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How to Use a Multimeter to Check a Car Battery

Updated on: December 12, 2018

The Introduction

This guide will reveal you exactly how to make use of a digital multimeter (DMM), an essential tool that you can utilize to diagnose circuits, find out about other individuals’s electronic layouts, as well as also check a car battery. Thus the ‘multi’-‘meter’ or multiple dimension name.

One of the most standard points we measure are voltage and also current. A multimeter is likewise terrific for some basic peace of mind checks as well as troubleshooting. Is your circuit not working? Does the button job? Place a meter on it! The multimeter is your initial defence when fixing a system. In this tutorial we will certainly cover measuring voltage, current, resistance and also continuity.

Every fixer ought to know their means around a multimeter, which has simply north of a zillion uses for testing electronic parts as well as circuits.

In this tutorial we’re going to reveal you exactly how to use a multimeter. This tutorial is mostly attended to for beginners who are starting in electronic devices and also have no idea just how to make use of a multimeter and how it can be valuable. We’ll discover the most typical functions on a multimeter and also just how to measure current, voltage, resistance and also just how to examine continuity.

What is a multimeter and why do you need one?

A multimeter is a measurement device definitely required in electronic devices. It incorporates three necessary features: a voltmeter, ohmeter, and also ammeter, as well as in some instances continuity.

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

  • is the button activate?
  • is this cord carrying out the electrical power or is it broken?
  • just how much current is flowing via this led?
  • just how much power do you have left on your batteries?

What could multimeters measure?

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

A handful of multimeters have a continuity check, leading to a loud beep if two things are electrically attached. This is helpful if, for circumstances, you are developing a circuit and also attaching cables or soldering; the beep suggests whatever is attached as well as absolutely nothing has actually come loose. You can also use it to make certain two things are not connected, to help stop brief circuits.

A lot of multimeters also have a diode check feature. A diode resembles a one-way shutoff that only lets electrical energy circulation in one direction. The precise feature of the diode check can differ from one type to another. If you’re functioning with a diode as well as can’t tell which method it enters the circuit, or if you’re uncertain the diode is working correctly, the check feature can be rather useful. If your DMM has a diode check function, reviewed the manual to learn precisely how it works.

Advanced models may have other features, such as the ability to measure and identify other electric elements, like transistors or capacitors. Because not all multimeters have these functions, we will certainly not cover them in this tutorial. You can review your multimeter’s guidebook if you require to make use of these attributes.

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 stuff, you won’t even utilize fifty percent of all the setups. In any situation, right here’s a review of what each symbol indicates:

Direct Current Voltage (DCV):Occasionally it will certainly be denoted with a V– instead. This setup is made use of to measure direct current (DC) voltage in things 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 sources, which is virtually anything that connects into an outlet, as well as the power coming from the electrical outlet itself.
Resistance (Ω): This gauges just how much resistance there remains in the circuit. The lower the number, the much easier it is for the current to stream with, as well as the other way around.
Continuity: Usually signified by a wave or diode sign. This just tests whether or not a circuit is complete by sending out a very tiny amount of current with the circuit and seeing if it makes it out the other end. If not, then there’s something along the circuit that’s causing an issue– discover it!
Straight Current Amperage (DCA): Similar to DCV, however rather than providing you a voltage reading, it will tell you the amperage.
Direct Current Gain (hFE): This setting is to check transistors as well as their DC gain, yet it’s mainly pointless, since a lot of electrical experts and also enthusiasts will certainly make use of the continuity check rather.

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

Again, you possibly won’t even make use of fifty percent of the settings revealed, so don’t get overwhelmed if you only recognize what a few of them do.

Exactly how to Utilize a Multimeter

For starters, allow’s review a few of the different components of a multimeter. At the extremely fundamental degree you have the tool itself, together with 2 probes, which are the black as well as red cable televisions that have plugs on one end as well as metal tips on the other.

The tool itself has a screen at the top, which offers you your readout, as well as there’s a huge selection knob that you can rotate around to select a details setup. Each setup might additionally have various number values, which are there to measure various toughness of voltages, resistances, and also amps. So if you have your multimeter set to 20 in the DCV area, it will measure voltages up to 20 volts.

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

  • the COM port mean “Common”, as well as the black probe will certainly constantly link into this port.
  • the VΩmA port (often signified as mAVΩ) is just an acronym for voltage, resistance, as well as current (in milliamps). This is where the red probe will link into if you’re measuring voltage, resistance, continuity, and also current less than 200mA.
  • the 10ADC port (occasionally denoted as just 10A) is utilized whenever you’re measuring current that’s greater than 200mA. If you’re uncertain of the current draw, begin with this port. On the various other hand, you would certainly not use this port in all if you’re measuring anything besides current.

Warning: Make sure that if you’re measuring anything with a current greater than 200mA, you plug the red probe into the 10A port, instead of the 200mA port. Otherwise you might blow the fuse that’s within of the multimeters. Furthermore, measuring anything over 10 amps might blow a fuse or destroy the multimeters also.

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

Anyhow, let’s obtain started in fact using 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 obtain you started and knowledgeable about utilizing a multimeter.

