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Hello, I am Rose. Welcome back to the new post today. The potentiometer is a type of electromechanical component that can be found in a variety of instruments and electronic devices. A potentiometer is a resistance that can be adjusted and changed, and it is an electronic component that can be modified. This article mainly introduces structure, classification, electrical parameters and model name and type of potentiometer.
The potentiometer is a type of electromechanical component that can be found in a variety of instruments and electronic devices. A potentiometer is a resistance that can be adjusted and changed, and it is an electronic component that can be modified. A resistor body and a revolving or sliding system make up this device. When a voltage is connected between the two fixed contacts of the resistor body, rotating or sliding the system changes the position of the contact on the resistor body, resulting in a moving contact position between the moving contact and the fixed contact. The intensity of a particular relationship.
The role of the potentiometer in the circuit of household appliances and other electronic equipment is to divide the voltage, divide the current, and act as a rheostat. It's usually utilized when the resistance value needs to be modified frequently and the resistance value needs to be stable and trustworthy. The resistance value is mostly used to modify the voltage and current in the circuit. It is frequently utilized in a variety of electronic equipment that requires the operating point and frequency point to be adjusted.
The lead-out terminals of potentiometers are normally three, with two fixed ends. The resistance between the fixed ends is the greatest, representing the potentiometer's nominal value; the other terminal is a moveable terminal. The resistance value between the matching terminals can be varied by altering the position of the moveable and fixed terminals. A common potentiometer's fundamental structure is depicted in the diagram below, which includes a resistor body, a sliding arm, a shaft, a shell, and a soldering piece. The resistance value between AB and BC can be altered by changing the position of the reed linked to the shaft. It has three lead-out ends, with AC having the highest resistance value.
Potentiometers are classified into two types based on their structural design: wire-wound potentiometers and non-wirewound potentiometers:
1. Resistance wires coiled on metal, ceramic, or plastic frames serve as resistance components in wire-wound potentiometers. Low resistance temperature coefficient, good resistance value stability, large power load, and extended operating life are all advantages. The fundamental flaw of the wire-wound resistance element, however, is that the resolution has a step. At the same time, when the frequency rises, the inductance of the multi-turn resistance element rises, resulting in poor high-frequency performance. There are also drawbacks, such as a limited range of total resistance.
2. Synthetic membrane potentiometers, glass glaze potentiometers, conductive plastic potentiometers, and other non-wirewound potentiometers are examples of non-wirewound potentiometers.
1) A synthetic membrane potentiometer is a resistor manufactured by coating a substrate with a mixture of carbon black, graphite, organic binders, fillers, and other materials, then solidifying it using a number of processes (such as screen printing). As a resistor, the film is used. Synthetic carbon film potentiometers may be mass-produced, are inexpensive, have minimal noise during adjustment, have better high-frequency performance, have a small inductance and dispersed capacity, and have a long working life. The value range is quite extensive. Carbon film potentiometers are always first thought of by circuit designers as a cost-effective solution to adjust resistance in electronic circuits. However, the overall resistance value of the synthetic carbon film potentiometer varies substantially with time and temperature, its ability to resist moisture is weak, and the carbon film resistor element's contact resistance is rather high.
2) The glass glaze potentiometer is a mixture of metal (or oxide) powder, glass glaze, and other materials that are screen printed or otherwise applied to a ceramic substrate, with the resistance film generated by drying and high-temperature sintering serving as the Resistor body. It has the following benefits: a wide range of total resistance, high resolution and stability, low noise, and a frequency response that is significantly greater than 100MHz. The temperature coefficient of resistance is low, the resistance element's surface is hard and wear-resistant, and the resistance element's working life is long. Preset potentiometers are increasingly using glass glaze resistance elements.
3) The conductive plastic potentiometer is made up of a mixture of carbon black, graphite, and ultrafine metal powder, DA P resin, and crosslinking agent that is screen printed or otherwise applied to a ceramic or special plastic substrate. As a resistive body, the resistive film is used. The contact resistance fluctuates very little, and the working life is extremely long. The resolution is really great due to the smoothness of the surface. There will be no visible friction and wear even after the moving contact has circulated millions of times on the resistor body. The linearity of the resistance element can be increased to 01001 by modifying it. The dynamic noise is very low, it performs well at high frequencies, and it is suited for high-gain servo systems. Conductive plastic potentiometers, on the other hand, have a lower moisture resistance and are less stable than glass glaze potentiometers. Moving contacts have a low-rated current, and the temperature coefficient is similar across wire-wound and glass glazing potentiometers.
Metal film potentiometers, metal body (foil) potentiometers, organic solid-core potentiometers, and inorganic solid-core potentiometers are also non-wire-wound potentiometers.
