Fuse: Cars and older homes that don’t use modern circuit breakers use fuses to prevent damage from electrical surges. Sometimes these fuses require testing to check that they are still in good working order. Testing fuses can be done using a multimeter, and doing so is both fast and easy to learn.

Understand fuses
Understand fuses

Understand fuses

Fuses are really just wires that are designed not to last, but their purpose is to prevent damage to more valuable electrical equipment or prevent fires (especially in homes) caused by power surges. If too much power runs through the fuse, it will “burn out,” quite literally, and open the circuit, preventing the current from flowing through the circuit. There are several varieties of fuses, but their differences are primarily in appearance. Here is a description of the two you are most likely to see:

The cartridge fuse is a cylindrical fuse that has been common in a wide variety of devices for many years, from homes to small electronic devices. They have metal contact or terminal points on either end and consist primarily of a tube that contains the wire.

The blade fuse is a common type of automotive fuse that has come into use in the last 20-30 years. They vaguely resemble the plug of a power cord, with two metal prongs emanating from a plastic housing that contains the wire. Previously, most vehicles also contained small glass cartridge fuses. Blade fuses plug conveniently into banks, and relatively little space is required to house a large number of them together.

Learn how a multimeter works
Learn how a multimeter works


Learn how a multimeter works.
 

Multimeters measure AC and DC voltage, electrical resistance, and the flow of current. For testing a fuse, you can either use it to measure the continuity (which tests if the circuit is complete) or the ohms (which tests resistance).

A multimeter has a positive and negative lead. When testing resistance in a circuit, the meter will transmit a small quantity of electricity from its own battery and then measure the amount that passes through the circuit or object.

Understand why you must test fuses
Understand why you must test fuses

Understand why you must test fuses

 Testing fuses is the simplest way to examine what is going on in the electrical systems of your car or home, and for that reason, it is a vital skill to possess.

It is easier to test fuses than it is to test other electrical equipment. Other components in your car or home involve complex wiring systems that run on for some length. In addition, most car parts can only be tested at repair shops, and to do so will usually cost quite a lot of money. Testing fuses with a multimeter is comparatively simple to do, and the equipment involved is cheap and easy to operate.

Many types of fuses allow for visual confirmation that the fuse is still functional. They are made clear so that you can see if the wire remains intact. If the translucent area is blackened, it is usually because the fuse has burned out. However, some fuses will create that blackened stain after only slightly overheating, and that may have even been the result of an unnoticed incident weeks or months earlier. If a device is not working, you should test the fuses. If the fuses are all still working, there is likely a more serious problem and it may be time to call on an expert.

Turn the equipment off and remove the fuse
Turn the equipment off and remove the fuse

Turn the equipment off and remove the fuse. Make sure the device, equipment, or vehicle is turned off before the fuse is removed. To remove the fuse, simply pull it straight out of the slot.

Turn the meter on and set it to measure continuity
Turn the meter on and set it to measure continuity

Turn the meter on and set it to measure continuity

 Turn the dial on the multimeter so it points to the continuity setting, which looks like 5 curved vertical lines. Before you test the fuse, put the positive and negative leads together and listen for the meter to beep to ensure it’s working properly.

If you want to measure the ohms, use the multimeter setting that has the omega symbol (Ω).

Put one lead on each end of the fuse and look at the display.
Put one lead on each end of the fuse and look at the display.


Put one lead on each end of the fuse and look at the display.
 Because the fuse is little more than a single wire—and no complex parts to worry about—it does not matter which side receives the positive or negative lead.

Test the fuse.
Test the fuse.


Test :
 Listen for the multimeter to beep continuously as you hold the probes against the fuse. If you don’t hear any noise coming from the meter, then the fuse is blown and should be replaced.

If you’re using a digital multimeter set to measure resistance, touch the probes together to get an initial reading. Then put the probes on either side of the fuse and check if the reading is similar. If it is, then the fuse works properly. If you get no reading or “OL”, then the fuse has blown.

If the multimeter reads “Open” or “Not complete,” it means the fuse is broken.

Resistor color codes are something that every electronics hobbyist should remember.

The old mnemonic was rather, well, disturbing, and a conscientious person would never recite it. Anyway, on with the better one! Write this down in a prominent place and you’ll have it committed to permanent memory in no time


Here’s one mnemonic “Bright Boys Rave Over Young Girls But Veto Getting Wed.
 Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey, White <=> 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.

Best method to memorize is - B.B. Roy of Great Britain Veto getting wed.
Best method to memorize is – B.B. Roy of Great Britain Veto getting wed.

Best method to memorize is – B.B. Roy of Great Britain Veto getting wed.

Alternatively, most of the colors are those from the traditional rainbow. Black is 0 (as in ‘nothing’), Brown is 1, then Red through Violet, and finally Gray and White are 8 and 9.

The multiplier band goes by the same code and can be read as "followed by N zeros", plus Gold for "divide by 10" and Silver for "divide by 100".
The multiplier band goes by the same code and can be read as “followed by N zeros”, plus Gold for “divide by 10” and Silver for “divide by 100”.

The multiplier band goes by the same code and can be read as “followed by N zeros”, plus Gold for “divide by 10” and Silver for “divide by 100”.

Tolerances are something of a mess
Tolerances are something of a mess


Tolerances are something of a mess:
 Brown and Red are 1% and 2% (you usually spot them because they have an extra significant digit), Gold and Silver are 5% and 10%, and 20% doesn’t even get a tolerance band (you will rarely, if ever, come across one of these).

