The concept of accurate resistor

 

Accurate resistor, be the block value error that points to resistor, resistor thermal stability (temperature coefficient) , the distributinging parameter of resistor (distributinging capacitance and distributinging inductance) the resistor that waits for an index to all reach certain level.

 

To 1Ω (ohmic) the resistor that above block is worth, the resistor that compares block of ±0.5% less than to be worth an error with label block value can call accurate resistor, of taller nicety can accomplish 0.01% precision, namely what electronic engineer says extremely one of precision, this kind of resistor is filmy resistor commonly, the resistor that uses this material to pledge just can satisfy manufacturing technology requirement commonly. The common series precision that this kind of block is worth 1Ω above resistor is in ±5% above, the commonnest on electronic product is the resistor of 5% precision, do not belong to accurate resistor limits.

 

The resistor that block is worth under 1Ω , can achieve ±1% precision commonly in, calculate category of block of the cipher telegram that make choice, because block value cardinal number is very small, it is the error of 1% , actual block is worth an error already very small. Of taller nicety can accomplish ±0.5% less than, but craft requirement, technical demand is higher.

 

The character of accurate resistor

 

The thermal stability that accurate resistor asks the block of resistor is worth error, resistor (temperature coefficient) , the distributinging parameter of resistor (distributinging capacitance and distributinging inductance) the resistor that waits for an index to all reach certain level.

 

 

Accurate resistor is classified

 

Accurate resistor presses material to divide, block of cipher telegram of metallic film essence, line circles accurate resistor and tinsel nicety resistor a few kinds. The precision of block of cipher telegram of metallic film essence is taller, but block is worth temperature coefficient and distributinging parameter index slightly low; The block value precision that the line circles accurate resistor and temperature coefficient index are very high, but on the low side of distributinging parameter index; The precision of block of tinsel essence cipher telegram, block is worth temperature coefficient and distributinging parameter each index is very high: Precision can amount to 10-6, temperature coefficient can amount to ±0.3&TImes;10-6/ ℃ , distributinging capacitance but under 0.5pF, distributinging inductance but under 0.1μH. Follow performance as a result of the price of 3 kinds of afore-mentioned accurate resistor and rise, the basis answers in applying so actual condition is reasonable choose. For example, it is in the alternating current road with dc or very low frequency, need to choose a line to circle accurate resistor or resistor of metallic film nicety only commonly can, not was necessary to choose the tinsel nicety resistor with high price.

 

The main body of block of cipher telegram of metallic film essence is normally cylindrical; The line circles accurate resistor to have form of cylindrical, flat column and look of long square frame a few kinds; Block of tinsel essence cipher telegram often submits diamonds form or piece form. The v/LIT all over the ground number that the line circles accurate resistor relatively a long time, often use without feeling circle make a law circle make, to circle the v/LIT all over the ground number that make and circle the v/LIT all over the ground number that make reversely identical, with reducing distributinging inductance as far as possible. Growing the line of square frame form to circle accurate resistor is equipment manufactory basis normally need is special and custom-built, commonly used at instrument appearance.

 

Once the long pane in instrument appearance wears look line to circle accurate resistor to damage, the silk of new alloy resistor that can use homogeneous phase of the material with silk of former resistor alloy, diameter, length to be the same as is circled on former frame to replace equably. If grow line of square frame look to circle accurate resistor formerly,be damaged of exterior insulation layer only, need silk of will former resistor to be torn open from frame only below, new dip lacquer (appropriate chooses the 1260 insulation varnish with function actor, low price) , grow square frame to go up formerly via after air is handled, be being circled afresh again can.

