They'll give you a solid rundown about what multimeter is as well as everything it can do , and keep reading to get some tips from our of our favorite electricians. Starting with the simplest, most basic test, use the voltage mode on your meter to check battery output. Most modern meters make this setup all but foolproof by also color coding the jacks. The black common probe goes into the black jack; the red probe goes in the red jack.
For example, a fully charged AA battery should have a reading of at least 1. And you can use your multimeter to test virtually any battery ranging from AAAs to car batteries. The test gives you a rough idea of whether the battery is good, shot, or needs to be charged. Then turn the rotary switch to Volts AC Vac , which is also indicated by a wavy line on the dial.
Push the tip of the red probe into the shorter hot of the two vertical slots on the outlet. Insert the black probe into the longer slot neutral. A properly functioning outlet should produce to volts. Next, remove the black probe from the outlet—leave the red probe in place—and insert the black probe into the small, rounded hole ground below the two slots. The reading should remain the same. Got a faulty ceiling light? First, turn off the power to the switch, remove the cover plate, and unscrew the switch from its wires.
Before disconnecting the wires, label them or take a photo with your phone to ensure you reconnect them correctly. Loosen the switch terminal screws, unhook the wires from them, and remove the switch. Set the resistance range to X1. Skip this step if your meter has auto-range you can tell you have an auto-ranging meter if you turn the dial to the Volts AC Vac setting, the word "auto" appears on the screen. Plug the black probe into the COM jack and the red probe into the red V jack.
To test a single-pole switch the simplest kind; it has two brass screws and one green screw. Flip the switch to the Off position. With the switch turned off, you should get a reading of O. L you may also get other readings, such as or a symbol like this I or even this: L.
This means Over Load or Over Limit; the resistance is so high that it can't be measured. At first this doesn't seem to make sense you would think the meter would read zero ohms , but the meter is telling you that when no internal contacts are touching inside the switch, the resistance across the open contacts is so large that the meter can't read it. Now flip the switch On and the meter should read less than one ohm. Another simple test is to rotate the meter dial to the position for continuity.
Note that sometimes the continuity check can be combined with other functions on a single setting. Diode check triangle with some lines through it : This function is used to test a diode , which is like a one-way valve for electricity; it only lets current flow in one direction. The exact function of the diode check can be different on different multimeters. Check your multimeter's manual to learn about how the diode check function works for your model.
Table 1. Some symbol examples from different multimeters. Check out the gallery for more examples. Figure 4. A typical pair of multimeter probes. Figure 5. This section includes answers to the following questions: How do I measure voltage?
How do I measure current? How do I measure resistance? How do I do a continuity check? How do I do a diode check? How do I know which scale to pick for voltage, current, or resistance, and how do I read the numbers at different scales? My multimeter isn't working! What's wrong? How do I know if I need to change the fuse? How do I change the fuse? How do I measure voltage?
To measure voltage, follow these steps: Plug your black and red probes into the appropriate sockets also referred to as "ports" on your multimeter.
For most multimeters, the black probe should be plugged into the socket labeled "COM," and the red probe into the socket labeled with a "V" it might also have some other symbols. Remember to check out our image gallery, the Multimeter Overview tab, or your multimeter's manual if you have trouble identifying the right socket. Choose the appropriate voltage setting on your multimeter's dial. Remember that most battery-powered circuits will have direct current, but the setting you select will depend on the science project you are doing.
If you are working with a manual-ranging multimeter, you can estimate the range you need based on the battery or batteries powering your circuit.
For example, if your circuit is powered by a single 9V battery, it probably doesn't make sense to select the setting for V, and 2V would be too low. If available, you would want to select 20V. Touch the probe tips to your circuit in parallel with the element you want to measure voltage across refer to the Multimeter Overview tab for an explanation of series and parallel circuits. For example, Figure 6 shows how to measure the voltage drop across a lightbulb powered by the battery.
Be sure to use the red probe on the side connected to the positive battery terminal, and the black probe on the side connected to the negative battery terminal nothing will be harmed if you get this backwards, but your voltage reading will be negative.
Figure 6. Measuring voltage across a lightbulb by attaching the multimeter probes in parallel. Current flow is represented by the yellow arrows. In voltage-measurement mode, the multimeter's resistance is very high , so almost all of the current flows through the lightbulb, and the multimeter does not have a big impact on the circuit. Figure 7. Measuring the current through a lightbulb by attaching a multimeter in series. In current-measurement mode, the multimeter's resistance is very low , so the current can easily flow through the multimeter without affecting the rest of the circuit.
Notice how the knob has been set to measure direct current DCA and the red probe is plugged into the port for measuring current, labeled with an "A. Figure 8. Measuring the resistance of a lightbulb using a multimeter. Notice how the lightbulb has been disconnected from the circuit. The multimeter supplies its own small amount of current, which allows it to measure the resistance. Figure 9. Using a multimeter to do a continuity test. If a conductive path is formed between the probe tips, the multimeter will beep.
If the conductive path is broken possibly due to a wire that has come loose in your circuit, or a bad solder connection , the multimeter will not beep. Readings when measuring voltage of a single AA battery using different dial settings on a manual-ranging multimeter. Figure A typical fuse. This section answers the questions: What can I do with a multimeter around the house?
