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What Is a Lithium-Ion Capacitor?

A lithium ion capacitor is an energy storage device that combines the properties of an electric double-layer capacitor and a lithium ion battery.

It is abbreviated as “LiC” because it is written as “lithium-ion capacitor” to distinguish it from LiB, which is a lithium-ion battery.

Compared to the electric double layer capacitor (EDLC), the LIC has a higher energy density and a larger power density than the LIB. Due to these differences in characteristics, there are different types of lithium-ion capacitors for different applications.

Uses of Lithium-Ion Capacitors

A Lithium-Ion Capacitor is an energy storage material with high energy density and output density, as well as excellent safety and durability. They are expected to replace lithium-ion batteries in fields requiring high output, which lithium-ion batteries are not good at. It can also be used in situations requiring energy density, in which electric double-layer capacitors are not good at, and in applications where high temperature and high voltage loads are applied.

It features excellent rapid charge/discharge characteristics, high- temperature characteristics, durability, and reliability, and can be handled safely. Because they can be used stably for a long time, even after repeated charging and discharging, they are being considered for a wide range of applications, including solar power generation, wind power generation, instantaneous voltage drop compensation devices, industrial machinery, and transportation and vehicle-related applications.

Lithium-Ion Capacitor have also been considered for use as a power source for electric vehicles, but their energy density is lower than that of lithium-ion batteries and they are inferior in terms of cruising range, so lithium-ion batteries are mostly used for electric vehicle applications. However, compared to lithium-ion batteries, lithium-ion capacitors are superior in terms of rapid charging and discharging, so they are being considered for use in vehicles with a fixed route, such as trams and buses, where they are charged at stops and stations to store power for the journey.

Principle of Lithium-Ion Capacitors

A Lithium-Ion Capacitor consists of a cell, cathode, anode, and electrolyte, and can be charged and discharged repeatedly by adsorption and desorption of lithium ions in the electrolyte to the cathode and anode. When voltage is applied to a Lithium-Ion Capacitor, lithium ions are adsorbed on the negative electrode and anions are physically adsorbed on the positive electrode.

When discharged from this state, the lithium ions on the negative electrode are desorbed and lithium ions are adsorbed on the positive electrode after the anions are desorbed. With charging and discharging, the positive electrode uses physical adsorption and desorption as in an electric double layer capacitor, while the negative electrode uses adsorption and desorption of lithium ions, involving a chemical reaction as in a lithium-ion secondary battery.

Lithium-Ion Capacitors require a higher cell voltage to increase energy density. This is because the amount of energy stored is expressed as E = CV2/2 (C: capacitance, V: cell voltage). The voltage is the potential difference between the positive and negative electrode potentials, but raising the positive electrode potential causes oxidative degradation of the material, so in Lithium-Ion Capacitor, the negative electrode is doped with lithium in advance at the manufacturing stage to lower the negative electrode potential so that the potential difference increases during charging.

Structure of Lithium-Ion Capacitors

A capacitor is a capacitor, which mainly consists of a cell, a positive electrode, a negative electrode, an electrolyte, and a separator. Lithium-Ion Capacitor uses activated carbon as the active material of the positive electrode, and the active material of the negative electrode has a small specific surface area, similar to that of a lithium-ion battery.

Carbon materials such as hard carbon, which can be doped with lithium ions, are used. Aluminum is used for the positive electrode and copper for the negative electrode current collectors, but they are porous because they must allow lithium ions to permeate through them for lithium doping in the manufacturing process described below.

As electrolyte, organic electrolyte made by dissolving lithium salts such as LiBF4 (lithium tetrafluoroborate) and LiPF6 (lithium hexafluorophosphate) in organic solvents is usually used. Separators with excellent lithium ion permeability and electrolyte impregnation properties are used.

What Is a Reflow Oven?

A reflow oven is a heating device used in the production of printed circuit boards (PCBs), bonding electronic components to boards using solder.

Operating typically at temperatures between 150°C and 230°C, the reflow oven’s temperature range may vary depending on whether the solder contains lead.

Uses of Reflow Ovens

Reflow ovens are crucial in bonding electronic components to PCBs in unit board production. They are particularly advantageous when soldering a large number of components or those with small bonding surfaces. The precision of reflow ovens becomes essential as components get smaller and more densely packed, avoiding issues like weak adhesion or short circuits often encountered in manual soldering.