Parts of a Multimeter

Multimeters are made up by 4 important sections:

  • Display: this particular is where the measurements are presented
  • Selection Knob: this chooses what you desire to measure
  • Ports: this is where you plug in the probes
  • Probes: a multimeter includes two probes. Generally, one is red and also the 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 made use of when measuring large currents, higher than 200mA.
  • µAmA is made use of to measure current.
  • permits you to measure voltage as well as resistance and examination continuity.

COM

COM represent usual and also is practically always attached to Ground or ‘-‘ of a circuit.The COM probe is conventionally black yet there is no difference between the red probe as well as black probe aside from color.

10A

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

Selection Knob

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

Probes

Two probes are connected into 2 of the ports on the front of the device. The probes have a banana type adapter on the end that connects into the multimeter. Any kind of probe with a banana plug will work with this meter. This permits different kinds of probes to be utilized.

Probe Types

There are several sorts of probes readily available. Below are a few of our favorites:

  • Banana to Alligator Clips: These are terrific cables for attaching to big cables or pins on a breadboard. Helpful for doing longer term tests where you do not have to need to hold the probes in position while you control 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 needing to evaluate SMD parts.
  • Banana to Test Probes: If you ever before break a probe, they are economical to replace!

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) array. Nearly all mobile electronic devices utilize straight current), not alternating current. Link the black probe to the battery’s ground or ‘-‘ and also the red probe to power or ‘+’. Press the probes with a little stress against the favorable and also unfavorable terminals of the AA battery. If you’ve obtained a fresh battery, you need to see around 1.5 V on the screen (this battery is brand brand-new, so its voltage is slightly higher than 1.5 V).

You may measure DC voltage or AC voltage. The V with a straight line implies DC voltage. The V with the wavy line means AC voltage.

So as to measure voltage understand these steps:

  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. See to it the red probe is attached to the port with a V beside it.
  3. Attach the red probe to the silver lining of your component, which is where the current is coming from.
  4. Connect the COM probe to the other side of your component.
  5. Check out the worth on the screen.

Tip: to measure voltage you need to connect your multimeter in parallel with the component you wish 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 going to measure the voltage of a 1.5 V battery. You know that you’ll have around 1.5 V. So, you need to select a variety 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 obtain an autorange one, you don’t need to stress concerning the array you require to pick.

Begin by activating it, connecting the probes right into their particular ports and after that establishing the selection knob to the highest possible number value in the DCV area, which in my situation is 500 volts. If you don’t understand at least the voltage series of the important things you’re measuring, it’s always a great concept to begin with the highest possible value initially and afterwards function your method down until you get an accurate analysis.

In this case, we understand the AA battery has an extremely reduced voltage, but we’ll begin at 200 volts simply for the benefit of example. Next, position the black probe on the adverse end of the battery and also the red probe on the favorable end. Take an appearance at the analysis on the screen. Because we have the multimeter set to a high 200 volts, it reveals “1.6” on the display, indicating 1.6 volts.

Nevertheless, I want a more accurate analysis, so I’ll relocate the selection knob lower down to 20 volts. Below, you can see that we have a more accurate 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 things you’re checking, the multimeter would certainly just review “1”, signifying that it’s overwhelmed. So if I were to establish the handle 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.

In any kind of case, you could be asking why you would certainly require to test the voltage of something to begin with. Well, in this instance with the AA battery, we’re examining 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 read 1.2 volts, it’s close to being unusable.
In an extra sensible scenario, you can do this sort of measuring on a car battery to see if it might be passing away or if the generator (which is what charges the battery) is going negative. An analysis in between 12.4-12.7 volts suggests that the battery remains in good condition. Anything lower which’s proof of a passing away battery. Furthermore, start your car up and also rev it up a bit. If the voltage does not boost to about 14 volts or two, after that it’s most likely that the generator is having issues.

Overload

What occurs if you pick a voltage setting that is also reduced for the voltage you’re trying to measure? Absolutely nothing negative. The meter will simply present 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 particular setup. Attempt transforming the multimeter handle to a the following highest possible setting.

Selection Knob

Precisely why does the meter knob checked out 20V and also not 10V? If you’re wanting to measure a voltage less than 20V, you resort to the 20V setup. This will permit you to read from 2.00 to 19.99. The first digit on numerous multimeters is only able to present a ‘1’ so the arrays are restricted to 19.99 rather than 99.99. For this reason the 20V max array rather than 99V max variety.

Measuring Resistance

Plug the red probe into the appropriate port and also turn the selection knob to the resistance area. Then, attach the probes to the resistor leads. The way you connect the leads does not matter, the result coincides.

Normal resistors have shade codes on them. If you don’t know what they imply, that’s ok! There are a lot of online calculators that are very easy to use. Nonetheless, if you ever before locate yourself without net accessibility, a multimeter is very useful at measuring resistance.

Choose a random resistor and also established the multimeter to the 20kΩ setting. Then hold the probes against the resistor legs with the very same amount of pressure you when pressing a trick on a key-board.

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

In this case, the meter reads 0.97, implying this resistor has a worth of 970Ω, or regarding 1kΩ (remember you remain in the 20kΩ or 20,000 Ohm mode so you require to relocate the decimal three places to the right or 970 Ohms).

