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The last edit to this post was made by goldliyang on 2020-7-10 at 16:43. Precision resistors are those whose resistance value error, thermal stability (temperature coefficient), and distributed parameters of the resistor (distributed capacitance and distributed inductance) all meet certain standards； Precision resistors can be classified by material into metal film precision resistors, wire-wound precision resistors, and metal foil precision resistors. Metal film precision resistors have high accuracy, but their temperature coefficient of resistance and distribution parameter values are slightly lower ； Wire-wound precision resistors have high accuracy and temperature coefficient values, but lower distribution parameter values ； Precision metal foil resistors exhibit very high values for various parameters such as precision, temperature coefficient of resistance, and distributed parameters: the precision can reach 10-6, the temperature coefficient can be as high as ±0.3×10-6/℃, the distributed capacitance can be less than 0.5pF, and the distributed inductance can be less than 0.1μH. Since the prices of these three types of precision resistors increase with their performance, it is necessary to select them appropriately based on actual conditions in applications. For example, in DC or low-frequency AC circuits, it is generally sufficient to use wire-wound precision resistors or metal-film precision resistors; there is no need to opt for the more expensive metal-foil precision resistors. The main body of precision metal-film resistors is usually cylindrical in shape ； Wire-wound precision resistors come in cylindrical, flat-cylindrical, and rectangular-frame types ； Precision resistors made of metal foil are usually square or sheet-shaped. When wire-wound precision resistors have a large number of turns, a senseless winding method is often used, with the same number of turns in the forward and reverse directions in order to minimize distributed inductance. Precision wire-wound resistors in a rectangular frame shape are usually custom-made by equipment manufacturers according to specific requirements, and are often used in instruments and meters.