How To Read A Capacitor? The Complete Guide

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If you want to buy a capacitor, you need to ensure that it is a perfect one for your application. But how can you know if you don’t know how to read it?

There are different types of capacitors and they come in different sizes, capacities, and other technical specifications.

Every piece of information that is printed on the capacitor gives details of how it is designed to perform. This implies that you have no option but to know how to read a capacitor.

The markings on the capacitor could be defining the capacitance, voltage, current, polarity, or any other relevant information that will ultimately determine how the capacitor will perform.

Keep reading as I guide you on how to properly read capacitors.

Overview of a capacitor

What is a capacitor and what does it do?

Capacitors are electronic components designed to store and release electric charges when necessary. Given their ability to store and release energy, capacitors are used for different purposes including filtering noise, voltage balancing, and timing circuits among many other applications.

Capacitors are charged and discharged. Charging entails feeding a capacitor with an electric charge where it will be stored. Discharging is when the capacitor releases its stored energy. Capacitor size is measured in farads and it determines the amount of charge stored in the capacitor.

Also, there are different types of capacitors in the market. The most common types include ceramic capacitors, metal film capacitors, electrolytic capacitors, and paper capacitors. These different types differ in the way they are made or assembled. The materials used also differentiate one type of capacitor from another.

Regardless of the type, the parameters and specifications used to gauge the performance of the capacitors remain the same though we may have some slight variations.  This is just another reason why you need to be keen on those capacitor readings.

Capacitance value

This is the main reading that you should know about a capacitor. It defines the amount of charge that a capacitor can hold and its SI unit is farads. Since charges are measured in coulombs, we will have to do some conversion arithmetic whereby one farad is equal  to one coulomb.

You can check out the side of the capacitor for the capacitance. It is usually printed alongside other parameters such as the voltage of the capacitor.

For example, a capacitor will be labeled 50V and 0.60µFb which means that its voltage capacity is 50 volts while its capacitance is 50 microfarads.

Also, when reading the capacitor, you should be able to convert farads into microfarads. 1 farad=1000,000 microfarads. Using our example, 0.60 farads = 4700 µF. Capitalization does not matter when it comes to labeling capacitors. In most cases, you will see µF or just UF.

The capacitance value is also measured in picofarads (pF) and 1 farad= 1000000000000 pF.

The capacitance value in the capacitor determines the amount of charges a capacitor can hold per given voltage. Usually, the higher the capacitance, the more charges a capacitor can store. Actually, this is the main reason why you should know how to read capacitor.

A 20µF capacitor is large than a 3µF capacitor. So, if an application is labeled capacitance of 20µF, you should use the exact capacitor. Choosing a value lower than that will result in underperformance issues.

Voltage rating

Since capacitors are power sources, they also have voltage ratings. This information is also printed on the side of the capacitor and you should check it out before buying a capacitor. The voltage rating defines the maximum operation voltage that a capacitor can support.

A capacitor’s voltage rating is usually marked in volts (V). It varies from one capacitor to another. The voltage rating of a capacitor that you buy will depend on the specific application area.

What should I look at when choosing the voltage rating of a capacitor?

It is recommended that the voltage rating should be equal or slightly higher than the recommended circuit’s voltage.

A lower voltage rating will deprive the circuit power that is needed to run electronic components.

Another specification that is closely related to the voltage rating is voltage dependence. This specification means that the capacitance value can change when you alter the voltage across the plates of the capacitor. In most applications, the voltage can cause a change the capacitance by a small percentage not exceeding +20%.

Read the polarity of the capacitor

You should also be able to read the polarity of the capacitor before you buy one. However, this will matter only to specific types of capacitors such as electrolytic capacitors. Such capacitors have different poles, cathode, and anode which are basically positive and negative terminals.

You can read the polarity of capacitors by checking out the makings of positive (+) and negative (-). Other than the making, you can identify the two poles by their dimensions. The positive terminal has a longer terminal than the negative.

You should be careful when it comes to the polarity of the capacitors. This is vital when connecting the capacitor to the electric circuit. Reversing the polarity can damage the capacitor and even critical components on the circuits.

On the other side, you will have no issues with non-polarized capacitors such as ceramic and metal film capacitors. They give you the freedom to install it in any orientation.

Tolerance value of the capacitor

When reading a capacitor, you should be able to point out its tolerance value. This is the acceptance variation of the capacitance. If you take your time to test the capacitance of a capacitor at any given time, you will discover that you will not get the exact value. It should vary within a certain range due to both internal and external factors.

The capacitor tolerance value is usually expressed in terms of percentage and the value rarely exceeds +-20%. However, in some capacitors it is expressed in raw figures such as 0.37µF or 0.56µF.

Take note that the lower the tolerance value the more accurate the capacitor is. Like other information, the capacitor tolerance value is indicated on its side or surface.

Why should I be keen on the tolerance value of a capacitor? It is mainly for the sake of the capacitor’s accuracy.

Reading and understanding the capacitor codes

Now that you know the basic specifications and parameters of capacitors, let’s get into the reading of the codes and numbers on the capacitor. A typical capacitor code comprises of numbers and letters. So, what do the numbers stand for and what do the letters mean?

To read the capacitor, you should start with the first two digits. They represent the capacitance value. This is if the capacitor has a three-digit code printed on it. The third digit will serve as a multiplier.

In other cases, the digit code will comprise of two digits and a letter. In this case, the letter will serve as a multiplier meaning that you will not have to do the conversions.

Using the third digit as a zero multiplier

If the code has three digits and a letter, the third number will still serve as a zero multiplier. In this case, you will need to multiply the capacitance value by ten enough times so that you can find the actual capacitance.

An example is if the capacitor read 106K. The K stands for the value of one thousand pico-Farads so your conversion will entail multiplying 106 ×1000 which will be 106,000pF or simply 106nF

What if the third number on the capacitor’s code is 8? Let’s say if the capacitor is 188K.You will have to multiply the digit by 0.01. You will have 0.18F.

What do letter codes on the capacitors mean?

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Although we have already covered some letters, there are many other letters that ae used on capacitors and we are going to look at some of them and what they mean.

The letter can represent the tolerance of the capacitor. Different letters represent different tolerance values. This implies that you can choose a capacitor depending on the letter used. Check out the list below to have some understanding of what each letter stands for:

• B: +- 0.1 pf
• C: +- 0.25 pf
• D: +- 0.5 pf
• F: +- 1%
• G: +- 2%
• J: +- 5%
• K: +- 10%
• M: +- 20%

Next time you see these letters next to the numbers, you should be able to know what they mean.

Conclusion

From this guide, you have learned how to read a capacitor. You will be able to tell whether the capacitor is of the right size and whether its specifications will meet your power needs.  You need to pay attention to the first three digits and the letters.

All the capacitors have codes printed on their bodies which give all the details and specifications that you should know. We have just covered the meanings of these codes so you should not have any difficulties reading them.

You can only buy well-labeled capacitors from reputable manufacturers and suppliers. Such capacitors will give you easy time reading and understanding.

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