How To Use A Multimeter To Measure Current

Updated on: July 8, 2019

Contents

Introduction

This tutorial will certainly show you exactly how to utilize a digital multimeter (DMM), an important device that you can make use of to identify circuits, learn more about other individuals’s digital designs, as well as also to measure current. For this reason the ‘multi’-‘meter’ or numerous measurement name.

One of the most standard points we measure are voltage as well as current. A multimeter is likewise wonderful for some fundamental sanity checks as well as troubleshooting. Is your circuit not functioning? Does the switch work? Put a meter on it! The multimeter is your very first defence when fixing a system. In this tutorial we will cover measuring voltage, current, resistance and also continuity.

Every fixer must recognize their method around a multimeter, which has simply north of a zillion utilizes for screening digital components as well as circuits.

In this tutorial we’re mostly likely to reveal you how to use a multimeter. This tutorial is mainly attended to for novices who are beginning in electronic devices and have no suggestion just how to use a multimeter and how it can be useful. We’ll check out the most common attributes on a multimeter and also just how to measure current, voltage, resistance and also how to check continuity.

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

A multimeter is a measurement tool absolutely essential in electronics. It integrates three necessary functions: a voltmeter, ohmeter, and also ammeter, and also in many cases continuity.

The tool allows you to comprehend what is going on in your circuits. Whenever something in your circuit isn’t working, it will certainly aid you repairing. Right here’s some circumstances in electronics jobs that you’ll find the multimeter valuable:

is the switch turn on?
is this cable carrying out the electrical power or is it broken?
exactly how much current is flowing with this led?
how much power do you have left on your batteries?

What should multimeters measure?

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

A bunch of multimeters have a continuity check, leading to a loud beep if two things are electrically linked. This is handy if, as an example, you are developing a circuit and connecting cables or soldering; the beep indicates whatever is attached and also absolutely nothing has actually come loose. You can likewise use it to make sure two things are not attached, to aid prevent short circuits.

Various multimeters also have a diode check feature. A diode is like a one-way shutoff that just allows electricity flow in one direction. The precise function of the diode check can vary from one type to another. If you’re collaborating with a diode as well as can’t tell which way it goes in the circuit, or if you’re uncertain the diode is working properly, the check feature can be rather useful. If your DMM has a diode check feature, read the guidebook to learn specifically how it works.

Advanced models might have other features, such as the capability to measure and recognize various other electrical elements, like transistors or capacitors. Since not most multimeters have these features, we will 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 look at the selection knob, however if you’re only mosting likely to be doing some fundamental things, you will not even use half of all the setups. Regardless, below’s a run-through of what each icon means:

Direct Current Voltage (DCV):once in a while it will be represented with a V– instead. This setting is utilized to measure direct current (DC) voltage crazes like batteries.
Alternating Current Voltage (ACV): Sometimes it will certainly be represented with a V ~ rather. This setup is utilized 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 measures just how much resistance there remains in the circuit. The reduced the number, the less complicated it is for the current to move through, as well as the other way around.
Continuity: Usually represented by a wave or diode icon. This just examines whether or not a circuit is full by sending an extremely percentage of current through 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 a trouble– discover 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 test transistors and also their DC gain, yet it’s mostly pointless, because the majority of electricians as well as enthusiasts will utilize the continuity check instead.

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

Once again, you most likely won’t even make use of fifty percent of the setups revealed, so do not obtain bewildered if you just know what a few of them do.

Exactly how to Use a Multimeter

For beginners, allow’s look at a few of the various parts of a multimeter. At the really fundamental level you have the tool itself, along with 2 probes, which are the black as well as red cables that have plugs on one end and metal tips on the various other.

The tool itself has a display screen at the top, which offers you your readout, as well as there’s a huge selection knob that you can spin around to choose a specific setup. Each setup may likewise have different number worths, which exist to measure various strengths of voltages, resistances, and amps. So if you have your multimeter set to 20 in the DCV section, it will certainly measure voltages approximately 20 volts.

