One of the failure modes of resistors is “disconnection/open”. And one of the causes of the disconnection/open is “electric corrosion”. If the resistor is broken due to electric corrosion, a serious malfunction that sometimes leads to the stoppage of the electronic device occurs. Electric corrosion is a phenomenon that tends to occur in high humidity and corrosive environments. As a measure to prevent electric corrosion even in such environments, we recommend a resistor using a metal glazed film. The features of metal glazed film resistors are as described below.
In addition, the results of our electric corrosion acceleration experiments and the lifecycle of metal glazed film resistors considered from the results are also explained below.
Metal Glazed Film Resistors
Anti Electrical Corrosion Resistors AEC series
Special Power Type Anti Surge Resistors ASR/ASRM series
Thick Film Chip Resistors CR series
Anti Sulfurated Thick Film Chip Resistors CRA series
Surge Current Thick Film Chip Resistors CRS series
→ Application
Power supply, UPS, Semiconductor manufacturing equipment,
FA equipment, In-vehicle products, Lighting, and General home appliances
Structure of Metal Glazed Film Resistors
Structure of a metal glazed film resistor is the same as a general resistor, but as shown in Fig. 1 and Table 1, the structure of the conductive layer (film) part is different from a general resistor and is advantageous in withstanding electric corrosion and causticity.
Fig. 1 Structural diagram of the conductive layer in the resistor
Table 1 Comparison of conductive layer structure
Explanation of the principle that “failure due to electric corrosion does not occur”
The following two points are important.
Most of the malfunctions caused by electric corrosion of resistors on the market are due to the use of carbon resistors. The mechanism is that carbon (C), which is a conducting substance, and OH-ions generated by electrolysis of water chemically react and become CO2 (gas), resulting in loss of conductivity (increased resistance, disconnection).
On the other hand, as the conducting substance of the metal glazed film is ruthenium oxide (RuO2), the above electric corrosion mechanism does not apply.
(2) Conducting substance is protected by glass
If the conducting substance is not carbon and the conductive layer is only ruthenium oxide, a malfunction may occur due to a mechanism other than the above, such as electrochemical migration. （→Wikipedia）
However, the entire conductive layer of the metal glazed film is mainly made of glass (borosilicate glass). This is a structure in which the conducting substance is protected by glass, so to speak.
It is well known that glass is used in various fields because it has excellent corrosion resistance. Among them, borosilicate glass has higher heat resistance than general glass and corrosion resistance to halogen, water, neutral/acidic solutions, so it is used in optical components, physical/chemical appliance, medical equipment, and thermometers, etc. Examples of borosilicate glass that are easy to imagine are brown bottles, beakers, and flasks containing reagents used in chemical experiments. The metal glazed film, which has the same structure as those, is the strongest resistor in terms of corrosion resistance. Although the price is higher than general resistors, we promise cost performance (reliability and durability) higher than that price.
For Your Information
Glass is not all-purpose and corrodes with limited substances such as hydrogen fluoride (HF) and alkalis.
Hydrogen fluoride is often used in glass crafts, etc., taking advantage of the above properties.
Hydrogen fluoride is unlikely to be present in nature or in electrical equipment where resistors are used. Also, the rate at which hydrogen fluoride is corroded by alkali is very slow at room temperature, and such corrosion is not severe and only “the surface becomes matte glass”. Therefore, even if hydrogen fluoride is present to some extent, the effect on resistors is extremely small.
Electric corrosion (causticity) acceleration experiments of metal glazed film resistors – “Lifecycle is 48,000 years!?”
◎ Experiment description
Resistors are energized while immersed in tap water and an aqueous solution of phosphoric acid, and the resistance to electric corrosion is evaluated by the change in resistance value.
◎ Samples and conditions
We conducted a comparative experiment with “Anti Electrical Corrosion Resistors (AEC series) and general-purpose carbon resistors (RDM series). The details are as follows.
We used resistors with the exposed conductive layer (without film protection/exterior coating).
N=10 each
Fig. 2 Picture of the experiment
◎ Result of experiment
Carbon Resistors:
Within 20 seconds after the start of the test, all of them got into the OPEN state. Especially the resistors under phosphoric acid solution, they got disconnected in a few seconds.
