RTD vs Thermocouple
Published by Hoyt Meter on 5th Jan 2018
RTD vs Thermocouple: What is the Best Choice for an Analog Panel Meter?
Temperature reigns as the most often measured process parameter in industry. While temperature measurement utilizes sensors of many forms, the actual measurement of temperature is accomplished via only five basic sensor types:
- Thermocouple (T/C)
- Resistance Temperature Detector (RTD)
- Thermistor
- Infrared Detector and via
- Semiconductor or integrated circuit (IC) temperature sensors
Of these five common types, the thermistor is perhaps the most commonly applied for general purpose applications. Semiconductor sensors dominate most printed circuit board or board level sensing applications. Infrared is used for non-contact line-of-sight measurement. But for industrial applications that typically employ remote sensing, thermocouples and RTD’s reign as the most popular sensor types.
Hoyt Analog Panel Meters 250 Series are used in measuring the temperature of exhaust gases (EGT) on diesel engines (boats, semi-trucks and industrial equipment).
For Thermocouples, our 250 Series accepts Type K and Type J.
Most industrial applications require that a temperature be measured remotely, and that this signal be transmitted some distance. An industrial transmitter or transducer like the Hoyt Electric M100 series is commonly used to amplify, isolate, and convert the low-level sensor signal to a high level signal suitable for monitoring or retransmission.
With respect to these transmitters, your choice of sensor type is generally limited to T/C, or RTD. But given the wide variety of RTD and T/C types, how do you choose the best sensor type for your specific application?
Conclusion: What is best solution for the application?
- In general, if your application requires the highest accuracy, cost is not a concern, and your operating ambient is less than 800°C, then the choice of an RTD over a thermocouple sensor is probably the right one. The RTD is more accurate, more stable, more repeatable, and offers a more robust output signal with better sensitivity and linearity than a thermocouple. However, the RTD does have a narrower operating range with a lower maximum operating temperature, it is generally more expensive, and it does require excitation which might drive the need for an external power source.
- If you instead decide that a thermocouple is best for your application, perhaps because of its lower cost, wider temperature range, faster response time, and simpler construction, plus its many physical sizes and wider range of configurations available, then you might start by picking a Type K thermocouple until you can find a specific reason to choose another type. That is, type K is the most common and least expensive of available T/C types, and it also has a wide operating temperature range with high sensitivity. It is constructed from nickel-based metals which have good resistance to corrosion and are cheaper than the comparable platinum-based metals.
Whatever your choice may be, Hoyt has metering for your application. Hoyt has been building Analog meters for Exhaust Gas Temperature (EGT) since the 1950’s as well as Pyrometers for Kiln manufacturers. Need lower temp measurement? Hoyt can do those too! Hoyt carries a complete line of Analog and Digital meters and controllers to fit your application and has the expertise to explain what might work better for your products
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