If the multimeter reviews 1 or presents OL, it’s overwhelmed. You will certainly need to attempt a higher setting such as 200kΩ setting or 2MΩ (megaohm) mode. There is no injury if this happen, it merely indicates the range knob needs to be adjusted.

If perhaps the multimeter reviews 0.00 or nearly absolutely no, then you need to reduce the setting to 2kΩ or 200Ω.

Remember that several resistors have a 5% resistance. This implies that the color codes may indicate 10,000 Ohms (10kΩ), but due to inconsistencies in the manufacturing procedure a 10kΩ resistor can be as reduced as 9.5 kΩ or as high as 10.5 kΩ. Don’t stress, it’ll work simply great as a pull-up or general resistor.

Generally of thumb, it’s uncommon to see a resistor much less than 1 Ohm. Keep in mind that measuring resistance is not excellent. Temperature can impact the reading a lot. Likewise, measuring resistance of a tool while it is literally mounted in a circuit can be very tricky. The bordering components on a motherboard can significantly influence the analysis.

The mockup usually resembles with a basic clock escaping of a AA battery. On the favorable side, the cable going from the battery to the clock is separated. We simply position our two probes in between that break to complete the circuit once more (with the red probe attached to the source of power), only this time our multimeter will certainly read out the amps that the clock is pulling, which in this instance is around 0.08 mA.

While the majority of multimeters can also measure rotating current (AC), it’s not truly an excellent concept (specifically if its real-time power), considering that AC can be harmful if you wind up slipping up. If you need to see whether or not an electrical outlet is working, utilize a non-contact tester rather.

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

SUGGESTION: to place the multimeter in series, you require to position 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 cord in your circuit. If you separate the multimeter, your circuit will not function.

Before measuring the current, be certain that you’ve plugged at a loss probe in the ideal port, in this case µAmA. In the example below, the same circuit of the previous example is utilized. The multimeter belongs to the circuit.

Test Continuity

If there is very low resistance between two factors, which is much less than a few ohms, the two points are electrically linked and also you’ll listen to a constant noise. If the sound isn’t continual or if you do not hear any kind of sound whatsoever, it means that what you’re testing has a damaged connection or isn’t connected whatsoever.

WARNING: To examine continuity you need to turn off the system. Switch off the power supply.

Touch both probes with each other as well as, as they are linked, you’ll listen to a continual sound.To examination the continuity of a wire, you just require to attach each probe to the cable pointers.

Continuity is an excellent means to test if two SMD pins are touching. If your eyes can’t see it, the multimeter is normally a great second testing resource. When a system is not working, continuity is another thing to assist troubleshoot the system.

  • Set your multimeter to the continuity setting making use of the selection knob.
  • The readout on the screen will promptly check out “1”, which means that there isn’t any kind of continuity. This would be correct because we haven’t linked the probes to anything yet.
  • Next off, make certain the circuit is unplugged as well as has no power. After that link one probe to one end of the wire and the various other probe to the other end– it matters not which probe takes place which end. If there is a total 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 full.
  • You can additionally check that the continuity attribute services your multimeter by touching both probes to each other. This completes the circuit and also your multimeter should allow you understand that.

A continuity test informs us whether 2 things are electrically attached: if something is constant, an electric current can stream freely from one end to the other.

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

Altering the Fuse

Among the most common blunders with a new multimeter is to measure current on a bread board by penetrating from VCC to GND. This will immediately brief power to ground via the multimeter triggering the bread board power supply to brownish out. As the current hurries via the multimeter, the inner fuse will heat up and also then wear out as 200mA flows through it. It will occur in an instant as well as without any type of real distinct or physical indicator that something is wrong.

Keep in mind that measuring current is performed in collection (disrupt 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 see that the meter reviews ‘0.00’ which the system doesn’t turn on like it should when you affix the multimeter. This is since the inner fuse is damaged and functions as a busted cord or open.

To change the fuse, locate your useful dandy mini screw driver, and start getting screws. The parts and also PCB traces inside the multimeter are developed to take various amounts of current. You will certainly damage and also potentially spoil your multimeter if you inadvertently push 5A through the 200mA port.

There are times where you require to measure high current tools like a motor or burner. Do you see both places to put the red probe on the front of the multimeter? 10A on the left as well as mAVΩ on the right? If you try to measure even more than 200mA on the mAVΩ port you run the threat of blowing the fuse. However if you utilize the 10A port to measure current, you run a much lower danger of blowing the fuse. The trade-off is level of sensitivity. As we spoke about above, by utilizing the 10A port as well as knob setting, you will just be able to check out down to 0.01 A or 10mA. The majority of systems utilize greater than 10mA so the 10A setting as well as port functions well sufficient. If you’re trying to measure very reduced power (micro or nano amps) the 200mA port with the 2mA, 200uA, or 20uA could be what you need.

Conclusion

You’re currently all set to use your digital multimeter to start measuring the globe around you. Do not hesitate to begin using it to address several concerns. A digital multimeter will respond to lots of inquiries regarding electronic devices.

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