Metal glazed film resistors:
Even 300 seconds after the start of the experiment, the rate of change in resistance was less than 10%.
As the lead wires of resistors under the phosphoric acid solution got broken due to corrosion, the experiment was stopped. But the damage to the resistive film was slight.
Fig. 3 shows how the resistance values changed. (Plotted resistance value changes of each n = 10)
Fig. 3 Graph of time-resistance change rate (Note: “①② “and “③④ “have different time scales)
Pictures of sample resistors after the experiment
◎ Considerations: How many hours does the experiment result correspond to when applied to products on the market?
Normally, evaluation is performed using commercially available products (with film protection and exterior coating), so it is difficult to verify under the conditions of our experiment as the above. However, we referred to our database of results of the electric corrosion acceleration test we conducted in the past using carbon resistors (commercially available) and calculated simply the lifecycle using the data. The calculation result was amazing that “5 seconds under tap water conditions in the above experiment” is “equivalent to more than 100 years”. (Assuming “resistance value change rate + 20% = lifetime”)
Assuming that “5 seconds = 100 years”, the “300 seconds” obtained from the above experiment results of metal glazed film resistors is equivalent to “100 years x 300 seconds/5 seconds = 6,000 years”!!
Furthermore, comparing the degree of resistance change between the tap water condition and the phosphoric acid solution condition in the above experiment, the latter can be estimated to be about 10 times the change in the former, so the lifecycle of the metal glazed resistor under the phosphoric acid solution condition is equivalent to “6,000 years x 10x (240 seconds/300 seconds) = 48,000 years”!!!
It is an unreal number of years that is hard to understand, but it certainly takes a considerable amount of time for the lead wires of resistors inside electronics devices to corrode (to disappear?) and break. Therefore we guess that you could understand that “48,000 years” is not so unreal.
The last point we would like to emphasize is that 48,000 years is the lifetime of the lead wire, and it can be inferred from the above experiment results that the metal glazed film is much more durable.
Metal Glazed Film Resistors
Anti Electrical Corrosion Resistors AEC series
Special Power Type Anti Surge Resistors ASR/ASRM series
Thick Film Chip Resistors CR series
Anti Sulfurated Thick Film Chip Resistors CRA series
Surge Current Thick Film Chip Resistors CRS series
⇒ Application
Power supply, UPS, Semiconductor manufacturing equipment, FA equipment,
In-vehicle products, Lighting, and General home appliances
Related columns:
Electric corrosion mechanism & Design for countermeasures
What is electric corrosion? – Our efforts
There are a wide range of types of resistors, and with the development of electronic technology, new types of resistors will continue to increase.
Resistors are generally divided into two categories: fixed resistors and variable resistors. Fixed resistors can be divided into two types of wire-wound type and non-wire-wound type according to the material of the resistor body. The non-wire-wound type resistors can also be divided into two types: film type and composite type; according to the structure of the resistor, it can be divided into tubular resistors, disc resistors and planar resistors, etc .; according to the form of the lead wire, the resistors can be divided into lead type, radial lead type, co-lead type and no lead type, etc. . According to different protection methods, resistors can be divided into unprotected, painted, plastic pressed, sealed and vacuum sealed.
This article will mainly introduce the classification of resistors, as well as the characteristics, advantages and disadvantages of different types of resistors. It is definitely worth reading as the basics of resistor.
Types of Resistor
(1) Carbon Film Resistor
Carbon film resistors are made by depositing crystalline carbon which is thermally decomposed by vacuum high temperature on a cylindrical or tubular ceramic skeleton. Control the thickness of the carbon film and the groove to control the resistance value.
Carbon film resistors have good stability, low negative temperature coefficient, good high-frequency characteristics, less influenced by voltage and frequency, less electric noise, stable pulse load, wide resistance range, simple production process, low production cost. So it is widely used in various electronic products.
Figure1. The Appearance and Structure of Carbon Film Resistor
(2) Metal Film Resistor
Metal film resistors are made by heating and evaporating metal or alloy materials on a ceramic substrate to form a thin film on the ceramic substrate. They can also be manufactured by methods such as pyrolysis, chemical deposition, and infiltration.
Metal film resistors have good stability and heat resistance, a small temperature coefficient, a large operating frequency range, and a small noise electromotive force. They are often used in high-frequency circuits.
