How Do I Know My Amp Service

Download Article

If you're working on an electrical project, sometimes you may demand to check the amperage, or how much electricity is flowing through the circuit.^[1] While this is not a common test, you might need to measure amps to make up one's mind if something is pulling more energy than information technology should. For instance, measuring the amperage can be useful when you're trying to determine if a component in your vehicle is draining the battery. Fortunately, measuring amps is easy if you have a multimeter and you use safety around electrical components.

1
Check the nameplate on your battery or breaker to decide its maximum amps. Before y'all attach your multimeter to the circuit, yous need to make sure that the meter is rated for the number of amps traveling through that circuit. Virtually power sources will accept the judge maximum amps printed on a nameplate, and you can find the maximum amps the multimeter can handle on the dorsum of the device or in the education manual. Y'all could also only check how loftier the dial goes—exercise non attempt to test more currents than the highest dial setting.^[2]
- The maximum amps may also be called the maximum electric current.
2
Utilise a plug-in clamp if your multimeter isn't rated loftier enough for the circuit. The plug-in clamp accessory can extend the range. Just plug the leads into the multimeter and attach the other stop to the circuit the way you would attach the multimeter clamps. Place the clench effectually the hot or live wire, which is usually black, red, blue, or some other color except white or dark-green.
- When you utilize a clamp, it doesn't become part of the circuit, different when you lot are just using a multimeter.
Advertisement
3
Push the blackness probe into the "COM" socket on the multimeter. Your multimeter should have a red probe and a black probe, whether you're using a clench attachment or the probes that came with the meter. I end of the probe will have a prong that plugs into the meter. The blackness probe, which indicates a negative wire, should always be plugged into the COM socket.^[3]
- "COM" stands for "common." If the port isn't marked with "COM," you lot may encounter a negative symbol, instead.
- If your leads have prongs, y'all'll accept to concur them in place when you measure out the current. If they accept clamps, you lot can attach them to the circuit, freeing up your hands. Withal, both types of probes volition connect to the meter in the same manner.
4
Place the scarlet probe in the socket labeled "A." You may have several places where you can plug in a reddish probe, depending on the functions of your meter. The port marked with "A" measures amperage.^[iv]
- Y'all may see 2 sockets with an "A," i labeled every bit "A" or "10A" and one labeled "mA." The one that says "A" or "10A" is designed to measure current up to ten amps, while the ane that says "mA" measures milli-amps, upwards to about 300 mA. If you're non sure which one to use, select the higher "A" or "10A" setting to be sure you don't overload the meter.
- You lot might too encounter ports labeled "V" for voltage or "Ω" for ohms. You lot can condone these for this examination.
five
Select either Ac or DC current on the meter. Unless your meter is designed to only be used on AC or DC circuits, you'll demand to select which one you're testing. If you lot're not sure, check the nameplate on your power source again for that information.^[5] It should exist listed along with the voltage.^[6]
- AC, or alternating current, is typically used in items similar household appliances and electric motors, while DC, or direct current, is commonly used in battery-powered motors and devices.
- The ability in a residential setting is going to be Air conditioning unless there'south a transformer converting that electricity to DC.^[7]
half-dozen
Turn the dial to an amp setting that'southward higher than what you're measuring. One time you've determined the maximum currents you lot're expecting to test, look for a dial on your meter and plow information technology a fiddling higher than that number. If you'd similar, you tin plough the dial all the way to the maximum but to be safe, just if the electric current you're measuring is also low, yous may not get a reading. If that happens, you'll need to turn the dial down and take the reading once more.^[8]
- By setting your meter to handle more than amps than y'all wait to measure out, you help protect against blowing the fuses if the current is stronger than you thought. If the electric current is significantly higher than the amp setting, you could destroy the meter.
- Some dials are auto-ranging, which means you do not take to manually adjust a punch. If this is the instance, you lot will non run across a punch with the amp settings, and the meter volition be labeled as "auto-ranging," or you lot may see "AUTO" on the display.^[9]

1

Turn off the ability to the circuit. If your circuit is powered by a battery, unplug the negative atomic number 82 that'due south running from that battery. If you have to turn off the ability at a breaker, plow off the switch, then disconnect the negative pb. Do not attach the meter with the power turned on to the circuit.

