A brief introduction to the DS18B20 temperature sensor.
Release Date:
2022-01-13
Author:
DS18B20 temperature sensor It is one of the most commonly used temperature-sensing elements in industry. Its advantages include high measurement accuracy, as the thermocouple directly contacts the object being measured without being affected by any intermediate medium; a wide measurement range—standard thermocouples can continuously measure from –50°C to 1600°C, while certain specialized thermocouples can handle temperatures as low as –269°C and as high as 2800°C; and a simple, user-friendly design. Thermocouples typically consist of two dissimilar metal wires, with no restrictions on wire diameter or reference junction type. They are encased in a protective sheath, making them extremely convenient to use.
DS18B20 temperature sensor The basic principle of temperature measurement: Two conductors or semiconductors, A and B, made of different materials are welded together to form a closed circuit. When a temperature difference exists between the two junctions, 1 and 2, of conductors A and B, an electromotive force is generated, resulting in a current—of varying magnitude—flowing through the circuit. This phenomenon is known as the thermoelectric effect. Temperature sensors based on thermocouples operate by exploiting this effect.
Types of the DS18B20 temperature sensor: Commonly used thermocouple temperature sensors can be classified into standard and non-standard types. A standard thermocouple is one for which the national standard specifies the relationship between thermoelectric potential and temperature, the permissible error, and a unified calibration table, and which is available with matching indicating instruments. Non‑standard thermocouples, by contrast, are inferior to standard ones in terms of application scope or measurement range; they typically lack a unified calibration table and are primarily used for measurements in specialized applications.
Structure of the DS18B20 temperature sensor: To ensure the reliable and stable operation of the thermocouple‑based temperature sensor, the following structural requirements must be met: the two thermoelectric electrodes that comprise the thermocouple must be securely welded; the electrodes must be properly insulated to prevent short circuits; the connection between the compensation lead and the free end of the thermocouple must be convenient and dependable; and the protective sheath must fully isolate the thermoelectric electrodes from harmful media.
Because the materials used in the DS18B20 temperature sensor are generally quite expensive—especially when costly metals are employed—and because the distance between the measurement point and the instrument can be considerable, thermocouple compensation wires are typically used to extend the cold junction (free end) of the thermocouple to a control room where the temperature is relatively stable, connecting it to the instrument’s terminals. It should be noted that the compensation wire for the DS18B20 temperature sensor merely serves to extend the thermoelectric leads, relocating the thermocouple’s cold junction to the instrument terminal in the control room. It cannot independently eliminate the influence of cold-junction temperature variations on temperature measurement, nor does it provide any compensation function; therefore, additional correction methods are required to account for the effect of the cold-junction temperature t0 on the measured temperature. Using… DS18B20 temperature sensor When using compensation lead wires, be sure to match the correct model; moreover, the temperature at the connection between the compensation lead wire and the thermocouple’s temperature sensor should not exceed 100°C.
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