Method and installation for the non-invasive read-out of data of a passive strain sensor with inherent calibration structure

摘要

The method is determined for the non-invasive read-out of data of a passive strain sensor (1) which is covered by sound permeable material (12). The sensor (1) consists of a flat housing incorporating one or more micro channels (3) filled with a strain-dependent quantity of fluid (6)/gas (5) and it comprises a calibration structure (2). A focused ultrasound beam is moved along predetermined paths in order to scan the entire sensor structure (1). The reflected ultrasound echo signals of all these paths are acquired. The echoes reflected by the micro channel(s) (3) and those reflected by the calibration structure (2) are then extracted. The obtained signals are then calibrated in order to compensate the influence of the material (12) between the ultrasound probe and the passive strain sensor (1), by comparing the reflected echoes of the micro channel(s) (3) with those of the calibration structure (2). The strain-depended fill level of the micro channel (3) is then determined based on a predetermined relation between the fill level and the micro channel's (3) reflected and calibrated sonic energy. The installation for executing the method comprises an ultrasonic transducer (16) connected to a pulser for generating a focused ultrasonic beam and a device, e.g. an XYZ scanner, which moves the focused ultrasonic beam along a predetermined path over the sensor (1) to be read out. Further, it comprises a flat sensor (1) built into sound permeable material (12), encompassing at least one micro channel (3) filled with a strain-dependent quantity of fluid (6)/gas (5), whereas this micro channel (3) laying on a plane parallel to the sensor's (1) surface (7) has an arbitrary shape, e.g. a spiral. Additionally, the sensor (1) includes at least one calibration structure (2) which is located in such a way, that its reflected ultrasound echoes are clearly separable from the ones reflected by the micro channel(s) (3). A receiver for the ultrasonic signals reflected by the micro channel(s) and the calibration structure is connected to a microprocessor (14) for further signal processing.