fbpx

How To Use A Multimeter To Test A Car Battery

Updated on: December 7, 2018

The Intro

These instructions will show you exactly how to use a digital multimeter (DMM), a vital tool that you can use to diagnose circuits, find out about other individuals’s digital layouts, as well to test a car battery. Hence the ‘multi’-‘meter’ or several dimension name.

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

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

In this tutorial we’re going to reveal you just how to utilize a multimeter. This tutorial is mainly resolved for newbies who are beginning in electronic devices and have no idea exactly how to make use of a multimeter and just how it can be helpful. We’ll check out the most common functions on a multimeter as well as exactly how to measure current, voltage, resistance and just how to inspect continuity.

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

A multimeter is a measurement device absolutely essential in electronic devices. It integrates three essential attributes: a voltmeter, ohmeter, and also ammeter, and in some instances continuity.

The tool enables you to recognize what is going on in your circuits. Whenever something in your circuit isn’t functioning, it will help you fixing. Below’s some situations in electronics tasks that you’ll discover the multimeter valuable:

  • is the switch activate?
  • is this wire carrying out the electrical power or is it damaged?
  • just how much current is streaming with this led?
  • how much power do you have left on your batteries?

What could multimeters measure?

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

Certain multimeters have a continuity check, resulting in a loud beep if 2 points are electrically attached. This is valuable if, for circumstances, you are constructing a circuit and also attaching cords or soldering; the beep indicates whatever is linked as well as nothing has come loose. You can also use it to make certain two points are not linked, to help prevent short circuits.

Certain multimeters likewise have a diode check function. A diode is like a one-way shutoff that just allows electricity circulation in one instructions. The specific feature of the diode check can vary from one type to another. If you’re dealing with a diode as well as can not tell which means it goes in the circuit, or if you’re unsure the diode is functioning properly, the check attribute can be rather handy. If your DMM has a diode check feature, reviewed the manual to learn precisely how it functions.

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

What Do All the Symbols Mean?

There’s a lot going on when you look at the selection knob, yet if you’re only mosting likely to be doing some standard things, you won’t even make use of half of all the settings. In any type of case, below’s a review of what each sign means:

Direct Current Voltage (DCV):Sometimes it will certainly be signified with a V– rather. This setting is made use of to measure straight current (DC) voltage in things like batteries.
Alternating Current Voltage (ACV): Sometimes it will be denoted with a V ~ instead. This setting is used to measure the voltage from alternating current resources, which is pretty much 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 is in the circuit. The reduced the number, the much easier it is for the current to stream via, as well as the other way around.
Continuity: Usually represented by a wave or diode sign. This simply checks whether a circuit is complete by sending out an extremely little amount of current with the circuit and seeing if it makes it out the other end. Otherwise, after that there’s something along the circuit that’s causing an issue– discover it!
Straight Current Amperage (DCA): Similar to DCV, but as opposed to providing you a voltage reading, it will tell you the amperage.
Direct Current Gain (hFE): This setting is to evaluate transistors and also their DC gain, however it’s primarily ineffective, because many electricians as well as hobbyists will certainly make use of the continuity check instead.

Your multimeter may additionally have a specialized setup for checking the amperage of AA, AAA, and 9V batteries. This setup is generally signified with the battery icon.

Again, you most likely won’t also make use of fifty percent of the settings shown, so do not obtain overwhelmed if you only know what a few of them do.

Exactly how to Utilize a Multimeter

For starters, allow’s go over several of the various parts of a multimeter. At the very standard 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 and metal ideas on the various other.

The tool itself has a display on top, which gives you your readout, and there’s a large selection knob that you can rotate around to choose a specific setting. Each setup may likewise have different number worths, which are there to measure various strengths of voltages, resistances, as well as amps. So if you have your multimeter collection to 20 in the DCV section, it will certainly measure voltages as much as 20 volts.

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

  • the COM port mean “Common”, and also the black probe will always plug into this port.
  • the VΩmA port (in some cases denoted as mAVΩ) is just an acronym for voltage, resistance, as well as current (in milliamps). This is where the red probe will certainly connect into if you’re measuring voltage, resistance, continuity, as well as current much less than 200mA.
  • the 10ADC port (often represented as simply 10A) is utilized whenever you’re measuring current that’s even more than 200mA. If you’re uncertain of the current draw, begin with this port. On the other hand, you would certainly not utilize this port in all if you’re measuring anything apart from current.

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

Your measurement tool might have completely separate ports for measuring amps, while the various other port is specifically simply for voltage, resistance, and continuity, yet the majority of more affordable multimeters will share ports.

Anyhow, let’s get going actually utilizing a multimeter. We’ll be measuring the voltage of a AA battery, the current draw of a wall clock, as well as the continuity of an easy wire as some instances to obtain you began as well as accustomed to using a multimeter.