Figure2. Metal Film Resistor
(3) Metal Oxide Film Resistor
Metal oxide film resistors are made by spraying metal salt solutions (tin tetrachloride and antimony trioxide), such as tin and antimony, onto the surface of the hot ceramic skeleton in a heating furnace at about 550 ° C and depositing them. The conductive film layer of this kind of resistor is uniform, the film and skeleton matrix are firmly combined, and some performances are better than metal film resistors. The shape of the ordinary metal oxide film resistor is basically the same as that of the metal film resistor, and its structure is mostly cylindrical and is an axial lead-out wire.
Metal oxide film resistors have stronger oxidation resistance, acid resistance and salt resistance than metal film resistors, and have good heat resistance. The disadvantage of metal oxide film resistors is that due to the limitations of material characteristics and film thickness, the resistance range is small, and the resistance range is 1Ω ~ 200 kΩ; the rated power is 1/8 ~ 10 W; 25 W ~ 50 kW.
Figure3. Metal Oxide Film Resistor
Composition resistors can be divided into solid core resistors and paint film resistors according to resistor shape; they can be divided into organic types (such as phenolic resin) and inorganic types (such as glass, ceramics, etc.) according to the type of binder. It can be divided into general-purpose type, high-resistance type and high-pressure type according to usage.
The most prominent advantage of synthetic resistors is high reliability. For example, the reliability of high-quality solid-core resistors is usually 5 to 10 times higher than that of the metal film and carbon film resistors. Therefore, despite its poor electrical performance (large noise, poor linearity, low accuracy, poor high-frequency characteristics, etc.), due to its high reliability, it is still widely used in some special fields, such as the aerospace industry, submarine cables Wait. Here are some common synthetic resistors.
(1) Solid Core Resistor (model S)
The common model is RS11 type, the resistance value range is 4.7Ω ～ 22MΩ, the accuracy is ± 5%, ± 10%, ± 20%, the volume is the same as the metal resistor at the same power.
(2) High Voltage Composite Film Resistor
Common domestic models are RHY-10 and RHY-35. The withstand voltage of the former can be 10kV, and the latter can reach 35kV; the resistance range is 47MΩ ~ 1000MΩ, and the accuracy is ± 5% and ± 10%.
(3) Carbon Film Composition Resistor
Carbon Film Composition resistors are made by mixing carbon black, filler and organic binder into a suspension, coated on an insulating skeleton, and polymerized by heating. Its resistance range is high, which can reach 10 ~ 106 MΩ; rated power is 1/4 ~ 5 W; maximum working voltage is 35kV. The disadvantages are poor moisture resistance, low voltage stability, poor frequency characteristics, and high noise.
This kind of resistor is not suitable for general-purpose resistors, but mainly suitable for high-voltage and high-resistance resistors. It is usually packaged in a glass shell to make a vacuum megohm resistor for micro-current testing.
(4) Organic Solid Composition Resistor
Organic Solid Composition resistors are made of carbon black, graphite and other conductive substances and fillers mixed with organic binders to form powders, which are hot pressed by special equipment and made into plastic shells. The leads of solid resistors are compression molded in the resistor body. One is a resistor without end cap, and the other is a resistor with end cap and using the end cap as an electrode.
This resistor has high mechanical strength, good reliability, and strong overload capacity; small size and low price; large inherent noise, large distribution parameters, poor voltage and temperature stability, and resistance range of 4.7Ω ~ 22 MΩ; Working voltage is 250 ~ 500 V; rated power is 1/4 ~ 2 W.
However, such resistors are not suitable for use in demanding electrical circuits. At present, common organic synthetic solid resistors are RS11 type and RS type. RS type organic solid resistors are commonly used in automobile instruments (oil pressure gauges).
(5) Glass Glaze Resistor
The glass glaze resistor is made of metal silver, rhodium, ruthenium and other metal oxides mixed with glass glaze adhesive to form a slurry, which is coated on the ceramic skeleton and sintered at high temperature. At present, resistors are often made of ruthenium oxide and glass glaze adhesives. Metal glass glaze resistors have ordinary and precision types.
