fbpx

How to Use a Multimeter to Check a Circuit

Updated on: December 5, 2018

The Introduction

These guidelines will certainly show you just how to utilize a digital multimeter (DMM), an important tool that you can utilize to detect circuits, find out about various other people’s electronic styles, as well as even check a circuit. For this reason the ‘multi’-‘meter’ or multiple dimension name.

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

Every fixer ought to know their way around a multimeter, which has just north of a zillion utilizes for screening digital parts and circuits.

In this tutorial we’re going to reveal you how to make use of a multimeter. This tutorial is mostly addressed for newbies who are beginning out in electronic devices and also have no concept exactly how to use a multimeter and also how it can be helpful. We’ll explore the most usual attributes on a multimeter as well as just how to measure current, voltage, resistance as well as how to examine continuity.

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

A multimeter is a measurement device absolutely necessary in electronics. It incorporates three necessary attributes: a voltmeter, ohmeter, and ammeter, and sometimes continuity.

The tool enables you to recognize what is taking place in your circuits. Whenever something in your circuit isn’t functioning, it will certainly aid you repairing. Below’s some situations in electronics jobs that you’ll discover the multimeter beneficial:

  • is the button turn on?
  • is this wire conducting the electrical power or is it damaged?
  • just how much current is moving through this led?
  • just how much power do you have left on your batteries?

What should multimeters measure?

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

A handful of multimeters have a continuity check, resulting in a loud beep if two things are electrically attached. This is useful if, for example, you are developing a circuit and also connecting wires or soldering; the beep shows every little thing is connected as well as nothing has actually come loose. You can also utilize it to make certain 2 things are not attached, to assist stop brief circuits.

A number of multimeters likewise have a diode check function. A diode is like a one-way valve that only lets electrical power flow in one direction. The precise function of the diode check can differ from one type to another. If you’re collaborating with a diode and also can not tell which way it enters the circuit, or if you’re unsure the diode is functioning effectively, the check attribute can be rather handy. If your DMM has a diode check function, read the guidebook to learn specifically just how it works.

Advanced models could have various other features, such as the capacity to measure and also determine various other electrical parts, like transistors or capacitors. Since not all of the multimeters have these features, we will certainly not cover them in this tutorial. You can review your multimeter’s manual if you need to make use of these functions.

What Do Each Of the Symbols Mean?

There’s a lot taking place when you consider the selection knob, but if you’re only going to be doing some fundamental stuff, you won’t also utilize half of all the setups. All the same, here’s a rundown of what each symbol indicates:

Direct Current Voltage (DCV):quite often it will certainly be denoted with a V– instead. This setup is utilized to measure direct current (DC) voltage in things like batteries.
Alternating Current Voltage (ACV): Sometimes it will be denoted with a V ~ instead. This setting is made use of to measure the voltage from alternating current sources, which is virtually anything that connects into an electrical outlet, along with the power originating from the electrical outlet itself.
Resistance (Ω): This determines how much resistance there is in the circuit. The reduced the number, the simpler it is for the current to flow through, as well as vice versa.
Continuity: Usually signified by a wave or diode symbol. This just evaluates whether or not a circuit is full by sending a very percentage of current with the circuit and also seeing if it makes it out the other end. Otherwise, after that there’s something along the circuit that’s triggering an issue– locate it!
Straight Current Amperage (DCA): Similar to DCV, but as opposed to giving you a voltage analysis, it will tell you the amperage.
Direct Current Gain (hFE): This setup is to test transistors and their DC gain, yet it’s primarily worthless, because most electrical experts as well as hobbyists will certainly utilize the continuity check instead.

Your multimeter might additionally have a devoted setting for evaluating the amperage of AA, AAA, and also 9V batteries. This setup is usually represented with the battery sign.

Once again, you possibly will not also utilize half of the settings shown, so don’t obtain overwhelmed if you just recognize what a few of them do.

Just how to Utilize a Multimeter

For beginners, allow’s review a few of the various parts of a multimeter. At the really basic degree you have the tool itself, in addition to 2 probes, which are the black and also red wires that have plugs on one end as well as steel pointers on the other.

The tool itself has a screen 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 specific setting. Each setup might also have different number values, which are there to measure different toughness of voltages, resistances, and amps. So if you have your multimeter set to 20 in the DCV section, it will certainly measure voltages up to 20 volts.