What shouldn't I do with my multimeter? Which Science Buddies projects require a multimeter? What can I do with a multimeter around the house? Test batteries! Have you ever wondered if a device or toy stopped working because the batteries were dead? With a multimeter, you can make sure batteries are actually dead before recycling them by testing their voltage. However, batteries will effectively be "dead" long before they reach 0V.
For example, if a battery is supplying 0. Do you have rechargeable batteries? You can test their voltage over time as they recharge, and then make a plot of voltage vs.
How long does it take for the voltage to stop increasing? Is the graph a straight line? Do you have anything you can take apart with a circuit board inside, like an old toy, or a TV remote? Use the continuity check on your multimeter if it has one to test which parts of the circuit are directly connected to each other.
Warning: Old circuit boards are constructed with a lead-based solder, which is toxic. Always wash your hands carefully after handling solder, and check your local waste disposal guidelines to see if there are special rules about disposing of lead as hazardous waste.
Set your multimeter to measure resistance, and have everyone in your house take turns grabbing the metal tips of the probes one in each hand. Who has the highest resistance? The lowest? Use the continuity check or resistance measurement to test different materials in your house. Which ones are conductors and which ones are insulators? Hook the multimeter leads up to a speaker using speaker wire, and set the multimeter to measure AC amps or AC volts if AC amps is not available.
Who can get the multimeter to display the biggest number by yelling into the speaker? In this case, the speaker is working like a microphone, generating current when it detects sound.
Do not use a multimeter to test electricity from the wall outlets in your home. Electricity from wall outlets is very dangerous and can be fatal. Do not connect the probes directly to a battery or other power supply when you have a "current" measurement setting selected.
This will cause a "short circuit" across the battery terminals, and a very high current will flow through your multimeter. This will probably blow a fuse, or possibly damage the multimeter. In fact, there are too many to list, but here is a sampling of a few that cover a variety of topics: Electrolyte Challenge: Orange Juice Vs. Sports Drink. This project compares the amount of electrolytes in a sports drink to the amount in typical orange juice.
Do sports drinks live up to their promise? Use a multimeter to find out how well these different liquids conduct electricity. Did you know that you can make a battery and even light up LEDs with everyday fruits and vegetables?
Use a multimeter to test the current and voltage that can be supplied by your afternoon snack. Help save the planet with this green energy project! Use fuel cells to store energy produced by solar panels for use when it's dark out, and use your handy multimeter to keep track of your power generation.
Measure It! Using a light sensor, a simple circuit, and a multimeter, you can measure the amount of light given off by glow-in-the-dark objects. Does generating electricity from mud sound crazy? Believe it or not, with help from some friendly bacteria, you can turn an everyday scoop of dirt into a battery.
Use a multimeter to help design this green-energy fuel cell. Harnessing the power of the ocean is yet another green energy technology that could help reduce our dependence on fossil fuels. Use a multimeter to measure the electrical power generated by your oscillating water column.
A Battery That Makes Cents. Did you ever think you could make a battery out of pocket change? In this project you will make a battery out of pennies and nickels, and use a multimeter to measure the current and voltage that it can produce. This multimeter is a combination of auto-ranging and manual ranging. For example, it only has one setting to measure DC voltage, but it has three settings for measuring DC current.
It also has one socket for measuring voltage and resistance, and another socket for measuring both high and low current. It also has a "Logic" test function for measuring digital circuits not covered in this tutorial. Multimeters are covered in cryptic symbols and buttons, but don't let that intimidate you.
There are three basic functions you'll use most often: measuring voltage, continuity and resistance in electrical components and circuits. This guide will walk you through using these functions for tackling common tasks around the house. Those are pro models designed to handle tasks well beyond the needs of a DIYer. Some retail chains, like Harbor Freight, have even been known to give them away. You're stuck with a drawer full of old disposable batteries.
The trouble is you don't remember how they got there. You don't know if they're all dead or if some are still kicking. Don't worry, your multimeter's voltage modes can help. Your multimeter comes with two insulated probes. You'll need to connect them to the right ports terminals on the device depending on what you'd like to measure.
Your multimeter should have two wired probes color-coded red and black. They're insulated in plastic, have metal tips and are typically pen-shaped.
The black probe connects to your multimeter's "COM" terminal. The red probe goes in the terminal labeled volts V and ohms omega symbol. Turn the multimeter dial to the DC voltage position. If your meter has autorange abilities adjusts its voltage sensitivity by itself just look for the voltage symbol V with a straight line above it.
That signifies direct current voltage. A wavy line above the voltage symbol indicates alternating current. If your multimeter lacks autorange, then set the voltage range yourself. Turn its dial to the position marked " Now turn the multimeter on. Touch the black probe COM to the negative end of the battery you're testing.
Next touch the red probe to the positive end of the battery the end that sticks out. You should now see the live voltage value displayed on the multimeter's screen.
If you see "0L" displayed, then the voltage range is set too low. A CR watch battery doles out 3 volts. So, if you see a value that matches a battery's rated voltage or slightly higher it's still good.
A reading that's lower marks a battery that's dying or dead.
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