RTD stands for Resistance Temperature Detector and is a form of temperature measurement using resistance. An RTD contains a (platinum) resistor that changes its resistance value as the temperature changes. After calculating the resistance, one can determine the temperature.
RTD sensors are devided in three categories; thin films, ceramic wire wounds and SMD sensors.
High temperature capability, excellent chemical resistance, biological inertness and long-term electrical stability make platinum a natural choice as the base material for temperature measurement resistance elements.
Due to the special properties of platinum, Pt measurement resistors with 100, 200, 500 and 1,000 ohm provide a range of advantages compared to competing sensors such as semiconductor sensors (KTY®) or thermistors (NTC). Such as;
Pt temperature sensors in thin-film technology can also be described as a two-dimensional, microscopic variation of the traditional wire wound type. The wire length and diameter are replaced by a very fine meander structure on a substrate. The manufacturing process is largely automated and thus incorporates the latest technologies, such as is found, for example, in silicon chip production.
Thin film platinum elements are constructed by placing a sensing layer of platinum on a ceramic substrate, covered with passivation glass layers. This results in excellent shock and vibration resistance and protects the Pt sensor element from environmental influences.
The platinum wire of a ceramic wire wound sensor is wound into a small coil which is inserted into the holes of a high purity alumina tube. The ODs of these high purity alumina tube vary from 0.80 mm to 4.50 mm. Therefor they are even suitable for the thinnest RTD mineral insulated cables.
SMD (surface mounted devices) sensors are specifically designed to fit on PCBs (printed circuit boards) and forms the active measurement element on a PCB. SMD sensors are mainly used for automatic assembly in large-scale applications.
Sensor modules are multi-functionally constructed foundation modules based on platinum thin-film technology. They consist, for example, of sensor/heater combinations and application-specific structured electrodes. Sensitive layers can be applied to the electrodes by the customer. Through the application of metal oxides, for example, multi-sensor platforms become gas sensors with which concentrations of oxygen, carbon monoxide, nitrogen or methane can be detected down to the ppm range. Apart from the typical applications in gas and humidity measurement, analytical techniques in aqueous media, for example for medical technology or biotechnology, are conceivable.
Based on IEC 60751:2008 we can define 4 different classes for resistance temperature detectors. Take a look at mour overview of the different classes in sequence based on accuracy.
This depends mainly on the temperature range and accuracy. Furthermore, it also depends on other variables, such as costs, ruggedness of the application, vibration resistance, etc.
This depends on the following things: Temperature range, Nominal resistance, Dimensions and Costs