How to Read a Dc Amp Meter

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If yous're working on an electrical project, sometimes you lot may need to check the amperage, or how much electricity is flowing through the circuit.^[1] While this is not a mutual examination, y'all might need to measure out amps to determine if something is pulling more than free energy than it should. For case, measuring the amperage can exist useful when you're trying to determine if a component in your vehicle is draining the battery. Fortunately, measuring amps is easy if yous accept a multimeter and y'all apply condom around electrical components.

1. 1

   Check the nameplate on your battery or breaker to decide its maximum amps. Before you attach your multimeter to the circuit, you lot need to make sure that the meter is rated for the number of amps traveling through that circuit. Most power sources will accept the approximate maximum amps printed on a nameplate, and y'all can notice the maximum amps the multimeter can handle on the back of the device or in the instruction manual. You could also only bank check how high the dial goes—do not endeavour to exam more than currents than the highest dial setting.^[2]

   • The maximum amps may also exist called the maximum current.

2. 2

   Utilise a plug-in clamp if your multimeter isn't rated high plenty for the circuit. The plug-in clamp accessory tin can extend the range. Just plug the leads into the multimeter and attach the other terminate to the circuit the way you would attach the multimeter clamps. Place the clamp around the hot or live wire, which is ordinarily black, ruddy, blue, or some other color except white or dark-green.

   • When yous use a clench, it doesn't become function of the circuit, different when you are just using a multimeter.

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3. three

   Button the black probe into the "COM" socket on the multimeter. Your multimeter should have a red probe and a black probe, whether you're using a clamp attachment or the probes that came with the meter. 1 stop of the probe will accept a prong that plugs into the meter. The blackness probe, which indicates a negative wire, should ever be plugged into the COM socket.^[three]

   • "COM" stands for "common." If the port isn't marked with "COM," y'all may see a negative symbol, instead.
   • If your leads have prongs, you'll have to hold them in place when you measure the current. If they have clamps, you can attach them to the excursion, freeing up your hands. However, both types of probes will connect to the meter in the same fashion.

4. four

   Place the cherry-red probe in the socket labeled "A." Y'all may have several places where you lot can plug in a red probe, depending on the functions of your meter. The port marked with "A" measures amperage.^[4]

   • You lot may see 2 sockets with an "A," one labeled as "A" or "10A" and ane labeled "mA." The one that says "A" or "10A" is designed to mensurate current upwardly to 10 amps, while the one that says "mA" measures milli-amps, upwardly to virtually 300 mA. If y'all're non sure which 1 to use, select the higher "A" or "10A" setting to exist sure you don't overload the meter.
   • Y'all might also encounter ports labeled "5" for voltage or "Ω" for ohms. You tin can condone these for this test.

5. 5

   Select either AC or DC current on the meter. Unless your meter is designed to merely be used on Air conditioning or DC circuits, you'll demand to select which one you're testing. If you're not sure, check the nameplate on your power source again for that information.^[5] It should exist listed along with the voltage.^{[half dozen]}

   • AC, or alternating electric current, is typically used in items like household appliances and electrical motors, while DC, or direct current, is commonly used in battery-powered motors and devices.
   • The ability in a residential setting is going to exist AC unless there's a transformer converting that electricity to DC.^[vii]

6. vi

   Turn the dial to an amp setting that's college than what yous're measuring. Once you've determined the maximum currents you're expecting to test, look for a dial on your meter and plow information technology a little higher than that number. If you'd like, you can turn the dial all the way to the maximum just to be safe, but if the current you're measuring is too low, yous may non get a reading. If that happens, yous'll need to turn the dial down and accept the reading over again.^[eight]

   • By setting your meter to handle more amps than you await to measure, yous help protect against blowing the fuses if the current is stronger than you idea. If the current is significantly higher than the amp setting, yous could destroy the meter.
   • Some dials are auto-ranging, which means you do non accept to manually adjust a dial. If this is the example, you will non see a dial with the amp settings, and the meter will be labeled as "motorcar-ranging," or you may see "AUTO" on the brandish.^[nine]

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1. 1

   Plow off the power to the circuit. If your circuit is powered by a battery, unplug the negative lead that's running from that bombardment. If y'all have to turn off the ability at a breaker, turn off the switch, then disconnect the negative lead. Exercise not attach the meter with the power turned on to the circuit.

