Thermal-ribbon sensors a cost-effective option for fluid measurement, study shows

Process control and energy management systems require the accurate temperature sensing of liquids flowing in pipes. Typically, probe-style sensors and thermowells are immersed into the fluid stream to capture the temperature. But there’s another solution, according to Minco — a more cost-effective and easier-to-install solution. 

The manufacturer published a study, “Sensing Fluid Temperature with Thermal-Ribbons”, that shows how thermal-ribbon flexible RTDs make an economical alternative to thermowells, offering surface-mounted simplicity with no loss of accuracy. 

Thermal-ribbons are thin, flexible resistance thermometers that contain flat wire-wound elements laminated between layers of electrical insulation. This design improves thermal response in three ways: 

• Flexible sensors conform tightly to sensed surfaces, leaving no air gaps to block heat transfer. 
• Thin electrical insulation reduces the thermal gradient between the sensing element and sensed surface. Response is rapid and self-heating is negligible. 
• The element winding senses over an area to reduce point measurement errors. 

The study demonstrates how these benefits apply to fluid measurement. 

The question that most readers will have, though, is whether thermal-ribbon performance is truly comparable to immersed sensors. The study addresses this by providing test data that compares a thermal-ribbon against a thermowell installation. 

Two conclusions came out of the study. First, the authors learned that a thermal-ribbon reacts to temperature changes more quickly than a probe inside a brass thermowell. Second, after the system reaches steady state, all three sensors tested gave identical readings, proving that the surface mounted thermal-ribbon is effectively sensing true liquid temperature. 

These conclusions were verified by an independent manufacturer of energy management systems, who conducted a side-by-side comparison in a working installation. 

Minco’s Flexible Thermal-Ribbon Sensors, which mount on the pipe surface, are available from Mod-Tronic Instruments. Contact Mod-Tronic for more information. 

• Tweet