This resistor has high-temperature resistance, good humidity resistance, good stability, low noise, small temperature coefficient, large resistance range, resistance range is 4.7Ω ~ 200 MΩ; rated power is 1/8 W, l / 4 W, l / 2 W, 1 W, 2 W, high power 500 W; maximum voltage is 15 kV.
Figure4. Different Types of Resistors
(1) Precision Wire Wound Resistor (model RX)
In the measurement instrument into other circuits that require high precision, precision wire-wound resistors can be used. The resistance of such resistors is generally ± 0.01%, up to 0.005% or higher, the temperature coefficient is less than l0-6 ℃, and the long-term working stability is high , The resistance range can be between O.O1Ω ~ lOMΩ. However, this type of resistor is not suitable for use in high-frequency circuits because the process is wire wound, so the distribution parameters are large.
Figure5. Presicion Wire Wound Resistor
(2) Power Type Wire Wound Resistor (model RX)
The rated power of this resistor is above 2W, the maximum power can reach 200W, the resistance range is 0.15Ω to hundreds of kΩ, and the accuracy level is ± 5% ～ ± 20%. This type of resistance is divided into fixed type and adjustable type. The adjustable type draws a sliding head from the resistor body, which can adjust the resistance value, which is convenient for debugging in the whole machine.
(3) Precision Alloy Foil Resistor
This resistor has the function of automatically compensating for the temperature coefficient of the resistor, and can maintain a very small temperature coefficient in a wide temperature range, so it has the characteristics of high precision, high stability, high frequency and high-speed response, making up for the metal film and wire winding Insufficient resistance. The accuracy of this type of resistance can reach ± 0.001%, the stability is ± 5 × 10-5% / year, and the temperature coefficient is (0 ± 1) × 10-6 / ℃.
(1) General Type
Refers to the resistance that can meet the general technical requirements, the power is 0.05 (1/20 ~ 2W, the resistance value is 1Ω ~ 22MΩ deviation is ± 5 ~ ± 20%.
(2) Precision Type
Resistance with high precision and stability, the power is generally not greater than 2W, the resistance value is 0.01Ω ~ 20MΩ, the deviation is 2% ~ 001%.
(3) High Frequency Type
The inductance of the resistor itself is extremely small, often called non-inductive resistance. Used in high-frequency circuits, the resistance is less than 1kΩ, the power range is wide, and the maximum can reach 100W.
(4) High Voltage Type
Suitable for high-voltage devices, working at 1000V ~ 100KV, high up to 35GV, power between 0.5 ~ 100W, resistance up to 1000 MΩ.
(5) High Resistance Type
The resistance is above 10 MΩ, up to 1014Ω.
(6) Integrated Resistance
Combined with mask, lithography, sintering and other process technologies, multiple resistors with consistent parameters and performance are formed on a substrate, and connected into a resistor network. It has the characteristics of small size, regularization and high precision. It is suitable for electronic instruments and computer products.
(7) Insurance Type
Made of non-combustible metal film, it has the dual function of resistance and fuse, the resistance value range is 0. 33Ω ～ 10 KΩ. When the actual power is 30 times the rated power, 7s is off. When the actual power is 12 times the rated power, 30 ~ 120s off.
Figure6. Different Resistors
(1) Thermistor
The thermistor can be divided into MF: negative temperature coefficient; MZ: positive temperature coefficient.
The thermistor is a resistor whose resistance value changes with temperature and is usually made of a semiconductor material such as single crystal or polycrystal. It is made of barium titanate as the main raw material, supplemented with trace amounts of strontium, titanium, aluminum and other compounds. It can be divided into negative temperature coefficient thermistors whose resistance decreases with increasing temperature and resistance increases with temperature The high and rising positive temperature coefficient thermistor has a slow change type and a sudden change type.
Thermistor is mainly used for temperature measurement, temperature control (temperature control of electromagnetic oven), fire alarm, meteorological sounding, microwave and laser power measurement, temperature compensation in radio, and demagnetization current limiting resistor in TV.
Figure7. Thermistor
(2) Photoresistor
A photoresistor is a kind of element made by using the photosensitive effect of semiconductors. The resistance value changes with the intensity of incident light. The stronger the light, the smaller the resistance. When there is no light irradiation, the high impedance resistance value can reach 1.5MΩ or more; when there is light irradiation, the material excites free electrons and holes, and its resistance value decreases. With the increase of light intensity, the resistance value can be as low as 1kΩ.