Components of a Multimeter

Multimeters are composed by 4 crucial sections:

  • Display: this particular is just where the dimensions are shown
  • Selection Knob: this selects what you intend to measure
  • Ports: this is where you plug in the probes
  • Probes: a multimeter comes with 2 probes. Usually, one is red and also the other is black.

Ports

  • “COM” or “–” port is where the black probe should be attached. The COM probe is conventionally black.
  • 10A is made use of when measuring large currents, better than 200mA.
  • µAmA is used to measure current.
  • enables you to measure voltage and resistance as well as examination continuity.

COM

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

10A

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

Selection Knob

The selection knob enables the user to set the tool to review different things such as milliamps (mA) of current, voltage (V) as well as resistance (Ω).

Probes

Two probes are linked into 2 of the ports on the front of the unit. The probes have a banana kind adapter on completion that links into the multimeter. Any probe with a banana plug will collaborate with this meter. This enables different kinds of probes to be used.

Probe Types

There are various types of probes available. Here are a few of our faves:

  • Banana to Alligator Clips: These are great cable televisions for attaching to huge cables or pins on a breadboard. Helpful for performing longer term examinations where you don’t need to need to hold the probes in position while you control 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 evaluate SMD components.
  • Banana to Test Probes: If you ever before damage a probe, they are cheap to change!

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. Nearly all mobile electronics make use of direct current), not alternating current. Attach the black probe to the battery’s ground or ‘-‘ and the red probe to power or ‘+’. Squeeze the probes with a little stress against the positive as well as negative terminals of the AA battery. If you’ve got a fresh battery, you must see around 1.5 V on the screen (this battery is all new, so its voltage is slightly greater than 1.5 V).

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

To measure voltage:

  1. Set the setting to V with a wavy 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 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 coming from.
  4. Attach the COM probe to the various other side of your component.
  5. Read the value on the display screen.

Tip: to measure voltage you need to connect your multimeter in parallel with the component you intend 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 understand that you’ll have roughly 1.5 V. So, you need to pick 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 get an autorange one, you don’t need to fret about the range you require to pick.

Start by turning on it, connecting the probes right into their respective ports and also after that setting 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 a good idea to begin with the highest possible worth initially and after that function your means down till you get an exact analysis.

In this situation, we know the AA battery has an extremely reduced voltage, however we’ll begin at 200 volts just for the sake of instance. Next off, place the black probe on the adverse end of the battery and the red probe on the positive end. Take a look at the analysis on the display. Considering that we have the multimeter set to a high 200 volts, it shows “1.6” on the screen, indicating 1.6 volts.

Nevertheless, I desire a more exact reading, so I’ll relocate the selection knob lower down to 20 volts. Here, you can see that we have a more exact analysis that hovers in between 1.60 and also 1.61 volts. If you were to ever before set the selection knob to a number value lower than the voltage of the important things you’re testing, the multimeter would just review “1”, representing that it’s overloaded. 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 take care of at that setup.

All the same, you could be asking why you would need to evaluate the voltage of something in the initial location. Well, in this case 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 check out 1.2 volts, it’s close to being unusable.
In an extra sensible scenario, you might do this kind of measuring on a car battery to see if it may be dying or if the alternator (which is what charges the battery) is spoiling. A reading between 12.4-12.7 volts indicates that the battery remains in good condition. Anything lower which’s proof of a passing away battery. Additionally, begin your car up and also rev it up a bit. If the voltage doesn’t boost to around 14 volts approximately, after that it’s likely that the alternator is having problems.

Overload

What occurs if you select a voltage setting that is as well low for the voltage you’re trying to measure? Nothing negative. The meter will merely present a 1. This is the meter trying to tell you that it is overloaded or out-of-range. Whatever you’re attempting to review is excessive for that specific setup. Attempt altering the multimeter knob to a the next highest setting.

Selection Knob

For what reason does the meter knob read 20V and also not 10V? If you’re wanting to measure a voltage much less than 20V, you look to the 20V setup. This will allow you to read from 2.00 to 19.99. The initial number on several multimeters is just able to show a ‘1’ so the arrays are restricted to 19.99 as opposed to 99.99. Therefore the 20V max variety rather than 99V max variety.

Measuring Resistance

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

Normal resistors have color codes on them. If you don’t understand what they imply, that’s ok! There are a lot of on-line calculators that are easy to use. Nonetheless, if you ever discover on your own without net gain access to, a multimeter is very helpful at measuring resistance.

Pick a random resistor and also established the multimeter to the 20kΩ setup. After that hold the probes versus the resistor legs with the very same amount of stress you when pushing a secret on a keyboard.

The meter will certainly review among 3 things, 0.00, 1, or the real resistor worth.

