How to Read Polyester & Ceramic Capacitor Codes

Complete guide for identifying polyester and ceramic capacitors

🌐 You can read this article in: Português | Español

Hello, electronics enthusiasts!

Ever felt lost when faced with those tiny electronic components with mysterious codes? You’re not alone! With the vast number of manufacturers and standards on the market, deciphering the information on polyester and ceramic capacitors can seem like a puzzle.

But don’t worry! Today we’re going to unravel these secrets together. In this complete guide, you’ll learn to interpret capacitor codes, identify capacitance values in microfarads (μF) and picofarads (pF), understand tolerance and working voltage, and much more!

Fig. 2 – Examples of codifications found on polyester and ceramic capacitors

Get ready to transform these electronic enigmas into practical knowledge that will boost your projects!

Quick Tip: Before we dive into the details, know that capacitors with values above 1μF usually have their value written directly on the body, while smaller ones use numerical codes that we’ll decipher together!

🧐 The Challenge of Reading Capacitors: Why Is It So Complicated?

Imagine you’re assembling a circuit and come across a tiny capacitor marked only with “104”. What does this mean? And why isn’t it clearly written as “0.1μF”?

The answer lies in space economy and industrial standardization. For values greater than 1μF (1 microfarad), as in aluminum electrolytic or tantalum capacitors, manufacturers generally write the value directly on the body. However, for values below 1μF, the story is different!

Most polyester and ceramic capacitors use a three-digit code followed by a letter. But don’t worry, we’ll transform this “secret alphabet” into something you’ll understand with your eyes closed!

Fun Fact: The correct symbol for microfarad is μ (Greek letter mu), but since not all keyboards have this character, it’s common to replace it with the letter “u” in technical texts. Now you know why you see “uF” instead of “μF” out there!

📚 Understanding Farad Submultiples

Before deciphering the codes, let’s review (or learn) about the submultiples of the Farad, the unit of measurement for capacitance. Think of it like measuring distances: we use kilometers for long distances and meters or centimeters for shorter ones. With capacitors, something similar happens!

A pF (picofarad) is the smallest practical submultiple used in electronics. To give you an idea, 1 picofarad is 1,000,000 times smaller than 1 microfarad (μF). That’s right, a million times smaller!

Between the picofarad and the microfarad, we have the nanofarad (nF), which is exactly 1000 times larger than the picofarad and 1000 times smaller than the microfarad.

Relationship between units:

1 μF = 1,000,000 pF
1 μF = 1,000 nF
1 nF = 1,000 pF

And to give you an idea of the scale, 1 Farad (F) is equal to 1,000,000 μF – an extremely high capacitance for common applications!

Multiple (10ⁿ)	Name	Symbol	Submultiple (10ⁿ)	Name	Symbol
10⁰	farad	F
10¹	decafarad	daF	10^-1	decifarad	dF
10²	hectofarad	hF	10^-2	centifarad	cF
10³	kilofarad	kF	10^-3	millifarad	mF
10⁶	megafarad	MF	10^-6	microfarad	µF
10⁹	gigafarad	GF	10^-9	nanofarad	nF
10¹²	terafarad	TF	10^-12	picofarad	pF
10¹⁵	petafarad	PF	10^-15	femtofarad	fF
10¹⁸	exafarad	EF	10^-18	attofarad	aF
10²¹	zettafarad	ZF	10^-21	zeptofarad	zF
10²⁴	yottafarad	YF	10^-24	yoctofarad	yF

Need to convert between these units? Use our online capacitance conversion calculator!

Capacitance Conversion Calculator: Picofarad pF, Nanofarad nF, Microfarad μF and Farad F!

✅ Decoding Capacitors: The Three-Digit System

Now that we understand the units, let’s get to what matters: decoding capacitors! For most capacitors with values between 1pF and 1μF (practically all, except electrolytics), the values are indicated with a three-digit code.

The rule is simple: the first two digits represent the significant numbers, and the third digit indicates how many zeros should be added to these numbers. The result is always expressed in picofarads (pF).

