and 9V batteries. This setting is usually signified with the battery sign.

Once more, you possibly won’t even utilize fifty percent of the setups revealed, so do not get overwhelmed if you just know what a few of them do.

How to Use a Multimeter

For starters, let’s review some of the different parts of a multimeter. At the extremely standard level you have the tool itself, in addition to 2 probes, which are the black and also red cables that have plugs on one end and metal pointers on the various other.

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

Your DMM will additionally have two or 3 ports for connecting in the probes:

  • COM port mean “Common”, and also the black probe will certainly always connect into this port.
  • VΩmA port (often represented as mAVΩ) is just an acronym for voltage, resistance, and current (in milliamps). This is where the red probe will connect right into if you’re measuring voltage, resistance, continuity, and current less than 200mA.
  • the 10ADC port (in some cases signified as just 10A) is used whenever you’re measuring current that’s greater 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 besides current.

Warning: Make sure that if you’re measuring anything with a current greater than 200mA, you connect the red probe into the 10A port, instead than the 200mA port. Otherwise you could blow the fuse that’s within the multimeters. In addition, measuring anything over 10 amps can blow a fuse or destroy the multimeter as well.

Your measurement tool could have totally separate ports for measuring amps, while the various other port is particularly simply for voltage, resistance, as well as continuity, but the majority of less expensive multimeters will certainly share ports.

Anyway, let’s get going really using a multimeter. We’ll be measuring the voltage of a AA battery, the current draw of a wall surface clock, and the continuity of an easy cord as some instances to get you began and accustomed to making use of a multimeter.

Parts of a Multimeter

A multimeter includes 4 components:

  • Display: this specific is exactly where the measurements are presented
  • Selection Knob: this picks what you wish to measure
  • Ports: this is where you connect in the probes
  • Probes: a multimeter comes with 2 probes. Normally, one is red and the various other is black.
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Ports

  • “COM” or “–” port is where the black probe must be attached. The COM probe is traditionally black.
  • 10A is used when measuring huge currents, more than 200mA.
  • µAmA is made use of to measure current.
  • allows you to measure voltage as well as resistance and also test continuity.

COM

COM mean common as well as is generally linked to Ground or ‘-‘ of a circuit.The COM probe is traditionally black but there is no distinction between the red probe and black probe apart from color.

10A

10A is the special port utilized when measuring huge currents (above 200mA).

Selection Knob

The selection knob allows the user to set the tool to check out different points such as milliamps (mA) of current, voltage (V) and also resistance (Ω).

Probes

Two probes are linked into 2 of the ports on the front of the system. The probes have a banana type port on completion that connects right into the multimeter. Any kind of probe with a banana plug will collaborate with this meter. This enables various sorts of probes to be used.

Probe Types

There are lots of different kinds of probes available. Here are a few of our favorites:

  • Banana to Alligator Clips: These are great cable televisions for connecting to huge wires or pins on a breadboard. Helpful for executing longer term examinations where you do not need to have to hold the probes in location while you adjust a circuit.
  • Banana to IC Hook: IC hooks function well on smaller sized ICs as well as legs of ICs.
  • Banana to Tweezers: Tweezers are helpful if you are needing to examine SMD parts.
  • Banana to Test Probes: If you ever before damage a probe, they are cheap to change!

Measuring Voltage

To start, allow’s measure voltage on a AA battery: Plug the black probe into COM as well as the red probe into mAVΩ. Establish to “2V” in the DC (straight current) range. Mostly all portable electronic devices make use of direct current), not alternating current. Connect the black probe to the battery’s ground or ‘-‘ and the red probe to power or ‘+’. Press the probes with a little stress versus the positive and also unfavorable terminals of the AA battery. If you’ve got a fresh battery, you must see around 1.5 V on the display (this battery is brand name new, so its voltage is a little greater than 1.5 V).

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

To measure voltage:

  1. Set the setting 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 certain the red probe is linked to the port with a V beside it.
  3. Connect the red probe to the positive side of your component, which is where the current is originating from.
  4. Link the COM probe to the opposite of your component.
  5. Read the worth on the display.

Pointer: to measure voltage you need to link your multimeter in parallel with the component you want 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 recognize that you’ll have around 1.5 V. So, you ought to pick a variety with the selection knob that can check out the 1.5 V. So you should choose 2V in the case of this multimeter. If you have an autorange one, you don’t have to fret concerning the range you require to choose.