The photoresistor is made by coating materials sensitive to light on the glass and drawing out the electrodes. Depending on the material, a photosensitive resistor sensitive to a certain light source can be made. Such as: visible photoresistor, the main material cadmium sulfide, used in photoelectric control. Infrared photoresistor, the main material is lead sulfide, used in missile and satellite monitoring.
Figure8. Photoresistor
(3) Varistor
The varistor is a semiconductor ceramic element made of zinc oxide as the main material, and the resistance value changes according to the non-linear characteristics with the change of the voltage applied at both ends. When the voltage applied to both ends does not exceed a certain value, it shows high impedance, and the current flowing through the varistor is very small, which is equivalent to an open circuit. When the voltage exceeds a certain value, its resistance suddenly decreases, and the current flowing through the resistance increases sharply. Varistors are widely used in electronic and electrical circuits and are mainly used for overvoltage protection and as voltage stabilizing components.
Figure9. Metal Oxide Varistor
(4) Magneto-resistor
Magneto-resistors are made of materials such as indium arsenide or indium antimonide, based on the magnetoresistance effect of semiconductors, and the resistance increases with the increase of the magnetic flux passing through it. It is a semiconductor element sensitive to the magnetic fields, which can convert magnetic induction signals into electrical signals. Mainly used to measure the strength of the magnetic field, magnetic card text recognition, magnetoelectric coding, AC-DC conversion.
Figure10. Magneto Resistor
(5) Force Sensitive Resistor
The resistance becomes larger as the applied stress changes. It is a special element that can transform force into an electrical signal. Commonly used in sensors such as tensiometers, accelerometers, semiconductor microphones.
Figure11. Force Sensitive Resistor
(6) Gas-sensitive Resistor
Made of semiconductor materials such as tin dioxide. After absorbing a certain gas on the surface of the semiconductor, an oxidation or reduction reaction occurs, and the resistance changes with the concentration of the measured gas.
Gas-sensitive resistors are often used in gas detectors, such as the electronic nose mounted on range hoods, and are also used to measure automobile exhaust, drunk driving and other devices.
Figure12. Gas-sensitive Resistor
(7) Humidity Resistor
The resistance of the humidity-sensitive resistor changes with the change of the relative humidity of the environment, and the surface moisture content can be measured.
Figure13. Humidity Resistor
The potentiometer is a kind of resistor with adjustable resistance, which is derived from the variable resistor. The general potentiometer is composed of a resistor body, a sliding arm, a rotating handle (sliding handle), a housing and a soldering piece.
In addition to ordinary potentiometers, there are potentiometers with switches, which are controlled by the rotary handle. Traditionally, the adjustable resistance with handle and housing is generally called a potentiometer, the one without handle or without housing is called a trimming resistor, and it is also called a preset resistance.
(1) Classification by Material
Carbon film: Carbon film is used as a resistance film.
Metal Film: A special ceramic film made of ceramic and metal is used as a resistance film.
Wirewound: A metal wirewound is used as a resistor. Compared with carbon film or porcelain gold film, it can withstand greater power.
(2) Classification by Structure
Rotating: common form. The usual rotation angle is about 270 to 300 degrees.
Single-turn type: a common form.
Multi-turn type: used for occasions requiring precise adjustment.
Linear sliding type: usually used in the mixer, it is easy to immediately see the position of the volume and do fade control.
(3) Classification by Quantity
Single connection: One rotary shaft only controls a single potentiometer.
Double-connected: Two potentiometers are controlled by the same shaft, which is mainly used in dual-channel, which can control two channels at the same time.
(4) Classification According to the Change Scale of Resistance Value
Linear scale type: The change in resistance value is linearly related to the rotation angle or moving distance. This type of potentiometer is called a B-type potentiometer.
Logarithmic scale type: The change of resistance value is a logarithmic relationship with the rotation angle or moving distance. The main purpose of this type of potentiometer is volume control, of which the type A potentiometer is commonly used, suitable for large volume in the clockwise direction and counterclockwise direction. For low volume; in addition, there is a C-type potentiometer with a logarithmic scale that changes in the opposite direction.