Warning: Apply extreme caution when you're treatment electricity. Wear heavy condom gloves, do non work near water or on a metal surface, and do not grab exposed wires with your bare hands. It's also a practiced idea to take someone nearby (not touching the excursion) who can assist you or call for emergency aid in case you go an electrical shock.
ii
Disconnect the red wire coming from the ability supply. In order to test the amount of current flowing through a circuit, yous have to attach the multimeter so information technology completes that circuit. To do this, start by shutting off the power to the circuit, then disassemble the positive wire, which is nearly always red, from the power source.^[ten]
- This procedure is chosen "breaking the circuit."
- You may have to cut the wire with wire clippers to break the circuit. However, if you come across a cap where the wire from the power source meets the wire going to the device you're testing, yous can simply unscrew the cap and unwind the wires from around each other. The wires may likewise be connected by clips you lot 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
Strip the ends of the wire , if necessary. Yous'll need 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 cease, clench your wire clippers virtually 1 in (2.five cm) from the end of the wire and squeeze just enough to cut into the prophylactic insulation. Then, pull the clippers sharply away from you to remove the insulation.^[11]
- If you accidentally cut into the wire, snip that portion off of the end and attempt again.
- You lot'll need to strip the end of the wire that's coming abroad from the power source and the wire coming from the device you're testing.
iv
Wrap the positive wire around the positive probe on the multimeter. Take the exposed stop of the crimson 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 style, brand sure you attach the wire securely to ensure yous get an accurate reading.^[12]
- Technically, it doesn't really matter if y'all connect the positive probe to the wire coming from the ability source or the device, since the meter simply needs to complete the circuit. If information technology's easier for some reason to attach the wires the other manner, that's fine.
- Attaching the positive wire first tin assistance preclude a curt 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, it means you put the leads on backward. Fix it by reversing the leads.
5
Connect the blackness multimeter probe to the remaining wire and turn on the circuit. Next, discover the positive wire coming from the electrical component you're trying to test and attach it to the blackness multimeter probe. If you bankrupt a battery-powered circuit by disconnecting the wires, power will be restored to the circuit one time yous impact the black probe to the wire. If you turned off the power with a breaker or a switch, turn it back on.^[13]
- This will be the other end of the wire yous cut or asunder from the power supply.
- If you're testing in a motorcar, don't start the car, and don't try to plow on whatever fans, lights, or anything else in the vehicle, as y'all could overload the meter.
6
Leave the probes in place for about a minute equally you read the meter. Once the meter is in identify, you should see a number on the digital brandish immediately. This is the measurement of your current, or amperage. Although this initial reading may be accurate, for the most precise measurement, leave the probes on the circuit for at to the lowest degree 60 seconds to ensure the current is steady.^[14]
- If the reading is less than the sensitive setting (for instance, if information technology reads less than 0.3 A and the sensitive setting measures upwards to 300 mA), disconnect the meter, movement the red probe to mA, and echo the test.
- This reading will testify yous the amperage, or the current, of the circuit you're testing. That'south basically how much electricity can flow through that current at one fourth dimension.^[15]

Add New Question

Question

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

Ralph Childers is a chief electrician based in the Portland, Oregon area with over 30 years of conducting and teaching electrical work. Ralph received his B.S. in Electric Applied science from the University of Louisiana at Lafayette and holds an Oregon Journeyman Electrical License as well as electrician licenses in Louisiana and Texas.

Electrical Professional person

Proficient Reply

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

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

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

Electrical Professional person

Expert Answer

There will be 20A betwixt all the outlets on that item circuit. Brand sure that the outlet in question does actually connect to that circuit breaker, though.
Question

What practise I put the multimeter on to run across if I am getting power to my breaker?

Ralph Childers is a main electrician based in the Portland, Oregon area 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 equally well as electrician licenses in Louisiana and Texas.

Electrical Professional

Expert Reply

In order to practice that you would need to accept off the breaker panel embrace, which is non recommended unless you are trained. If you lot have ability to other parts of the house, it is a good assumption that the breaker is getting power.
Question

How do I test the amps on a battery?

Ralph Childers is a main electrician based in the Portland, Oregon area with over thirty years of conducting and pedagogy electrical work. Ralph received his B.S. in Electrical Engineering from the University of Louisiana at Lafayette and holds an Oregon Journeyman Electrical License besides equally electrician licenses in Louisiana and Texas.

Electrical Professional

Expert Respond

First, yous'll take to disconnect the battery positive pb. Then, you'll insert the meter into circuit by connecting the meter probes to the wire and battery post. Wait at the article again for more data.
Question

Should I apply "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 also the author of four eBooks on home wiring including "Residential Electrical Troubleshooting" which covers bones electrical troubleshooting in residential homes.

Master Electrician

Expert Reply

In a residential setting, virtually things are going to be run on AC power. Still, if there's a transformer that'south converting the electricity to DC, you lot'd need to apply the DC setting, then you have to check the voltage label to be sure.

Ask a Question

200 characters left

Include your email address to get a message when this question is answered.

Submit

Advert

Exist very cautious when you're working with electricity. Ensure the power is turned off, do non work near water or on a metal surface, and have someone standing nearby in example of an emergency.
Practise not utilize a multimeter to measure the electric current in a wall socket in your home. They are not rated for that amount of power, and y'all could destroy the meter and suffer electrical shock.^[sixteen]

Things You lot'll Demand

Digital multimeter
Wire cutters or strippers (optional)

About This Commodity

Article Summary X

Before you attempt to measure amperage, put on condom gloves and make sure you're not working on or about a metallic surface so you don't electrocute yourself. To get started, configure the multimeter y'all'll be using by pushing the blackness probe into the "COM" socket and the red probe into the "A" socket. Select AC or DC amperage on the meter, depending on the electrical system you are testing, and make sure the multimeter is gear up to the range of the amperage y'all're testing. Then, plow off the ability and break the circuit y'all're testing. In one case the power to the circuit has been turned off, adhere the red probe on the multimeter to the negative terminal of the power supply, and touch the black probes to the negative wire and turn on the circuit. Leave the probes fastened for ane infinitesimal before checking the amperage reading on the display. To learn how to examination your multimeter before you lot take your reading, scroll down!

Did this summary assist you lot?

Thanks to all authors for creating a folio that has been read 966,592 times.

Did this commodity help you?