 

 

The accurate resistor technology of the mainstream reachs its actor defect

 

(one) resistor of accurate thick film

 

Improve through the abidance that expects to oar of thick film resistor, technology of the most accurate thick film resistor can have accomplished the Wen Piao of ±5ppm/°C, achieve the Wen Piao of ±2ppm/°C finally through using chip of resistor of thick film of many OK and mutual compensatory even. Its are highest precision also can achieve ±0.01% . Resistor of accurate thick film is the technology of the mainstream in the application that is worth tall nicety in high-pressured tall block. The defect of thick film resistor is the part that is worth in low block accomplishs high accurate low temperature very hard to wave, noise index is bad also, long-term stability compares other and accurate resistor to differ commonly.

 

(2) accurate and filmy resistor

 

It is OK that the technical development of accurate and filmy resistor was represented by technology of resistor of many commercial nicety, also be current the most popular accurate resistor technology. Pass long multilayer velar layer is deposit, move the filtration of block and later period accurately high, best accurate and filmy resistor can achieve the precision of the Wen Piao of ±2ppm/°C and ±0.01% , and very good long-term stability. Its defect is power is done not quite, index of section of low block value is bad, do not fight electrostatic, power coefficient is poor, of very difficult contented small lot offer money, and the consistency of different batch is bad.

 

(3) resistor of accurate metal film

 

Each index of resistor of accurate metal film and accurate and filmy resistor are similar, resistor of accurate metal film has brilliant circle to be stuck a climate that accurate and filmy resistor supersedes, but the accurate resistor technology of the low cost that inserts resistor of accurate metal film to remain the main aspect. With accurate and filmy resistor, the meeting that move block causes heat effect, affect the stability of resistor and reliability.

 

(4) narrow line circles resistor

 

Regard the earliest accurate resistor as the technology, the line of tall nicety circles resistor Wen Piao to be able to accomplish ±1ppm/°C, and precision can accomplish ±0.001% , film and thick film resistor accomplish this without method. Best narrow line circles resistor its block value can be accomplished be close to 50M, suit to exceed the application that nicety tall block is worth. As a result of the development of other resistor technology, narrow line circles resistor to tend the edge that is eliminated, because its price is high, have the drawback such as inductance.

 

(5) accurate foil resistor

 

Although foil resistor is in nicety early to was invented 1962, up to now it remains the most accurate resistor technology, pass a nickel chromium alloy is sticky stick on substrate of pottery and porcelain to undertake stress is balanced, get immediateness Yu Ling’s Wen Piao, engrave corrode resistor graph and tone block through laser, can get is as high as the precision of ±0.001% . Best foil resistor stores 6 years block is worth only drift ±2ppm, fight electrostatic, without feeling without the look, without heat design, low noise, low voltage coefficient. The defect of foil resistor is block value cannot be done very tall, of the largest size stick a resistor highest can accomplish 150K only, the value of block of the resistor that insert a foot of the largest size is highest can accomplish 2M only.

 

 

The type selecting of accurate resistor

 

Block value arrives from Europe of 1 fine long hair the demand of accurate sampling resistor between 1 ohm, can use accurate foil resistor only commonly. Keep stable below the circumstance that because have the resistor ability of alloy material only,is worth big electric current in low block, wen Piao is OK low to ±5ppm/°C, precision can arrive ±0.1% is taller even. Wen Piao’s size is the main factor that decides value of this kind of resistor. Basically applying as a result of its is electric current detects, so the structure of 4 feet is helpful for accurate sampling. Use larger size or obligate more power vacuums, and raise the temperature that auxiliary radiator is helpful for reducing ohmmeter range, the stability of improved sampling resistor. Accurate voltaic sampling resistor can replace sensor of suddenly Er electric current, and have cost advantage.

 

Block value arrives from 1 ohm between 10 ohm to any resistor technologies it is a challenge. Because this block is worth paragraph belong to low block to be worth limits, only thick resistor material and short voltaic method ability accomplish low block to be worth. Thick resistor material is gone against and the union of substrate balances Wen Piao, and short voltaic way also goes against nicety to move block. Accurate and filmy resistor and resistor of accurate metal film are in very hard this block offers outstanding Wen Piao inside value scope, best can arrive only ±20ppm/°C, in finite temperature limits less than may better. Narrow line circles the Wen Piao of resistor to be based on itself of resistor alloy silk completely, can accomplish ±10ppm/°C left and right sides, but the product that the line circles resistor to insert a foot only commonly and have inductance. Accurate foil resistor is worth the Wen Piao inside limits to be able to be controlled in this block in ±5ppm/°C less than, it is better perhaps that precision can accomplish ±0.1% , stick piece and insert a foot to be able to be offerred.

