Posted to News on 25th Nov 2010, 11:57
Temperature compensation for optical strain gauges
HBM is introducing the K-OTC sensor that is claimed to resolve the challenge of compensating optical strain gauge measurements for temperature fluctuations. 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 gauge 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 that is applied to an aluminium sensor body. Attached to the object under test, it 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.
Because they use light instead of electrical signals, optical strain gauges are typically used for experimental stress analysis in difficult conditions such as where high-voltages or powerful magnetic fields are encountered, or in potentially explosive atmospheres.
HBM provides all the components needed 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.
Millbrook Proving Ground
Station Lane
MK45 2RA
UNITED KINGDOM
+44 (0)1525 304980
