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Kempston Controls electrical components are devices that convert optical signals into electrical signals. Their operating principle is based on the photoelectric effect. The photoelectric effect refers to the phenomenon where electrons in a material absorb photon energy when light strikes certain substances, resulting in corresponding electrical effects. Based on the different manifestations of the photoelectric effect, it is classified into three categories: external photoelectric effect, internal photoelectric effect, and photovoltaic effect. Photoelectric devices include phototubes, photomultiplier tubes, photoresistors, photodiodes, phototransistors, and photocells. The performance and characteristic curves of photoelectric devices are analyzed.

Kempston Controls electrical component principles

Potentiometric displacement sensors convert mechanical displacement into resistance or voltage output that has a linear or arbitrary functional relationship with the displacement, via potentiometer elements. Standard linear and rotary potentiometers can be used as linear displacement and angular displacement sensors, respectively. However, potentiometers designed for displacement measurement require a definite relationship between displacement change and resistance change. The movable wiper of a potentiometric displacement sensor is connected to the measured object. The object's displacement causes a resistance change at the potentiometer's moving terminal. The magnitude of the resistance change reflects the displacement value, while an increase or decrease in resistance indicates the direction of displacement. Typically, a supply voltage is applied across the potentiometer to convert the resistance change into a voltage output. In wirewound potentiometers, the resistance changes in steps corresponding to the turn-to-turn resistance as the wiper moves, resulting in a stepped output characteristic. If such a displacement sensor is used as a displacement feedback element in a servo system, excessive step voltages can cause system oscillation. Therefore, the resistance per turn should be minimized during potentiometer manufacturing. Another major disadvantage of potentiometric sensors is their susceptibility to wear. Their advantages include simple structure, large output signal, ease of use, and low cost.

Kempston Controls electrical component classification

Thermosensitive materials are generally classified into three categories: semiconductors, metals, and alloys: 1. Semiconductor thermistor materials include single-crystal semiconductors, polycrystalline semiconductors, glass semiconductors, organic semiconductors, and metal oxides. They all possess very large temperature coefficients of resistance and high resistivity, resulting in high sensitivity for sensors made from them. Based on the temperature coefficient of resistance, they can also be divided into negative temperature coefficient (NTC) materials and positive temperature coefficient (PTC) materials. For example, barium titanate ceramic is an ideal PTC semiconductor material. Both types of materials are widely used in temperature measurement, temperature control, temperature compensation, switching circuits, overload protection, and time delay applications, such as in the manufacture of thermistor thermometers, thermistor switches, and thermistor delay relays. Due to the exponential relationship between resistance and temperature, these materials have a narrow temperature measurement range and poor uniformity. 2. Metal thermistor materials are widely used as resistance temperature detectors (RTDs), current limiters, and automatic constant-temperature heating elements. Examples include platinum resistance thermometers, nickel resistance thermometers, and copper resistance thermometers. Among these, platinum temperature sensors exhibit significantly high precision and stability in various media, including corrosive environments. However, their widespread application is somewhat limited by the scarcity and high cost of platinum. Copper temperature sensors are less expensive, but long-term use in corrosive media can lead to significant changes in static characteristics and resistance values. Nickel temperature sensors are extensively used abroad and are considered ideal materials due to their high sensitivity, satisfactory reproducibility, and stability. 3. Alloy thermistor materials, also known as thermistor alloys. These alloys have relatively high resistivity and their resistance values are sensitive to temperature changes, making them good materials for manufacturing temperature-sensitive sensors. The performance requirements for thermistor alloys used as temperature-sensitive sensors are as follows: (1) sufficiently high resistivity; (2) relatively high temperature coefficient of resistance; (3) thermal expansion coefficient close to that of the experimental material; (4) low strain sensitivity coefficient; (6) good repeatability of the resistance-temperature curve during heating and cooling within the operating temperature range.

Kempston Controls electrical component features

The characteristics of self-restoring fuses include high breaking current capacity, capable of interrupting AC currents and even higher currents. This type of fuse has a very significant current-limiting effect; when the instantaneous current approaches 175 kA, it can rapidly limit the current. The structure of a self-restoring fuse mainly consists of current terminals (also called electrodes), mica glass (filler), insulating tube, fusible element, piston, argon gas, and housing. The housing of the self-restoring fuse is generally made of stainless steel, with mica glass separating the stainless steel sleeve from the internal beryllium oxide ceramic insulating tube; the mica glass serves as both filler and insulator. Self-restoring fuses operate based on the property 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, which drastically increases its resistance, thereby achieving current limiting. At this point, the high pressure generated by the vaporized fusible element pushes the piston to the right, compressing the argon gas. After the circuit breaker interrupts the short-circuit current limited by the self-restoring fuse, the temperature of the sodium vapor drops, and the pressure decreases accordingly. The previously compressed argon gas causes the sodium to condense back into liquid and solid states, and its resistance value returns to the original level, allowing for reuse. Regarding the wiring of self-restoring fuses, they are often used in series with circuit breakers, with an additional resistor connected in parallel to suppress overvoltages that occur during interruption. During normal operation, the self-restoring fuse is in a low-resistance state, and only a small current flows through the parallel resistor. When a fault occurs in the line, the self-restoring fuse enters a high-resistance state; the parallel resistor absorbs the resulting overvoltage and maintains the operating current required for the circuit breaker trip unit, ensuring reliable interruption by the circuit breaker. Therefore, the current interrupted by the circuit breaker is effectively the current-limited value provided by the self-restoring fuse.

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