How to Measure Amperage
Determine the amperage rating for your digital multimeter., Select the appropriate function on your multimeter., Set the range on your multimeter., Plug the leads into the appropriate terminals., Run the circuit through the multimeter to measure the...
Step-by-Step Guide
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Step 1: Determine the amperage rating for your digital multimeter.
A multimeter is a small hand held device that can be used to measure voltage, resistance, and amperage.
Each model will only be rated to handle a certain amount of current, and this rating needs to be adequate for the electrical system you want to test.
For example, running 200 amps through a multimeter rated for 10 amps will ruin the multimeter's fuse.
The amperage rating will be printed on the unit or in the owner's manual. -
Step 2: Select the appropriate function on your multimeter.
Most multimeters have functions for measuring several different quantities.
To measure amperage, you need to set the function to either measure AC amperage or DC amperage, depending on the electrical system you are testing.
The power source for your system will determine the type of current.
For example, household power is AC, while power from a battery is DC. , To ensure that you don't blow your device's fuse, set the maximum amperage sensitivity to well above your expected reading.
You can adjust this downward if the multimeter does not read anything when hooked into your system. , Your multimeter should come with 2 cords, each with a probe on 1 end and a lead on the other.
Plug both cords into the correct terminals for measuring amperage; the owner's manual will specify the correct terminals if they are not labeled clearly. , This is extremely dangerous and can cause electrical shock if measuring household AC or other high voltage or high amperage sources or even lower sources.
Turn off all breakers before working with this and use an AC current sense probe to see if AC is absolutely off before touching any wires especially bare ones.
Do not work in a wet environment on even a high humidity one.
This can conduct electricity and hurt you.
Wear heavy rubber gloves.
Additional precautions may be necessary.
Consult a real electrical workbook (not an online source) before attempting this.
Assume wires can have missing insulation from accidental damage during installation or old age.
Missing insulation can cause electrical shock.
Always have someone ready with a cell phone who is not touching you who can call an Emergency number in case of worst case scenario.
This person should also be trained in first aid and CPR.
If electrical shock occurs, this person may have to remove you using some type of insulated material (a dry article of clothing for example but something else may need to be used) or else that person will also undergo shock due to the conductivity of skin and maybe some clothing (and other materials).
Always consult a real electrical safety book before attempting this and know what type of signal you are dealing with.
Consult a real electrical manual before attempting this about the dangers involved and how to prevent them (not an online source).
Clip the wire in a single spot and strip back the insulation on both exposed ends.
Secure these ends separately to the leads of the amp meter.
Only do the measurement after the wires are securely attached to the amperage meter probes.
Make sure these wires especially the exposed ends cannot touch you.
Turn back on the breaker and adjust the meter sensitivity if no reading is produced. , Follow the precautions outlined in step 5 and consult a real electrical book (not an online source) for safety precautions.
After taking your reading, you will need to complete the broken circuit again.
It is much safer to do this by buying and installing new wire rather than trying to patch the area where you cut it. -
Step 3: Set the range on your multimeter.
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Step 4: Plug the leads into the appropriate terminals.
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Step 5: Run the circuit through the multimeter to measure the current.
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Step 6: Turn off the breaker and use an AC current sense probe to make sure AC is off and then and only then rewire the circuit.
Detailed Guide
A multimeter is a small hand held device that can be used to measure voltage, resistance, and amperage.
Each model will only be rated to handle a certain amount of current, and this rating needs to be adequate for the electrical system you want to test.
For example, running 200 amps through a multimeter rated for 10 amps will ruin the multimeter's fuse.
The amperage rating will be printed on the unit or in the owner's manual.
Most multimeters have functions for measuring several different quantities.
To measure amperage, you need to set the function to either measure AC amperage or DC amperage, depending on the electrical system you are testing.
The power source for your system will determine the type of current.
For example, household power is AC, while power from a battery is DC. , To ensure that you don't blow your device's fuse, set the maximum amperage sensitivity to well above your expected reading.
You can adjust this downward if the multimeter does not read anything when hooked into your system. , Your multimeter should come with 2 cords, each with a probe on 1 end and a lead on the other.
Plug both cords into the correct terminals for measuring amperage; the owner's manual will specify the correct terminals if they are not labeled clearly. , This is extremely dangerous and can cause electrical shock if measuring household AC or other high voltage or high amperage sources or even lower sources.
Turn off all breakers before working with this and use an AC current sense probe to see if AC is absolutely off before touching any wires especially bare ones.
Do not work in a wet environment on even a high humidity one.
This can conduct electricity and hurt you.
Wear heavy rubber gloves.
Additional precautions may be necessary.
Consult a real electrical workbook (not an online source) before attempting this.
Assume wires can have missing insulation from accidental damage during installation or old age.
Missing insulation can cause electrical shock.
Always have someone ready with a cell phone who is not touching you who can call an Emergency number in case of worst case scenario.
This person should also be trained in first aid and CPR.
If electrical shock occurs, this person may have to remove you using some type of insulated material (a dry article of clothing for example but something else may need to be used) or else that person will also undergo shock due to the conductivity of skin and maybe some clothing (and other materials).
Always consult a real electrical safety book before attempting this and know what type of signal you are dealing with.
Consult a real electrical manual before attempting this about the dangers involved and how to prevent them (not an online source).
Clip the wire in a single spot and strip back the insulation on both exposed ends.
Secure these ends separately to the leads of the amp meter.
Only do the measurement after the wires are securely attached to the amperage meter probes.
Make sure these wires especially the exposed ends cannot touch you.
Turn back on the breaker and adjust the meter sensitivity if no reading is produced. , Follow the precautions outlined in step 5 and consult a real electrical book (not an online source) for safety precautions.
After taking your reading, you will need to complete the broken circuit again.
It is much safer to do this by buying and installing new wire rather than trying to patch the area where you cut it.
About the Author
Sandra Bell
Professional writer focused on creating easy-to-follow home improvement tutorials.
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