Principles of Reflow Ovens

The reflow oven heats up by blowing hot air inside, with the temperature increased by directing hot air perpendicularly onto the board. When the solder, placed on the board, melts due to the heat, electronic components positioned on the solder adhere to the board. After soldering, the oven cools down, solidifying the solder and securing the components to the board.

Other Reflow Oven Information

1. Difference Between Flow Oven and Reflow Oven

A flow oven, used for flow soldering, involves boards passing over a bath of molten solder, requiring a solder bath and resulting in larger equipment. In contrast, a reflow oven utilizes paste solder or cream solder, applied to the board or component, which forms a metallic bond when heated in the oven, eliminating the need for a solder bath.

2. Filling the Reflow Oven with N2 Gas

Filling the reflow oven with nitrogen gas (N2) can reduce the oxygen concentration, preventing oxidation of the rosin in the solder paste. However, this can sometimes lead to the soldering appearing cleaner than its actual quality, potentially passing inspection even if the bonding is insufficient. Decisions regarding the use of nitrogen gas should involve consultation with manufacturing, design departments, or contractors.

What Is a Piezoelectric Actuator?

A piezoelectric actuator is a device that converts electrical energy from sources like ICs into physical kinetic energy, manifesting as linear motion or deformation. This conversion is achieved through a piezoelectric element within the actuator, making piezoelectric actuators distinct for their high precision, rapid response, and absence of electromagnetic noise.

These actuators are notable for their compact size, lack of a need for driving coils, and low power consumption, making them ideal for precision instruments such as digital cameras and mobile devices.

Uses of Piezoelectric Actuators

Piezoelectric actuators find applications across various industrial products and household appliances, particularly in precision equipment. They are valued for their compactness, swift response, and energy efficiency. Uses span single-lens reflex cameras, hard disk drives, inkjet printers, medical devices, and more.

Principle of Piezoelectric Actuators

The operation of piezoelectric actuators is based on the inverse piezoelectric effect, where applying an electric field to a piezoelectric material causes it to deform. This effect is harnessed to achieve precise mechanical movement through electrical control. By thinning the ceramic substrate, these actuators can operate at lower voltages, enhancing their efficiency.

Other Information on Piezoelectric Actuators

1. Comparison With Electromagnetic Actuators

Piezoelectric actuators offer several advantages over traditional electromagnetic actuators, including the potential for greater displacement and reduced drive voltages. Electromagnetic actuators, requiring coils, struggle with miniaturization and cannot match the precision, controllability, and energy efficiency of piezoelectric actuators.

2. Hysteresis of Piezoelectric Actuators

While piezoelectric actuators can achieve nano-level control, they exhibit hysteresis, meaning their displacement is not perfectly linear with control voltage. This necessitates external precision control mechanisms, such as strain gauges and ASICs, for accurate operation.

3. Development of Energy Harvesting Applications

Interest in piezoelectric actuators for energy harvesting is growing, driven by environmental sustainability goals. These devices can convert mechanical displacement into electrical energy, with potential applications in power generation from environmental sources, including vibration, light, heat, and electromagnetic waves. This technology is also being explored for use in wireless communication tags powered by vibration energy.

What Is a Variable Inductor?

An inductor (coil) is an electronic component made by wrapping copper wire around an iron core. When an electric current is applied to the copper wire in the inductor and the amount of the current is varied, it generates an induced electromotive force. This is called inductance and is expressed in units of Henleys (H).

A variable inductor is a device whose inductance can be varied by placing a small driver or adjusting the rod on top of the device and rotating a knob to slide the internal iron core up and down.

Applications of Variable Inductors

In general, inductors are used in many electrical products. A familiar example is an AC transformer.

Since it transmits high frequencies, it is also used in various wireless devices (WiFi and non-contact IC chips) and microwave ovens. They are also used in fluorescent light ballasts and various electrical products and are indispensable components for rectifying electronic circuits.

Variable inductors are used in a limited number of applications, such as tuning circuits for car tuners, but are now used less frequently due to the digitization of circuits.

Principles of Variable Inductors

The basic principle of operation of variable inductors is the same as that of fixed inductors.
When a DC current is applied to the coil, a magnetic field is generated in the iron core, and the core becomes an electromagnet.

