Learn about the different types of multimeters to prepare you for how to use them alongside test leads for measurements within a circuit! Understand how to measure current, voltage, continuity, resistance, and temperature.
Follow Along on SkillCat: "Using A Multimeter" Course!
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Function of Multimeters
Multimeters and probes are common tools you will use in any skilled trade. They are devices used for diagnosing problems in a circuit by measuring resistance, voltage, continuity, and more.
For example, here's what a multimeter can be used to measure in a circuit:
Types of Multimeters
There are two main types of multimeters you'll encounter:
Digital multimeters
Clamp multimeters
Digital Multimeters
Before digital multimeters, there would be a tool for measuring resistance, another for current, another for voltage, and so on. Digital multimeters combined all of these tools into one.
Digital multimeters have the following features:
Dial that determines what you are measuring
Display that shows measurement results
Ports for connecting accessories like test leads
Clamp Multimeters
A clamp multimeter is a digital multimeter with an additional current sensor. The current sensor sits in a red claw at the top of the meter. A clamp meter can perform all of the same measurements as a digital multimeter.
Clamp meters are much safer to use for measuring higher amounts of current in a circuit. Some clamp meters can measure up to 2500A of current whereas most digital meters can only measure 10A.
Multimeter Ratings
Range
Range is the max and min values a multimeter can measure in a circuit. A multimeter should have the range to measure the range of the equipment you're working on. If you see "OL" displayed, it means you measured a component above its range.
Knowing the range of your multimeter is incredibly important. While measuring below the range would just result in "OL" being displayed, measuring above the range can blow the fuse and injure you (more on that later).
Resolution
Resolution is how many decimal points the meter can display. Higher resolution means more accurate measurement.
Resolution is measured in “counts”. Once the measurement goes over the count limit, the measurement will lose a decimal place. For example, a digital multimeter with a 2000 count may display a maximum value on 1.999. Once the measurement goes over 1.999, the measurement will display 2.00.
Accuracy
Accuracy is how close to the real value the digital multimeter can measure. The multimeter measure will be over or under the real value by the accuracy percentage.
For example, a digital multimeter rated with a +/- 5% accuracy may display a number between 95-105V when measuring the voltage of a 100V wire, since 5% of 100V is 5V.
Multimeter Parts
Fuses
Normally, measuring current that is too high for your meter's range would shock you. Fortunately, we have a device in a multimeter called a fuse to protect us.
A fuse is designed to protect equipment from surges in current or voltage. They're built into the range multimeter so that when the multimeter experiences too much current or voltage, a wire in the fuse melts. When the wire melts, the circuit within the multimeter is broken. The broken circuit prevents more current or voltage from flowing into the meter.
A fuse with a melted wire and broken circuit is called a blown fuse. Fuses can only be used once, so after wire melts and the circuit breaks, your multimeter won't function. Replace the fuse and check that your multimeter comes with a fuse built in.
Ports For Probes
2-4 ports can be found at the bottom of your multimeter. Accessories like probes can be plugged into multimeter ports. Based on the measurement you're looking to check, your probes can be plugged into different ports.
COM Port
The COM or common port has a black label with "COM" written next to it. The COM port is used for most multimeter measurements. It's the most general port on the multimeter.
Current Ports
The “A” port usually has a red color and is used for measuring current within a circuit. The port will also be labeled with a large “A”, which stands for amps, the unit of measurement for current.
The “A” port will have a number label next to it, like “10A”. This is the maximum current in a circuit that your multimeter can safely handle.
The port labeled “mA” allows your meter to measure current in a circuit in smaller amounts more accurately, but may not be present on all meters. The port measures current in mA, or milliamps (1000mA are in an amp). Some “mA” ports can also be used for measuring µA, or microamps (1,000,000 microamps are in an amp). The label on the port will look like this “mA/µA.”
Similar to the “A” port, the “mA” port will have a number in front of mA. This number is the maximum amount of mA you can safely measure while using the “mA” port.
VΩ Ports
The VΩ port is used most commonly when you are measuring resistance or voltage in a circuit. The port will have a red border and the label VΩ.