Your DMM will certainly likewise have two or three ports for connecting in the probes:

  • the COM port stands for “Common”, and also the black probe will always connect into this port.
  • VΩmA port (sometimes denoted as mAVΩ) is just an acronym for voltage, resistance, and also current (in milliamps). This is where the red probe will connect into if you’re measuring voltage, resistance, continuity, as well as current much less than 200mA.
  • the 10ADC port (sometimes signified as just 10A) is used whenever you’re measuring current that’s more than 200mA. If you’re unsure of the current draw, begin with this port. On the various other hand, you would not use this port whatsoever if you’re measuring anything aside from current.

Caution: Make certain that if you’re measuring anything with a current greater than 200mA, you connect the red probe right into the 10A port, instead of the 200mA port. Or else you could blow the fuse that’s inside of the multimeter. Moreover, measuring anything over 10 amps might blow a fuse or damage the multimeters also.

Your measurement tool may have totally different ports for measuring amps, while the other port is especially simply for voltage, resistance, and continuity, however a lot of less costly multimeters will share ports.

Anyhow, allow’s start really utilizing a multimeter. We’ll be measuring the voltage of a AA battery, the current draw of a wall clock, and also the continuity of a straightforward wire as some examples to get you started and acquainted with using a multimeter.

Components of a Multimeter

A multimeter is made up by 4 crucial sections:

  • Display: this specific is where the dimensions are shown
  • Selection Knob: this picks what you want to measure
  • Ports: this is where you connect in the probes
  • Probes: a multimeter features two probes. Usually, one is red as well as the other is black.
Read Also:  Best Auto Range Multimeter

Ports

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

COM

COM mean usual 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 as well as black probe aside from shade.

10A

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

Selection Knob

The selection knob allows the user to establish the tool to check out various things such as milliamps (mA) of current, voltage (V) and resistance (Ω).

Probes

Two probes are connected into two of the ports on the front of the unit. The probes have a banana type connector on the end that connects into the multimeter. Any type of probe with a banana plug will collaborate with this meter. This allows for various sorts of probes to be made use of.

Probe Types

There are various kinds of probes available. Right here are a few of our faves:

  • Banana to Alligator Clips: These are wonderful cords for linking to big wires or pins on a breadboard. Helpful for carrying out longer term examinations where you don’t need to have to hold the probes in location while you adjust a circuit.
  • Banana to IC Hook: IC hooks work well on smaller ICs and legs of ICs.
  • Banana to Tweezers: Tweezers are convenient if you are requiring to evaluate SMD parts.
  • Banana to Test Probes: If you ever before break a probe, they are low-cost to replace!

Measuring Voltage

To start, allow’s measure voltage on a AA battery: Plug the black probe right into COM and the red probe right into mAVΩ. Set to “2V” in the DC (straight current) array. Mostly all mobile electronic devices make use of straight current), not alternating current. Link the black probe to the battery’s ground or ‘-‘ as well as the red probe to power or ‘+’. Press the probes with a little stress against the favorable and also negative terminals of the AA battery. If you’ve got a fresh battery, you ought to see around 1.5 V on the display (this battery is new, so its voltage is a little more than 1.5 V).

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

Measuring voltage

  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. Ensure the red probe is linked to the port with a V following to it.
  3. Attach the red probe to the positive side 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 worth on the screen.

Pointer: to measure voltage you have to connect your multimeter in parallel with the component you intend to measure the voltage. Putting the multimeter in parallel is placing each probe along the leads of the component you desire 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 approximately 1.5 V. So, you must select an array with the selection knob that can review the 1.5 V. So you ought to select 2V when it comes to this multimeter. If you take an autorange one, you don’t have to fret about the variety you need to pick.

Start by switching on it, plugging the probes right into their particular ports and afterwards establishing the selection knob to the greatest number value in the DCV section, which in my situation is 500 volts. If you do not know at the very least the voltage variety of the important things you’re measuring, it’s constantly an excellent suggestion to begin with the highest worth initially and after that function your method down till you get a precise analysis.