When a voltage is initially applied or when the voltage is lowered, an induced current flows instantaneously in the moving wires. This causes electrical energy to be stored in the form of a magnetic field.

After a magnetic field of a certain strength is generated, a direct current flows, just like an ordinary copper wire. In contrast, when an alternating current flows through an inductor coil, a magnetic field of varying magnitude is generated in the iron core.

As the magnetic field changes, induced electromotive force in the opposite direction of the current is generated, resulting in resistance (inductance). If an alternating current continues to flow, an induced electromotive force in the opposite direction is always generated, so the current continues to have difficulty flowing.

In the case of an inductor coil, DC current can pass through smoothly, but AC current is challenging to flow because of the resistance generated. Therefore, it is an electronic component with the opposite characteristics of a capacitor, allowing AC current to pass through but not allowing DC current to pass through.

What Is an Optical Connector?

An optical connector is a terminal for connecting an optical fiber line.

In the Internet connection, the conventional method used telephone lines, but now optical fiber lines using optical communication have become the mainstream. Optical connectors are indispensable components for connecting optical fiber cables.

Compared to fusion splicing, which is another splicing method, optical connectors are highly versatile because they can be easily and accurately connected and disconnected.

Uses of Optical Connectors

As mentioned above, optical connectors serve as connection terminals in optical fiber lines. There are a wide variety of types, and different types of optical connectors are used for different purposes. The most common type is the “push-pull” type, which has a structure that allows easy insertion and removal. For applications where insertion and removal are rarely required, the “screw-tightening type” is recommended, as it provides a strong connection.

In addition to fiber-optic lines, optical connectors are sometimes used in devices that handle light, such as optical measuring instruments.

Principle of Optical Connectors

A typical optical connector consists of a ferrule and housing that fixes the tip of an optical fiber. In an optical fiber line, the principle of connector connection is to butt these tips directly against each other. Even the slightest misalignment of the connection causes an increase in loss (connection loss), so a structure that allows a high-precision connection is necessary.

The device to which an optical connector is connected is called an optical adapter. The optical adapter has a built-in split sleeve inside that matches the shape of the connector, enabling a high-precision connection.

The connection surface (end face) is finished by polishing. The most common method is PC polishing, also known as spherical polishing. The spherical end faces are butted together in such a way that the tops are concave due to the springs inside the connector. This prevents the formation of an air layer between the optical fibers, thereby enabling a connection with minimal loss.

What Is a Photomultiplier Tube?

A photomultiplier tube is one of the light sensors that can convert light into electricity. The PMT consists of a glass tube in a vacuum with an incident window, a photocathode, a dynode, and other components. The principle is based on the external photoelectric effect, a phenomenon in which electrons are emitted from the surface of a metal when light is irradiated on it in a vacuum.

Since even very weak light signals can be converted into large electrical signals, photomultiplier tubes are used as photodetectors in spectrophotometers, spectroscopic analyzers, and other instruments.

Applications of Photomultiplier Tubes

Photomultiplier tubes are very sensitive and can convert very weak light into a sufficient amount of electrical signals. On the other hand, they also have disadvantages, such as requiring high voltage for use and being prone to picking up noise.

They are used in detectors for optical analyzers, such as UV-visible spectrophotometers and emission spectrometers. They are also used in dust counters to measure particles in the atmosphere, laser radar (LiDAR) to detect scattered light from suspended particles in the air, and medical devices such as PET and CT for cancer screening.

Photomultiplier Tube Principle

A photomultiplier tube is an optical sensor that can detect light and convert it into an electrical signal. A window through which light enters, a photocathode, a focusing electrode, a dynode, and an anode are mounted inside a glass tube under vacuum conditions.

PMTs, apply the external photoelectric effect, in which electrons are emitted when light strikes them. This phenomenon occurs when light is irradiated onto a metal under a vacuum, causing electrons to be emitted from the metal surface. When light strikes the photocathode, electrons are knocked out of the photocathode. The knocked-out electrons are accelerated by the focusing electrode, and when they strike the dynode, multiple secondary electrons are emitted. The emitted secondary electrons then collide with the next dynode, where more secondary electrons are emitted. Repeating this process increases the number of electrons many times over, and eventually, a sufficient amount of electrons are detected as an electrical signal.

