Measuring temperature with electronic sensing devices is advantageous as even the smallest change in degree can be detected. In this article, two different temperature sensor types, contact and non-contact, are compared, discussing the differences in their working principle and the advantages of each temperature sensor.
Types of Temperature Probes
Contact temperature sensors rely on physical contact with an object and use conduction to monitor temperature changes. On the other hand, non-contact sensors do not require physical contact and detect temperature changes based on optical analysis of infrared radiation.
Contact Temperature Sensors
There are a few types of contact temperature sensors, including thermocouples, thermistors, and resistance temperature detectors. In a thermocouple, a voltage difference is created by the temperature difference between two dissimilar wires., and temperature is calculated when the thermocouple sensor measures the voltage difference.
Thermistors are typically made from ceramic or polymers and differ from thermocouples by measuring a resistance change. A common type of this type of contact temperature probe is the negative temperature coefficient thermistor, where the resistance decreases as the temperature increases. Resistance temperature detectors are similar to thermistors and are often made of platinum.
Non-Contact Temperature Sensors
Non-contact temperature sensors include optical pyrometers, radiation thermometers, thermal imagers, and fiber optic sensors.
Radiation thermometers measure the radiation emitted from an object to gauge temperature differences. Thermal imagers are similar to radiation thermometers. However, they can calculate a two-dimensional space rather than measuring temperature based on a given point on the surface of an object.
Fiber-optic temperature sensors are variants of radiation thermometers. Radiation is sensed by an active sensing device, and the system processes and converts it into a temperature readout.
Optical pyrometers have an optical system and a detector, measuring temperatures that are too bright to see with the naked eye. The optical system focuses the radiation onto the detector, providing the temperature measurement.