How to Use a Multimeter to Test Current

Updated on: December 11, 2018

Contents

The Introduction

This tutorial will certainly reveal you just how to utilize a digital multimeter (DMM), a vital device that you can utilize to detect circuits, discover concerning other individuals’s electronic designs, and also even test current. Therefore the ‘multi’-‘meter’ or several dimension name.

The most basic points we measure are voltage and current. A multimeter is additionally terrific for some standard sanity checks and troubleshooting. Is your circuit not functioning? 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 certainly cover measuring voltage, current, resistance as well as continuity.

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

In this tutorial we’re mostly likely to reveal you exactly how to utilize a multimeter. This tutorial is mostly dealt with for newbies that are starting in electronic devices and also have no suggestion how to use a multimeter as well as how it can be useful. We’ll explore the most usual features on a multimeter as well as how to measure current, voltage, resistance as well as exactly 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 incorporates three vital attributes: a voltmeter, ohmeter, and ammeter, and sometimes continuity.

The tool enables you to understand what is taking place in your circuits. Whenever something in your circuit isn’t working, it will assist you repairing. Here’s some scenarios in electronics jobs that you’ll locate the multimeter valuable:

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

What can multimeters measure?

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

A bunch of multimeters have a continuity check, resulting in a loud beep if two points are electrically attached. This is helpful if, as an example, you are constructing a circuit and also attaching cables or soldering; the beep indicates every little thing is attached and also nothing has actually come loose. You can additionally utilize it to make certain two things are not linked, to aid avoid brief circuits.

Some multimeters likewise have a diode check function. A diode is like a one-way valve that just lets electrical power flow in one instructions. The specific feature of the diode check can vary from one type to another. If you’re functioning with a diode and can not inform which method it goes in the circuit, or if you’re unsure the diode is working properly, the check function can be quite useful. If your DMM has a diode check function, reviewed the guidebook to figure out specifically how it functions.

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

What Do All the Symbols Mean?

There’s a lot taking place when you look at the selection knob, but if you’re only mosting likely to be doing some fundamental things, you will not even make use of fifty percent of all the setups. In any type of case, below’s a review of what each symbol means:

Direct Current Voltage (DCV):quite often it will be signified with a V– instead. This setup is made use of to measure straight current (DC) voltage in points like batteries.
Alternating Current Voltage (ACV): Sometimes it will be signified with a V ~ instead. This setting is made use of to measure the voltage from alternating current sources, which is practically anything that links into an electrical outlet, along with the power coming from the electrical outlet itself.
Resistance (Ω): This gauges exactly how much resistance there is in the circuit. The lower the number, the much easier it is for the current to move with, and vice versa.
Continuity: Usually represented by a wave or diode symbol. This simply examines whether or not a circuit is total by sending out a really small amount of current via the circuit as well as seeing if it makes it out the other end. If not, after that there’s something along the circuit that’s creating a problem– find it!
Direct Current Amperage (DCA): Similar to DCV, however as opposed to offering you a voltage reading, it will tell you the amperage.
Straight Current Gain (hFE): This setting is to examine transistors as well as their DC gain, but it’s mostly useless, since many electricians as well as hobbyists will use the continuity check instead.

Your multimeter could additionally have a devoted setting for examining the amperage of AA, AAA, and 9V batteries. This setting is normally represented with the battery sign.

Once again, you possibly will not even utilize half of the setups revealed, so don’t get overwhelmed if you only recognize what a few of them do.

Exactly how to Utilize a Multimeter

For starters, let’s look at a few of the different components of a multimeter. At the very basic level you have the tool itself, in addition to 2 probes, which are the black and also red cords that have plugs on one end and metal ideas on the various other.

The tool itself has a display on top, which gives you your readout, as well as there’s a large selection knob that you can rotate around to pick a details setup. Each setting may also have various number values, which exist to measure various staminas of voltages, resistances, and amps. So if you have your multimeter set to 20 in the DCV section, it will certainly measure voltages as much as 20 volts.

Your DMM will likewise come with 2 or three ports for connecting in the probes:

COM port stands for “Common”, and also the black probe will certainly always link into this port.
the VΩmA port (sometimes denoted as mAVΩ) is merely a phrase for voltage, resistance, as well as current (in milliamps). This is where the red probe will plug into if you’re measuring voltage, resistance, continuity, and current much less than 200mA.
the 10ADC port (often denoted as just 10A) is made use of 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 use this port in any way if you’re measuring anything various other than 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, rather than the 200mA port. Otherwise you can blow the fuse that’s inside of the multimeter. Furthermore, measuring anything over 10 amps could blow a fuse or ruin the multimeter also.

Your measurement tool may have completely separate ports for measuring amps, while the other port is specifically simply for voltage, resistance, and also continuity, but the majority of less expensive multimeters will certainly share ports.