To read the whole thing, put the tolerance band at your right, and go like this: “green-brown-red-gold = 5-1-00-5% = 5.1K 5%”. You’ll get used soon enough, and a bit later you’ll be spotting what you want at once. It’s also easy to classify them by decade: red is Ks, orange is 10Ks ..

Resistors are very common components in electronic circuits of all kinds

Their function is to resist the current flowing in the circuit, and how much resistance they provide is measured in ohms. Most are printed with either a color code or an alphanumeric code to indicate their ohmic value and tolerance — how much their resistance may vary. Learning the codes, along with using a helpful mnemonic device, will allow you to identify resistors easily

۱٫ Axial resistors are cylindrical with leads extending from each end.

1. Axial resistors are cylindrical with leads extending from each end.
۱٫ Axial resistors are cylindrical with leads extending from each end.


Look at the resistor so the group of 3 or 4 color bands are on the left side.
 These are sometimes followed by a gap, then an additional color band

Look at the resistor so the group of 3 or 4 color bands are on the left side.
Look at the resistor so the group of 3 or 4 color bands are on the left side.

Read the color bands from left to right. The colors on the first 2 or 3 bands correspond to numbers from 0 to 9, which represent the significant digits of the resistor’s ohmic value. The last band gives the multiplier. For example, a resistor with brown, green and green bands is rated at 15 mega-ohms (15,000,000 ohms). The code is as follows

Black: 0 significant digit, multiplier of 1

Brown: 1 significant digit, multiplier of 10

Red: 2 significant digit, multiplier of 100

Orange: 3 significant digit, multiplier of 1,000 (kilo)

Yellow: 4 significant digit, multiplier of 10,000 (10 kilo)

Green: 5 significant digit, multiplier of 100,000 (mega)

Blue: 6 significant digit, multiplier of 1,000,000 (10 mega)

Violet: 7 significant digit

Gray: 8 significant digit

White: 9 significant digit

Gold: multiplier of 1/10

Silver: multiplier of 1/100

Read the color bands from left to right
Read the color bands from left to right

Read the color on the last color band, which is farthest right. This represents the tolerance of the resistor. If there is no color band, the tolerance is 20 percent. Most resistors have no band, a silver band or a gold band, but you may find resistors with other colors. The tolerance color code is as follows

Read the color on the last color band, which is farthest right
Read the color on the last color band, which is farthest right

Brown: ۱ percent tolerance

Brown: 1 percent tolerance
Brown: ۱ percent tolerance

Red: ۲ percent tolerance

Red: 2 percent tolerance
Red: ۲ percent tolerance

Orange: ۳ percent tolerance

Orange: 3 percent tolerance
Orange: ۳ percent tolerance


Green:
 ۰٫۵ percent tolerance

Green: 0.5 percent tolerance
Green: ۰٫۵ percent tolerance

Blue: ۰٫۲۵ percent tolerance

Blue: 0.25 percent tolerance
Blue: ۰٫۲۵ percent tolerance

Violet: ۰٫۱ percent tolerance

Violet: 0.1 percent tolerance
Violet: ۰٫۱ percent tolerance

Gray: ۰٫۰۵ percent tolerance

Gray: 0.05 percent tolerance
Gray: ۰٫۰۵ percent tolerance

Gold: ۵ percent tolerance

Gold: 5 percent tolerance
Gold: ۵ percent tolerance

Silver: ۱۰ percent tolerance

Silver: 10 percent tolerance
Silver: ۱۰ percent tolerance

Memorize a mnemonic for resistors. Several exist, so choose the one that you won’t forget. Remember that the first color is black, and afterward each first letter corresponds to a color in order from 0 to 9. Some popular mnemonic devices include:

“Bad beer rots our young guts but vodka goes well.”

“Bright boys rave over young girls but veto getting wed.”

Surface mounted resistors
Surface mounted resistors

Surface mounted resistors are rectangular in shape with leads that extend from opposite sides or the same side and are bent downward for mounting on circuit boards. Some resistors have contact plates on the bottom

Read the 3 or 4 numbers on the resistor
Read the 3 or 4 numbers on the resistor

Read the 3 or 4 numbers on the resistor. The first 2 or 3 represent the significant digits and the last indicates the number of 0s that should follow. For example, a resistor reading 1252 indicates a rating of 12,500 ohms or 1.25 kilo-ohms

Compare the letter at the end of the code with the tolerance it represents
Compare the letter at the end of the code with the tolerance it represents

Compare the letter at the end of the code with the tolerance it represents

A: 0.05 percent tolerance
A: ۰٫۰۵ percent tolerance

A: ۰٫۰۵ percent tolerance

B: 0.1 percent tolerance
B: ۰٫۱ percent tolerance

B: ۰٫۱ percent tolerance

C: 0.25 percent tolerance
C: ۰٫۲۵ percent tolerance

C: ۰٫۲۵ percent tolerance

D: 0.5 percent tolerance
D: ۰٫۵ percent tolerance

D: ۰٫۵ percent tolerance

F: 1 percent tolerance
F: ۱ percent tolerance

F: ۱ percent tolerance

G: 2 percent tolerance
G: ۲ percent tolerance

G: ۲ percent tolerance

J: 5 percent tolerance
J: ۵ percent tolerance

J: ۵ percent tolerance

K: 10 percent tolerance
K: ۱۰ percent tolerance


K:
 ۱۰ percent tolerance

M: 20 percent tolerance
M: ۲۰ percent tolerance

M: ۲۰ percent tolerance

Check to see if there is a letter "R" within the numeric code
Check to see if there is a letter “R” within the numeric code

Check to see if there is a letter “R” within the numeric code. This indicates a very small resistor, and the letter takes the place of a decimal point. For instance, a 5R5 resistor is rated at 5.5 ohms