vestel de electrical components Germany vestel de model vestel de price

vestel de electrical component is a sensor resistor whose resistance value changes with temperature. According to different temperature coefficients, it is divided into positive temperature coefficient thermistors and negative temperature coefficient thermistors. The resistance value of a positive temperature coefficient thermistor increases as the temperature rises, while the resistance value of a negative temperature coefficient thermistor decreases as the temperature rises; they both belong to semiconductor devices.

vestel de electrical component principle

When high-frequency current flows through a conductor, an electric field and a magnetic field are generated in the surrounding space. According to the distribution characteristics of the electromagnetic field in space, it can be divided into the near zone, intermediate zone, and far zone. Let R be the distance from a point in space to the conductor. The region where R << λ/2π is called the near zone, where the electromagnetic field is closely related to the current and voltage in the conductor. The region where R >> λ/2π is called the far zone, where the electromagnetic field can leave the conductor and propagate into space. Its change lags behind the current and voltage on the conductor for a period of time. At this time, the propagated electromagnetic wave is no longer directly related to the current and voltage on the wire. The electromagnetic field in this region is called the radiation field. It must be pointed out that when the length of the wire L is much smaller than the wavelength λ, the radiation is very weak; when the length of the wire L increases to be comparable to the wavelength, the current on the wire will increase significantly, thus forming stronger radiation. Transmitting antennas utilize this property of the radiation field, allowing the transmitted signal to radiate fully into space after passing through the transmitting antenna. How to make the conductor an effective radiating system? Here we first analyze the situation on the transmission line. On a parallel two-wire transmission line, to ensure only energy transmission without radiation, it is necessary to ensure that the two-wire structure is symmetrical, the current magnitude at corresponding points on the lines is equal but opposite in direction, and the distance between the two lines<π. To effectively radiate the electromagnetic field, this symmetry of the transmission line must be broken. For example, separating the two conductors at a certain angle or removing one side can break the conductor symmetry and produce radiation. Separating the open-circuit transmission line or the conductor at a distance of π/4 from the terminal into a straight shape, the current on the terminal conductor is no longer in opposite phase but in the same phase, so that the radiation fields of this segment of the conductor at spatial points superimpose in phase, constituting an effective radiation system. This is the simplest and most basic unit antenna, called a half-wave symmetric dipole antenna, with a characteristic impedance of 77Ω. After the electromagnetic wave is radiated from the transmitting antenna, it propagates in all directions. If a symmetric dipole is placed in the direction of electromagnetic wave propagation, an induced electromotive force will be generated on the antenna dipole under the action of the electromagnetic wave. If the antenna is connected to receiving equipment at this time, high-frequency current will be generated at the input end of the receiving equipment. In this way, the antenna plays a receiving role and converts electromagnetic waves into high-frequency current, meaning the antenna acts as a receiving antenna. The quality of reception depends not only on the strength of the radio wave but also on the directivity of the antenna and the matching between the half-wave symmetric dipole and the receiving equipment.

vestel de electrical component applications

Thermistors can also be used as electronic circuit components for temperature compensation in instrument circuits and cold junction temperature compensation for thermocouples. Utilizing the self-heating characteristic of NTC thermistors enables automatic gain control, forming RC oscillator amplitude stabilization circuits, delay circuits, and protection circuits. When the self-heating temperature is much higher than the ambient temperature, the resistance value is also related to the heat dissipation conditions of the environment. Therefore, this characteristic of thermistors is often utilized in flow meters, gas analyzers, and thermal conductivity analysis to create specialized detection elements. PTC thermistors are mainly used for overheat protection of electrical equipment, contactless relays, constant temperature control, automatic gain control, motor starting, time delay, automatic degaussing of color TVs, fire alarms, and temperature compensation. Main disadvantages: (1) severe nonlinearity in the relationship between resistance value and temperature; (2) poor consistency and interchangeability of components; (3) components are prone to aging and have poor stability; (4) except for special high-temperature thermistors, most thermistors are only suitable for the range of 0 to 151℃, which must be noted during use.

vestel de electrical component classification

1. Classification by relay outline dimensions: (1) miniature relay, (2) sub-miniature relay, (3) small miniature relay. 2. Classification by relay load: (1) micro-power relay, (2) weak-power relay, (3) medium-power relay, (4) high-power relay. 5. Classification by relay protection features: (1) Sealed relay: A relay with contacts and coils sealed inside a cover by welding or other methods, isolated from the surrounding medium, having a low leakage rate. (2) Enclosed relay: A relay protected by sealing (non-hermetic) contacts and coils with a housing. (3) Open relay: A relay that does not use a protective cover to protect contacts and coils. Among the above relays, electromagnetic relays and reed relays are the most commonly used in electronic fabrication.

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