Anyway, let’s get started in fact making use of a multimeter. We’ll be measuring the voltage of a AA battery, the current draw of a wall surface clock, as well as the continuity of a straightforward cable as some instances to obtain you began and also acquainted with using a multimeter.

Components of a Multimeter

Multimeters are made up by four essential sections:

Display: this is exactly where the dimensions are shown
Selection Knob: this picks what you desire to measure
Ports: this is where you plug in the probes
Probes: a multimeter comes with two probes. Typically, one is red as well as the various other is black.

Ports

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

COM

COM stands for typical and is often attached to Ground or ‘-‘ of a circuit.The COM probe is traditionally black but there is no distinction in between the red probe and also black probe apart from color.

10A

10A is the special port made use of when measuring large currents (more than 200mA).

Selection Knob

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

Probes

2 probes are linked into two of the ports on the front of the system. The probes have a banana type adapter on completion that links into the multimeter. Any probe with a banana plug will certainly collaborate with this meter. This permits various types of probes to be used.

Probe Types

There are many various kinds of probes readily available. Below are a few of our favorites:

Banana to Alligator Clips: These are terrific cable televisions for attaching to large cords or pins on a breadboard. Great for executing longer term examinations where you don’t have 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 come in handy if you are requiring to check SMD components.
Banana to Test Probes: If you ever break a probe, they are affordable to change!

Measuring Voltage

To begin, allow’s measure voltage on a AA battery: Plug the black probe into COM and the red probe right into mAVΩ. Set to “2V” in the DC (straight current) variety. Mostly all mobile electronics make use of straight 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 favorable and adverse 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 brand brand-new, so its voltage is slightly greater 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 bumpy line suggests AC voltage.

Measuring voltage

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.
Ensure the red probe is linked to the port with a V beside it.
Link the red probe to the silver lining of your component, which is where the current is originating from.
Attach the COM probe to the various other side of your component.
Read the value on the display screen.

Tip: to measure voltage you need to attach your multimeter in parallel with the component you wish to measure the voltage. Positioning the multimeter in parallel is putting each probe along the leads of the component you want to measure the voltage.

Measuring a battery’s voltage

In this instance we’re mosting likely to measure the voltage of a 1.5 V battery. You know that you’ll have about 1.5 V. So, you should pick a variety with the selection knob that can check out the 1.5 V. So you must choose 2V in the instance of this multimeter. If you obtain an autorange one, you do not need to stress over the range you need to pick.

Begin by switching on it, connecting the probes right into their respective ports and afterwards setting the selection knob to the highest possible number worth in the DCV section, which in my case is 500 volts. If you do not recognize 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 possible value first and after that work your method down up until you get a precise analysis.

In this case, we know the AA battery has a really low voltage, however we’ll begin at 200 volts simply for the purpose of instance. Next off, position the black probe on the adverse end of the battery and the red probe on the positive end. Take an appearance at the reading on the display. Given that we have the multimeter collection to a high 200 volts, it shows “1.6” on the display, suggesting 1.6 volts.

Nevertheless, I want an even more precise reading, so I’ll relocate the selection knob lower to 20 volts. Below, you can see that we have a more precise analysis that floats in between 1.60 and 1.61 volts. If you were to ever establish the selection knob to a number worth lower than the voltage of the point you’re evaluating, the multimeter would just read “1”, representing that it’s overloaded. So if I were to set the handle to 200 millivolts (0.2 volts), the 1.6 volts of the AA battery is way too much for the multimeter to manage at that setting.

Regardless, you may be asking why you would require 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 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 pointless.
In an extra sensible circumstance, you could do this kind of measuring on a cars and truck battery to see if it might 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 and that’s proof of a dying battery. In addition, start your auto up and also rev it up a bit. If the voltage doesn’t boost to about 14 volts or so, after that it’s most likely that the alternator is having issues.

Overload

What takes place if you select a voltage setting that is as well reduced for the voltage you’re attempting to measure? Nothing bad. The meter will just display a 1. This is the meter trying to inform you that it is overloaded or out-of-range. Whatever you’re attempting to read is excessive for that specific setup. Try altering the multimeter knob to a the following highest setting.

Selection Knob

Precisely why does the meter knob read 20V and also not 10V? If you’re looking to measure a voltage less than 20V, you look to the 20V setting. This will allow you to read from 2.00 to 19.99. The very first number on several multimeters is only able to present a ‘1’ so the ranges are limited to 19.99 instead of 99.99. Therefore the 20V max range as opposed to 99V max variety.

Measuring Resistance

Plug the red probe into the appropriate port and also turn the selection knob to the resistance area. Then, connect the probes to the resistor leads. The means you attach the leads doesn’t matter, the result is the exact same.