Total resistance
It's the resistance between the potentiometer's two terminals (terminal 1, 3) that's measured. You must give the nominal resistance when calibrating any potentiometer. At the same time, the nominal resistance value's permissible deviation should be indicated, and the total resistance value should be within that range.
A digital ohmmeter is commonly used to determine the total resistance value. The movable contact on a potentiometer with a mechanical stop should be as close to a terminal lead as practicable. If the potentiometer is continuously rotating, the movable contact should be adjusted until it is fully separated from the resistance element's working area. The maximum (DC) voltage for measuring the total resistance value is also specified in the standard test to keep the temperature of the resistance body from rising too much during the measurement.
Terminal resistance (zero resistance)
When the moving contact is positioned at the neighboring stop, it is defined as the minimum resistance value achieved between the leading end of the moving contact and the leading end of the terminal. There is no stop on the continually revolving potentiometer, and no terminal resistance is stated.
The voltage applied to the potentiometer should not cause the movable contact current to exceed the limit value defined in the product standard while measuring terminal resistance. When the moving contact is in the stop position, the front terminal resistance is the least resistance between terminals 1, 2, and the rear terminal resistance is the least resistance between terminals 2, 3.
Change in contact resistance
When the moving contact moves at a certain speed, the resistance between the moving contact and the resistor changes. Poor contact between the moving contact and the resistance element causes contact resistance. Surface metal oxides, sulfides, and other materials can form on the contact or resistance element's surface. These films form a contact resistance and operate as an insulating layer.
The contact resistance will change when the current is measured. The material of the component, the material of the moving contact, the state of the contact surface, and the contact pressure between the moving contact and the resistance element all affect contact resistance.
Temperature Coefficient of Resistance
It is defined as the difference in resistance between two temperatures within a specified ambient operating temperature range divided by the temperature difference that caused the change and the total resistance before the change (average temperature coefficient), with 10-6 °C-1 as the unit of measurement. The temperature coefficient of resistance is mostly determined by the resistance element's material and the component's individual structure.
rated power
The greatest power that can be dissipated under specific conditions is defined as. It is the maximum power capable of ensuring the potentiometer's continuous and normal operation between the lowest ambient temperature and the rated ambient temperature. P = I 2R = U 2öR is the rated power. The maximum rated power is the amount of energy that the line designer claims the potentiometer can safely dissipate without causing damage. The maximum permissible dissipation value of the rated power will be affected by the use of each specific potentiometer.
The maximum rated power of most potentiometers pertains to when the potentiometer is utilized as a voltage divider. As a result, when a voltage is provided to the potentiometer's input terminal, the load current through the movable contact is not very big. The power reduction curve, as depicted in the picture, is commonly used by potentiometer makers.
The permissible power dissipation is specified in the figure by the load shedding characteristics generated by the straight line connecting the two points A and B when the ambient temperature is between t1 and tmax. The rated power is the maximum permissible power dissipation at ambient temperature between tmin and t1.
The installation conditions, whether the surrounding environment is still air or forced convection, should be specified in the comprehensive technical specification of the rated power. It is usually the maximum permitted value for a potentiometer to be installed in still air using a standard method. The permissible power dissipation should be reduced when the potentiometer is located near heating elements such as power transistors, transformers, high-power resistors, and so on, or when it is adjacent to another potentiometer.
When the potentiometer is employed as a voltage divider, the rated power mentioned on the product and on the performance data sheet applies. The dissipated power can be considered evenly distributed across the entire resistance element at this point.
Only a portion of the resistance element consumes power when the potentiometer is used as a rheostat or two-terminal connection method, corresponding to a certain adjustment position of the moving contact, and all current flowing through the resistance element flows through the moving contact circuit. Furthermore, the pressure contact point between the moving contact and the resistance element is not always capable of sustaining the same current as the resistance element alone. The voltage divider connection method's rated power is based on the assumption that the moving contact current is minimal. As a result, the maximum permissible value of the moving contact current Im = PöRT for the varistor connection method must be regulated. The maximum power dissipation is P, while the total resistance value is R T. You may ensure that the potentiometer's maximum power is not exceeded by using this maximum current limit value.
The law of resistance change
It is defined as the relationship between the mechanical position of the moving contact and the ratio of the potentiometer output voltage (V 122 or V 223) to the input voltage (V 123). (for a rotary potentiometer, it refers to the angle of rotation).
Straight-line law, logarithmic law, reverse logarithmic law, and super-logarithmic law are the resistance laws of general potentiometers.
Durability
Mechanical durability (wear life):
the number of operating cycles acquired by the potentiometer drive mechanism under defined test conditions while potentiometer performance degradation is kept within the technical requirements' permitted range (the moving contact runs back and forth along the resistance element working path for one week).
