RTDs vs. Thermocouples: What You Need to Know When Validating Biopharmaceutical Processes

RTDs are highly accurate, usually within ±0.05 to ±0.1 °C, ideal for precise measurements under 500 °C. In contrast, thermocouples have a wider temperature range, up to 1400-1800 °C, but with a slightly lower accuracy of ±0.2 to ±0.5 °C, suitable for processes that need broader temperature coverage.

RTDs respond quickly to temperature changes, offering fast reaction times. They also maintain stable readings over longer periods due to low drift-over-time.

Thermocouples, on the other hand, are highly sensitive at their point of contact and may take longer to reach thermal equilibrium. Regular calibration is necessary due to their higher relative drift, which is caused by factors like heat, chemicals, and mechanical stress.

Thermocouples provide precise measurements at the exact welding spot of the metals, whereas RTDs calculate averages along the surface of the platinum (PT) element. Larger RTD elements can therefore face challenges with this method, as their surface areas are larger. However, smaller RTD sensors, like the PT1000 elements found in Ellab’s data loggers, overcome this concern.

In terms of cost, thermocouples are generally more economical, with prices ranging from half to one-third of that of RTDs. However, it is important to note that thermocouples require frequent adjustments and calibration, and incur additional long-term costs.

RTDs, despite being more expensive initially, provide excellent stability and require fewer maintenance activities. An Ellab study found that working with RTDs and data loggers is far cheaper over a longer period, as they require fewer calibrations, repairs, and replacements, and are faster to set up.

Selecting the right temperature sensor depends on different factors. If accuracy, stability, and repeatability are critical for your application, RTDs are likely the preferred choice. However, if you have processes that require a wider temperature range, faster response times, and the ability to measure specific points — thermocouples are probably your best bet.

To fully explore the differences between RTDs and thermocouples and make an informed decision, we invite you to download our free white paper.