Begin by turning on it, connecting the probes right into their respective ports and afterwards setting the selection knob to the highest possible number value in the DCV section, which in my instance is 500 volts. If you don’t recognize a minimum of the voltage series of things you’re measuring, it’s always a good idea to begin with the highest value initially as well as after that function your way down up until you get an accurate analysis.

In this case, we recognize the AA battery has a really reduced voltage, yet we’ll start at 200 volts simply for the sake of instance. Next, place the black probe on the unfavorable end of the battery as well as 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 reveals “1.6” on the display, meaning 1.6 volts.

Nonetheless, I desire a more exact analysis, so I’ll relocate the selection knob reduced down to 20 volts. Here, you can see that we have an even more precise analysis that floats in between 1.60 as well as 1.61 volts. If you were to ever establish the selection knob to a number worth lower than the voltage of things you’re testing, the multimeter would simply read “1”, symbolizing that it’s overloaded. So if I were to set the knob to 200 millivolts (0.2 volts), the 1.6 volts of the AA battery is excessive for the multimeter to handle at that setting.

All the same, you may be asking why you would certainly need to examine the voltage of something to begin with. Well, in this situation with the AA battery, we’re inspecting to see if it has any kind of juice left. At 1.6 volts, that’s a fully-loaded battery. Nonetheless, if it were to review 1.2 volts, it’s close to being pointless.
In a more useful circumstance, you might do this kind of measuring on a car battery to see if it may be dying or if the generator (which is what charges the battery) is going negative. A reading in between 12.4-12.7 volts suggests that the battery remains in good form. Anything lower as well as that’s proof of a passing away battery. Additionally, start your vehicle up as well as rev it up a little bit. If the voltage doesn’t boost to about 14 volts or two, after that it’s most likely that the generator is having concerns.

Overload

What takes place if you choose a voltage setting that is also low for the voltage you’re attempting to measure? Absolutely nothing bad. The meter will merely present a 1. This is the meter attempting to inform you that it is overloaded or out-of-range. Whatever you’re attempting to review is excessive for that specific setup. Attempt altering the multimeter knob to a the next highest setup.

Selection Knob

Why does the meter knob checked out 20V as well as not 10V? If you’re seeking to measure a voltage less than 20V, you turn to the 20V setting. This will allow you to read from 2.00 to 19.99. The first digit on lots of multimeters is only able to show a ‘1’ so the ranges are restricted to 19.99 rather of 99.99. Therefore the 20V max variety rather than 99V max variety.

Measuring Resistance

Plug the red probe right into the right port and turn the selection knob to the resistance section. Then, attach the probes to the resistor leads. The method you attach the leads does not matter, the result is the same.

Normal resistors have shade codes on them. If you don’t recognize what they mean, that’s ok! There are a lot of on the internet calculators that are simple to use. However, if you ever before find yourself without net access, a multimeter is really convenient at measuring resistance.

Choose an arbitrary resistor and also established the multimeter to the 20kΩ setting. After that hold the probes against the resistor legs with the very same quantity of stress you when pushing a key on a key-board.

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The meter will read among 3 things, 0.00, 1, or the actual resistor worth.

In this instance, the meter reads 0.97, suggesting this resistor has a worth of 970Ω, or concerning 1kΩ (remember you remain in the 20kΩ or 20,000 Ohm setting so you require to relocate the decimal 3 locations to the right or 970 Ohms).

If the multimeter checks out 1 or displays OL, it’s overloaded. You will certainly need to try a higher setting such as 200kΩ setting or 2MΩ (megaohm) setting. There is no injury if this take place, it simply suggests the range knob needs to be readjusted.

If perhaps the multimeter reviews 0.00 or virtually no, then you require to reduce the mode to 2kΩ or 200Ω.

Bear in mind that numerous resistors have a 5% tolerance. This implies that the color codes may show 10,000 Ohms (10kΩ), but due to inconsistencies in the production process a 10kΩ resistor might be as reduced as 9.5 kΩ or as high as 10.5 kΩ. Do not stress, it’ll function just great as a pull-up or general resistor.

Generally of thumb, it’s rare to see a resistor much less than 1 Ohm. Bear in mind that measuring resistance is not excellent. Temperature can influence the checking out a lot. Also, measuring resistance of a gadget while it is physically set up in a circuit can be extremely challenging. The bordering parts on a circuit board can considerably influence the analysis.

The mockup generally looks like with a fundamental clock running of a AA battery. On the silver lining, the wire going from the battery to the clock is damaged up. We simply position our two probes in between that break to finish the circuit again (with the red probe linked to the power resource), only this time our multimeter will review out the amps that the clock is drawing, which in this situation is around 0.08 mA.