(5) Classification According to the Material of the Resistor
Potentiometers can be divided into wire-wound potentiometers and non-wire wound potentiometers according to the material of the resistor body. Wire-wound potentiometers can be divided into general wire-wound potentiometers, precision wire-wound potentiometers, high-power wire-wound potentiometers and preset wire-wound potentiometers. Non-wire wound potentiometers can be divided into two types: solid potentiometers and membrane potentiometers. The solid potentiometer is divided into an organic synthetic solid potentiometer, inorganic synthetic solid potentiometer and conductive plastic potentiometer. Membrane potentiometers are divided into carbon membrane potentiometers and metal membrane potentiometers.
(6) Classification by Adjustment Method
Potentiometers can be divided into rotary potentiometers, push-pull potentiometers, straight slide potentiometers, etc. according to the adjustment method.
(7) Classification According to the Change Law of Resistance Value
Potentiometers can be divided into linear potentiometers, exponential potentiometers and logarithmic potentiometers according to the change rule of resistance value.
(8) Classification According to Structural Characteristics
Potentiometers can be divided into single-turn potentiometers, multi-turn potentiometers, single-connect potentiometers, double-connect potentiometers, multi-connect potentiometers, tapped potentiometers, switch potentiometers, locking potentiometers There are many types of non-locking potentiometers and patch-type potentiometers.
(9) Classification by Driving Method
Potentiometers can be divided into manual adjustment potentiometers and electric adjustment potentiometers according to the driving mode.
Figure14. Potentiometer
Figure15. Mind Map of Types of Resistor
Resistor Introduction Application Range Advantage Disadvantage Carbon Film Resistor (RT) Hydrocarbons decompose in high temperature and vacuum and deposit on porcelain rods or tubes to form a crystalline carbon film. Different resistance values can be obtained by changing the thickness and length of the carbon film.
①The main tolerances are:
± 5%, ± 10%, ± 20%。
②Mostly used in less demanding circuit occasions.
Low cost of carbon film Poor stability and large errors Metal Film Resistor (RJ) Heating the alloy in a vacuum, the alloy evaporates, forming a conductive metal film on the surface of the ceramic rod. The resistance can be controlled by changing the thickness of the metal film.
①The allowable errors are: ± 0.1%, ± 0.2%, ± 0.5%, ± 1%.
②Mostly used in occasions with high accuracy requirements.
Small size, low noise and good stability High cost Metal Oxide film resistor (RY) The metal salt solution of tin and antimony is sprayed onto the surface of the hot ceramic skeleton and formed by hydrolysis and deposition. It is suitable for non-combustible, temperature change resistance, humidity resistance and other occasions. Good oxidation resistance and thermal stability -
Wire Wound Resistor
(RX)
- Suitable for circuits with low frequency and high accuracy requirements. Precise resistance, stable operation, small temperature coefficient, good heat resistance, and high power The resistance value is small, the distributed inductance and distributed capacitance are large, and the manufacturing cost is also high High power wire wound resistor (RX) It is made of constantan or nickel-chromium alloy resistance wire wound on the ceramic skeleton. Suitable for high power occasions, the rated power is generally more than 1W. Stable work, good heat resistance, small error range - Organic Solid Resistor (RS) The organic solid resistor is a resistor composed of granular conductive materials, fillers and adhesives, evenly mixed and then hot pressed together, and then installed in a plastic shell. Its leads are directly molded in the resistor body. Generally used in places where the load cannot be disconnected and the work load is large, such as the circuit where the audio output is connected to the headset Strong overload capacity, high reliability and low price Low Precision Fusing Resistor (RF) A fuse resistor is an element with dual functions of resistance and fuse. It is used in series with high value and circuit components that need to be protected. It is commonly used in power supply and secondary power supply circuits. - - Cement Resistor(RX) Cement resistor is also a fuse resistor, which is formed by winding the resistance wire on the heat-resistant ceramics, and protecting it with heat-resistant, moisture-resistant and corrosion-resistant materials. A Good choice in a circuit where a large amount of current is being passed through a resistor and with it needing to be resistant to high heat and flame. Good explosion-proof performance, complete insulation, shock resistance, humidity resistance, heat resistance and good heat dissipation Large size, high heat generation during use, easy to radiate 0 ohm Resistor Zero-ohm resistors, also called jumper resistors, are resistors used for special purposes.
