A Pt100 is a Platinum RTD (Resistance Temperature Detector) with a resistance of 100 ohms at 0°C which changes with temperature. They are suitable for applications in the temperature range of -200°C to 600°C but are more commonly used in the range -50°C to +250°C, for instance water cooling, oil cooling, refrigeration, food processes and at ambient. These temperature sensors are reliable and can offer a higher degree of accuracy.
Thermocouples are made with two dissimilar metals or conductors where a temperature difference between the hot and cold junctions (join) of the thermocouple generates a small voltage signal which changes with temperature. They are best suited to elevated temperatures (up to 1700°C) or very low temperatures (down to -200°C) and are also ideal where there is any vibration (where a Pt100 is more likely break).   If you need a fast response temperature sensor we recommend the use of thermocouples. If the measured temperature is around ambient a Pt100 or Pt1000 will give a more reliable reading.
Process Parameters are experts in industrial temperature sensors including Pt100s and thermocouples. We offer free advice on the best choice of probe for your application and can make them to your exact specifications. Let us help you decide whether to use a Pt100 or Thermocouple.