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How to Use a Multimeter to Test a Switch

Updated on: December 6, 2018

The Intro

These tips will certainly reveal you how to use a digital multimeter (DMM), a crucial device that you can utilize to detect circuits, discover various other people’s electronic styles, as well as also test a switch. For this reason the ‘multi’-‘meter’ or numerous measurement name.

The most basic points we measure are voltage and also current. A multimeter is likewise wonderful for some basic sanity checks and troubleshooting. Is your circuit not functioning? Does the switch job? Place a meter on it! The multimeter is your first protection when repairing a system. In this tutorial we will certainly cover measuring voltage, current, resistance and continuity.

Every fixer needs to understand their method around a multimeter, which has just north of a zillion utilizes 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 attended to for novices who are starting in electronic devices and have no concept exactly how to make use of a multimeter and also how it can be beneficial. We’ll check out one of the most typical attributes on a multimeter as well as just how to measure current, voltage, resistance and just how to check continuity.

What is a multimeter and why do you need one?

A multimeter is a measurement device absolutely required in electronic devices. It combines three vital attributes: a voltmeter, ohmeter, and ammeter, as well as in some instances continuity.

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

  • is the switch turn on?
  • is this wire performing the electricity or is it damaged?
  • how much current is flowing with this led?
  • just how much power do you have left on your batteries?

What can multimeters measure?

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

A lot of multimeters have a continuity check, causing a loud beep if two points are electrically linked. This is valuable if, for example, you are constructing a circuit and also linking wires or soldering; the beep suggests everything is connected and also nothing has come loose. You can also utilize it to make sure two points are not linked, to aid stop short circuits.

Quite a few multimeters also have a diode check function. A diode is like a one-way valve that only allows electrical energy circulation in one direction. The precise feature of the diode check can vary from one type to another. If you’re collaborating with a diode as well as can not tell which means it enters the circuit, or if you’re unsure the diode is working properly, the check feature can be fairly handy. If your DMM has a diode check feature, reviewed the handbook to learn specifically just how it functions.

Advanced models may have various other functions, such as the capacity to measure as well as identify various other electrical parts, like transistors or capacitors. Considering that not just about all multimeters have these features, we will certainly not cover them in this tutorial. You can read your multimeter’s guidebook if you need to utilize these attributes.

What Do Every One Of the Symbols Mean?

There’s a whole lot going on when you check out the selection knob, but if you’re only mosting likely to be doing some basic stuff, you will not also make use of fifty percent of all the settings. In any type of situation, right here’s a review of what each sign implies:

Direct Current Voltage (DCV):at times it will certainly be signified with a V– rather. This setting is utilized to measure straight current (DC) voltage in things like batteries.
Alternating Current Voltage (ACV): Sometimes it will certainly be denoted with a V ~ instead. This setup is utilized to measure the voltage from alternating current resources, which is pretty much anything that links into an outlet, in addition to 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 stream through, and also the other way around.
Continuity: Usually represented by a wave or diode sign. This just examines whether a circuit is full by sending out a really percentage of current with the circuit and also seeing if it makes it out the various other end. Otherwise, then there’s something along the circuit that’s creating a problem– discover it!
Direct Current Amperage (DCA): Similar to DCV, but as opposed to offering you a voltage reading, it will tell you the amperage.
Straight Current Gain (hFE): This setup is to examine transistors and their DC gain, yet it’s mainly useless, given that a lot of electrical experts as well as hobbyists will use the continuity check instead.

Your multimeter may additionally have a dedicated setting for testing the amperage of AA, AAA, as well as 9V batteries. This setup is normally signified with the battery sign.

Once more, you most likely won’t also make use of fifty percent of the settings revealed, so do not get overwhelmed if you only recognize what a few of them do.

Just how to Utilize a Multimeter

For beginners, allow’s look at a few of the various components of a multimeter. At the very basic degree you have the gadget itself, in addition to 2 probes, which are the black and red cables that have plugs on one end as well as metal pointers on the various other.

