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Introduction of potentiometer

Author: Tanssion Date: 2023-08-08 Hits: 0

Ⅰ. What is a potentiometer
Ⅱ. Function of potentiometer
Ⅲ. The principle of potentiometer
Ⅳ. The relationship between potentiometer and resistance position
Ⅴ. Measuring the resistance value of the potentiometer
Ⅵ. Linear taper potentiometer and logarithmic potentiometer
Ⅶ. What is the potentiometer kit?
Ⅷ. Application of potentiometer
Ⅸ.Definition of potentiometer
X. How does a potentiometer measure potential difference?

Ⅰ. What is a potentiometer

A potentiometer is a three-terminal resistor with sliding or turning contacts that form an adjustable voltage divider. If only two terminals are used (one end and the wiper), it works as a variable resistor or rheostat. When the brush moves along the resistor body, a resistance value or voltage that has a certain relationship with the displacement is obtained at the output end.

Introduction of potentiometer

The potentiometer can be used as a three-terminal element or as a two-terminal element. The latter can be regarded as a variable resistor. Since its function 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. The potentiometer is mainly composed of a sliding contact point and a resistance element.

The potentiometer is usually connected to a fixed resistance track by a slidable sliding contact point. By adjusting the position of the sliding contact point, the effective resistance value of the potentiometer can be changed. Potentiometers are mainly used in applications such as signal conditioning, voltage division, and volume control in electronic circuits.

Potentiometers are often used to control electrical devices, such as volume controls on audio equipment. Potentiometers operated by mechanical devices are used as position sensors, for example in joysticks. Potentiometers are rarely used to directly control large amounts of power (beyond watts) because the power dissipated in the potentiometer is comparable to the power in the load being controlled.

Potentiometers, also known as variable resistors or variable resistors for short, are mostly three terminals, including two fixed contacts and a sliding contact, which can change the resistance value between the sliding end and the two fixed ends by sliding. Electronic components are passive components, which can form different voltage division ratios and change the potential of the sliding point when used.

Ⅱ. Function of potentiometer

1. Voltage divider

The potentiometer is a continuously adjustable resistor. When the knob or slider of the potentiometer is adjusted, the movable contact slides on the resistor body. At this time, 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 at the output terminal of the potentiometer.

2. Volume control

In audio equipment, potentiometers are used as volume controls. By adjusting the sliding contact point of the potentiometer, the gain of the amplifier can be changed, thereby adjusting the output volume.

3. Varistor

When the potentiometer is used as a rheostat, it should be connected as a two-terminal device, so that a smooth and continuously changing resistance value can be obtained within the stroke range of the potentiometer.

4. Sensor interface

In the sensor circuit, the potentiometer can be used as an adjustable resistor to adjust the working range of the sensor or calibrate the sensor output signal.

5. Current controller

When the potentiometer is used as a current controller, one of the selected current outputs must be a sliding contact lead-out.

6. Analog signal conditioning

In analog circuits, potentiometers can be used to adjust signal amplitude, frequency response, etc. This is often used in filter circuits, oscillators, and other analog circuits.

7. Equipment debugging

Potentiometers are used to calibrate and adjust circuit parameters during the manufacturing and debugging of electronic equipment to ensure the performance and accuracy of the equipment.

Ⅲ. The principle of potentiometer

The working principle of a potentiometer is based on its internal resistive track and sliding contact point. It allows the adjustment of voltage, current and signal by changing the resistance value in the circuit by adjusting the position of the sliding contact point.

The resistive track of a potentiometer is a long, thin resistive element, usually made of a conductive material. This resistance track can be linear, that is, the resistance changes uniformly on the track, or nonlinear, that is, the resistance changes according to a nonlinear curve as the position of the track changes.

A sliding contact is a movable connection, usually a slider or knob. This sliding contact can slide on the resistive track, moving from one end point to the other. The position of the sliding contact on the resistance track determines the resistance value of the potentiometer.

The two terminals of the potentiometer are connected to two different parts of the circuit, often referred to as fixed terminals (terminals 1 and 2). The sliding contact connects to the third part of the circuit, usually called the output (terminal 3). In the case of connections, the sliding contact point can change its position by sliding on the resistive track.

When the sliding contact slides from one end point to the other, the resistance value in the circuit changes accordingly. If the resistance track is linear, the change in resistance will be uniform. If the resistance track is non-linear, the change in resistance will be adjusted according to the non-linear curve.

A change in the resistance value of a potentiometer affects the current and voltage distribution in the circuit. By connecting potentiometers to different circuit parts, functions such as current shunting, voltage dividing, and signal conditioning can be realized.

Introduction of potentiometer

Ⅳ. The relationship between potentiometer and resistance position

The relationship between slider position and drag (called "taper" or "law") is controlled by the manufacturer. In principle, any relationship is possible, but for most purposes a linear or logarithmic (also called "audio taper") potentiometer will suffice.

