A detailed guide to capacitor symbols

A detailed guide to capacitor symbols

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What is a capacitor?

A capacitor is an electronic component that stores charge and creates an electric field. It is a very common component in electronic devices and is used for a variety of functions, including filtering, coupling, timing, and energy storage.

The basic working principle of a capacitor is to store charge by using an insulator (called the "dielectric") between two conductors (usually called the "plates" of the capacitor). When the capacitor is charged, positive charge accumulates on one plate and negative charge accumulates on the other plate. The two charges attract each other and form an electric field that stores electrical energy.

The key parameters of a capacitor include its capacitance and withstand voltage. Capacitance is usually measured in farads (F), and smaller capacitors may only have a capacity of picofarads (pF) or nanofarads (nF). The withstand voltage is the maximum voltage that the capacitor can withstand, exceeding which may cause the capacitor to break down or be damaged.

Types and meanings of capacitor symbols

The symbol for a capacitor in a circuit diagram is usually a parallelogram or two tangential arcs representing the two capacitor plates, with a short line in the middle representing the dielectric. These symbols represent the basic physical structure of a capacitor, which is two conductors (capacitor plates) separated by an insulator (dielectric).

Below are a few different types of capacitor symbols and their meanings:

Parallel Plate Capacitor Symbol:

1. Usually represented by two parallel lines, similar to an open book.
2. This symbol represents the basic structure of a capacitor, which is two parallel metal plates with a certain distance between them. This distance can be air or other insulating materials.

Electrolytic Capacitor Symbol:

1. Usually represented by a shape similar to the capital letter "C", where the long line represents the anode and the short line represents the cathode.
2. This symbol represents a special type of capacitor, where the anode plate is usually long-lived and the cathode plate is relatively short-lived.

Tantalum Capacitor Symbol:

1. Similar to the electrolytic capacitor symbol, but usually has a "T" shaped mark, indicating that tantalum material is used as the anode of the capacitor.

Ceramic Capacitor Symbol:

1. Usually represented by a dot or small circle, because ceramic capacitors are usually small.

Film capacitor symbol:

1. Usually represented by a rectangle, which may contain a short line to represent the dielectric.

2. This symbol represents a capacitor that uses a very thin layer of insulating material as the dielectric.

These symbols are used to represent the connection and function of capacitors in circuits. In circuit diagrams, the identifier of a capacitor may include the letter "C" followed by a number and unit representing its capacitance. For example, "C1" represents a capacitor with a capacitance of 1 microfarad (μF). Different types of capacitors have different characteristics, such as capacitance, withstand voltage, temperature coefficient, etc. These characteristics will be considered in circuit design and the appropriate capacitor type will be selected according to the needs.

Capacitor symbol on multimeter

There is usually a special capacitance measurement position on the multimeter for measuring the capacitance of capacitors. This position is usually represented by "Cap" or a symbol with two semicircles (like a C shape), and the unit is farad (F) or microfarad (uF).
When using a multimeter to measure capacitance, you need to make sure that the capacitor is fully discharged, otherwise it may affect the measurement results. At the same time, the choice of different ranges may affect the measurement accuracy, so this should also be taken into account when choosing the range.

If you are looking for a specific capacitor symbol, such as electrolytic capacitors, ceramic capacitors, etc., they will be represented by specific symbols in the circuit diagram. However, these different capacitor types are generally not specifically marked on the multimeter because the multimeter is designed to measure standard capacitance rather than identify the type of capacitor.

How to measure capacitance with a multimeter

The steps for measuring capacitance using a multimeter are as follows:

1. Find the capacitance measurement position on the multimeter, which is usually marked with "Cap" or a shape like C.

2. Turn off the power and disconnect the circuit to ensure that the capacitor is fully discharged to avoid damaging the multimeter or the capacitor.

3. Slide the multimeter's range switch to the appropriate range. If you don't know the specific capacity of the capacitor, you should start from the highest range and gradually reduce it to the appropriate range.

4. Insert the red test lead into the jack marked "+" or "COM" and the black test lead into the jack marked "-" or "GND".

5. Touch the two test leads to the two pins of the capacitor.

6. Read the value displayed on the multimeter display, which is the capacitance value of the capacitor. If it shows "1" or "OL", it means that the range is too high and you should select a lower range to retest.

7. If the reading is unstable or shows zero, the capacitor may be damaged or have poor contact.

8. After the measurement, discharge the capacitor to prevent accidents caused by residual charge.

Note: When making capacitance measurements, ensure the safety of the operator and the equipment under test and follow the correct operating procedures. Special care must be taken with high-voltage capacitors because they can store a lot of electrical energy and can cause electric shock even if the power is disconnected.

Differences in capacitor symbols

Capacitor symbols do have some differences in different countries and regions, and these differences are mainly due to historical reasons. Under the standards of the International Electrotechnical Commission (IEC), the symbol for a capacitor is usually a simple letter "C" followed by a number and unit representing its capacitance. However, in the United States and some other countries that use the IEEE standard, the capacitor symbol may be slightly different.

Here are some common capacitor symbols and how they are represented in different standards:

International Electrotechnical Commission (IEC) Standards:
Capacitors are usually represented by "C" followed by its capacitance value and unit, such as "C100n" for a capacitor with a capacitance of 100 nanofarads.

American Electrical Manufacturers Association (IEEE) Standards:
Capacitors are usually represented by two vertical segments with a horizontal segment in the middle, similar to the shape of the letter "C".
The value and unit of capacitance are usually marked directly next to the symbol, such as "100nF".