While the majority of multimeters can likewise measure alternating current (AC), it’s not actually a great suggestion (particularly if its real-time power), considering that AC can be dangerous if you finish up slipping up. If you need to see whether an outlet is functioning, make use of a non-contact tester rather.

To measure current you need to birth in mind that elements in series share a current. So, you require to attach your multimeter in series with your circuit.

POINTER: to put the multimeter in series, you need to place the red probe on the lead of a component as well as the black probe on the following component lead. The multimeter acts as if it was a wire in your circuit. If you disconnect the multimeter, your circuit won’t function.

Prior to measuring the current, be certain that you’ve plugged at a loss probe in the right port, in this instance µAmA. In the instance below, the same circuit of the previous instance is made use of. The multimeter becomes part of the circuit.

Test for Continuity

If there is very low resistance between two factors, which is much less than a few ohms, the 2 factors are electrically attached and you’ll hear a continuous sound. If the sound isn’t continuous or if you do not hear any audio in any way, it means that what you’re testing has a malfunctioning link or isn’t attached in any way.

WARNING: To check continuity you must turn off the system. Turn off the power source.

Touch both probes with each other and also, as they are linked, you’ll hear a continual sound.To test the continuity of a cable, you simply require to connect each probe to the cord suggestions.

Continuity is an excellent way to examine if two SMD pins are touching. If your eyes can’t see it, the multimeter is typically a wonderful 2nd testing source. When a system is not working, continuity is another point to assist troubleshoot the system.

  • Establish your multimeter to the continuity setting making use of the selection knob.
  • The readout on the display will quickly check out “1”, which indicates that there isn’t any kind of continuity. This would be right considering that we have not attached the probes to anything yet.
  • Next, make sure the circuit is unplugged as well as has no power. Then attach one probe to one end of the cord as well as the other probe to the other end– it does not matter which probe takes place which end. If there is a complete circuit, your multimeter will certainly either beep, reveal a “0”, or something aside from a “1”. If it still reveals a “1”, then there’s an issue and also your circuit isn’t complete.
  • You can additionally evaluate that the continuity function functions on your multimeter by touching both probes to each various other. This finishes the circuit and also your multimeter ought to let you understand that.

A continuity examination informs us whether 2 points are electrically attached: if something is continual, an electrical 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 might show anything from a blown fuse or bad solder joint to an improperly wired circuit.

Changing the Fuse

One of one of the most typical errors with a brand-new multimeter is to measure current on a bread board by probing from VCC to GND. This will instantly brief power to ground through the multimeter creating the bread board power supply to brown out. As the current rushes via the multimeter, the internal fuse will certainly warm up and afterwards wear out as 200mA streams via it. It will happen in an instant and also without any type of real audible or physical indicator that something is incorrect.

Bear in mind that measuring current is carried out in collection (disturb the VCC line to the breadboard or microcontroller to measure current). If you try to measure the current with a blown fuse, you’ll possibly see that the meter reviews ‘0.00’ and that the system doesn’t activate like it should when you affix the multimeter. This is due to the fact that the internal fuse is damaged and serves as a broken cable or open.

To change the fuse, locate your handy dandy mini screw chauffeur, and begin securing screws. The components and PCB traces inside the multimeter are designed to take different quantities of current. You will certainly harm as well as possibly spoil your multimeter if you accidentally press 5A with the 200mA port.

There are times where you require to measure high current tools like an electric motor or burner. Do you see the 2 areas to put the red probe on the front of the multimeter? 10A on the left as well as mAVΩ on the right? If you attempt to measure more than 200mA on the mAVΩ port you risk of blowing the fuse. But if you utilize the 10A port to measure current, you run a much lower risk of blowing the fuse. The trade-off is sensitivity. As we spoke about above, by using the 10A port and handle setting, you will just be able to check out to 0.01 A or 10mA. Many of systems utilize greater than 10mA so the 10A setup and port works all right. If you’re attempting to measure really reduced power (micro or nano amps) the 200mA port with the 2mA, 200uA, or 20uA might be what you require.

Conclusions

You’re currently prepared to utilize your digital multimeter to begin measuring the globe around you. Do not hesitate to start using it to answer numerous questions. A digital multimeter will respond to many inquiries concerning electronics.

A multimeter is a crucial device in any type of electronic devices laboratory. In this guide, we’ve shown you How To Use a Multimeter. You’ve discovered how to measure voltage, current as well as resistance, and exactly how to inspect continuity.