Normal resistors have shade codes on them. If you don’t recognize what they mean, that’s ok! There are lots of online calculators that are very easy to use. Nevertheless, if you ever before discover yourself without net access, a multimeter is very useful at measuring resistance.

Pick out a random resistor as well as established the multimeter to the 20kΩ setup. Then hold the probes against the resistor legs with the exact same amount of pressure you when pushing a secret on a key-board.

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

In this situation, the meter reviews 0.97, indicating this resistor has a worth of 970Ω, or regarding 1kΩ (remember you remain in the 20kΩ or 20,000 Ohm mode so you need to move the decimal three areas to the right or 970 Ohms).

If the multimeter reviews 1 or shows OL, it’s overloaded. You will need to attempt a higher setting such as 200kΩ mode or 2MΩ (megaohm) setting. There is no damage if this happen, it merely means the variety handle requires to be changed.

In case the multimeter checks out 0.00 or nearly absolutely no, after that you require to lower the setting to 2kΩ or 200Ω.

Bear in mind that several resistors have a 5% tolerance. This implies that the shade codes may suggest 10,000 Ohms (10kΩ), yet due to inconsistencies in the production process a 10kΩ resistor could be as low as 9.5 kΩ or as high as 10.5 kΩ. Do not worry, it’ll function simply great as a pull-up or general resistor.

As a regulation of thumb, it’s unusual to see a resistor less than 1 Ohm. Bear in mind that measuring resistance is not best. Temperature level can impact the checking out a lot. Additionally, measuring resistance of a tool while it is literally mounted in a circuit can be very challenging. The surrounding components on a circuit card can significantly impact the reading.

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

While many multimeters can likewise measure alternating current (AC), it’s not truly an excellent concept (especially if its live power), since AC can be harmful if you finish up making an error. If you need to see whether an electrical outlet is functioning, make use of a non-contact tester instead.

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

IDEA: to put 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 cord in your circuit. If you disconnect the multimeter, your circuit will not work.

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

Check Continuity

If there is very low resistance between 2 points, which is less than a few ohms, both points are electrically attached and you’ll listen to a constant noise. If the noise isn’t continuous or if you do not listen to any kind of sound in all, it means that what you’re testing has a malfunctioning link or isn’t connected in any way.

CAUTION: In order to test continuity you ought to switch off the system. Turn off the power source.

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

Continuity is a fantastic way to examine if two SMD pins are touching. If your eyes can not see it, the multimeter is typically a great 2nd testing source. When a system is not working, continuity is another thing to aid repair the system.

Set your multimeter to the continuity setting utilizing the selection knob.
The readout on the display will instantaneously read “1”, which means that there isn’t any kind of continuity. This would be proper given that we haven’t connected the probes to anything yet.
Next off, make sure the circuit is unplugged and has no power. Then attach one probe to one end of the cord and the various other probe to the various other end– it does not matter 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 shows a “1”, then there’s a problem and also your circuit isn’t total.
You can also check that the continuity function works on your multimeter by touching both probes to each other. This completes the circuit and also your multimeter should let you know that.

A continuity examination tells us whether two things are electrically linked: if something is continual, an electrical current can flow freely from one end to the other.

If there’s no continuity, it indicates there is a break somewhere in the circuit. This can suggest anything from a blown fuse or poor solder joint to an improperly wired circuit.

Altering the Fuse

Among the most usual blunders with a brand-new multimeter is to measure current on a bread board by penetrating from VCC to GND. This will promptly brief power to ground through the multimeter creating the bread board power supply to brown out. As the current rushes with the multimeter, the internal fuse will warm up and afterwards stress out as 200mA flows via it. It will certainly happen in a split 2nd as well as with no genuine distinct or physical indicator that something is wrong.

Remember that measuring current is done 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 notice that the meter reads ‘0.00’ which the system does not switch on like it ought to when you connect the multimeter. This is because the interior fuse is damaged as well as serves as a busted wire or open.

To change the fuse, discover your convenient dandy mini screw chauffeur, and begin taking out screws. The parts as well as PCB traces inside the multimeter are made to take different quantities of current. You will damage and also perhaps destroy your multimeter if you inadvertently push 5A through 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 on the left and also mAVΩ on the right? If you try to measure more than 200mA on the mAVΩ port you run the threat of blowing the fuse. Yet if you use the 10A port to measure current, you run a much lower threat of blowing the fuse. The compromise is sensitivity. As we discussed above, by using the 10A port and knob setting, you will just have the ability to review to 0.01 A or 10mA. A lot of systems use even more than 10mA so the 10A setup and also port functions all right. If you’re trying to measure really low power (micro or nano amps) the 200mA port with the 2mA, 200uA, or 20uA could be what you require.

Final thought

You’re currently ready to utilize your digital multimeter to start measuring the globe around you. Really feel totally free to begin using it to address numerous questions. A digital multimeter will certainly respond to lots of inquiries about electronic devices.

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