There are several factors to consider when choosing a temperature sensor.
A Resistance Temperature Detector (RTD) is typically a metal coil wrapped around a ceramic or glass core. The RTD sensor measures the electrical resistance of the metal as the temperature increases. This resistance provides an extremely accurate and repeatable measurement. An RTD sensor offers long-term stability with minimal shift in measurement as the sensor ages. An RTD sensor is immune to electrically noisy environments making it ideal for process control and industrial automation environments.
Thermocouples consist of two dissimilar metal conductors joined together to form a junction. The temperature gradient across the length of the conductors produces a a slight potential difference (the Seebeck Effect) that can be measured to determine temperature. The junction produces a small voltage that is proportional to the temperature increase or decrease. Thermocouples can measure much higher temperature ranges with a slight trade-off in accuracy. Thermocouples are generally less expensive, but choosing the proper type can be difficult due to the different metal combinations available. Thermocouples are ideal for applications where higher temperature sensing is required over accuracy.
After you have selected your temperature sensor, check out Sealevel SeaRAQ I/O modules, which plug into our Relio industrial computers. SeaRAQ modules are available for both RTD and Thermocouple sensors as well as other real world I/O interfaces.