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

the COM port mean “Common”, and also the black probe will certainly constantly connect into this port.
the VΩmA port (often signified as mAVΩ) is merely an acronym for voltage, resistance, and also current (in milliamps). This is where the red probe will link into if you’re measuring voltage, resistance, continuity, as well as current less than 200mA.
the 10ADC port (sometimes signified as simply 10A) is made use of whenever you’re measuring current that’s greater than 200mA. If you’re not certain of the current draw, start with this port. On the various other hand, you would not use this port whatsoever if you’re measuring anything apart from current.

Warning: Make certain that if you’re measuring anything with a current greater than 200mA, you connect the red probe into the 10A port, instead of the 200mA port. Or else you can blow the fuse that’s within of the multimeters. Additionally, measuring anything over 10 amps might blow a fuse or damage the multimeter too.

Your measurement tool may have entirely separate ports for measuring amps, while the various other port is specifically simply for voltage, resistance, and also continuity, but most less costly multimeters will share ports.

Anyway, let’s get going in fact 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 basic wire as some instances to get you started and knowledgeable about using a multimeter.

Components of Multimeters

Multimeters are made up by 4 crucial sections:

Display: this particular is where the measurements are displayed
Selection Knob: this chooses what you intend to measure
Ports: this is where you connect in the probes
Probes: a multimeter features 2 probes. Generally, one is red as well as the various other is black.

Ports

“COM” or “–” port is where the black probe should be connected. The COM probe is conventionally black.
10A is utilized when measuring large currents, better than 200mA.
µAmA is made use of to measure current.
VΩ allows 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 yet there is no distinction in between the red probe as well as black probe apart from shade.

10A

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

Selection Knob

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

Probes

2 probes are connected into 2 of the ports on the front of the system. The probes have a banana type adapter on completion that connects into the multimeter. Any kind of probe with a banana plug will certainly collaborate with this meter. This allows for various kinds of probes to be utilized.

Probe Types

There are several sorts of probes available. Right here are a few of our faves:

Banana to Alligator Clips: These are great cords for connecting to large cords or pins on a breadboard. Great for carrying out longer term tests where you do not have to have to hold the probes in place while you adjust a circuit.
Banana to IC Hook: IC hooks work well on smaller ICs as well as legs of ICs.
Banana to Tweezers: Tweezers come in handy if you are needing to evaluate SMD components.
Banana to Test Probes: If you ever break a probe, they are low-cost 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. Establish to “2V” in the DC (direct current) array. Nearly all mobile electronics utilize straight current), not alternating current. Connect the black probe to the battery’s ground or ‘-‘ and also the red probe to power or ‘+’. Squeeze the probes with a little stress against the positive and also adverse terminals of the AA battery. If you’ve obtained a fresh battery, you must see around 1.5 V on the display (this battery is brand-new, so its voltage is somewhat greater than 1.5 V).

You can easily measure DC voltage or AC voltage. The V with a straight line suggests DC voltage. The V with the curly line implies AC voltage.

To measure voltage:

Set the mode 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.
See to it the red probe is attached to the port with a V beside it.
Connect the red probe to the favorable side of your component, which is where the current is coming from.
Link the COM probe to the opposite of your component.
Read the worth on the display screen.

Tip: to measure voltage you have to attach your multimeter in parallel with the component you wish to measure the voltage. Placing the multimeter in parallel is putting 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 understand that you’ll have roughly 1.5 V. So, you ought to choose an array with the selection knob that can review the 1.5 V. So you should select 2V when it comes to this multimeter. If you have an autorange one, you don’t need to stress over the array you require to choose.

Start by turning on it, plugging the probes into their respective ports and afterwards establishing the selection knob to the greatest number value in the DCV area, which in my case is 500 volts. If you don’t recognize at the very least the voltage series of the important things you’re measuring, it’s always a good suggestion to start with the highest possible value first and afterwards work your way down up until you get a precise reading.