Solar cells and photodiodes can also output electrical signals from light, but PMTs are superior because they can output electrical signals from feeble light.

What Is a High-Voltage Resistor?

A high-voltage resistor is designed to handle significantly high voltages, typically in the kilovolt (kV) range. These components, which can have resistance values up to 100 Ω, are crucial in circuits for controlling the flow of electricity, thereby ensuring circuit stability and signal integrity. Their construction from high-resistivity materials allows them to maintain superior insulation properties, making them integral in managing high-voltage applications.

Uses of High-Voltage Resistors

Due to their ability to withstand high voltages, these resistors find applications across a wide array of high voltage circuitry in sectors including:

1. Medical Applications

Utilized in various medical equipment, from home health devices to advanced hospital machinery, including X-ray and ultrasound machines, defibrillators, and patient monitoring systems.

2. Automotive Applications

Key in electric and hybrid vehicle systems such as engine and inverter controls, battery management, and navigation systems, enhancing efficiency and safety.

3. Industrial Applications

Employed in control circuits, automation, power supplies, and test/measurement equipment, supporting the backbone of industrial operations.

4. Communication Applications

Critical in telecommunications for devices like smartphones, base stations, and IoT systems, ensuring reliable signal transmission and power management.

5. Energy Applications

Applied in smart meters, energy storage systems, and LED lighting solutions, contributing to energy efficiency and sustainability.

Principle of High-Voltage Resistors

A high-voltage resistor comprises a substrate, insulative base, resistive element, protective coating, and internal and external electrodes. Its construction, often using alumina for insulation, is tailored to endure high voltages. The resistive element may feature solid, meander, or serpentine patterns to optimize voltage withstand capability. Adjustments to the resistance value are made through precise trimming techniques, including single-cut, double-cut, and L-cut methods.

Other Information on High-Voltage Resistors

Ultra-Precision Class High-Voltage Resistors

These resistors represent the pinnacle of precision and stability, suitable for -55 to +150°C operation with minimal temperature-induced resistance changes. They are designed for applications demanding long-term reliability under high voltage conditions, such as in laboratory and medical imaging equipment. Special surface treatments enhance their resistance to surface leakage, with compatibility with solvent-based cleaning processes.

What Is a Schottky Rectifier?

A Schottky rectifier, a type of rectifier diode, is used to convert AC voltage to DC. Unlike conventional rectifier diodes, Schottky diodes offer faster switching and lower reverse leakage current, leading to more efficient power conversion. These diodes are typically made of metal and n-type semiconductor junctions, forming a Schottky barrier that facilitates rapid switching and a low forward voltage drop, thus reducing power losses.

Uses of Schottky Rectifiers

Schottky rectifiers are essential in high-frequency rectifier circuits, power electronics, and power conversion devices. Their high-speed switching and energy efficiency make them ideal for applications like DC/DC converters where these characteristics are advantageous.

Principle of Schottky Rectifiers

The Schottky rectifier functions based on the Schottky barrier, which is a junction between a metal and an n-type semiconductor, serving as an electron barrier. The barrier height, determined by the metal and semiconductor types, is crucial to the diode’s characteristics. A forward bias allows easy electron movement across the barrier, resulting in a low forward voltage drop. Conversely, a reverse bias raises the barrier and reduces the reverse current.

Features of Schottky Rectifier Diodes

Schottky rectifier diodes differ from ordinary rectifiers in several ways:

• Low Forward Voltage: Their forward voltage is typically 0.2 to 0.3 V, compared to 0.6 to 0.7 V for general rectifier diodes.
• Short Reverse Recovery Time: These diodes switch off rapidly, making them suitable for high-frequency rectifier circuits.
• Risk of Thermal Runaway: Due to a larger reverse current, Schottky diodes are susceptible to thermal runaway and potential breakdown, especially under high reverse voltage.

It’s crucial to balance the advantages and potential disadvantages of circuit design.

Types of Schottky Rectifiers

Schottky rectifiers come in various types for different applications:

• Regular Type: Standard diodes for general rectification.
• Ultra-Fast Type: Suitable for fast switching and high-frequency operations.
• Low-Voltage Type: Features a low forward voltage drop, ideal for low power applications, but with higher reverse current.
• Ultra-Low Leakage Type: Offers very low reverse leakage current, perfect for precision measurement, but with a higher forward voltage.
• Diode Array: Integrates multiple Schottky diodes in one package, used for high-density mounting and high-current applications.

