The potentiometer is a resistance element with three terminals and the resistance value can be adjusted according to a certain change rule. Potentiometers usually consist of resistors and movable brushes. When the brush moves along the resistor body, a resistance value or voltage having a certain relationship with the displacement is obtained at the output end.
The potentiometer can be used as a three-terminal component or a two-terminal component. The latter can be regarded as a variable resistor. Because its role in the circuit is to obtain an output voltage that has a certain relationship with the input voltage (applied voltage), it is called a potentiometer.
itumo:
Potentiometer is a kind of variable resistor. It is usually composed of a resistor and a rotating or sliding system, that is, a moving contact moves on the resistor to obtain a partial voltage output.
The role of the potentiometer-adjust the voltage (including DC voltage and signal voltage) and the size of the current.
The structural characteristics of the potentiometer-the resistor body of the potentiometer has two fixed ends. By manually adjusting the rotating shaft or slider to change the position of the moving contact on the resistor body, the moving contact and any fixed end are changed. The value of the resistance changes the magnitude of voltage and current.
Potentiometer is an adjustable electronic component. It is composed of a resistor and a rotating or sliding system. When a voltage is applied between the two fixed contacts of the resistor, the position of the contact on the resistor can be changed by rotating or sliding the system, and a moving contact position can be obtained between the moving contact and the fixed contact Voltage. It is mostly used as a voltage divider, then the potentiometer is a four-terminal element. The potentiometer is basically a sliding rheostat. There are several styles. It is generally used in the volume control of the speaker and the power adjustment of the laser head. The potentiometer is an adjustable electronic component.
Variable resistor for voltage division. One to two movable metal contacts are pressed tightly on the bare resistor body. The position of the contact determines the resistance between either end of the resistor and the contact. According to the material, it is divided into wire winding, carbon film, solid core type potentiometer; according to the relationship between output and input voltage ratio and rotation angle, it is divided into linear type potentiometer (linear relationship) and function potentiometer (curve relationship). The main parameters are resistance, tolerance and rated power. Widely used in electronic equipment, used for volume control in audio and receiver.
classification:
The key parts that make up the potentiometer are the resistor and the brush. Potentiometers can be divided into several types according to the structure between them and whether they have switches.
Potentiometers can also be classified according to the material of the resistor body, such as wire winding, synthetic carbon film, metal glass glaze, organic solid core and conductive plastic. The electrical properties mainly depend on the materials used. In addition, there are potentiometers made of metal foil, metal film and metal oxide film, which have special purposes. Potentiometers are distinguished according to the characteristics of use, including general-purpose, high-precision, high-resolution, high-resistance, high-temperature, high-frequency, high-power and other potentiometers; according to the resistance adjustment method, there are adjustable, semi-adjustable and fine-tuning types , The latter two are also called semi-fixed potentiometers. In order to overcome the adverse effect of the moving contact of the brush on the resistor body on the performance and life of the potentiometer, there are non-contact non-contact potentiometers, such as photosensitive and magnetosensitive potentiometers, etc., which are used for a small number of special applications.
1. Wirewound potentiometer: it has the advantages of high precision, good stability, small temperature coefficient, reliable contact, etc., and it is resistant to high temperature and strong power load capacity. The disadvantage is that the resistance range is not wide enough, the high frequency performance is poor, the resolution is not high, and the high resistance wire wound potentiometer is easy to break, the volume is large, and the price is high. This potentiometer is widely used in electronic instruments and meters. The resistance body of the wire wound potentiometer is composed of a resistance wire wound on an insulation. There are many types of resistance wire. The material of the resistance wire is selected according to the structure of the potentiometer, the space for accommodating the resistance wire, the resistance value and the temperature coefficient. The thinner the resistance wire, the greater the resistance value and resolution in a given space. But the resistance wire is too thin, it is easy to disconnect during use, which affects the life of the sensor.
2. Synthetic carbon film potentiometer: It has the characteristics of wide resistance range, better resolution, simple process and low price, but it has large dynamic noise and poor moisture resistance. This type of potentiometer should be used as a functional potentiometer, which is widely used in consumer electronics. The printing process can automate the production of carbon membranes.
3. Organic solid core potentiometer: wide resistance range, high resolution, good heat resistance, strong overload capacity, good wear resistance, high reliability, but poor resistance to hot heat and dynamic noise. This type of potentiometer is generally made into a small semi-fixed form, which is used for micro-transfer in the circuit.
4. Metal glass glaze potentiometer not only has the advantages of organic solid core potentiometer, but also has a small temperature coefficient of resistance (similar to wire-wound potentiometer), but it has a large dynamic contact resistance and a large equivalent noise resistance, so it is mostly used for Semi-fixed resistance adjustment. This type of potentiometer has developed rapidly, and its ability to withstand temperature, humidity, and load shock has been improved, and it can work reliably under harsh environmental conditions.