In this instance, we recognize the AA battery has a really reduced voltage, however we’ll start at 200 volts just for the benefit of example. Next, position the black probe on the unfavorable end of the battery and the red probe on the positive end. Take an appearance at the analysis on the display. Because 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 accurate analysis, so I’ll relocate the selection knob reduced to 20 volts. Right here, you can see that we have a more precise analysis that hovers in between 1.60 and also 1.61 volts. If you were to ever set the selection knob to a number worth less than the voltage of the thing you’re testing, the multimeter would certainly just read “1”, representing 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 way too much for the multimeter to deal with at that setting.

Regardless, you could be asking why you would need to evaluate the voltage of something to begin with. Well, in this instance with the AA battery, we’re inspecting to see if it has any type of juice left. At 1.6 volts, that’s a fully-loaded battery. Nonetheless, if it were to check out 1.2 volts, it’s close to being pointless.
In an extra functional circumstance, you can do this kind of measuring on a vehicle battery to see if it could be passing away or if the generator (which is what charges the battery) is going poor. An analysis between 12.4-12.7 volts means that the battery remains in excellent form. Anything reduced and also that’s evidence of a passing away battery. Furthermore, begin your vehicle up and also rev it up a little bit. If the voltage doesn’t increase to around 14 volts or so, then it’s likely that the alternator is having concerns.

Overload

What occurs if you choose a voltage setting that is as well reduced for the voltage you’re trying to measure? Nothing negative. The meter will merely display a 1. This is the meter attempting to tell you that it is overloaded or out-of-range. Whatever you’re attempting to read is way too much for that certain setup. Attempt altering the multimeter knob to a the following greatest setup.

Selection Knob

How come does the meter knob reviewed 20V as well as not 10V? If you’re looking to measure a voltage less than 20V, you look to the 20V setup. This will certainly permit you to read from 2.00 to 19.99. The first figure on numerous multimeters is just able to display a ‘1’ so the ranges are limited to 19.99 as opposed to 99.99. Thus the 20V max variety instead of 99V max array.

Measuring Resistance

Plug the red probe into the right port and turn the selection knob to the resistance area. After that, attach the probes to the resistor leads. The means you link the leads doesn’t matter, the result coincides.

Normal resistors have color codes on them. If you do not understand what they suggest, that’s ok! There are a lot of online calculators that are very easy to use. Nevertheless, if you ever locate on your own without internet access, a multimeter is extremely useful at measuring resistance.

Choose an arbitrary resistor and set the multimeter to the 20kΩ setup. Then hold the probes versus the resistor legs with the same amount of pressure you when pressing a key on a keyboard.

Read Also:  Best All Around Automotive Multimeter

The meter will certainly read one of 3 points, 0.00, 1, or the actual resistor worth.

In this instance, the meter reads 0.97, suggesting this resistor has a value of 970Ω, or about 1kΩ (remember you remain in the 20kΩ or 20,000 Ohm mode so you need to move the decimal 3 locations to the right or 970 Ohms).

If the multimeter checks out 1 or displays OL, it’s strained. You will certainly need to attempt a greater setting such as 200kΩ mode or 2MΩ (megaohm) mode. There is no damage if this take place, it merely suggests the array knob requires to be readjusted.

In case the multimeter reads 0.00 or almost zero, after that you need to lower the setting to 2kΩ or 200Ω.

Remember that many 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 reduced as 9.5 kΩ or as high as 10.5 kΩ. Do not worry, it’ll work just fine as a pull-up or general resistor.

As a guideline of thumb, it’s unusual to see a resistor much less than 1 Ohm. Keep in mind that measuring resistance is not excellent. Temperature can impact the checking out a great deal. Likewise, measuring resistance of a device while it is literally mounted in a circuit can be extremely complicated. The bordering elements on a circuit board can greatly influence the reading.

The mockup generally resembles with a fundamental clock running of a AA battery. On the silver lining, the cable going from the battery to the clock is separated. We just place our 2 probes in between that break to finish the circuit once again (with the red probe linked to the source of power), just this time around our multimeter will certainly review out the amps that the clock is pulling, which in this situation is around 0.08 mA.

While many multimeters can also measure alternating current (AC), it’s not truly a great concept (specifically if its real-time power), since AC can be hazardous if you wind up making a blunder. If you need to see whether or not an electrical outlet is functioning, use a non-contact tester rather.

