The concept of precision resistance refers to a resistor whose resistance value error, thermal stability, and distribution parameters meet certain standards. For resistors with a resistance value above 1 Ω and a resistance error within ± 0.5% compared to the marked resistance value, they can be called precision resistors. For higher precision resistors, they can achieve an accuracy of 0.01%, which is what electronic engineers call one thousandth accuracy. These types of resistors are generally thin film resistors, and resistors made of this material can generally meet the production process requirements. The precision of ordinary series resistors with resistance values above 1 Ω is above ± 5%. The most common type of resistor on electronic products is a 5% precision resistor, which is not within the precision resistance range. A resistor with a resistance value below 1 Ω can generally achieve a precision of ± 1%, which is considered a precision resistor. Because the resistance base is very small, even with a 1% error, the actual resistance error is already very small. Higher precision can be achieved within ± 0.5%, but the process requirements and technical requirements are high.

Classification of precision resistors: Precision resistors are classified by material, including metal film precision resistors, wire wound precision resistors, and metal foil precision resistors. The precision of metal film precision resistors is relatively high, but the resistance temperature coefficient and distribution parameter indicators are slightly lower; The resistance accuracy and temperature coefficient index of wire wound precision resistors are very high, but the distribution parameter index is relatively low; The precision, resistance temperature coefficient, and distribution parameters of metal foil precision resistors are all very high: the accuracy can reach 10-6, and the temperature coefficient can reach ± 0.3&TImes; 10-6/℃, distributed capacitance can be less than 0.5pF, and distributed inductance can be less than 0.1 μ H。 Due to the fact that the prices of the three types of precision resistors mentioned above increase with performance, they should be reasonably selected according to actual situations in application. For example, in DC or low frequency AC circuits, it is generally only necessary to choose wire wound precision resistors or metal film precision resistors, and there is no need to choose expensive metal foil precision resistors. The main body of metal film precision resistors is usually cylindrical; There are several types of wire wound precision resistors, including cylindrical, flat cylindrical, and rectangular frame shapes; Metal foil precision resistors are often square or sheet shaped. When the number of turns of wire wound precision resistors is large, non-inductive winding method is often used. The number of turns of forward winding and reverse winding is the same to minimize the distributed inductance. The rectangular frame shaped wire wound precision resistor is usually customized by equipment manufacturers according to their needs and is commonly used in instruments and meters. Once the precision resistance of the rectangular frame shaped wire wound in the instrument is damaged, a new alloy resistance wire with the same material, diameter, and length as the original resistance alloy wire can be uniformly wound on the original frame instead. If the original rectangular frame shaped wire wound precision resistor only has a damaged surface insulation layer, simply remove the original resistor wire from the frame, re dip it in paint, and then air dry it before rewinding it onto the original rectangular frame.
The characteristics of precision resistors require resistors that meet certain standards in terms of resistance error, thermal stability, and distribution parameters.