①On the PCB for debugging convenience or compatible design and other reasons
②Can be used as a jumper
③Wiring
- - Power Type Wire Wound Non-inductive Resistor (aluminum shell resistor)
①A special wire-wound method is adopted, which makes the inductance much lower than that of general wire-wound resistors.
②Adopt a metal shell to facilitate heat dissipation.
It is suitable for high-power circuits and harsh magnetic fields, so it is often called a Power Resistor. - - Network Resistor(Wire-wound Resistor) Network resistor is made by encapsulating several resistors with the same parameters together and combining them. Generally used in digital circuits, instrument circuits and computer circuits, such as attenuators in instrument circuits. Easy assembly and high installation density -
Which two types are resistors mainly classified into?
①Fixed resistors
②Variable resistors
Introduction of wire wound resistance:
Wire-wound resistors are made of constantan, manganin or nickel alloy wire wound on a ceramic skeleton, with protective paint or glass glaze on the surface. There are two types: fixed and adjustable.
Wire wound resistors are one of the more commonly used resistors. The resistance body of the wire wound resistor is a resistance wire. The resistance wire is wound on the ceramic frame, the lead is connected, and the surface is coated with a layer of glass glaze or insulating paint to make the wire wound resistor.
Winding resistance characteristics:
A: Non-flammable wire-wound coating resistors
B: Can withstand high-pressure shock
C: Faster heat dissipation
D: In a short time
E: Low noise
F: Resistance has not changed for many years
G: The error range is small, ±5%, ±2%, ±1%
H: Power range: 1/2W-10W
Advantages and disadvantages of wire wound resistors:
The advantages and disadvantages of wire-wound resistors include high resistance accuracy, low noise, stability, and reliability, but the large size and relatively large capacitance inductance. For detailed advantages and disadvantages, please refer to another article about wire wound resistors.
Application areas of wire wound resistors:
Wire-wound resistors are mainly used to reduce voltage, shunt, load, feedback, transfer energy, and match in low-frequency AC circuits, or act as absorbers and voltage dividers in power circuits, and can also be used as attenuation adjustment in the oscillating circuit and the transformer and the shunt in the pulse forming circuit.
In addition, it can also be used for discharge and spark suppression of filter stage capacitors in rectifiers. It is also widely used in household appliances, medical equipment, the automobile industry, railway, aviation, military equipment, and other fields.
Introduction of
metal film resistors
Metal film resistors are a type of film resistor. It uses high-temperature vacuum coating technology to closely adhere nickel-chromium or similar alloys to the surface of the ceramic rod to form a film. After cutting and adjusting the resistance, it can achieve the final required precision resistance. , Then cut with appropriate joints, and coat the surface with epoxy resin for sealing protection.
Because it is a lead-type resistor, it is convenient for manual installation and maintenance and is used in most household appliances, communications, and instruments.
Performance parameters of metal resistors:
Temperature coefficient: ±100PPM/°C
Large power load, low current noise
High stability, good high-frequency performance
Operating temperature range: -55°C-155°C
Accuracy: 0.25 [%], 0.5 [%], 1 [%], 5 [%]
Resistance range: 1Ω～10MΩ
Nominal resistance: E-96
Features of metal resistors:
A: High thermal conductivity porcelain core
B: High-stability metal film
C: High insulation and solvent-resistant epoxy paint
D: Meet the standards set by MIL&EIA
E: Good solderability
The difference between wire wound resistors and metal film resistors:
1. The metal film resistor heats the alloy in a vacuum, and the alloy evaporates, so that a conductive metal film is formed on the surface of the porcelain rod. The resistance value can be controlled by changing the thickness of the metal film. Compared with carbon film resistors, this type of resistor has the advantages of small size, low noise, and good stability, but the cost is higher. Metal film resistors are bright in color and can be subdivided into multiple types high frequency, high voltage, and precision. Most applications are in high precision requirements.
2. Wire-wound resistors have accurate resistance, stable operation, low-temperature coefficient, good heat resistance, large power but small resistance, large distributed inductance and distributed capacitance, and high production costs. It is suitable for low-frequency and high-precision circuits.
For more information power resistors used, metal glaze resistor, please get in touch with us!