Temperature Sensor

A temperature sensor plays an important role in many applications.  For example, maintaining a specific temperature is essential for equipment used to fabricate medical drugs, heat liquids, or clean other equipment.  For applications like these, the responsiveness and accuracy of the detection circuit can be critical for quality control. Temperature sensing is one of the most sensitive properties or parameters for industries like petrol chemical, automotive, aerospace, and defense, consumer electronics, etc. These sensors are installed with the purpose of measuring the temperature of a medium accurately and efficiently in a given set of requirements.

 There are three commonly used temperature sensor types:

1. Negative Temperature Coefficient (NTC) thermistor

A thermistor is a thermally sensitive resistor that exhibits a large, predictable, and precise change in resistance correlated to variations in temperature. NTC thermistor provides a very high resistant at low temperatures. As temperature increases, the resistance drops quickly.  Because an NTC thermistor experiences such a large change in resistance per °C, small changes in temperature are reflected very fast and with high accuracy (0.05 to 1.5 °C).  Because of its exponential nature, the output of an NTC thermistor requires linearization.  The effective operating range is -50 to 250 °C for gas encapsulated thermistors or 150°C for standard.

2. Resistance Temperature Detector (RTD)

An RTD, also known as a resistance thermometer, measures temperature by correlating the resistance of the RTD element with temperature. An RTD consists of a film or, for greater accuracy, a wire wrapped around a ceramic or glass core.  The most accurate RTDs are made using platinum but lower cost RTDs can be made from nickel or copper. However, nickle and copper are not as stable or repeatable.  Platinum RTDs offer a fairly linear output that is highly accurate (0.1 to 1 °C) across -200 to 600 °C.  While providing the greatest accuracy, RTDs also tend to be the most expensive of temperature sensors.

3. Thermocouple

This temperature sensor type consists of two wires of different metals connected at two points.  The varying voltage between these two points reflects proportional changes in temperature.  Thermocouples are non-linear, requiring conversion when used for temperature control and compensation, typically accomplished using a lookup table. Accuracy is low, from 0.5 to 5 °C.  However, they operate across the widest temperature range, from -200 to 1750 °C.

Designing a robust temperature detection circuit does not have to be expensive.  Nor does a low cost detection circuit have to compromise on responsiveness and accuracy. Dpstar has the expertise and technologies to help you to solve your temperature control requirement and we have been manufacturing temperature sensors for the past 30 years under the brand name Maltec-T.

Do you have questions about temperature sensor types? Send them to:  [email protected]