In this instance, the meter checks out 0.97, indicating this resistor has a value of 970Ω, or concerning 1kΩ (remember you are in the 20kΩ or 20,000 Ohm setting so you require to relocate the decimal three areas to the right or 970 Ohms).

If the multimeter reads 1 or displays OL, it’s overwhelmed. You will require to try a higher mode such as 200kΩ setting or 2MΩ (megaohm) setting. There is no injury if this occur, it simply implies the variety handle needs to be changed.

If the multimeter reads 0.00 or nearly no, then you need to reduce the mode to 2kΩ or 200Ω.

Keep in mind that many resistors have a 5% resistance. This indicates that the color codes might show 10,000 Ohms (10kΩ), yet as a result of inconsistencies in the manufacturing procedure a 10kΩ resistor might be as low as 9.5 kΩ or as high as 10.5 kΩ. Do not stress, it’ll function simply great as a pull-up or basic resistor.

Generally of thumb, it’s unusual to see a resistor less than 1 Ohm. Keep in mind that measuring resistance is not excellent. Temperature can affect the reading a whole lot. Also, measuring resistance of a gadget while it is literally installed in a circuit can be really tricky. The bordering parts on a circuit board can substantially affect the analysis.

The mockup normally appears like with a basic clock escaping of a AA battery. On the silver lining, the wire going from the battery to the clock is separated. We merely put our 2 probes in between that break to complete the circuit once again (with the red probe connected to the source of power), just this time our multimeter will review out the amps that the clock is drawing, which in this case is around 0.08 mA.

While many multimeters can likewise measure rotating current (AC), it’s not actually an excellent idea (especially if its online power), since AC can be dangerous if you wind up making a blunder. If you need to see whether an electrical outlet is functioning, utilize a non-contact tester instead.

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

SUGGESTION: to put the multimeter in collection, 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 cable in your circuit. If you disconnect the multimeter, your circuit will not work.

Before measuring the current, make sure that you’ve connected at a loss probe in the right port, in this instance µAmA. In the example below, the exact same circuit of the previous instance is made use of. The multimeter becomes part of the circuit.

How To Test For Continuity

If there is extremely reduced resistance between 2 factors, which is less than a couple of ohms, both points are electrically attached and also you’ll listen to a constant audio. If the audio isn’t constant or if you don’t hear any kind of audio whatsoever, it means that what you’re testing has a damaged connection or isn’t linked in any way.

CAUTION: In order to examine continuity you ought to turn off the system! Turn off the power source.

Touch the two probes together and, as they are attached, you’ll hear a continuous sound.To test the continuity of a wire, you just require to attach each probe to the cable tips.

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

  • Establish your multimeter to the continuity setup utilizing the selection knob.
  • The readout on the display will immediately review “1”, which means that there isn’t any kind of continuity. This would be proper because we haven’t attached the probes to anything yet.
  • Next off, see to it the circuit is unplugged and also has no power. Then link one probe to one end of the cord as well as the various other probe to the other end– it matters not which probe goes on which end. If there is a full circuit, your multimeter will either beep, show a “0”, or something apart from a “1”. If it still shows a “1”, then there’s an issue as well as your circuit isn’t total.
  • You can also examine that the continuity feature works with your multimeter by touching both probes per other. This completes the circuit and also your multimeter must allow you understand that.

A continuity test informs us whether 2 points are electrically attached: if something is continual, an electrical current can flow openly from one end to the other.

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

Changing the Fuse

One of one of the most common mistakes with a brand-new multimeter is to measure current on a bread board by penetrating from VCC to GND. This will immediately short power to ground with the multimeter creating the bread board power supply to brownish out. As the current rushes via the multimeter, the interior fuse will heat up and after that stress out as 200mA streams via it. It will take place in a flash and with no real audible or physical sign that something is wrong.

Keep in mind that measuring current is performed in collection (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 probably discover that the meter reviews ‘0.00’ which the system does not switch on like it must when you connect the multimeter. This is since the interior fuse is broken and also works as a damaged cable or open.

To alter the fuse, locate your useful dandy mini screw motorist, and also start getting screws. The elements and PCB traces inside the multimeter are made to take various amounts of current. You will certainly harm and perhaps wreck your multimeter if you accidentally push 5A via the 200mA port.

There are times where you require to measure high current tools like a motor or burner. Do you see the 2 locations to place 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 greater than 200mA on the mAVΩ port you run the threat of blowing the fuse. But if you utilize the 10A port to measure current, you run a much lower danger of blowing the fuse. The compromise is level of sensitivity. As we spoke about above, by utilizing the 10A port and handle setup, you will just 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 setting and also port functions all right. If you’re trying to measure extremely reduced power (micro or nano amps) the 200mA port with the 2mA, 200uA, or 20uA might be what you need.

Final thought

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

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