The tool itself has a display screen at the top, which offers you your readout, and also there’s a big selection knob that you can rotate around to select a details setup. Each setup might also have different number worths, which exist to measure different staminas of voltages, resistances, and amps. So if you have your multimeter collection to 20 in the DCV section, it will certainly measure voltages approximately 20 volts.

Your DMM will certainly also come with 2 or 3 ports for plugging in the probes:

  • the COM port represent “Common”, and the black probe will always connect into this port.
  • VΩmA port (occasionally 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 much less than 200mA.
  • the 10ADC port (sometimes denoted as simply 10A) is utilized whenever you’re measuring current that’s greater than 200mA. If you’re not certain of the current draw, begin with this port. On the various other hand, you would certainly not utilize this port at all if you’re measuring anything aside from current.

Warning: Make certain 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 might blow the fuse that’s within the multimeter. Moreover, measuring anything over 10 amps could blow a fuse or damage the multimeter also.

Your measurement tool could have entirely separate ports for measuring amps, while the other port is particularly simply for voltage, resistance, and continuity, yet the majority of less costly multimeters will share ports.

Anyway, let’s get going in fact making use of 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 simple wire as some examples to obtain you started and acquainted with utilizing a multimeter.

Parts of Multimeters

Multimeters are made up by 4 essential sections:

  • Display: this is just where the measurements are displayed
  • Selection Knob: this selects what you intend to measure
  • Ports: this is where you connect in the probes
  • Probes: a multimeter comes with 2 probes. Typically, one is red and the other is black.
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Ports

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

COM

COM stands for common and also is nearly always attached to Ground or ‘-‘ of a circuit.The COM probe is conventionally black however there is no distinction between the red probe and also black probe aside from shade.

10A

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

Selection Knob

The selection knob permits the individual to establish the tool to check out different things such as milliamps (mA) of current, voltage (V) and also resistance (Ω).

Probes

2 probes are linked into two of the ports on the front of the device. The probes have a banana type connector on the end that connects into the multimeter. Any kind of probe with a banana plug will certainly function with this meter. This enables various kinds of probes to be used.

Probe Types

There are several kinds of probes offered. Below are a few of our favorites:

  • Banana to Alligator Clips: These are fantastic cable televisions for attaching to large wires or pins on a breadboard. Helpful for performing longer term examinations where you don’t have to need to hold the probes in place while you manipulate a circuit.
  • Banana to IC Hook: IC hooks work well on smaller sized ICs and also legs of ICs.
  • Banana to Tweezers: Tweezers are helpful if you are needing to examine SMD components.
  • Banana to Test Probes: If you ever before damage a probe, they are low-cost to replace!

Measuring Voltage

To start, let’s measure voltage on a AA battery: Plug the black probe right into COM and also the red probe into mAVΩ. Establish to “2V” in the DC (straight current) array. Nearly all portable electronic devices utilize 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 versus the favorable as well as unfavorable terminals of the AA battery. If you’ve obtained a fresh battery, you ought to see around 1.5 V on the screen (this battery is new, so its voltage is slightly more than 1.5 V).

You should measure DC voltage or AC voltage. The V with a straight line implies DC voltage. The V with the bumpy line suggests AC voltage.

To measure 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 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 coming from.
  4. Link the COM probe to the opposite side of your component.
  5. Check out the value on the display screen.

Idea: to measure voltage you have to connect your multimeter in parallel with the component you want 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 instance we’re going to measure the voltage of a 1.5 V battery. You recognize that you’ll have around 1.5 V. So, you should pick an array with the selection knob that can check out the 1.5 V. So you must choose 2V in the situation of this multimeter. If you take an autorange one, you don’t need to stress over the variety you require to pick.

Start by turning on it, connecting the probes into their respective ports as well as then establishing the selection knob to the greatest number value in the DCV area, which in my situation is 500 volts. If you do not understand at least the voltage variety of the important things you’re measuring, it’s constantly a great idea to begin with the highest worth initially and after that function your way down up until you get an accurate reading.

