Sensor Gives Automatic Temperature Compensation For Optical Strain Gages

It is essential 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 gages are sensitive to temperature variations because of the sensitivity of the fiber Bragg grating that forms the strain gage and the thermal dilatation of the object being measured. This can be up to 30 µm/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 gage applied to an aluminum sensor body. It is attached to the object under test and only measures the thermal dilatation of the aluminum and the temperature-dependent signal change of the fiber 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 gage signal using HBM’s catman®AP software to provide automatic compensation.

Optical strain gages 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, rather than electrical signals.

HBM provides all the components users need from one source. As well as optical strain gages and the new K-OTC temperature compensation sensor, this includes interrogators and the data acquisition software catman®AP, which has a special EasyOptics module for optical SGs.