It is common for the VΩ port to be used for other measurements in a circuit as well. For reference, here are all measurements and units this port can be used for:
Measure AC voltage and DC voltage in Volts
Measure resistance in Ohms
Measure continuity in Ohms
Measure capacitance in Farads
Probes
To measure using a multimeter, you use probes that plug into the ports we just covered. Probes, sometimes referred to as leads or test leads, are long wires with two different heads at each end; one end of the probe connects into your multimeter ports, and the other end of the probe is used to touch the component in a circuit that you're measuring.
The end of the probe that connects into your multimeter ports will have a circular plug head. This plug looks similar to a power cord for a desktop computer. Since it plugs into the ports, it's referred to as the plug end.
The other end of the probe is called the probe end, since it's used to probe the component. Probes have a rubber handle and a sharp metal point extending from it.
Multimeters come with two probes - a black one and a red one. The black lead represents the negative probe and is used to take measurements, while the red lead represents the positive probe. The color of the lead determines which port to plug the probe into.
To connect a probe to your multimeter, hold the probe by the plug end. Press the plug end into the correct port on the multimeter. Be sure to hold the plug by the rubber grip. This makes it easier and safer to insert the probe.
When using them, hold the probe end of the probe by the rubber handle. Keep your hands as far from the metal tips as you can to reduce the chance of getting shocked. Press the metal tips of the probes onto the component you are measuring.
Another common type of probes are alligator clips. Alligator clips are used just like a standard probe, but instead have metal jaws. The metal jaw can be used to grip and hook the probe onto what you are measuring. There are two types of alligator clips: push on are the most common and attach to multimeter probes, and standard clips replace your multimeter probes entirely.
The main benefit of alligator clips is that you can attach them to what you are measuring. Conventional multimeter probes require you to hold the probe against the component.
So how do we connect alligator clips to our multimeter? For push on clips, press the tip of your probe into the hole on the opposite side of the jaws. The probe should fully plug into the push on alligator clips. To connect standard alligator clips, follow the same process as you would for standard multimeter test leads. Press the port end of the alligator probes into the correct port on the multimeter.
Measuring With A Multimeter
The measuring process using a multimeter and probes are pretty standard amongst all measurements. Check these multimeter articles for more in-depth information:
To start measuring any measurements using your multimeter, start by plugging your probes into the correct ports. Turn the dial on your multimeter to represent which you want to measure: current, voltage, resistance, continuity, capacitance, or temperature.
If you're using a clamp multimeter instead of a digital multimeter to measure the current of a wire, you won't be using probes. Instead, press the left button on the multimeter to open the clamp jaws. Move the multimeter so that one wire is centered inside the clamp - then close the jaws. Don't touch the wire, only move the multimeter. The wire shouldn't touch edges of the clamp or multimeter. Live wires are wires with current or voltage running through. Keep your hand below the meter's display to avoid live wires.
Keep in mind that there are two types of current: alternating current (AC) and direct current (DC). Alternating current is an A with a wave, whereas direct current is an A with a straight and dashed line. Schematic diagrams for equipment typically indicate if a system is set to direct or alternating current, so be sure to check for this. To learn more about measuring current with a multimeter, click here.
The same goes for voltage; there is alternating voltage (AC) and direct voltage (DC). Both AC voltage and DC voltage can be measured with a multimeter. The “V” symbol with a wavy line is for AC voltage; the “V” symbol with a solid and dashed line is for DC voltage. The meter's function key may be used to switch between AC and DC voltage as well. To learn more about measuring voltage with a multimeter, click here.
To measure continuity, turn the meter dial to the "))))" symbol for a continuity test. If you don't see this on your meter, use the function key. Unlike other measurements, you measure continuity using a continuity test since there's no specific measurement needed. An "OL" on the display implies the component fails the continuity test and has no continuity. Alternatively, passing the continuity test results in a low number being displayed with a beep, implying there is continuity. To learn more about continuity tests, click here.
Measuring resistance with a multimeter is quite simple. Your black probe can be plugged into the COM port for resistance. Turn the meter dial to the Ohm symbol to measure resistance. Generally, Ohms is the symbol for resistance. Ensure the component is disconnected from the circuit before measuring resistance. You may need to manually set your range to measure resistance if your meter doesn't auto range. To learn more about measuring resistance, click here.