Letter codes can be used to identify which taper to use, but letter code definitions are not standardized. Potentiometers in Asia are usually marked with an "A" for a logarithmic taper and a "B" for a linear taper. "C" stands for the rare reverse log taper. Others, especially those from Europe, can have an "A" for a linear taper, a "C" or "B" for a log taper, or an "F" for a log taper.

The codes used also vary between different manufacturers. When the percentage is based on the nonlinear taper, it is related to the resistance value at the midpoint of the shaft rotation. So a 10% log taper will measure 10% of the total resistance at the midpoint of rotation; that is, a 10% log taper on a 10 kOhm potentiometer will produce 1 kOhm at the midpoint. The higher the percentage, the steeper the logarithmic curve.

The bit device can be used to implement voltage division, that is, divide the input voltage into output voltages of different proportions. By moving the sliding terminal, the resistance position in the potentiometer can be changed, thereby changing the output voltage. When the slider is close to a port, the voltage of that port will have a larger proportion.

Ⅴ. Measuring the resistance value of the potentiometer

1. Oscilloscope method: If you have an oscilloscope and a frequency source, you can use the potentiometer to form a simple RC filter, and then measure the phase difference of the output signal. By measuring the phase difference and frequency, the resistance value of the potentiometer can be calculated.

2. Bridge measurement method: This method requires the use of a resistance bridge or Wheatstone bridge. By adjusting the balance of the bridge, the ratio between the unknown resistance (i.e. the potentiometer resistance) and the known resistance can be measured. This method is suitable for precise measurements, but requires more equipment and operations.

3. Multimeter measurement method: This is one of the most common methods. Use a digital multipurpose tester (multimeter) to measure the resistance of the potentiometer. The following are the specific steps:

Set the multimeter to resistance measurement mode (usually Ω or R).

Disconnect the potentiometer from the circuit and make sure no current flows through it.

Connect the two probes of the multimeter between the two ports of the potentiometer.

Read the resistance value displayed on the multimeter.

Ⅵ. Linear taper potentiometer and logarithmic potentiometer

1. Linear taper potentiometer:

A linear taper potentiometer is a special type of potentiometer whose resistance value varies linearly with the position of the slider. Different from ordinary linear potentiometers, linear taper potentiometers show a tapered resistance change curve when the position of the sliding terminal changes.

The Linear Taper Potentiometer works similar to other potentiometers, it still has a wiper terminal and a resistive element. However, the resistive element is designed such that the resistance value tapers with the position of the slider to achieve a linear response curve.

A linear taper potentiometer has a resistive element of constant cross-section, yielding a device in which the resistance between the contact (wiper) and a terminal terminal is proportional to the distance between them. Linear taper potentiometers are used when the divider ratio of the potentiometer must be proportional to the angle of rotation of the shaft (or the position of the slider), for example, to adjust the centering of the display on an analog cathode ray oscilloscope. Precision potentiometers have a precise relationship between resistance and slider position.

2. Logarithmic potentiometer:

Logarithmic potentiometer, also known as logarithmic potentiometer, audio potentiometer or volume potentiometer, is a potentiometer whose resistance value changes with the position of the sliding terminal according to the logarithmic law. Unlike linear potentiometers, the resistance change of logarithmic potentiometers presents a logarithmic curve, which is suitable for simulating human perception characteristics, especially in fields such as volume control.

Logarithmic taper potentiometers are commonly used for volume or signal level in audio systems. Applications of logarithmic potentiometers are common, especially in audio equipment such as sound systems, amplifiers, and radios. This is because human hearing perception changes according to the logarithmic law, so using a logarithmic potentiometer can make the volume adjustment more in line with the perception of the human ear. Typically, a dB (decibel) scale is marked on a logarithmic potentiometer so that the user understands the relative change in volume.

When the sliding terminal of the logarithmic potentiometer slides up, the speed of changing the resistance value will slow down, so as to achieve smoother volume adjustment. This design provides finer control at lower volume levels, while providing greater range at higher volume levels.

A logarithmic taper potentiometer is a bias potentiometer with a built-in resistive element. Basically, this means that the center position of the potentiometer is not half of the total value of the potentiometer. Resistive elements are designed to follow a logarithmic taper, which is a mathematical exponential or "squared" profile. Logarithmic taper potentiometers consist of a resistive element that "tapers" from one end to the other, or is made of a material whose resistivity varies from one end to the other. This results in a device where the output voltage is a logarithmic function of the slider position.

Most "logarithmic" potentiometers are not exactly logarithmic, but use two regions of differing resistance to approximate the logarithmic law. The two resistance traces overlap at about 50% of the potentiometer rotation; this gives a stepwise logarithmic taper. A logarithmic potentiometer can also be simulated using a linear resistor and an external resistor. True log potentiometers are much more expensive.

Ⅶ. What is the potentiometer kit?

