stahl electrical components German stahl models stahl prices

stahl electrical components refer to electronic components that can open a circuit, interrupt current flow, or direct it to another circuit. The most common switches are manually operated electromechanical devices with one or more electrical contacts. "Closed" contacts indicate conduction, allowing current to flow; "open" switches indicate non-conduction, forming an open circuit and preventing current flow. The simplest switch consists of two metal pieces called "contacts"; when they touch, current forms a loop, and when they do not touch, the current is interrupted. When selecting contact metals, consideration must be given to their corrosion resistance, as most metals form insulating oxides after oxidation, preventing normal contact operation. Selection also requires considering electrical conductivity, hardness, mechanical strength, cost, and toxicity. Contacts are sometimes plated with corrosion-resistant metals, typically on the contact surface, to prevent performance degradation due to oxides. Non-metallic conductive materials, such as conductive plastics, are sometimes used for contact surfaces. In addition to contacts, switches have moving parts that make or break the connection. Switches can be classified by their moving parts into lever switches, push-button switches, rocker switches, etc., and the moving parts can also be other types of mechanical linkages.

stahl electrical component characteristics

(1) Volt-ampere characteristics: When a forward voltage is applied to a diode, the current is extremely small at low voltage values; when the voltage exceeds a certain value, the current begins to increase exponentially. This is usually called the diode's turn-on voltage, and the diode is in a fully conducting state; this voltage is usually called the diode's forward voltage drop. For germanium diodes, when a reverse voltage is applied, the current is extremely small at low voltage values, known as the reverse saturation current. When the reverse voltage exceeds a certain value, the current increases sharply, known as reverse breakdown, and this voltage is called the diode's reverse breakdown voltage. Breakdown voltages vary significantly among different diode models, ranging from tens of volts to thousands of volts. (2) Forward characteristics: When a forward voltage is applied, in the initial part of the forward characteristic, the forward voltage is too small to overcome the barrier effect of the electric field within the PN junction, so the forward current is almost zero; this region is called the dead zone. The forward voltage that cannot cause the diode to conduct is called the dead-zone voltage. When the forward voltage exceeds the dead-zone voltage, the electric field within the PN junction is overcome, the diode conducts forward, and the current rises rapidly with increasing voltage. Within the normal operating current range, the terminal voltage of the conducting diode remains almost constant; this voltage is called the diode's forward voltage drop. When the forward voltage across the diode exceeds a certain value, the internal electric field is quickly weakened, the characteristic current grows rapidly, and the diode conducts forward; this is called the threshold voltage or knee voltage. (3) Reverse characteristics: When the applied reverse voltage does not exceed a certain range, the current through the diode is a reverse current formed by the drift motion of minority carriers. Since the reverse current is very small, the diode is in the cutoff state. This reverse current is also called reverse saturation current or leakage current, and it is greatly affected by temperature. Generally, the reverse current of silicon diodes is much smaller than that of germanium diodes; the reverse saturation current of low-power silicon diodes is in the order of nA, while that of low-power germanium diodes is in the order of μA. As temperature rises, semiconductors are thermally excited, the number of minority carriers increases, and the reverse saturation current also increases. (4) Breakdown characteristics: When the applied reverse voltage exceeds a certain value, the reverse current suddenly increases; this phenomenon is called electrical breakdown. The critical voltage causing electrical breakdown is called the diode's reverse breakdown voltage. During electrical breakdown, the diode loses its unidirectional conductivity. If the diode does not overheat due to electrical breakdown, unidirectional conductivity is not necessarily permanently destroyed; after removing the applied voltage, its performance can recover; otherwise, the diode is damaged. Therefore, excessive reverse voltage should be avoided during use. Reverse breakdown is mechanistically divided into Zener breakdown and avalanche breakdown. In cases of high doping concentration, the depletion region width is very small; at higher reverse voltages, the covalent bond structure within the depletion region is disrupted, freeing valence electrons from covalent bonds and generating electron-hole pairs, causing a sharp increase in current; this is called Zener breakdown. If the doping concentration is lower and the depletion region is wider, Zener breakdown is less likely to occur. Another type is avalanche breakdown. When the reverse voltage increases to a large value, the external electric field accelerates electron drift velocity, causing collisions with valence electrons in covalent bonds, knocking them out and generating new electron-hole pairs. The newly generated electron-hole pairs are accelerated by the electric field and knock out other valence electrons, causing an avalanche increase in carriers and a sharp increase in current; this is called avalanche breakdown. Regardless of the breakdown type, if the current is not limited, it may cause permanent damage to the PN junction. (5) Reverse current: Reverse current refers to the current flowing through the diode at ambient temperature and maximum reverse voltage. The smaller the reverse current, the better the unidirectional conductivity of the device. It is worth noting that reverse current is closely related to temperature; it doubles with temperature rise. Therefore, silicon diodes have better stability at high temperatures than germanium diodes. (6) Dynamic resistance: The ratio of the change in voltage to the corresponding change in current near the static operating point on the diode characteristic curve. (7) Voltage temperature coefficient: The voltage temperature coefficient refers to the relative change in stable voltage for every one degree Celsius increase in temperature. (8) Maximum operating frequency: The maximum operating frequency is the upper frequency limit for diode operation. Since the diode, like the PN junction, has junction capacitance composed of barrier capacitance, the maximum operating frequency mainly depends on the size of the PN junction capacitance. If this value is exceeded, unidirectional conductivity will be affected. (9) Maximum rectified current: Maximum rectified current refers to the maximum allowable average forward current when the diode operates continuously for a long period. Its value is related to the PN junction area and external heat dissipation conditions. Because current flow causes heating of the chip, raising the temperature, exceeding the permissible limit will cause overheating and damage. Therefore, under specified heat dissipation conditions, the diode must not exceed its maximum rectified current rating during use.(10) Maximum reverse working voltage: When the reverse voltage applied across the diode reaches a certain high value, the device will break down and lose its unidirectional conductivity. To ensure safe operation, a maximum reverse working voltage value is specified.

