How to Check a Fuse with an Analog Voltmeter How to Check a Fuse with an Analog Voltmeter
You have an analog voltmeter and a circuit that isn’t working. You have a good, verifiable power source, and the circuit appears to be in good working order. However, the circuit is protected by a fuse. If you can’t visually determine whether or not the fuse is in good working condition, it can be tested using the analog voltmeter you have, as long as the meter is capable of also reading resistance. Below you will be presented with a number of steps that you will need to take to test the fuse using your analog voltmeter.
Step1: De-Energize the Circuit
This is a safety measure that you should never skip. Prior to doing any testing using your voltmeter, you should make sure that there is absolutely no power flowing in the circuit.
Step 2: Remove the Fuse
After making sure there is no voltage present which can cause injury or a dangerous spark, you will need to remove the fuse from the circuit. This can be done by either grasping the fuse and pulling straight up and out, or opening the fuse holder and pulling the fuse out of the holder.
Step 3: Set up Your Meter to Take Readings
For this step you will need to properly and completely insert the test leads into your analog voltmeter. This type of measurement is polarity insensitive, so making sure red and black leads are in the red and black socket connectors isn’t vital. A fuse is a type of current limiting device that introduces zero resistance to the circuit, so you will need to set your analog voltmeter to the lowest resistance scale possible with your meter. On most analog meters, this will most likely be a 200 Ohm scale.
Step 4: Calibrate the Meter
On analog meters, there will be a knob that is used to calibrate your meter to zero resistance. With the meter set on the lowest resistance scale, touch the two leads together and watch the deflection. If the pointer doesn’t deflect all the way to zero, use the knob to adjust the needle deflection until it reads zero. Once the meter is properly calibrated, you can take accurate readings.
Step 5: Take Your Reading
In order to take your resistance reading, touch the conductive leads or ends of the fuse with the conductive ends of the test leads on your meter. If the fuse is in working condition, the meter needle should deflect to the far right and point directly at zero. Any reading except zero means that the fuse is questionable and should be replaced as soon as possible.
Save Your Meter
Whether you’re using an analog or a digital meter, when taking resistance measurements, it is imperative that you remove power from the circuit being tested. Power being applied to a meter that is configured for resistance measurements will destroy the meter. Also, whenever possible, remove the component from the circuit before taking resistance readings. This is because of the fact that if the part isn’t removed from the circuit prior to measuring, the rest of the circuit can affect the reading you receive.
Above you have been given five steps required to test a fuse as well as some safety steps you should keep in mind.