5. Conductive plastic potentiometer: wide resistance range, high linear accuracy, strong resolution, and particularly long wear life. Although its temperature coefficient and contact resistance are large, it can still be used to automatically control the analog and servo systems in the instrument.
6. Digital potentiometer: Potentiometer made by integrated circuit technology; integrate a series of resistors into a chip, use MOS tube to control the resistance in series
The network is connected to the public terminal; the control accuracy is determined by the number of bits controlled, generally 8 bits, 10 bits, 12 bits, etc.; it can be used in analog circuits for impedance matching, amplification circuit amplification control, etc.; jitter adjustment is avoided Troublesome operation; provides a convenient way for automatic gain, voltage change, impedance matching, etc
Resistance value change scale classification
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 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 applications; in addition, there is a C-type potentiometer whose logarithmic scale changes in the opposite direction.
According to the material classification 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. Solid potentiometers are divided into organic synthetic solid potentiometers, inorganic synthetic solid potentiometers and conductive plastic potentiometers. Membrane potentiometers are divided into carbon membrane potentiometers and metal membrane potentiometers.
Classification by adjustment
Potentiometers can be divided into rotary potentiometers, push-pull potentiometers, straight slide potentiometers, etc. according to the adjustment method.
According to the change rule of resistance value
Potentiometers can be divided into linear potentiometers, exponential potentiometers and logarithmic potentiometers according to the change rule of resistance value.
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, potentiometers with switches, lock-type potentiometers, A variety of non-locking potentiometers and patch-type potentiometers.
Classified by driving method
Potentiometers can be divided into manual adjustment potentiometers and electric adjustment potentiometers according to the driving mode.
Other special types
Potentiometer with switch: usually used to combine the volume switch and the power switch, that is, turn it counterclockwise to the bottom to cut off the switch and turn off the power.
ipa:
The main function of the potentiometer in the circuit has the following aspects
1. Used as a voltage divider
The potentiometer is a continuously adjustable resistor. When the rotary or sliding handle of the potentiometer is adjusted, the moving contact slides on the resistor body. At this time, at the output of the potentiometer, an output voltage that has a certain relationship with the applied voltage of the potentiometer and the angle or stroke of the movable arm can be obtained.
2. Used as a rheostat
When the potentiometer is used as a varistor, it should be connected to both ends of the device, so that within the travel range of the potentiometer, a smooth and continuously changing resistance value can be obtained.
3. Used as a current controller
When the potentiometer is used as a current controller, one of the selected current output terminals must be the sliding contact terminal.
Awọn iṣọra:
1. The resistors of potentiometers are mostly made of carbonic acid synthetic resins. Avoid contact with the following items: ammonia, other amines, alkaline aqueous solutions, aromatic hydrocarbons, ketones, lipid hydrocarbons, Strong chemicals (acid value is too high), etc., otherwise it will affect its performance.
2. When welding the terminals of the potentiometer, avoid the use of water-compatible flux, otherwise it will promote metal oxidation and material mold; avoid the use of inferior flux, poor soldering may cause difficulty in soldering, resulting in poor contact or open circuit.
3. If the welding temperature of the terminal of the potentiometer is too high or the time is too long, it may cause damage to the potentiometer. Pin-type terminals should be soldered at 235°C±5°C within 3 seconds. Soldering should be more than 1.5MM away from the potentiometer body. Do not use solder to flow through the circuit board during soldering; solder wire-type terminals should be soldered at 350°C± 10 ℃, completed within 3 seconds. And the terminal should avoid heavy pressure, otherwise it is easy to cause poor contact.
4. During soldering, the height of the rosin (flux) entering the printing machine board is adjusted properly, and the flux should be avoided from entering the potentiometer, otherwise it will cause poor contact between the brush and the resistor, resulting in INT and poor noise.
5. The potentiometer is best applied to the voltage adjustment structure, and the wiring method should choose the "1" pin to ground; the current adjustment structure should be avoided, because the contact resistance between the resistor and the contact piece is not conducive to the passage of large currents.
6. Avoid condensation or water droplets on the surface of the potentiometer, and avoid using it in a humid place to prevent insulation degradation or short circuit.
7. When installing the "rotary" potentiometer when fixing the nut, the strength should not be too tight to avoid damage to the teeth or poor rotation; when installing the "iron shell straight slide" potentiometer, avoid using too long screws, otherwise it may hinder sliding The movement of the handle even directly damages the potentiometer itself.
8. In the process of putting the potentiometer on the knob, the pushing force used should not be too large (it cannot exceed the parameter index of the pushing and pulling force of the shaft in the "Specifications"), otherwise it may cause damage to the potentiometer.
9. The potentiometer's rotary operating force (rotation or sliding) will become lighter as the temperature increases, and tighten as the temperature decreases. If the potentiometer is used in a low-temperature environment, it needs to be explained in order to use special low-temperature grease.
10 The design of the potentiometer shaft or slider should be as short as possible. The shorter the shaft or slider length, the better the feel and stability. Conversely, the longer the shaking, the greater the change in feel.
