How to Know If A Multimeter Fuse is Blown

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Did you know that older homes and vehicles that do not utilize modern circuit breakers use fuses to stop the damage from electrical surges? Often, those fuses need testing to determine if they’re still in top working condition. Testing could be done using a multimeter and doing such is both simple and fast to learn. 

Normally, a multimeter is not broken when it stops reading (assuming it has a good battery). What you may have is a blown fuse. 

What is a Multimeter, by the way? 

In case you didn’t know yet, a multimeter is a device measuring DC and AC voltage, electrical resistance, and the flow of current. If you want to test it, you can either utilize it to measure the ohms or the continuity. 

Keep in mind that a multimeter has a negative and positive lead. When you’re testing resistance in a circuit, the meter will send a small amount of electricity from its battery. It will then calculate the quantity of electricity passing through the object or circuit. 

People use a multimeter for many different purposes: to measure current, resistance, and voltage. What most people don’t realize is the difference between measuring current and voltage. When you don’t understand the workings of a multimeter, you will just end up blowing the multimeter fuse. 

Well, the cause of those fuses to be blown is due to the massive difference between how current is measured and how voltage is measured. One measurement is intended to be resistive, whereas the other measurement is built to be passive. Hence, understanding the inner mechanisms of both the current meter and voltage meter will help avoid blowing a fuse—that simple. 

Parts of a Multimeter

A multimeter has three different parts:

  1. Ports
  2. Display
  3. Selection Knob

The selection knot enables you to set the multimeter to read various things like resistance (Ω), current voltage (V), and milliamps (mA).

The display normally has four digits, and it can show a negative sign. Several multimeters have illuminated displays for improved viewing, especially in low light conditions. 

Two probes are plugged into the two ports on the unit’s front. COM refers to common and is often connected to the Ground or “–” of the circuit. Remember that the COM probe is black, but there’s no difference between the black probe and the red probe apart from the color itself. 

10A is the special port utilized when calculating big currents. mAVΩ is the port to which the red probe is plugged into. That port enables the measurement of current, resistance, and voltage. Further, the probe features a banana-type connection on end plugging into the multimeter. 

Blown Multimeter Fuse—A Common Problem 

A blown multimeter fuse is one of the most common problems with a multimeter. Digital multimeters could blow up and cause not just equipment damage but also severe personal injuries. Further, when the electrical powers become a risk, a person’s know-how becomes his most vital tool for survival. 

Even though such convenient devices come with many safety features, you should still understand the limitations of such features and understand the things to avoid when using the measuring device. 

So how do you tell when your multimeter fuse is blown? 

A continuity test tells you whether two things are electrically connected. When something is continuous, then an electric current could flow freely from one end to another end. But when there’s no continuity, it indicates there’s a break somewhere within the circuit.

That could suggest a blown fuse. Remember that continuity is one of the most practical tests for electronics repair. 

In case these multimeter fuses blow up, it is of utmost importance to change them only with those specified by the manufacturer that created the digital multimeter. On top of that, using the tool in a wrong power category can immediately cause the power to increase across the destroyed fuse. 

All good-quality multimeters have fuses inside them which are engineered to blow in the event of too much current through them. Keep in mind that like all overcurrent protective tools, such fuses are mainly created to safeguard the equipment (in this situation, the multimeter itself) from too much damage and only secondarily to safeguard the user from any harm. 

A multimeter can be utilized to measure its current fuse by selecting the selector switch to the resistance position and establishing a connection among the two red sockets. 

Take note that a good fuse will show very minimal resistance, whereas a blown fuse will always display O.L. (or any indication the model of multimeter utilizes to show no continuity). The real number of ohms shown for a good fuse is of little consequence, so long as it’s a randomly low figure. 

How to Test the Fuse?

Lucky for you, there’s a simple way to test if your fuse is blown or not. 

Try to listen for the multimeter to continuously beep as you hold the probes over the fuse. Don’t you hear any noise coming from the meter? Then that’s a clear sign that the fuse is blown and should be immediately replaced. 

Here are some steps you can follow:

  1. Are you using a digital multimeter set to calculate resistance? Touch the probes together to obtain a preliminary reading. Then place the probes on either side of your fuse and check if the reading is alike.

Do you get reading? If yes, then the fuse is working properly. However, if you didn’t get any reading or it’s O.L., then the fuse has completely blown. 

  1. Does the multimeter read Not Complete or Open? It also means the fuse is broken. 

Final Thoughts

A multimeter can be a safety tool and a practical work device in the hands of a professional technician. This tool can effectively measure electrical parameters, locate electrical faults, and improve your skill at your trade. However, it could also be a major source of electrical incidents if you’re ignorant and careless.

Why don’t you follow the necessary safety precautions and say goodbye to the possible risks associated with your device? 

We hope you find this post informative and useful at the same time. Remember all the insights and tips mentioned above so you’ll know next time what to do in case your multimeter fuse is blown. 

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