RTD advantages:
- RTDs are commonly used in applications where repeatability and accuracy are important considerations.
- Properly constructed Platinum RTD’s have very repeatable resistance vs temperature characteristics over time. If a process will be run at a specific temperature, the specific resistance of the RTD at that temperature can be determined in the laboratory and it will not vary significantly over time.
- RTDs also allow for easier interchangeability since their original variation is much lower than that of thermocouples.
- RTDs also can be used with standard instrumentation cable for connection to display or control equipment, where thermocouples must have matching thermocouple wire to obtain an accurate measurement.
- RTDs are popular because of their excellent stability, and exhibit the most linear signal with respect to temperature of any electronic temperature sensor.
RTD disadvantages:
- RTDs are characterized by a slow response time,
- RTDs are characterized by a low sensitivity,
- Because they require current excitation, they can be prone to self-heating.
- RTDs are more expensive than thermocouples,
- RTD’s do not do as well as thermocouples in high vibration and mechanical shock environments due to the construction of the sensing element.
- RTD’s are also limited in temperature to approximately 850 ºC.
In the same configuration, you can expect to pay from 4 to 10 times more for an RTD than for a base metal thermocouple because there is more construction required to make the RTD including manufacture of the sensing element, the hooking up of extension wires and assembly of the sensor.