A potentiometer kit generally refers to a set or assembly containing multiple potentiometers. These potentiometers may be of different characteristics, specifications or types and may be used in different electronic, electrical or engineering applications.

The kit includes different types of potentiometers such as linear potentiometers, logarithmic potentiometers, rotary potentiometers, etc. Each type of potentiometer has its own unique advantages in different applications.

Potentiometers with different resistance values are also included in the kit. The resistance value of the potentiometer determines its use range and effect in the circuit, so multiple options can be provided to meet the needs of different circuits.

Some potentiometer kits may also include accessories and connecting wires such as knobs, screws, nuts, labels, etc. These accessories can help users install and use potentiometers more conveniently.

Kits usually come with an instruction booklet or spec sheet that contains details about the various potentiometers such as resistance range, power rating, connections, etc. This information is critical for proper selection and use of potentiometers.

Ⅷ. Application of potentiometer

Potentiometers are rarely used to directly control large amounts of power (more than a watt or so). Instead, they are used to adjust the level of analog signals (for example, volume controls on audio equipment) and as control inputs for electronic circuits. For example, a dimmer uses a potentiometer to control the switching of a TRIAC, which indirectly controls the brightness of the lamp.

Preset potentiometers are widely used throughout electronics and must be adjusted during manufacturing or repair.

User-actuated potentiometers are widely used as user controls and can control a variety of device functions. The widespread use of potentiometers in consumer electronics declined in the 1990s, and rotary incremental encoders, up/down buttons, and other digital controls are now more common. However, they still exist in many applications, such as volume controls and position sensors.

Ⅸ.Definition of potentiometer

A potentiometer is a type of variable resistor. It is usually composed of a resistor body and a rotating or sliding system, that is, a movable contact moves on the resistor body to obtain part of the voltage output.

Structural features of the potentiometer: The resistor body of the potentiometer has two fixed ends. By manually adjusting the shaft or the sliding handle, changing the position of the moving contact on the resistor body changes the distance between the moving contact and any fixed end. Resistance value, thus changing the magnitude of voltage and current.

A potentiometer is an adjustable electronic component. It consists of a resistive body and a turning or sliding system. When a voltage is applied between the two fixed contacts of the resistor body, the position of the contact on the resistor body is changed by rotating or sliding the system, and a position corresponding to the position of the movable contact can be obtained between the movable contact and the fixed contact. into a certain relationship with the voltage.

Variable resistors for voltage division. On the exposed resistor body, one or two movable metal contacts are pressed tightly. The position of the contacts determines the resistance between either end of the resistor body and the contacts. According to the material, it can be divided into wire-wound, carbon film, and solid core potentiometers; according to the relationship between the output and input voltage ratio and the rotation angle, it can be divided into linear potentiometers (linear relationship) and function potentiometers (curvilinear relationship).

Introduction of potentiometer

X. How does a potentiometer measure potential difference?

Potentiometers use the null deflection method to measure potential differences, which means no current is pulled from the cell, whereas voltmeters require a tiny current to demonstrate deflection. As a result, a potentiometer is used to accurately measure p.d.


Frequently Asked Questions

1、What does the accuracy of the potentiometer mean?
The accuracy of a potentiometer is the difference between its actual resistance value and its nominal (rated) resistance value, usually expressed as a percentage or as a fractional value. In electronic engineering and circuit design, the accuracy of potentiometers is important, especially in applications that require precise control and measurement. High-precision potentiometers can ensure the stability, accuracy and reliability of the circuit. Accuracy is often used as a measure of the quality of a potentiometer and is one of the factors to consider when making, selecting, or designing a circuit.
2、How does the potentiometer adjust the resistance value?
A potentiometer adjusts the resistance value by the position of a sliding terminal (also called a sliding contact). Potentiometers usually consist of a fixed resistive element and a movable sliding terminal. The sliding terminal can be moved along the length of the resistive element, thereby changing the equivalent resistance of the potentiometer. When the sliding terminal touches different positions of the resistance element, the contacted part will generate resistance. As the slider approaches one port, it connects to that port of the resistive element and reduces the resistance value to the other port. Therefore, the position of the slider determines the resistance value of the potentiometer.
3、In the circuit, what adjustment is the potentiometer generally used for?
The potentiometer can be used in the circuit as frequency adjustment, power adjustment, volume adjustment, sensor adjustment, brightness adjustment, etc.
4、Is potentiometer used only to compare potential difference?
Potentiometer is a device used to compare potential difference. Since the method involves a condition of no current flow, the device can be used to measure potential difference, internal resistance of a cell and compare emf's of two sources.
5、How is a potentiometer used to compare?
You can use the two-way key to connect one cell at a time in a circuit. Obtain the balancing length for each cell separately by placing the jockey on potentiometer wire such that the ammeter shows zero or null deflection. By taking the ratio of both balancing lengths you can compare emfs of two cells.

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