The choice between a thermocouple and an RTD (Resistance Temperature Detector) as a temperature sensor is not an easy one since none between the two is clearly superior to the other. The application in which the sensor will be used is what will determine which sensor will work best and even this varies between the different brands in the market.
Thermocouples are generally better than RTD’s in a number of characteristics. The first advantage of thermocouples over RTD’s is they are less costly averaging nearly 2-3 times less than RTD’s even when the cheaper installation costs of an RTD are factored in. This can make a huge difference in an industry. Thermocouples are also more durable than RTD’s and give faster readings due to their design which ensures that they react faster to temperature changes. This means that they will perform better than RTD’s in high temperature conditions and also in applications where faster response times are required. Perhaps the biggest selling point for thermocouples is their wide temperature ranges of between -200 0 C to +2300 0 C compared to RTD’s which operate between -200 0 C to around +850 0 C ( Silva, 2015).
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Thermocouples, however, fall short in a number of areas as compared to RTD’s. Their accuracy degrades with time unlike RTD’s which offer long-term accuracy. The readings from an RTD are also repeatable over a number of measurements as compared to a thermocouple meaning their readings are more stable and reliable. Another disadvantage of thermocouples is that they require an extension wire to be put in place unlike RTD’s which do not need an extension wire ( Silva, 2015).
Both thermocouples and RTD’s have their pros and cons with the differences appearing even in individual brands of the sensors and it is upon the user to consider his requirements of the temperature sensor and compare it to the brands of the sensors available to them.
Reference
Silva, C. W. (2015). Sensors and Actuators: Engineering System Instrumentation , Second Edition, CRC Press,