In this case, we understand the AA battery has a very low voltage, yet we’ll start at 200 volts simply for the sake of example. Next, place the black probe on the unfavorable end of the battery and the red probe on the favorable end. Take an appearance at the reading on the display. Because we have the multimeter collection to a high 200 volts, it shows “1.6” on the screen, indicating 1.6 volts.

However, I want an even more accurate reading, so I’ll move the selection knob lower down to 20 volts. Below, you can see that we have an even more accurate reading that hovers between 1.60 and also 1.61 volts. If you were to ever before set the selection knob to a number worth reduced than the voltage of things you’re checking, the multimeter would certainly just review “1”, indicating that it’s overloaded. So if I were to establish the handle to 200 millivolts (0.2 volts), the 1.6 volts of the AA battery is way too much for the multimeter to handle at that setup.

In any situation, you may be asking why you would require to check the voltage of something in the first area. Well, in this instance with the AA battery, we’re examining to see if it has any juice left. At 1.6 volts, that’s a fully-loaded battery. Nevertheless, if it were to review 1.2 volts, it’s close to being unusable.
In a more useful circumstance, you could do this sort of measuring on a car battery to see if it could be dying or if the alternator (which is what bills the battery) is going bad. A reading between 12.4-12.7 volts implies that the battery is in good condition. Anything lower as well as that’s proof of a passing away battery. In addition, begin your cars and truck up and rev it up a little bit. If the voltage does not boost to about 14 volts or two, then it’s most likely that the generator is having concerns.

Overload

What takes place if you select a voltage setup that is too reduced for the voltage you’re attempting to measure? Absolutely nothing negative. The meter will just display a 1. This is the meter attempting to tell you that it is overloaded or out-of-range. Whatever you’re trying to read is excessive for that certain setup. Try changing the multimeter knob to a the following greatest setting.

Selection Knob

Just why does the meter knob reviewed 20V and not 10V? If you’re wanting to measure a voltage much less than 20V, you count on the 20V setting. This will certainly allow you to check out from 2.00 to 19.99. The first number on several multimeters is only able to show a ‘1’ so the ranges are restricted to 19.99 rather than 99.99. Hence the 20V max array as opposed to 99V max range.

Measuring Resistance

Plug the red probe right into the ideal port and also turn the selection knob to the resistance section. After that, attach the probes to the resistor leads. The method you link the leads doesn’t matter, the outcome is the exact same.

Normal resistors have color codes on them. If you do not understand what they mean, that’s ok! There are lots of on-line calculators that are easy to use. Nonetheless, if you ever before discover on your own without internet accessibility, a multimeter is very handy at measuring resistance.

Choose a random resistor and set the multimeter to the 20kΩ setting. Then hold the probes versus the resistor legs with the exact same amount of stress you when pushing a trick 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 case, the meter reads 0.97, suggesting this resistor has a worth of 970Ω, or about 1kΩ (remember you remain in the 20kΩ or 20,000 Ohm setting so you need to move the decimal three places to the right or 970 Ohms).

If the multimeter checks out 1 or shows OL, it’s overloaded. You will need to try a greater setting such as 200kΩ mode or 2MΩ (megaohm) setting. There is no harm if this take place, it simply implies the range knob needs to be changed.

If the multimeter reviews 0.00 or nearly absolutely no, then you require to lower the mode to 2kΩ or 200Ω.

Keep in mind that lots of resistors have a 5% tolerance. This indicates that the color codes might suggest 10,000 Ohms (10kΩ), but due to discrepancies 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 simply great as a pull-up or general resistor.

As a regulation of thumb, it’s rare to see a resistor much less than 1 Ohm. Bear in mind that measuring resistance is not excellent. Temperature level can affect the checking out a whole lot. Additionally, measuring resistance of a tool while it is physically installed in a circuit can be very tricky. The bordering parts on a motherboard can significantly influence the reading.

The mockup typically resembles with a basic clock escaping of a AA battery. On the favorable side, the cord going from the battery to the clock is separated. We merely position our 2 probes in between that break to complete the circuit again (with the red probe attached to the power resource), just this time around our multimeter will read out the amps that the clock is pulling, which in this case is around 0.08 mA.

