Hi, I'm Vance and welcome to Repair and Replace.
Multimeters are an essential tool for testing electrical circuits and components.
Whether its checking a battery, extension cord, or troubleshooting an appliance,
multimeters can help determine exactly what has failed.
If you've never used a digital multimeter or if you're looking to refresh your knowledge,
then this episode will get you started.
First we'll review how electricity works.
Then we'll learn how to test for continuity.
Finally we'll do some safe voltage tests and talk about the limits of testing current.
Lets begin.
To understand what a multimeter can measure, lets quickly review some fundamentals.
Electricity is the movement of electrons from one atom to another.
The flow of electrons through a wire is somewhat similar to the flow of water inside of a pipe.
Voltage or potential difference is the pressure from the power source
that pushes the electrons through the wires.
Current or amperage is the flow of electrons within a circuit.
Resistance measured in ohms is the amount that a material will resist the flow of electrons.
Conductors have low resistance allowing electrons to move easily through them.
Insulators have an extremely high resistance to the flow of electrons.
For example copper wire is insulated by a plastic sheath.
If we connect these wires together to a power source we get a complete electrical circuit.
Batteries provide direct current or DC power as the current always flows in a single direction.
This is represented by a dashed line on the multimeter
Your home runs off 120 volts alternating current or AC power.
The direction that the current flows is changing 60 times a second or at 60 hertz.
This is represented by the sine wave.
In either case the electrons always need a continuous path to return to the source.
This is continuity, or a closed circuit.
If we disrupt this path with rubber, plastic, or by air in the case of a broken wire,
the electrons will not flow, as there is no continuity.
This is an open circuit.
In many cases the lack of continuity in a single component
will prevent an appliance from working properly.
To setup the multimeter, plug the meter leads into the terminals.
Usually they are color coded red for positive and black for neutral or common.
Some meters will have 2 positive terminals.
One terminal is for voltage and resistance, and the other is for measuring amperage.
Always inspect the multimeter before use.
Never use a multimeter that has a damaged case
or test leads with nicked or damaged insulation.
To be safe, always hold the multimeter from the insulated handles.
Even 120 volts in your home can be deadly so use caution before testing any live voltage.
If you're unsure at any point, then it's best to contact a professional.
Your model might look a little different but all multimeters have the same common controls.
Volts AC, Volts DC, resistance in Ohms, and resistance with tone,
which will beep when there's continuity.
As well you can test for capacitance, amps AC and amps DC.
Some multimeters are auto-ranging and will automatically adjust the units displayed.
In other models you'll have to set the multimeter to the most accurate range.
For example if we test continuity at the 20K setting,
and we get a reading of 2.6, then the resistance is 2600 ohms.
To test a component for continuity, first set the multimeter to the Ohms,
or resistance with tone setting.
Safely disconnect the power, and remove the wires or connectors.
Now remove the component or isolate it.
Next touch each probe to each component terminal.
If there is no continuity then the multimeter will display OL or Open Loop.
This means the component will need to be replaced.
If there is continuity you'll get a reading above 0 ohms but the resistance will vary
between load or non-load components.
Non-load components such as switches, thermostats or fuses,
provide an unrestricted path for the electricity to pass through.
These will typically have a resistance reading between 0 and 1 ohms.
Load components include heating elements, solenoids, motors,
or any component that consumes power.
They will need a specific resistance value to function correctly.
For example oven bake elements commonly have a resistance of 20 - 40 ohms.
Whereas hot surface ignitors can range from 30 to 200 ohms.
This is different for each component and will vary between models.
If you want to learn more about the various components in appliances,
then watch the video linked below.
As well continuity tests can be useful when
troubleshooting other electrical items in your home.
This includes extension cords, light switches, and receptacles.
The volts DC setting can be used to test batteries and other small electronics.
For example a fully charged AA battery will be close to 1.5 volts,
whereas a weak battery will be much lower at 1.2 volts and should be replaced.
By setting the multimeter to volts AC you can test to see if a receptacle has power
and is wired correctly.
The small plug is the hot wire that is providing the power.
The larger plug is the neutral wire which returns to the power source.
The rounded plug is the ground wire.
If at any point a hot wire touches the metal casing,
the ground wire provides a safe return path back to the source.
When testing live voltage it's essential to use caution.
Always start with the neutral wire first before connecting to the hot.
If you connect to the hot side first, the other multimeter probe now becomes energized
which increases the risk of a shock.
Testing from neutral to hot will show approximately 110 to 120 volts.
Testing from ground to hot will also show around 120.
This will verify if the ground wire has a complete path back to the breaker panel.
When testing from neutral to ground there should be no significant reading.
If there is a 120 volt reading then the receptacle might not be wired correctly
or there could be a short in the circuit.
A standard multimeter can be useful for testing the current in small DC circuits,
but in most cases it's not safe and it's impractical to test the current
in your appliances or in the live wires in your home.
Clamp meters can detect the magnetic fields around a single wire which allows amperage
to be measured without cutting any wires.
These meters are more expensive and require some expertise to use effectively.
Its best to leave these tests to the professionals.
For more troubleshooting on water heaters, furnaces and appliances,
then subscribe to our channel.
And if you need help, you can call or visit an AMRE location
to talk with our knowledgeable staff.
Thanks for watching.