Calibration facility for quality certification of surface-attached fiber optic and electrical strain sensors

How do application-related issues influence the reliability of fiber optic strain measurements?

“…Although surface-attached sensor fibers can visually be evaluated how the sensor is fixed at the surface and is often found to be good, extensive investigations revealed that bonding defects and thermal influences can lead to erroneous signal readings. Examples of strain transfer evaluation and details are given in another paper of this conference [5]. Alternatively, pre-fabricated fiber optic sensor patches are also used for strain measurements at surfaces; however, patches are quite complex.…”

“…The patch itself or the adhesive used could shrink. Test revealed that few commercially offered strain patches show aging effects after thermal cycling resulting in an inacceptable measurement result [5], [7].…”

“…The only way, by now, is the prediction of the long-term sensor function of applied and embedded sensors using test samples installed in validation and calibration facilities in labs. For surface-applied strain sensors, the newly developed KALFOS facility can be used [5]. This facility allows simulating long-term operating conditions, testing and evaluating the bonding behavior, and investigating creep and delamination effects of applied sensors.…”

Verification of Strain Transfer Characteristics of Distributed Surface-attached FBGs on Aircraft Wings

“…The measuring accuracy of the device is high, but its structure is complex. Habel et al [5] of Germany developed a calibration test device for FBGs. The unbiased digital image correlation (DIC) and electronic speckle interferometer (ESPI) are used for calibration measurement.…”