In this case, we understand the AA battery has a really low voltage, yet we’ll begin at 200 volts just for the purpose of instance. Next, place the black probe on the adverse end of the battery and also the red probe on the favorable end. Have a look at the analysis on the display. Since we have the multimeter collection to a high 200 volts, it reveals “1.6” on the display, implying 1.6 volts.

Nevertheless, I want a more precise reading, so I’ll move the selection knob reduced to 20 volts. Right here, you can see that we have an even more precise reading that floats in between 1.60 and also 1.61 volts. If you were to ever establish the selection knob to a number value less than the voltage of the thing you’re testing, the multimeter would simply review “1”, signifying that it’s overwhelmed. 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 deal with at that setting.

All the same, you may be asking why you would certainly need to test the voltage of something in the very first place. Well, in this instance 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. Nonetheless, if it were to check out 1.2 volts, it’s close to being unusable.
In a much more functional circumstance, you could do this sort of measuring on an auto battery to see if it may be passing away or if the generator (which is what bills the battery) is going bad. A reading in between 12.4-12.7 volts means that the battery is in excellent form. Anything reduced which’s proof of a passing away battery. In addition, start your auto up as well as rev it up a little bit. If the voltage does not enhance to about 14 volts or so, after that it’s most likely that the alternator is having concerns.

Overload

What happens if you pick a voltage setup that is also reduced for the voltage you’re trying to measure? Nothing bad. The meter will simply display a 1. This is the meter trying to inform you that it is overloaded or out-of-range. Whatever you’re trying to read is way too much for that specific setting. Try altering the multimeter handle to a the next highest possible setup.

Selection Knob

Why does the meter knob reviewed 20V as well as not 10V? If you’re wanting to measure a voltage less than 20V, you rely on the 20V setup. This will enable you to review from 2.00 to 19.99. The initial number on several multimeters is just able to display a ‘1’ so the varieties are limited to 19.99 as opposed to 99.99. For this reason the 20V max array rather than 99V max variety.

Measuring Resistance

Connect the red probe right into the appropriate port as well as turn the selection knob to the resistance area. After that, connect the probes to the resistor leads. The means you connect the leads does not matter, the outcome is the same.

Normal resistors have shade codes on them. If you don’t recognize what they imply, that’s ok! There are a lot of on the internet calculators that are easy to utilize. Nonetheless, if you ever locate yourself without web gain access to, a multimeter is really handy at measuring resistance.

Choose out an arbitrary resistor and also set the multimeter to the 20kΩ setup. Then hold the probes against the resistor legs with the exact same amount of stress you when pushing a key on a key-board.

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

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

If the multimeter reads 1 or displays OL, it’s overwhelmed. You will certainly need to try a higher mode such as 200kΩ mode or 2MΩ (megaohm) mode. There is no harm if this happen, it merely means the range handle requires to be changed.

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

Bear in mind that lots of resistors have a 5% tolerance. This indicates that the color codes may indicate 10,000 Ohms (10kΩ), yet due to disparities in the manufacturing process a 10kΩ resistor can be as low as 9.5 kΩ or as high as 10.5 kΩ. Do not worry, it’ll function simply fine as a pull-up or general resistor.

As a rule of thumb, it’s unusual to see a resistor less than 1 Ohm. Bear in mind that measuring resistance is not excellent. Temperature can impact the reading a whole lot. Likewise, measuring resistance of a tool while it is physically mounted in a circuit can be extremely difficult. The bordering components on a motherboard can greatly affect the reading.

The mockup usually appears like with a fundamental clock running off of a AA battery. On the favorable side, the cable going from the battery to the clock is damaged up. We just position our 2 probes in between that break to finish the circuit once again (with the red probe linked to the source of power), only this time around our multimeter will certainly read out the amps that the clock is drawing, which in this instance is around 0.08 mA.