While the majority of multimeters can also measure rotating current (AC), it’s not truly a good concept (specifically if its real-time power), since AC can be dangerous if you wind up slipping up. If you require to see whether or not an outlet is working, make use of a non-contact tester instead.

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

TIP: to position 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 next component lead. The multimeter acts as if it was a cord in your circuit. If you separate the multimeter, your circuit will not function.

Before measuring the current, make certain that you’ve connected in the red probe in the best port, in this case µAmA. In the instance below, the exact same circuit of the previous example is used. The multimeter is component of the circuit.

Check Continuity

If there is really low resistance in between two points, which is much less than a few ohms, the 2 factors are electrically connected and also you’ll hear a constant sound. If the noise isn’t constant or if you do not listen to any sound whatsoever, it implies that what you’re testing has a defective link or isn’t linked in any way.

WARNING: To check continuity you must switch off the system. Switch off the power source!

Touch the two probes with each other as well as, as they are linked, you’ll hear a constant sound.To examination the continuity of a cable, you just need to link each probe to the cable pointers.

Continuity is an excellent way to check if 2 SMD pins are touching. If your eyes can not see it, the multimeter is typically a wonderful 2nd testing resource. When a system is not functioning, continuity is one even more point to assist troubleshoot the system.

  • Set your multimeter to the continuity setup making use of the selection knob.
  • The readout on the display will instantaneously read “1”, which means that there isn’t any continuity. This would be right since we haven’t attached the probes to anything yet.
  • Next off, see to it the circuit is unplugged and has no power. After that connect one probe to one end of the cord and the other probe to the other end– it does not matter which probe goes on which end. If there is a total circuit, your multimeter will certainly either beep, reveal a “0”, or something besides a “1”. If it still shows a “1”, after that there’s a trouble and your circuit isn’t complete.
  • You can additionally examine that the continuity attribute services your multimeter by touching both probes to each other. This completes the circuit as well as your multimeter should let you understand that.

A continuity examination informs us whether 2 points are electrically linked: if something is constant, an electrical current can flow openly from one end to the various other.

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

Changing the Fuse

Among the most common blunders with a new multimeter is to measure current on a bread board by probing from VCC to GND. This will instantly brief power to ground via the multimeter causing the bread board power supply to brown out. As the current hurries through the multimeter, the interior fuse will heat up and afterwards wear out as 200mA flows via it. It will occur in a flash as well as without any kind of real audible or physical sign that something is incorrect.

Bear in mind that measuring current is performed in series (disrupt 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 reads ‘0.00’ and also that the system does not turn on like it needs to when you affix the multimeter. This is due to the fact that the inner fuse is broken as well as works as a broken wire or open.

To alter the fuse, locate your handy dandy mini screw driver, and begin obtaining screws. The parts as well as PCB traces inside the multimeter are designed to take various amounts of current. You will damage and also potentially destroy your multimeter if you accidentally push 5A via the 200mA port.

There are times where you need to measure high current tools like an electric motor or burner. Do you see the two places to put the red probe on the front of the multimeter? 10A on the left and mAVΩ on the right? If you attempt to measure greater than 200mA on the mAVΩ port you risk of blowing the fuse. However if you utilize the 10A port to measure current, you run a much reduced danger of blowing the fuse. The compromise is level of sensitivity. As we spoke about above, by making use of the 10A port and knob setup, you will just have the ability to check out to 0.01 A or 10mA. A lot of systems use greater than 10mA so the 10A setup as well as port functions all right. If you’re attempting to measure really low power (mini or nano amps) the 200mA port with the 2mA, 200uA, or 20uA might be what you need.

Final thought

You’re now prepared to use your digital multimeter to start measuring the world around you. Do not hesitate to begin using it to address lots of inquiries. A digital multimeter will answer many inquiries regarding electronics.

A multimeter is a vital device in any electronics lab. In this overview, we’ve revealed you How To Use a Multimeter. You’ve learned how to measure voltage, current as well as resistance, and also just how to inspect continuity.