Practical Example: A capacitor marked as “473” means 47 + 3 zeros = 47,000 pF, which is the same as 47 nF or 0.047 μF. Easy, isn’t it?

⛏️ Practical Examples of Codifications!

Let’s analyze 4 different categories of markings found on capacitors, as shown in Figure 4 below:

Fig. 3 – Examples of codifications on polyester capacitors

1. Capacitor with code “104”:

104 — Indicates the capacitance: 10 + 4 zeros = 100,000 pF = 100 nF = 0.1 μF
This is one of the most common values in electronic circuits!

2. Capacitor with code “104” and voltage “400V”:

400V — Maximum working voltage
104 — Capacitance: 100,000 pF = 100 nF = 0.1 μF

3. Capacitor with code “104J” and voltage “250V”:

104 — Capacitance: 100,000 pF = 100 nF = 0.1 μF
J — Tolerance of ±5%
250V — Maximum working voltage

4. Capacitor with code “2A104J”:

2A — Code for voltage of 100V (we’ll see this in detail)
104 — Capacitance: 100,000 pF = 100 nF = 0.1 μF
J — Tolerance of ±5%

Golden Tip: When you find a capacitor with a three-digit code, always calculate the value in picofarads first and then convert to the most appropriate unit (nF or μF). This will avoid confusion and interpretation errors!

🪛 In Practice: Converting Capacitor Values

Now let’s put into practice what we’ve learned with some real examples:

Example 1: Capacitor marked as “472”

47 + 2 zeros = 4,700 pF
Converting: 4,700 pF ÷ 1,000 = 4.7 nF
Converting again: 4.7 nF ÷ 1,000 = 0.0047 μF

Example 2: Capacitor marked as “103”

10 + 3 zeros = 10,000 pF
Converting: 10,000 pF ÷ 1,000 = 10 nF
Converting again: 10 nF ÷ 1,000 = 0.01 μF

Example 3: Capacitor marked as “220”

22 + 0 zeros = 22 pF
In this case, no conversion is necessary, as the value is already in picofarads!

📖 EIA Table: Decoding Voltages and Tolerances

Besides capacitance, we need to understand two other crucial parameters: working voltage and tolerance. For this, the EIA (Electronic Industries Alliance) established standardized codes that we’ll explore now.

📊 EIA Table of Voltage Codes

The maximum working voltage is crucial to ensure the capacitor is not damaged. The EIA established two-letter codes to represent these voltages:

Code	Voltage (VDC)	Code	Voltage (VDC)	Code	Voltage (VDC)
0G	4V	0L	5.5V	0J	6.3V
1A	10V	1C	16V	1E	25V
1H	50V	1J	63V	1K	80V
2A	100V	2Q	110V	2B	125V
2C	160V	2Z	180V	2D	200V
2P	220V	2E	250V	2F	315V
2V	350V	2G	400V	2W	450V
2H	500V	2J	630V	3A	1000V

📊 EIA Table of Tolerance Codes

Tolerance indicates the maximum allowed variation in the capacitor’s value. For example, a 100nF capacitor with a tolerance of 5% (J) can have an actual value between 95nF and 105nF.

Code	Tolerance	Code	Tolerance
B	± 0.10pF	H	± 3%
C	± 0.25pF	J	± 5%
D	± 0.5pF	K	± 10%
E	± 0.5%	M	± 20%
F	± 1%	N	± 30%
G	± 2%	P	+100%, -0%
Z	+80%, -20%

Attention: Asymmetrical tolerances (like P and Z) are used in filter capacitors, where a value higher than the nominal doesn’t affect the circuit’s operation, but a lower value may compromise its functioning.

👉 Practical Reading: Polyester Capacitor 2A104J

Let’s analyze a real capacitor of 100nF, with tolerance of +/- 5% and maximum working voltage of 100V, according to Figure 6 below:

Fig. 4 – Polyester Capacitor 100nF +/- 5% 100V

In this capacitor, we have the code 2A104J. Let’s decode each part:

2A — Code for voltage of 100V (according to the EIA table)
104 — Capacitance: 10 + 4 zeros = 100,000 pF = 100 nF = 0.1 μF
J — Tolerance of ±5%

Therefore, this is a 100nF (or 0.1μF) capacitor with tolerance of ±5% and maximum working voltage of 100V.

