The principles and characteristics of temperature sensors—explained by the manufacturer of the DS18B20 digital temperature sensor.
Release Date:
2021-12-26
Author:
DS18B20 digital temperature sensor Manufacturers believe that temperature measurement has a wide range of applications: not only does the production process require temperature control, but certain electronic products also need to monitor their own temperatures—for example, computers should track CPU temperature, and motor controllers should keep tabs on the temperature of power‑drive ICs. Below are several commonly used temperature sensors.
Temperature is a parameter that frequently needs to be measured in practical applications. From steel manufacturing to semiconductor production, many processes rely on temperature control. Temperature sensors serve as the bridge between application systems and the real world. This paper provides a brief overview of various types of temperature sensors and discusses their interfaces with circuit systems.
DS18B20 digital temperature sensor Manufacturers recognize that there are many types of temperature-sensing devices, and thermistors are one of them. Many thermistors exhibit a negative temperature coefficient (NTC), meaning their resistance increases as temperature decreases. Among all passive temperature sensors, thermistors offer relatively high sensitivity—i.e., a significant change in resistance for each degree of temperature variation—though their resistance–temperature relationship is nonlinear.
DS18B20 digital temperature sensor Manufacturers typically specify a tolerance range for thermistors to indicate consistency across samples. Depending on the materials used, this tolerance is usually in the range of… Between 1% and 10%. Some thermistors are interchangeable in applications where magnetic field adjustment is not feasible, such as in instrumentation. Users or field engineers can only replace the thermistor but cannot perform calibration. These thermistors are significantly more accurate and considerably more expensive than standard thermistors.
Since a thermistor is a resistor, it generates heat when current flows through it. Therefore, circuit designers should ensure that the pull-up resistor is sufficiently large to prevent the thermistor from overheating; otherwise, the system will measure the heat emitted by the thermistor rather than the ambient temperature.
The effect of the energy dissipated by a thermistor on its temperature is expressed as the dissipation constant, which is the power in milliwatts required to raise the thermistor’s temperature by 1°C above the ambient temperature. The dissipation constant varies with the thermistor’s package type, lead dimensions, packaging materials, and other factors.
DS18B20 digital temperature sensor The manufacturer believes that once the thermistor’s input calibration is complete, the relationship between actual resistance and temperature can be displayed graphically. Because thermistors are nonlinear, a graphical representation is necessary. The system must know the ADC value corresponding to each temperature. The resolution of the plot—whether it increments by 1 or by 5—depends on the specific application.
Manufacturers of the DS18B20 digital temperature sensor recommend that, when using a thermistor to measure temperature, the input circuit should be carefully selected to ensure compatibility with the required accuracy. In some applications, resistors with 1% tolerance are sufficient, while others may demand components with 0.1% tolerance. In all cases, tables should be used to quantify how the cumulative errors of all components—including resistors, the reference voltage, and the thermistor itself—affect the overall measurement accuracy.
Previous Page: Some key points about digital temperature sensors—here’s what the manufacturer of the DS18B20 digital temperature sensor has to share.
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