Measuring capacitance is similar to measuring resistance. The “-|(-” symbol represents capacitance. Power to the capacitor should be turned off before taking measurements, but still err on the side of caution. Measuring capacitance could lead to a shock from the capacitor. To learn more about measuring resistance, click here.
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FAQs
What is a digital multimeter?
A digital multimeter (DMM) is a tool used to measure various electrical parameters such as voltage, current, and resistance. It displays readings digitally, which makes it easy to use and highly accurate.
How do I measure AC voltage with a multimeter?
To measure AC voltage, set the multimeter to the AC voltage setting (often marked as "~V"), connect the probes to the circuit, and read the voltage on the display.
How do I measure DC Voltage with a multimeter?
Set the multimeter to the DC voltage setting (often marked as "—V"), connect the probes to the circuit, and read the voltage displayed. Ensure you have the correct polarity.
What is the difference between AC and DC voltage?
AC voltage (Alternating Current) changes direction periodically, while DC voltage (Direct Current) flows in one direction. Multimeters can measure both by switching to the appropriate setting.
How do I measure current with a multimeter?
To measure current, set the multimeter to the current measurement setting (A for amperes), place the multimeter in series with the circuit, and read the current value. Be mindful of the current range and limits of your multimeter.
How do I measure resistance with a multimeter?
Set the multimeter to the resistance measurement setting (Ω for ohms), connect the probes across the component, and read the resistance value. Ensure the circuit is powered off to avoid damage.
What is continuity and how to test it?
Continuity tests check if a circuit is complete. Set the multimeter to the continuity test mode (often marked with a sound wave symbol), connect the probes to the circuit, and listen for a beep, indicating continuity.
How do I use the multimeter probes?
Probes are connected to the multimeter's input terminals (commonly labeled COM and V/Ω). Place the probes on the points of measurement in the circuit.
What is the role of a circuit in using a multimeter?
Circuits are paths through which electrical current flows. Understanding circuits is essential for using a multimeter to measure various parameters and ensure safety during measurements.
How to troubleshoot with a multimeter?
Use the multimeter to measure voltage, current, and resistance across different points in the circuit to identify and isolate faults.
How do I use a digital multimeter to test a battery?
Set the multimeter to the DC voltage setting, place the red probe on the positive terminal and the black probe on the negative terminal of the battery. Read the voltage to determine if the battery is charged or needs replacement.
Quiz
Question #1: True or False = A clamp multimeter is a digital multimeter with an additional current sensor.
True
False
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Question #2: True or False - Clamp multimeters can measure higher current than a digital multimeter.
True
False
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Question #3: True or False - A fuse is not important to have in a multimeter.
True
False
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Question #4: A fuse can be used how many times?
2
5
1
Unlimited
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Question #5: True or False - A multimeter’s range describes the minimum and maximum values the multimeter can safely measure.
True
False
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Question #6: What number below would the multimeter display with a 20,000 count resolution?
1.9
1.99
1.999
1.9999
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Question #7: The wire you are measuring has 50V flowing through it. Your meter has an accuracy of +/-5%. What is the range of values your meter would display?
30V-60V
47.5V-52.5V
40V-80V
10V-20V
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Question #8: What is a multimeter port?
A screen that displays measurements
A hole where multimeter accessories are plugged in
A device used to measure temperature
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Question #9: When should you use the “A” port?
To measure temperature
When the current will be larger than the limit on your “mA” port.
To get the average measurement
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Question #10: What does the number next to the “A” port mean?
How many times you can measure current before changing the fuse.
The maximum current that the meter can safely handle while using the A port.
The accuracy of the A port.
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Question #11: How many “mA” are in an amp?
10
200
1000
5000
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Question #12: What is the VΩ port used to measure?
Voltage or resistance
Current
Pounds
All of the above
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Question #13: What connects into the ports on your multimeter?
Leads
Thermometers
Your fingers
Resistors
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Question #14: Which end of the lead do you press onto what you are measuring?
The probe end
The plug end
Neither
Both A and B
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Question #15: The black lead represents the negative lead.
True
False
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Question #16: What is the main benefit of using alligator clips?
They look cooler
They can be attached to what you are measuring
They are the same color
They require you to hold them when taking a measurement
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