11 The power of the carbon film of the potentiometer can withstand the surrounding temperature of 70 ℃, when the use temperature is higher than 70 ℃, it may lose its function.
O ga:
The resolution of the potentiometer is also called resolution. For the wire wound potentiometer, the output voltage changes discontinuously every time the moving contact moves one turn. The ratio of this change to the output voltage is the resolution. The theoretical resolution of a linear wirewound potentiometer is the reciprocal of the total number of winding turns N, and is expressed as a percentage. The more the total number of turns of the potentiometer, the higher the resolution.
Test and judgment:
The main requirements for the potentiometer are: ① The resistance value meets the requirements. ② The contact between the center sliding end and the resistor is good, and the rotation is smooth. For the potentiometer with switch, the switch part should act accurately, reliably and flexibly. Therefore, the performance of the potentiometer must be checked before use.
1) Resistance measurement: First, according to the resistance value of the potentiometer to be measured, select the appropriate resistance range of the multimeter, measure the resistance value, that is, the resistance value between the two ends of the AC, and compare it with the nominal resistance value. See if they are consistent. At the same time rotate the sliding contact, its value should be fixed. If the resistance is infinite, the potentiometer is damaged.
2) Then measure the contact between the center end and the resistor, that is, the resistance between the two ends of BC. The method is that the multimeter's ohm level is in the appropriate range. During the measurement process, slowly rotate the rotating shaft, pay attention to observe the multimeter's reading, under normal circumstances, the reading changes steadily in one direction, if there are jumps, drops or failures, it means that the movable contact has Failure of poor contact.
3) When the center end slides to the head end or end, the resistance value of the center end and the coincidence end is 0 under ideal conditions. In the actual measurement, there will be a certain residual value (generally depending on the nominal, generally less than 5Ω). normal phenomenon.
Potentiometer application:
Potentiometers are widely used and will be used in many products. Blue and white fine adjustments are used in power products such as switching power supplies, UPS power supplies, high-frequency switching power supplies, inverse frequency power supplies, chargers, and inverters. Potentiometers, precision potentiometers; on home appliances, such as induction cookers, humidifiers, air conditioners, range hoods, lighting, electric fans, and other small appliances control boards; on communications products, such as: walkie-talkies, cable TV equipment, tuning Platform, window intercom, etc. will use patch adjustable potentiometer, iron potentiometer and so on.
Precision potentiometers come in many forms and have different structures.
1. Resistor
The resistor body is a resistance component that provides a certain resistance value in the potentiometer, and its electrical properties determine the main electrical properties of the potentiometer. The resistor body should have good resistance stability, small temperature coefficient of resistance and static noise. In order to improve reliability, it should also have the properties of moisture resistance, heat resistance, wear resistance, oxidation resistance, high load resistance and resistance to sudden changes in heat and cold.
The resistive body of the contact potentiometer, the moving contact contacts and slides on it, so the surface of the resistor has a low resistivity, which makes the contact resistance with the moving contact small; at the same time, the surface resistivity should be evenly distributed to maintain the The change of contact resistance and track resistance within the effective electric stroke is small, and the ideal resistance law characteristics can be obtained. The surface of the resistor body should have proper smoothness, hardness and certain wear resistance to ensure its mechanical durability. For the wire-wound potentiometer, the resistance wire is wound on the skeleton to make a circular or spiral-shaped resistor. For the thin-film or thick-film potentiometer, the resistance film is formed on the male substrate, and the shape is mostly horseshoe-shaped and arc-shaped. Or long. For the synthetic solid core potentiometer, a horseshoe-shaped or strip-shaped resistance rail is molded on the base.
2. Skeleton and matrix
The skeleton is an insulating support of a wire-wound potentiometer resistor. The substrate (or substrate) is the support for the non-wire wound potentiometer resistor.
The skeleton and substrate are usually made of materials with good insulation properties, which require heat resistance, moisture resistance, good electrical insulation, good chemical stability and thermal conductivity, and only a certain mechanical strength. Generally, there are laminated paper, laminated cloth, plastic, ceramic, glass, and copper, aluminum, and aluminum alloys whose surfaces have been subjected to insulation treatment. Such metal substrates whose surfaces have been subjected to insulation treatment should have sufficient surface insulation This skeleton matrix has good heat dissipation and is easy to form.
Awọn ẹya ara ẹrọ:
Precision potentiometer, also called precision adjustable potentiometer, is a variable resistor that can adjust its own resistance with high precision. There are forms with pointers and without pointers, and the number of adjustments is 5 and 10. In addition to the same characteristics of wire-wound potentiometers, the potentiometer also has excellent linearity, fine adjustment and other advantages, and can be widely used in the occasion of precise adjustment of resistance. The main parameters are resistance, tolerance, and rated power. Widely used in electronic equipment, used for volume control in audio and receiver.
