Potentiometer

Principle structure

A potentiometer is an instrument constructed using the compensation principle. The characteristic of the compensation method is that it does not draw current from the measuring object, so it does not interfere with the measured value. The measurement result is accurate and reliable. The potentiometer is widely used, and it is equipped with standard battery, standard resistance and other instruments, which can not only meet the accuracy requirements. Very high-caliber measurement of electromotive force, potential difference (voltage), current, resistance and other electrical quantities, and with a variety of transducers, can also be used for temperature, displacement and other non-electrical measurement and control. When no current flows, the potential difference between the positive and negative terminals of the battery is equal to the electromotive force of the battery. If there is a current flowing, there is a certain voltage drop on the internal resistance of the battery (this is the case when the voltage between the two poles of the battery is measured with a voltmeter). At this time, the measured battery is no longer the battery electromotive force, but can only be called the end. Voltage. If the measurement can be made when no current flows, the electromotive force can be directly measured. The compensation method is such a method.

Introduction to the type of potentiometer

Traditional potentiometer

The potential difference is divided into a DC potentiometer and an AC potentiometer. The DC potentiometer is used to measure the DC voltage. When using, adjust the standard voltage to achieve the compensation of two voltages. The AC potentiometer is used to measure the sinusoidal AC voltage from the power frequency to the audio frequency. When the sinusoidal AC voltages of the same frequency are equal, the amplitude and phase are required to be equal, so the circuit of the AC potentiometer is more complicated and has at least two adjustable quantities.

Alternating potential

The differential meter has only products for power frequency in the market, and the AC potentiometers of other frequencies need to be designed and manufactured by themselves. With the continuous development and improvement of the theory and technology of DC current comparators, a highly accurate DC current comparison ritual potentiometer has appeared, and its measurement error is about one millionth.

When the ammeter is calibrated with a potentiometer, it is converted to a standard current by measuring the voltage on the standard resistor with a potentiometer, and then the current meter points are corrected. Estimate the error of the meter calibration device and determine whether it is less than 1/3 of the basic error limit of the meter, and then conclude that the calibration device is reasonable. The estimation only requires consideration of the basic error limit of the potentiometer and the error of the standard resistance, which can be determined by the following formula:

Obviously, the error of the meter calibration device should also include other factors such as standard electromotive force uncertainty, operating current fluctuation, and poor insulation between wires. However, considering these factors is too complicated for teaching experiments. The uncertainty of the measured voltage of the potential difference meter is estimated by the above formula (5.8.1); the uncertainty of the standard resistance of the stage (this experiment) can be simplified by the following formula

Digital potentiometer

Digital potentiometer / electronic potentiometer Model: tx-YJ108B/1

TX-YJ108B/1 digital potentiometer is a new generation of traditional DC potentiometer. It adopts advanced digital and intelligent technology combined with traditional technology to completely cover the original potentiometer UJ33a and UJ33a in use function. 1 product, can accurately detect millivolt signals output from thermocouples and sensors, transmitters, etc., and can also be used as a standard millivolt signal source to directly verify a variety of transmitters and meters.

Features

Digital direct reading (output) and measurement (input) voltage values;

The output standard voltage signal can be loaded with loads to directly verify various low impedance instruments;

Four-terminal button mode to eliminate measurement of wire error when outputting small signals

A millivolt value corresponding to a common temperature range of a plurality of thermocouple index numbers may occur, and the temperature is directly read and displayed;

A precision reference source is included to remove standard batteries to avoid environmental pollution, while eliminating the need for repeated standards and facilitating user operations;

With RS232 standard interface, it can communicate with computer;

Dimensions: 88 × 215 × 285mm.