While many multimeters can likewise measure alternating current (AC), it’s not really an excellent suggestion (particularly if its online power), because AC can be dangerous if you finish up making an error. If you require to see whether or not an outlet is functioning, utilize a non-contact tester rather.

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

IDEA: to put the multimeter in series, you require to place the red probe on the lead of a component and also the black probe on the next component lead. The multimeter acts as if it was a cord in your circuit. If you disconnect the multimeter, your circuit will not function.

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

Check for Continuity

If there is extremely reduced resistance between two factors, which is much less than a few ohms, both factors are electrically attached and you’ll listen to a continual sound. If the noise isn’t continuous or if you don’t hear any audio whatsoever, it suggests that what you’re testing has a defective link or isn’t linked at all.

WARNING: To evaluate continuity you ought to turn off the system! Turn off the power source!

Touch both probes together and, as they are linked, you’ll hear a continual sound.To examination the continuity of a cord, you simply need to link each probe to the cord suggestions.

Continuity is a wonderful means to check if 2 SMD pins are touching. If your eyes can’t see it, the multimeter is generally an excellent 2nd testing resource. When a system is not working, continuity is another point to assist fix the system.

Establish your multimeter to the continuity setting making use of the selection knob.
The readout on the display will promptly check out “1”, which indicates that there isn’t any kind of continuity. This would be right since we have not connected the probes to anything yet.
Next off, ensure the circuit is unplugged and also has no power. After that attach one probe to one end of the cable as well as the various other probe to the other end– it does not matter which probe goes on which end. If there is a complete circuit, your multimeter will either beep, reveal a “0”, or something apart from a “1”. If it still reveals a “1”, then there’s an issue and your circuit isn’t total.
You can likewise check that the continuity feature deals with your multimeter by touching both probes per various other. This completes the circuit and also your multimeter ought to allow you know that.

A continuity test informs us whether 2 things are electrically attached: if something is continuous, an electrical current can flow freely from one end to the various other.

If there’s no continuity, it suggests there is a break someplace in the circuit. This might suggest anything from a blown fuse or negative solder joint to an improperly wired circuit.

Altering the Fuse

One of 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 short power to ground via the multimeter causing the bread board power supply to brownish out. As the current hurries via the multimeter, the inner fuse will certainly warm up and afterwards melt out as 200mA flows with it. It will occur in a fraction of a second as well as with no real audible or physical indication that something is incorrect.

Bear in mind that measuring current is done in series (disturb the VCC line to the breadboard or microcontroller to measure current). If you attempt to measure the current with a blown fuse, you’ll possibly observe that the meter reads ‘0.00’ as well as that the system doesn’t transform on like it needs to when you connect the multimeter. This is since the inner fuse is damaged and acts as a broken cord or open.

To change the fuse, locate your useful dandy mini screw chauffeur, and also begin taking out screws. The elements as well as PCB traces inside the multimeter are developed to take different quantities of current. You will harm and also possibly destroy your multimeter if you mistakenly push 5A through the 200mA port.

There are times where you need to measure high current tools like a motor or burner. Do you see the 2 places to place 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 greater than 200mA on the mAVΩ port you risk of blowing the fuse. But if you make use of the 10A port to measure current, you run a much lower risk of blowing the fuse. The compromise is level of sensitivity. As we discussed above, by utilizing the 10A port and also handle setting, you will only have the ability to review to 0.01 A or 10mA. A lot of systems make use of even more than 10mA so the 10A setup and also port works well sufficient. If you’re attempting to measure really reduced power (mini or nano amps) the 200mA port with the 2mA, 200uA, or 20uA might be what you require.

Conclusion

You’re now ready to use your digital multimeter to start measuring the world around you. Do not hesitate to begin using it to respond to lots of inquiries. A digital multimeter will certainly address several concerns about electronic devices.

A multimeter is a vital device in any type of electronics laboratory. In this overview, we’ve shown you How To Use a Multimeter. You’ve found out exactly how to measure voltage, current and also resistance, and how to check continuity.