Cognex electrical components Germany Cognex model Cognex price

Cognex electrical components are specifically designed to suppress high-frequency noise and spike interference on signal lines and power lines, and also have the ability to absorb electrostatic pulses. Ferrite beads are used to absorb ultra-high-frequency signals. For example, some RF circuits, PLL, oscillator circuits, and circuits containing ultra-high-frequency memory (DDR SDRAM, RAMBUS, etc.) all require ferrite beads at the power input section. Inductors are energy storage components used in LC oscillator circuits, medium and low-frequency filter circuits, etc., and their application frequency range rarely exceeds 50MHZ. Ferrite beads have high resistivity and magnetic permeability, equivalent to a resistor and an inductor in series, but both the resistance and inductance values vary with frequency.

Cognex electrical component principles

A Schottky diode is a metal-semiconductor device made by using noble metals (gold, silver, aluminum, platinum, etc.) A as the anode and N-type semiconductor B as the cathode, utilizing the rectifying characteristics of the barrier formed at their contact surface. Because there are a large number of electrons in the N-type semiconductor and only a very small number of free electrons in the noble metal, electrons diffuse from the high-concentration B to the low-concentration A. Obviously, there are no holes in the metal A, so there is no diffusion movement of holes from A to B. As electrons continuously diffuse from B to A, the electron concentration on the surface of B gradually decreases, destroying surface electrical neutrality and forming a barrier. The direction of its electric field is B → A. However, under the influence of this electric field, electrons in A also produce a drift motion from A → B, thereby weakening the electric field formed by the diffusion motion. After a space charge region of a certain width is established, the electron drift motion caused by the electric field and the electron diffusion motion caused by the concentration difference reach a relative balance, forming a Schottky barrier. The internal circuit structure of a typical Schottky rectifier uses N-type semiconductor as the substrate, on which an N-epitaxial layer doped with arsenic is formed. The anode uses materials such as molybdenum or aluminum to form a barrier layer. Silicon dioxide is used to eliminate the electric field in the edge region and increase the voltage withstand value of the tube. The N-type substrate has a very small on-state resistance, and its doping concentration is 105% times higher than that of the H-layer. An N+ cathode layer is formed under the substrate to reduce the contact resistance of the cathode. By adjusting structural parameters, a Schottky barrier is formed between the N-type substrate and the anode metal.

Cognex electrical component applications

Metal waveguides and metal resonant cavities are widely used in decimeter waves, centimeter waves, and longer millimeter wave bands. Since the cross-section of the waveguide and the dimensions of the resonant cavity are close to the wavelength, the dimensions of metal waveguides and resonant cavities are too small and difficult to manufacture. It is even more impossible to apply metal waveguides or resonant cavities in the infrared or visible light bands, where the wavelength is on the order of micrometers. For this reason, dielectric waveguides and dielectric resonators have developed rapidly and gained widespread application. Although the dimensions of dielectric waveguides and dielectric resonators are also on the order of the wavelength, they are easy to manufacture in tiny sizes using microfabrication techniques. For example, optical fibers and optical waveguides with cross-sectional dimensions on the order of micrometers belong to dielectric waveguides. The field in a metal waveguide can be regarded as being caused by the reciprocal reflection of plane waves between conductor surfaces, and the field in a dielectric waveguide can also be regarded as being caused by the total reflection of electromagnetic waves between dielectric interfaces. Therefore, a dense medium surrounded by a sparse medium forms a dielectric waveguide. In an ideal metal waveguide, the electromagnetic field forms a standing wave transversely, and outside the waveguide boundary, it approximates an ideal conductor with no electromagnetic field. In a dielectric waveguide, the electromagnetic field forms a standing wave transversely, but an electromagnetic field still exists outside the dielectric waveguide, which presents a decaying state transversely, known as an evanescent field. In a metal waveguide filled with a uniform medium, the TE mode and TM mode can separately satisfy the short-circuit boundary conditions of the waveguide walls, so the TE mode and TM mode can always be separated, and both can propagate in the metal waveguide. When a metal waveguide is filled with two or more media, or partially filled with a dielectric, the electromagnetic field must satisfy not only the boundary conditions on the conductor walls but also the continuity conditions at the media interfaces. In the case of uniform filling with two or more media, only the mixed TE and TM HEM modes are possible. After understanding the above content, we can further learn about dielectric resonators. As early as 1939, the concept and theory of dielectric resonators were proposed, but due to the lack of suitable dielectric materials, this theory slept for more than 20 years without practical development. By the 20th century, in the 60s, the successful development of high-dielectric-constant ceramics such as rutile porcelain (ε≈80100) brought dielectric resonators back to attention. However, the high temperature coefficient of rutile porcelain limited its practical application. In the 20th century, in the 70s, barium titanate and zirconium titanate ceramics were developed. Their high dielectric constant, low loss, and low temperature coefficient made dielectric resonators practical. Dielectric resonators have advantages such as small size, light weight, high quality factor, and good stability. They are particularly suitable for application in microstrip circuits or microwave integrated circuits and in the millimeter wave band, receiving great attention and developing rapidly. When the dielectric constant is very high, the interface between the dielectric and air approximates an open circuit surface, and the reflection coefficient of electromagnetic waves at the interface is close to 2. At this time, the surface of the dielectric resonator can be regarded as an open circuit wall, i.e., a magnetic wall. Thus, the dielectric resonator becomes a closed system with homogeneous boundary conditions, i.e., an equivalent open circuit wall (magnetic wall) resonant cavity.

Cognex electrical component features

The characteristics of self-resetting fuses include high breaking current capacity, capable of breaking AC and even larger currents. This type of fuse has a very significant current-limiting effect; when the instantaneous current reaches close to 170 kA, it can be rapidly limited. The structure of a self-resetting fuse mainly consists of current terminals (also called electrodes), mica glass (filler), insulating tube, fusible element, piston, argon gas, and housing. Among these, the housing of the self-resetting fuse is generally made of stainless steel. The stainless steel sleeve is separated from the internal beryllium oxide ceramic insulating tube by mica glass, which serves as both filler and insulator. Self-resetting fuses operate based on the characteristic of sodium metal, whose resistance increases sharply at high temperatures. Under normal operating conditions, current flows from the left current terminal, through the sodium metal fusible element in the fine holes of the beryllium oxide ceramic insulating tube, to the right current terminal, forming a current path. When a short-circuit fault occurs, the short-circuit current heats the sodium metal, vaporizing it into a high-temperature, high-pressure plasma state, causing its resistance to increase sharply, thereby achieving current limiting. At this time, the high pressure generated by the vaporization of the fusible element pushes the piston to move to the right, compressing the argon gas. After the circuit breaker cuts off the short-circuit current limited by the self-resetting fuse, the temperature of the sodium vapor drops, and the pressure also decreases. The previously compressed argon gas condenses back into liquid and solid states, and its resistance value drops back to the original value, ready for reuse. Regarding the wiring of self-resetting fuses, they are often used in series with circuit breakers, with an additional resistor connected in parallel to suppress overvoltage during breaking. During normal operation, the self-resetting fuse is in a low-resistance state, and only a small current flows through the parallel resistor. When a line fault occurs, the self-resetting fuse enters a high-resistance state, and the parallel resistor can absorb the resulting overvoltage and maintain the operating current required for the circuit breaker trip unit, ensuring reliable breaking by the circuit breaker. Therefore, the current broken by the circuit breaker is actually the current-limited current of the self-resetting fuse.

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