 

10 ohm arrive 150K ohm is groovy block value paragraph, the product that is based on diverse accurate demand to be able to choose inside scope of this block value is very much. Under the requirement of ±2ppm/°C, the applied situation that perhaps has very high demand to long-term stability can use accurate foil resistor only, stick piece can choose with what insert a foot. Wen Piao asks to be controlled in ±5ppm/°C, the circumstance with long-term stability so not high demand can consider filmy resistance at the same time or metallic film resistor. The highest precision of foil resistor can accomplish ±0.001% , filmy resistor and metallic film resistor can accomplish ±0.01% . What need points out is to use stick piece the block value range that foil resistor needs to notice different measurement place is offerred is distinct, for instance the value of sticks a foil resistor to be able to be offerred the largest block of 0805 dimension is 10K. The supply that additionally nicety sticks a filmy resistor manufacturer is very much, the tagging of parameter very much the same, but real property is far apart, the circumstance that Wen Piao and precision exceed bid is very much, the index such as long-term stability and noise is different the gap between the brand is huge.

 

Exceed 150K to be worth limits to belong to intermediate block to be worth to the block of 1M paragraph. If need,stick inside this paragraph of interval piece accurate resistor, can use accurate and filmy resistor only. Under the Wen Piao of ±2ppm/°C the requirement can use resistor of foil of the nicety that insert a foot only commonly, but block cost is this kind higher the price of resistor also can be jumped over tall, because need uses many resistor chip,will reach the block value of need. A few insert crural film resistor to be able to be offerred low the Wen Piao to ±5ppm/°C, but long-term stability is poor at accurate foil resistor. It is OK also that the narrow line that inserts a foot circles resistor contented high accuracy and low the Wen Piao to ±2ppm/°C, but the price does not have an advantage.

 

1M arrives between 50M for close to essence of life resistor is tall block paragraph. The highest block cost that accurate and filmy resistor can bear arrives commonly 10M, best Wen Piao is ±5ppm/°C, highest precision ±0.01% . The precision that resistor of accurate thick film can offer and Wen Piao are similar to filmy resistor, but the block cost that can bear whole interval. The cost of the largest block that resistor of individual and accurate foil can bear at present is 2M, and the price is very high. Additionally one kind of high accurate resistor technology is the line circles resistor, singular resistance can offer the block value that is as high as 50M, low the Wen Piao to ±2ppm/°C and the precision that are as high as ±0.001% , want in long-term stability respect especially greatly excel film and technology of thick film resistor.

 

The demand of block of cipher telegram of essence of 1M-10T high pressure can choose resistor of high pressure of accurate thick film only, because have ability of thick film technology only,work below high pressure and offer tall block to be worth. The main technique index of the resistor of this kind of high pressure application has voltage coefficient, voltage invariability, long-term stability, noise, wen Piao, precision. Especially the index of voltage coefficient and voltage invariability is very main, thick film resistor is worth the trend that can produce to small drift mostly in the block below high-pressured environment, because the part was isolated from to medium is activationed and form shunt-wound resistor, the quality that resistor oar expects and thick film craft decide the stand or fall of voltage coefficient. Circumstance of additionally a few application needs the high-pressured resistor of low noise, the blemish place of layer of film of resistor of noise consist in, blemish may be original existence is likely also be to move block hind to be added newly, more noise can exceed this kind of limitation big, special thick film technology conduces to improved noise index.

 

Accurate resistor conversion table

 

 

Accurate resistor conversion is formulary