Transmission Metric
Strain sensor specifications include the fraction of deformation that is successfully transmitted from a substrate through the bonding adhesive to the sensing element. A high strain transfer ratio ensures that the sensor accurately measures the mechanical changes in the structure. This parameter is used in fiber Bragg grating and foil gauges.
It does not apply to non-contact optical sensors. Achieving a ratio close to unity is necessary for precision structural monitoring.
Elastic Interface
The adhesive layer acts as a mechanical link between the structural surface and the gauge. If the adhesive is too thick or too soft, it absorbs some of the displacement. This absorption reduces the measured strain.
The thickness of the glue must be controlled.
Adhesives Effect
Temperature changes can alter the elastic modulus of the bonding material, which affects measurement consistency. Softening of the adhesive decreases the efficiency of transmission. This change leads to lower output signals.
Mechanical drift can occur over long testing cycles.
Metrological Check
Strain transfer analysis is performed by comparing the sensor output against a reference strain gauge on the same structure. This test is executed under controlled load profiles. Calibration certifies the transmission efficiency.
Any variation outside the tolerance requires replacement of the sensor.