   Warning: Use farthermost caution when you're treatment electricity. Wear heavy rubber gloves, do not work most water or on a metallic surface, and practice not grab exposed wires with your bare hands. It's also a skillful idea to accept someone nearby (not touching the circuit) who tin assist you or call for emergency aid in case yous become an electrical shock.

2. 2

   Disconnect the red wire coming from the power supply. In society to test the corporeality of current flowing through a excursion, you lot have to adhere the multimeter so it completes that excursion. To exercise this, start by shutting off the power to the circuit, then disassemble the positive wire, which is almost always red, from the power source.^[ten]

   • This process is called "breaking the circuit."
   • You may have to cut the wire with wire clippers to break the excursion. Still, if y'all see a cap where the wire from the ability source meets the wire going to the device you're testing, you lot tin can simply unscrew the cap and unwind the wires from effectually each other. The wires may too be connected by clips y'all can disconnect.
   • There's no need to unplug the black wire. In a direct current circuit, the black is negative, while in an alternating electric current circuit, it's the "hot" wire.

3. 3

   Strip the ends of the wire , if necessary. Y'all'll demand to wrap a small piece of wire around the multimeter prongs, or take enough wire exposed that the alligator prongs will clamp on securely. If the wire is insulated all the way to the end, clamp your wire clippers most 1 in (2.5 cm) from the end of the wire and clasp only plenty to cut into the safe insulation. Then, pull the clippers sharply away from yous to remove the insulation.^[11]

   • If you lot accidentally cut into the wire, snip that portion off of the cease and endeavor again.
   • You'll need to strip the cease of the wire that's coming away from the power source and the wire coming from the device you're testing.

4. iv

   Wrap the positive wire effectually the positive probe on the multimeter. Accept the exposed end of the reddish wire that's coming abroad from the ability source and either wrap it around the prong on the multimeter probe or clamp the alligator clips to the wire, depending on the type of probe you're using. Either mode, make certain you attach the wire securely to ensure you get an accurate reading.^[12]

   • Technically, it doesn't actually thing if you connect the positive probe to the wire coming from the ability source or the device, since the meter only needs to complete the circuit. If it's easier for some reason to attach the wires the other way, that'south fine.
   • Attaching the positive wire kickoff can assist foreclose a short if the negative wire accidentally touches a ground.
   • If you're measuring a circuit without the amp clamp and the reading has a negative sign in front of it, information technology ways you put the leads on backward. Set it by reversing the leads.

5. five

   Connect the black multimeter probe to the remaining wire and turn on the circuit. Adjacent, find the positive wire coming from the electrical component y'all're trying to test and attach it to the black multimeter probe. If y'all broke a battery-powered circuit past disconnecting the wires, ability will be restored to the circuit once y'all bear upon the black probe to the wire. If y'all turned off the power with a breaker or a switch, turn it back on.^[13]

   • This will be the other end of the wire y'all cutting or asunder from the power supply.
   • If you're testing in a car, don't start the car, and don't try to turn on any fans, lights, or anything else in the vehicle, equally yous could overload the meter.

6. 6

   Leave the probes in place for nigh a minute equally you lot read the meter. Once the meter is in place, y'all should run across a number on the digital display immediately. This is the measurement of your electric current, or amperage. Although this initial reading may be authentic, for the nearly precise measurement, leave the probes on the excursion for at to the lowest degree 60 seconds to ensure the current is steady.^[xiv]

   • If the reading is less than the sensitive setting (for instance, if it reads less than 0.3 A and the sensitive setting measures up to 300 mA), disconnect the meter, move the red probe to mA, and echo the test.
   • This reading will show you the amperage, or the current, of the circuit you're testing. That's basically how much electricity can menstruum through that electric current at ane time.^[15]

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Add New Question

• Question

  How can I measure amperage of a plug by using a multimeter?