What Is an Earth Resistance Meter?

An Earth Resistance Meter is a device that measures the electrical resistance between an electrical device and the earth. It is one of the most familiar devices for electricians and electrical practitioners. Grounding refers to the connection between the earth and electrical equipment.

When an abnormality occurs in electrical equipment, a person touching the equipment may receive an electric shock. By grounding electrical equipment, it is possible to release the electric current to the earth in the event of an abnormality. Secure grounding is very important for the safety of electrical equipment. The state of being securely grounded is called “grounded.”

Uses of Earth Resistance Meters

Earth Resistance Meters are used for grounding work and electrical equipment inspections. Grounding is the process of burying a metal or other electrical conductor deep underground. It is one of the most important works for electricians, and is classified into four types from A to D according to the intended use of the grounding.

The grounding pole for high-voltage equipment is called Class A grounding, which must maintain a resistance of 10 Ω or less, and the grounding pole for low-voltage equipment of 100 to 200 V is called Class D grounding, which is specified as having a resistance of 100 Ω or less.

During grounding work, check the grounding resistance using an Earth Resistance Meter. Electricians and chief electrical engineers use Earth Resistance Meters on a daily basis.

Principle of the Earth Resistance Meters

The measurement principle of the Earth Resistance Meteris Ohm’s law. The Earth Resistance Meter applies an alternating voltage between the pole to be measured and the pole to be compared. After the voltage is applied, the current flowing between the two poles is measured, and the ground resistance is calculated by dividing the current by the applied voltage.

Although the above method can be used to calculate the ground resistance, this method measures the ground resistance of the target pole and the pole to be compared, plus the ground resistance of the two poles. Therefore, a separate grounding pole dedicated for voltage measurement is provided to measure the grounding resistance of the target pole only.

If a DC voltage is used in the Earth Resistance Meter, electrolysis occurs and the current value cannot be determined. Therefore, AC power is often used in Earth Resistance Meters. Since AC power supplies are affected by lead capacitance at higher frequencies, power supplies with a frequency of 1 kHz or lower are used.

How to Use an Earth Resistance Meter

There are three types of Earth Resistance Meters: analog display, digital display, and the method of reading the scale value when the scale needle displays “0”. As an example, the procedure for using an analog display type is shown below.

The Earth Resistance Meter comes with a metal rod called an auxiliary grounding pole, which is embedded in the ground when measuring earth resistance.

• Step 1: Embed the first auxiliary grounding pole P at a distance of about 10 m from the grounding pole to be measured (hereinafter referred to as “grounding pole E”).
• Step 2: Place an auxiliary grounding pole C at a distance of about another 10 meters on the straight line extension connecting the grounding pole E and the grounding pole P.
• Step 3: Connect each grounding pole to each terminal of the Earth Resistance Meter.
• Step 4: Confirm that the battery capacity is OK and that the voltage between E and P is less than the allowable value.
• Step 5: Press the measurement button, and the value displayed is the value of the grounding resistance.

The procedure for other Earth Resistance Meters is basically the same as the analog display method, but the “read the scale value when the scale needle shows “0”” method reads the scale value when the scale needle shows “0”. The green, red, and yellow wires attached to the Earth Resistance Meter are used to connect each grounding pole to the terminals on the body of the Earth Resistance Meter.

In addition to these, there are also clamp-type Earth Resistance Meters that measure earth resistance by clamping the ground wire. It is easy to measure because there is no need to bury the auxiliary pole in the ground, but it can be used only in the case of multiple grounding.

Other Information on Earth Resistance Meters

Difference Between an Earth Resistance Meter and an Insulation Resistance Meter

Insulation testers and Earth Resistance Meters differ in measurement items and objects to be measured. An insulation tester measures an electric circuit to check the insulation status, while a grounding tester measures the grounding pole to check the grounding resistance.

The insulation tester applies a DC voltage, while the Earth Resistance Meter applies an AC voltage. Although the appearance and names of the devices themselves are similar, it is important to understand the above-mentioned differences between them in advance.