stahl electrical component parameters

Rated voltage: The safe voltage allowed during normal switch operation. If the voltage across the switch exceeds this value, arcing and breakdown between the two contacts will occur. Rated current: The maximum safe current allowed to pass when the switch is closed; exceeding this value will burn out the switch contacts due to excessive current. Insulation resistance: The resistance value between the conductive parts and the insulating parts of the switch. Contact resistance: The resistance value between each pair of contacts when the switch is in the closed state. Dielectric strength: The maximum voltage the switch can withstand between conductors and ground. Service life: The number of operations the switch can perform under normal working conditions.

stahl electrical component classification

Thermosensitive materials are generally divided into three categories: semiconductor, metal, and alloy: 1. Semiconductor thermistor materials include single-crystal semiconductors, polycrystalline semiconductors, glass semiconductors, organic semiconductors, and metal oxides. They all have very large resistance temperature coefficients and high resistivity, resulting in high sensitivity for sensors made from them. Based on the resistance temperature coefficient, 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 thermal resistors for temperature measurement, current limiters, and automatic constant-temperature heating elements. Examples include platinum resistance thermometers, nickel resistance thermometers, and copper resistance thermometers. Among them, platinum temperature sensors exhibit high precision and high stability in various media (including corrosive media). However, their widespread application is limited by the scarcity and high price of platinum. Copper temperature sensors are cheaper, but long-term use in corrosive media can lead to significant changes in static characteristics and resistance values. Nickel temperature sensors are widely 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 high resistivity, and their resistance values are sensitive to temperature changes, making them good materials for manufacturing temperature-sensitive sensors. Performance requirements for thermistor alloys as temperature-sensitive sensors are as follows: (1) sufficiently high resistivity; (2) relatively high resistance temperature coefficient; (3) linear expansion coefficient close to that of the experimental material; (4) small strain sensitivity coefficient; (12) good repeatability of the resistance-temperature curve during heating and cooling within the operating temperature range.

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