Optical strain gauges with temperature compensation

Paul Boughton
HBM reports that it has resolved the challenges of compensating optical strain gauge measurements for temperature fluctuations with its latest K-OTC sensor. It is important to compensate for temperature sensitivity of optical strain gages, such as HBM's K-OL and K-OR models, especially when testing strains that are relatively small and temperature differences are high. Optical strain gauges are sensitive to temperature variations because of the sensitivity of the fibre Bragg grating that forms the strain gage and the thermal dilatation of the object being measured. This can be up to 30um/m/K, depending on the material involved but, in stress analysis, engineers are normally only interested in mechanical strain.
The K-OTC is based on an optical strain gauge applied to an aluminium sensor body. It is attached to the object under test and only measures the thermal dilatation of the aluminium and the temperature-dependent signal change of the fibre Bragg grating. This means that no mechanical strain is transferred, although temperature compensation does take place. The K-OTC signal is compared with the optical strain gauge signal using HBM's catmanAP software to provide automatic compensation.
Optical strain gauges are typically used for experimental stress analysis in difficult conditions such as high-voltage, powerful magnetic interference or in potentially explosive atmospheres because they use light instead of electrical signals.
HBM provides all the components users need from one source. As well as optical strain gauges and the new K-OTC temperature compensation sensor, the range includes interrogators and the data acquisition software catmanAP, which has a special Easyoptics module for use with optical strain gauges.
For more information, visit www.hbm.com

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