What is a precision resistor?
In fact, for the measurement is not to do not need to be divided so clearly, can generally think of high precision, high accuracy, low error, etc., is a meaning. However, the word "precision" can be broken down into three elements:
Temperature coefficient. Temperature change is the enemy of resistance, temperature coefficient is generally expressed as PPM /℃, that is, temperature change of 1 degree corresponds to resistance change of several parts per million. 100ppm/℃ is 0.01%/℃.
Aging. That is, long-term stability, usually expressed in terms of PPM/year, but also expressed in terms of %/ year. Factory again how accurate resistance, if aging is large, so soon changed, also lose the meaning of high accuracy.
The initial adjustment error, this is not really important, you know what the deviation is, as long as it doesn't change, you can correct it when you measure it. Therefore, it is not discussed in this article.
For resistors with low precision, we can say in general terms what the precision of a resistance is. For example, the resistance with 0.1% precision is a comprehensive error. In fact, at normal temperature (such as 10℃-35℃), within 1 year, including all the errors, the resistance should still be within 0.1%.
However, where the requirements are high, the specific characteristics of the resistance will be tested so that it is easy to choose. In this paper, the common high precision resistor according to the temperature coefficient and aging two indicators to do a description.
There are three types of common precision resistors: metal film resistors, wire wound resistors, and block resistors.
Metal film resistance is the most common, but some better for the precision metal film resistance, the characteristic is the temperature coefficient is not big, the resistance value is more stable. However, due to the thin film is relatively fragile, screw cutting and compression parts are prone to problems.
Wire - wound resistance is also very common, and even for a time was the main resistance for highly accurate equipment. There are now three types of resistance wire materials used:
-- constantan, older, heat-resistant but with a low temperature coefficient, has a higher thermoelectric emf than copper.
-- manganese copper, there is precision manganese copper, although the heat but the temperature is not too high but the temperature coefficient is very small, and copper thermoelectric electromotive force is small, is widely used wire wound resistance material.
Evanohm, translated into evohm, is a nickel chromium aluminum copper alloy, also known as nickel chromium resistance alloy, temperature coefficient is the smallest, the material is relatively hard, welding performance is not very good.
Block resistance, also known as metal foil resistance, is a ceramic substrate bonded to the alloy resistance layer and then non-inductive lithography, not only using nickel and chromium resistance alloy materials, and ceramic substrate to further temperature compensation, the temperature coefficient is very small, many can do "1ppm/℃.
The following is dedicated to the introduction of a high precision film resistance related knowledge
One, high precision film resistance
Vacuum sputtering technology is used in the production of high density ceramic substrate, with the widest range of resistance values and high precision ±0.01% and low TCR 5ppm/℃. Dimensions complete: 0201, 0402, 0603, 0805, 1206, 2010 and 2512. Resistance values range: 1ohm-3mohm, accuracy: ±0.01%,0.05%,0.1%,0.25%,0.5%,1%, temperature coefficient (TCR): 5, 10, 15, 25 and 50 PPM /℃.
It is mainly used in medical instrument, measuring equipment, automobile related control panel, computer peripheral control panel, power converter, LCD control panel, mobile phone, laptop and so on.
Second, the current induced resistance
With unique materials and process technology, provides the high quality, high reliability and low TCR 100 PPM / ℃, low resistance values 1 mohm - 1000 mohm resistance range, precision, plus or minus 1 and 5% of power up to 3 w. Another use thin film process unique, low resistance values can provide TCR 50 PPM / ℃ and + / - 0.5% accuracy. Full size: 0201, 0402, 0603, 0805, 1206, 2010, 2512, 3720, 7520 and 1225.
It is mainly used for laptop computer, motherboard, screen, toy charging control board, mobile phone and all kinds of charger control board, power supply, power converter and so on.
Third, the alloy ultra-low resistance
To meet the high power electric property, high purity and high thermal conductivity and low TCR and high temperature resistant special alloys, to meet customer demand, high thermal conductivity material can greatly reduce the heat dissipation area of circuit boards, a integrated structure without cutting, can achieve almost no inductance, resistance value range: 0.5 mohm - 22 mohm. Accuracy + / - 1% 2% 5%, which is the 50 PPM / ℃, size 1206, 2010 and 2512.
It is mainly used for laptop computer, motherboard, screen, toy charging control board, mobile phone and all kinds of charger control board, power supply, power converter and so on.
Four, thick film chip resistance/exclusion
Full size 0201, 0402, 0603, 1210, 1206, 2010 and 2512, precision: plus or minus 5%, 1% can provide more understanding of the value range: 1 Ω ~ 39 m Ω, and can provide high power and diversified exclusion, including 0603 & amp; 8 Pins 4R and 4 Pins 2R of 0402, concave and convex electrode structures, etc.
Widely used in all kinds of electronic products, miniaturization and network rejection can greatly reduce the area of the circuit board.
Five,TO-220 power resistor
A space-saving power supply design is provided
Can provide 20W, 30W, 35W and 50W, resistance range: 0.05 ~ 10Kohm, precision :±0.5 ~ 10%.
It is applied to electronic power equipment,UPS, electronic load, high frequency amplifier, medical power supply, electronic deceleration system, electric vehicle fuel cell and so on
Resistance to high voltage
This product is the use of membrane process, can provide high precision of + / - 0.1%, high voltage 1500 v, 15 and 25 PPM / ℃, low TCR value range: 10 k ~ 40 m Ω.
Mainly used in precision instruments, measuring equipment, wired and wireless communication network equipment and so on.