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Inductive sensing challenges IR and thermocouples
A British technology developer has come up with a novel non-contact way to measure temperatures in applications ranging from steel processing to food production. The patent-pending inductive technique has a temperature sensing range of several hundred degrees and an accuracy of 1°C. Its developers, at The Technology Partnership (TTP), near Cambridge, believe that it could replace existing contact-based methods of measuring heat, such as thermocouples, and non-contact technologies, such as infrared.
The technique applies an alternating current to a coil to induce eddy currents in metallic objects. The size of these currents depends the temperature of the material, and therefore provides a new way of making non-contact temperature measurements.
The TTP researchers have developed a special coil arrangement, sensing technique and algorithm to detect and measure the induced eddy currents. They have been able to sense the temperatures of targets in a wide range of challenging environments, including through metal barriers, and in applications where the geometry of the target material is unknown.
“Inductive temperature sensing is ideal for applications where contact methods are not reliable and where lack of line-of-sight access, variable emissivity, or high cost, limit the use of infrared techniques,” says senior TTP consultant, Dr David Pooley. “Because of the simplicity of applying the technology, it could also be used in low-cost consumer applications.”
Eddy currents were discovered by the French physicist Leon Foucault in 1851, following the discovery of electromagnetic induction by Michael Faraday in 1831. But it was not until the 1930s that eddy current technology began to find industrial applications such as proximity sensing, and non-destructive testing – looking for cracks or voids in materials, for example.
“It’s very exciting to take a 165-year-old principle and discover a completely new range of applications for it,” says Pooley. “We are continuing our practical trials to refine the process and explore new applications and we are already getting a lot of interest from potential partners to commercialise the technology and take it to market.”