Electrical durability refers to the length of time that the potentiometer may continue to function correctly and its performance remains within the permissible range of the technical parameters while the load is applied and the movable contact is not moving. The electrical endurance of the potentiometer is 1 000 hours, according to IEC norms.
Insulation voltage
Under continuous normal working conditions, it is defined as the greatest peak voltage that may be applied between the terminal of the potentiometer and its outside conductor. The measurement should be conducted between the terminals of each connection and the terminals of the other connections when using multiple potentiometers. The insulation voltage value should not be less than 1.42 times the resistor's limit voltage under normal air pressure.
Withstand voltage
It is defined as being added between the lead-out end of the potentiometer and its outer conductor; the multi-connected potentiometer should be between the lead-out end of each connection and the lead-out ends of other connections; the switch-out end of the potentiometer with a switch and the lead-out end of the potentiometer with a switch; the switch-out end of the potentiometer with a switch and the lead-out end of the potentiometer with The AC voltage is supplied for 1 minute between the external conductor and the external conductor (frequency is 40-60Hz), and no damage, sparks, or insulation damage should occur. For measurement, the lead-out ends can be joined together. Typically, the withstand voltage is between 100 and 1000 volts AC. The withstand voltage for certain products is specified in the product specification.
The four elements of the potentiometer model naming, according to the national standard, are:
WNM107 stands for straight sliding precision inorganic solid core potentiometer, WXJ2 for single-turn rotary precision wire-wound potentiometer, and WH122 for synthetic carbon film potentiometer, for example.
Wire wound potentiometer
Constantan wire and nickel-chromium alloy wire are coiled on ring support to make the wire-wound potentiometer. It has high power, high-temperature resistance, strong thermal stability, and low noise, as well as a linear resistance change. Yes, it's commonly used in circuits that regulate high currents. It is not suited for use in high-frequency circuits due to its enormous inductance.
Carbon film potentiometer
The carbon film potentiometer's resistor body is created by vapor-coating a layer of carbon film on an insulating substrate. It is frequently used in domestic electronic goods because of its simple form, good insulation, minimal noise, and inexpensive cost.
Single-turn and multi-turn potentiometers
Ordinary potentiometers and some precision potentiometers are mostly single-turn potentiometers, and multi-turn potentiometers have two structures: one is that the potentiometer's movable contact moves spirally along the spiral winding to adjust the resistance; it is driven by a worm wheel and worm, and the potentiometer's contact brush is mounted on the wheel and makes a circular motion on the resistor body. Multi-turn potentiometers are precision potentiometers with outstanding linearity and delicate adjustment capabilities. They're commonly utilized when resistance needs to be adjusted precisely.
Single and double potentiometers
The single potentiometer has an independent shaft, whereas the coaxial double potentiometer has two potentiometers mounted on the same shaft, reducing the number of electronic components and improving the appearance of electronic equipment.
Organic solid core potentiometer
Resistance powder is created from conductive material, organic filler, and thermosetting resin in the organic solid core potentiometer. On the base, a solid core resistor body is created after hot pressing. It has a simple structure, a small size, a high temperature resistance, and a wide resistance range, as well as excellent dependability. However, it has a low voltage resistance and a high noise level.
Conductive plastic potentiometer
Covering DAP (diethylene propylene phthalate) resistor paste over the insulating body, heating and polymerizing it to produce a resistive film, or thermoplastically pushing DAP resistor powder into the groove of the insulating base make a conductive plastic potentiometer. The core has good smoothness, wear resistance, long life, low noise, high reliability, and chemical corrosion resistance as a resistor. Servo systems in space gadgets, missiles, aircraft radar antennas, and other applications are common.
How do you see the size of the potentiometer?
Potentiometer, B exponential type, resistance value is to see the number after B:
After B is the first two digits of the resistance value of the potentiometer, and the number after the number, add a few 0s, and then read it out,
B103=10 000 ohm=10 K ohm
B502=50 00 ohms=5 K ohms.
F is a half shaft, S is a round shaft, and the number is the shaft length: F20=20mm; F25=25mm
Other alphanumerics are product codes, and this type of product is generally 1/4W.
How to measure the quality of a potentiometer?
1. Nominal resistance measurement of potentiometer
2. Performance measurement: Performance measurement mainly measures whether the center tap contact piece of the potentiometer is in good contact with the resistor body.
What do the pins of the potentiometer represent?
The potentiometer generally has three pins. The potentiometer is a resistor that can adjust the size of the resistance. Its first pin and third pin are the two ends of the resistor. The tripod is the value of the entire resistance.
Catalogue
FPGA / CPLD
Memory
MOS 
MCU 
DSP
OCEP
Secondary 
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