Japanese Industrial Standard (JIS) Symbols:
Similar to the IEC symbol, "C" is also used to represent capacitors, but sometimes additional markings are added to distinguish different capacitor types.

In practical applications, circuit designers need to follow specific standards to draw circuit diagrams. When reading circuit diagrams, it is important to understand the standards used and what the symbols represent. Although there are differences in symbols, in most cases, the basic symbol for capacitors (a simple "C") is universal.

How to read capacitor symbols?

Reading capacitor symbols mainly involves identifying the symbol itself and the numbers and units that follow it. Here are some basic steps to help you read capacitor symbols:

Identify the basic capacitor symbol:

In most cases, the capacitor symbol is a simple letter "C".

In some standards, the capacitor symbol may be a tilted parallelogram, or two vertical segments with a horizontal line segment in the middle.

Determine the value and unit of capacitance:

The number is usually written directly next to the symbol, indicating the capacitance of the capacitor.

The unit may be farad (F), millifarad (mF), microfarad (uF), nanofarad (nF), or picofarad (pF). Units are sometimes omitted, especially when the value is small and the unit is obvious.

Watch out for special markings:

Some symbols may have additional markings, such as the electrolytic capacitor symbol, which usually has a horizontal line through the center to indicate the negative pin.

The symbol for a variable capacitor may include a movable contact to indicate that the capacitance can be adjusted.

In a circuit diagram, the placement and connection of the capacitor can also provide clues about its function.

For example, a capacitor in series may indicate filtering or high-frequency suppression.

Use color codes:

Some capacitors, especially fixed capacitors, may use color codes to identify the capacity, similar to the color ring coding of resistors.

Read the data sheet or manual:
For complex electronic products or professional equipment, it is best to consult the relevant data sheet or user manual for precise capacitor information.

In short, reading capacitor symbols requires understanding different standards and conventions, and correctly interpreting the meaning of the symbols in context. If you have any questions, it is best to refer to relevant materials or consult professionals.

How are the circuit symbols of capacitors in the circuit classified?

According to the type of capacitor:

Fixed capacitors: have a fixed capacitance, common ones are ceramic capacitors, film capacitors, etc.
Variable capacitors: capacitors with adjustable capacitance, usually used for tuning radio receiving equipment.
Electrolytic capacitors: A capacitor with polarity, usually used for filtering and decoupling of power supply circuits.

According to the application of the capacitor:

Filter capacitors: used to filter out AC components and retain DC components.
Energy storage capacitors: used to store electrical energy and release it when needed, commonly used in energy recovery systems.
Tuning capacitors: used to tune the frequency of the circuit together with the inductor, commonly used in radio equipment.

According to the rated voltage of the capacitor:

Low voltage capacitor: Suitable for circuits with lower voltage levels, such as consumer electronics.

High voltage capacitor: Suitable for circuits with higher voltage levels, such as power electronic equipment.

According to the temperature coefficient of the capacitor:

Constant temperature capacitor: The capacitance remains stable within a certain temperature range.

Negative temperature coefficient capacitor: As the temperature increases, the capacitance decreases.

Positive temperature coefficient capacitor: As the temperature increases, the capacitance increases.

According to the dielectric material of the capacitor:

Ceramic capacitor: A capacitor using ceramic as a dielectric.

Mica capacitor: A capacitor using mica as a dielectric.

Metalized film capacitor: A capacitor using metal vapor deposited on a plastic film as a dielectric.

In the circuit diagram, different capacitor types may have different symbols, but the most basic symbol is a simple letter "C". The specific type and characteristics are usually marked next to the symbol, or detailed instructions are provided elsewhere in the circuit diagram. When reading the circuit diagram, you need to pay attention to the markings and units near the symbol, as well as the application and position of the capacitor in the circuit.

How to identify the positive and negative poles of electrolytic capacitors?

Electrolytic capacitors are a common type of capacitor that has polarity, which means that the positive and negative poles cannot be connected in reverse. Identifying the positive and negative poles of electrolytic capacitors usually follows the following steps:

Check the appearance of the capacitor:
The outer shell of the electrolytic capacitor usually has symbols indicating the positive and negative polarity.
The longer pin of most electrolytic capacitors is the positive pole and the shorter pin is the negative pole.

Observe the package of the capacitor:

Some electrolytic capacitors have a "+" sign on the package to indicate the positive pole.
Usually, the positive pin is also thicker than the negative pin.

Use a multimeter:
You can use the diode test range of the multimeter to measure the positive and negative poles of the electrolytic capacitor.
Connect the red test lead to one pin and the black test lead to the other pin. If the measured resistance value is small, the pin connected to the red test lead is the positive pole and the pin connected to the black test lead is the negative pole.

According to the circuit diagram:

In the circuit diagram, the positive pole of the electrolytic capacitor is usually marked with a "+" symbol or the word "Anode", and the negative pole is marked with a "-" symbol or the word "Cathode".

Using a pointer multimeter:
If it is a pointer multimeter in a no-load state, set it to the resistance range and connect it to both ends of the capacitor. The pointer will slowly return to the zero position after deflection. At this time, the direction where the pointer finally points to the zero position is the positive pole of the capacitor.

It is very important to correctly connect the positive and negative poles of the electrolytic capacitor. If they are connected in reverse, it may cause damage to the capacitor and even affect the function and safety of the entire circuit. Therefore, when welding or repairing the circuit, be sure to correctly identify and connect the positive and negative poles of the electrolytic capacitor.

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