  

  Ralph Childers is a principal electrician based in the Portland, Oregon expanse with over 30 years of conducting and didactics electrical work. Ralph received his B.Due south. in Electric Engineering from the University of Louisiana at Lafayette and holds an Oregon Journeyman Electrical License too every bit electrician licenses in Louisiana and Texas.

  

  Electric Professional

  Adept Answer

  If at that place is nothing plugged into a plug there will not be any current at that plug since current is a measure of the flow of electricity.

• Question

  If I have 20a breakers in my box, can I assume there is 20a at the outlets?

  

  Ralph Childers is a master electrician based in the Portland, Oregon expanse with over thirty years of conducting and teaching electrical work. Ralph received his B.S. in Electrical Engineering from the University of Louisiana at Lafayette and holds an Oregon Journeyman Electric License as well as electrician licenses in Louisiana and Texas.

  

  Electrical Professional

  Practiced Answer

  There will be 20A betwixt all the outlets on that detail circuit. Make certain that the outlet in question does actually connect to that excursion billow, though.

• Question

  What do I put the multimeter on to run into if I am getting power to my billow?

  

  Ralph Childers is a principal electrician based in the Portland, Oregon expanse with over xxx years of conducting and teaching electrical work. Ralph received his B.Southward. in Electrical Engineering from the Academy of Louisiana at Lafayette and holds an Oregon Journeyman Electrical License besides as electrician licenses in Louisiana and Texas.

  

  Electrical Professional

  Skillful Respond

  In society to do that you lot would need to take off the breaker panel comprehend, which is not recommended unless you are trained. If you have power to other parts of the house, it is a good assumption that the billow is getting power.

• Question

  How do I test the amps on a battery?

  

  Ralph Childers is a master electrician based in the Portland, Oregon expanse with over 30 years of conducting and teaching electric work. Ralph received his B.S. in Electrical Engineering from the University of Louisiana at Lafayette and holds an Oregon Journeyman Electrical License likewise as electrician licenses in Louisiana and Texas.

  

  Electrical Professional person

  Skillful Answer

  First, y'all'll have to disconnect the battery positive atomic number 82. Then, you lot'll insert the meter into circuit by connecting the meter probes to the wire and bombardment post. Expect at the article once again for more information.

• Question

  Should I use "Air-conditioning" or "DC" when I'm testing amperage with a multimeter?

  

  Jesse Kuhlman is a Master Electrician and the Owner of Kuhlman Electrician Services based in Massachusetts. Jesse specializes in all aspects of home/residential wiring, troubleshooting, generator installation, and WiFi thermostats. Jesse is as well the author of 4 eBooks on home wiring including "Residential Electrical Troubleshooting" which covers basic electrical troubleshooting in residential homes.

  

  Master Electrician

  Expert Answer

  In a residential setting, near things are going to be run on Air-conditioning power. However, if there's a transformer that's converting the electricity to DC, you'd need to apply the DC setting, so you have to cheque the voltage label to be sure.

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• Exist very cautious when you're working with electricity. Ensure the power is turned off, do not piece of work about water or on a metal surface, and have someone standing nearby in example of an emergency.

• Do not apply a multimeter to measure the electric current in a wall socket in your home. They are not rated for that amount of power, and you lot could destroy the meter and suffer electrical shock.^[16]

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Things You'll Need

• Digital multimeter
• Wire cutters or strippers (optional)

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Article Summary X

Earlier yous try to measure amperage, put on rubber gloves and brand sure you're non working on or nearly a metal surface so you lot don't assassinate yourself. To become started, configure the multimeter you'll be using by pushing the black probe into the "COM" socket and the red probe into the "A" socket. Select Air-conditioning or DC amperage on the meter, depending on the electrical system you are testing, and make certain the multimeter is set to the range of the amperage y'all're testing. So, turn off the ability and break the circuit you're testing. Once the power to the circuit has been turned off, adhere the cherry probe on the multimeter to the negative concluding of the power supply, and touch on the black probes to the negative wire and plough on the circuit. Exit the probes attached for ane infinitesimal before checking the amperage reading on the display. To learn how to test your multimeter before you lot have your reading, ringlet downwardly!

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