📝 Practical Tips for Capacitor Identification

In many cases, the maximum working voltage can be clearly written on the capacitor body, especially in models designed for high voltages. However, in low-voltage capacitors, this information may not be explicit.

Here are some practical tips to identify the working voltage when it’s not clearly marked:

Physical size: In general, capacitors with higher working voltage are physically larger for the same capacitance. As they say, “size matters”!
Application: Capacitors used in low-voltage circuits (5V, 12V, 24V) generally support between 50V and 100V.
Material type: Tantalum capacitors are smaller than polyester ones for the same capacitance, but generally have lower voltages.

Golden Rule: When in doubt about a capacitor’s voltage, always opt for one with a higher voltage than needed for your application. Using a capacitor with a lower voltage than required can result in damage to the component and the circuit!

🔧 Practical Applications of Different Types of Capacitors

Knowing how to read capacitor codes is essential, but understanding where to apply them is equally important. Let’s explore the most common applications for polyester and ceramic capacitors:

Ceramic Capacitors

Decoupling: Used to filter noise in power supply lines of integrated circuits
Signal coupling: To block DC components and allow AC signals to pass
Timing circuits: Together with resistors to create delays
Filters: In audio and RF circuits

Polyester Capacitors

Line filters: In power supplies to reduce interference
Audio circuits: In equalizers and crossovers
Motor starting: In single-phase motors
High-frequency applications: Where value stability is important

Electrolytic Capacitors

Power supply filters: used to smooth DC voltage after rectification, reducing ripple.
Audio coupling and decoupling: in amplifiers, they allow AC signal passage and block DC.
Timer circuits: together with resistors (RC), to define charge and discharge times.
Energy storage: in power supplies and inverters, they store energy to provide quick current during demand peaks.
Motor starting circuits: in single-phase motors, they provide initial torque.
Switching power supplies: act in filtering and stabilizing output voltage.
Linear supplies and regulators: help with voltage stability and elimination of residual noise.

🤔 Dúvidas Frequentes (FAQ)

❓ Frequently Asked Questions about Capacitors

1. Can I replace a polyester capacitor with a ceramic one of the same value?🔽

It depends on the application. In decoupling and high-frequency circuits, ceramic ones are generally better. In audio and filter applications, polyester ones may offer more linear characteristics. Always check your project’s specifications.

2. What happens if I use a capacitor with a lower voltage than needed?🔽

The capacitor may suffer dielectric breakdown, resulting in a short circuit. This can damage not only the capacitor but also other circuit components. Always use capacitors with voltage equal to or higher than required.

3. How to identify polarity in polyester and ceramic capacitors?🔽

Polyester and ceramic capacitors are generally non-polarized, meaning they can be connected in any direction. Only electrolytic and tantalum capacitors have defined polarity.

4. Why do some capacitors have asymmetrical tolerances?🔽

Asymmetrical tolerances (like +100%, -0%) are used in filter capacitors, where a value higher than the nominal doesn’t affect the circuit’s operation, but a lower value may compromise its functioning.

5. How to store capacitors correctly?🔽

Store in a dry place with controlled temperature. Polyester and ceramic capacitors are quite stable, but avoid places with excessive humidity or extreme temperatures.

🎯 Conclusion: Mastering the Art of Reading Capacitors

Congratulations! Now you’re equipped with the necessary knowledge to decipher the mysterious codes of polyester and ceramic capacitors. Remember the main points:

The three-digit code represents the capacitance in picofarads
The EIA tables help identify voltages and tolerances
Always check the working voltage before using a capacitor
Each type of capacitor has its ideal applications

With this skill, you’re ready to tackle electronic projects with more confidence and precision. Keep practicing and exploring the fascinating world of electronics!

🔗 Related Content

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Original article published on FVML (Portuguese) – February 19, 2019

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How to Read Polyester & Ceramic Capacitor Codes – Complete EIA Guide

🧐 The Challenge of Reading Capacitors: Why Is It So Complicated?