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

IDEA: to put the multimeter in collection, you need to put the red probe on the lead of a component and the black probe on the next component lead. The multimeter acts as if it was a cable in your circuit. If you separate the multimeter, your circuit won’t work.

Before measuring the current, make certain that you’ve connected in the red probe in the ideal port, in this instance µAmA. In the instance listed below, the very same circuit of the previous instance is used. The multimeter becomes part of the circuit.

Tests Continuity

If there is very reduced resistance between two points, which is much less than a few ohms, both factors are electrically connected and you’ll listen to a continual audio. If the noise isn’t continuous or if you do not hear any type of sound whatsoever, it means that what you’re testing has a faulty connection or isn’t linked in all.

CAUTION: To evaluate continuity you should turn off the system. Switch off the power supply!

Touch both probes together as well as, as they are linked, you’ll listen to a continuous sound.To test the continuity of a cable, you just need to attach each probe to the wire tips.

Continuity is an excellent way to examine if two SMD pins are touching. If your eyes can’t see it, the multimeter is normally an excellent second testing resource. When a system is not functioning, continuity is another thing to assist repair the system.

  • Establish your multimeter to the continuity setup making use of the selection knob.
  • The readout on the display will instantly read “1”, which implies that there isn’t any type of continuity. This would certainly be correct considering that we haven’t attached the probes to anything yet.
  • Next, ensure the circuit is unplugged and also has no power. Then attach one probe to one end of the cable and also the other probe to the other end– it does not matter which probe takes place which end. If there is a full circuit, your multimeter will certainly either beep, reveal a “0”, or something aside from a “1”. If it still shows a “1”, after that there’s an issue and also your circuit isn’t full.
  • You can likewise test that the continuity feature deals with your multimeter by touching both probes per other. This completes the circuit and also your multimeter ought to allow you recognize that.

A continuity examination tells us whether 2 points are electrically connected: if something is continual, an electrical current can stream easily from one end to the other.

If there’s no continuity, it implies there is a break somewhere in the circuit. This could show anything from a blown fuse or negative solder joint to an incorrectly wired circuit.

Altering the Fuse

One of one of the most common errors with a new multimeter is to measure current on a bread board by probing from VCC to GND. This will quickly short power to ground through the multimeter causing the bread board power supply to brownish out. As the current rushes via the multimeter, the inner fuse will certainly warm up and afterwards melt out as 200mA moves with it. It will happen in a fraction of a second as well as without any kind of actual audible or physical sign that something is wrong.

Bear in mind that measuring current is performed in collection (interrupt the VCC line to the breadboard or microcontroller to measure current). If you attempt to measure the current with a blown fuse, you’ll most likely notice that the meter checks out ‘0.00’ and that the system does not switch on like it must when you attach the multimeter. This is due to the fact that the internal fuse is broken and also serves as a busted cable or open.

To change the fuse, locate your handy dandy mini screw chauffeur, as well as start obtaining screws. The parts and also PCB traces inside the multimeter are developed to take different amounts of current. You will harm as well as potentially wreck your multimeter if you unintentionally press 5A through the 200mA port.

There are times where you require to measure high current tools like an electric motor or heating element. Do you see the two areas to place the red probe on the front of the multimeter? 10A left wing and mAVΩ on the right? If you try to measure more than 200mA on the mAVΩ port you risk of blowing the fuse. However if you use the 10A port to measure current, you run a much reduced danger of blowing the fuse. The trade-off is sensitivity. As we discussed above, by utilizing the 10A port as well as handle setting, you will only be able to check out down to 0.01 A or 10mA. Most of systems utilize greater than 10mA so the 10A setup as well as port works well enough. If you’re trying to measure very low power (micro or nano amps) the 200mA port with the 2mA, 200uA, or 20uA can be what you require.

Conclusion

You’re now all set to use your digital multimeter to begin measuring the world around you. Do not hesitate to begin utilizing it to address lots of concerns. A digital multimeter will certainly respond to many inquiries about electronics.

A multimeter is a vital device in any kind of electronic devices laboratory. In this guide, we’ve revealed you How To Use a Multimeter. You’ve found out how to measure voltage, current as well as resistance, and exactly how to check continuity.