Dehnungsmelder

Dehnungsmelder (German for strain sensor or strain gauge) is a device used to detect and measure deformation (strain) in structures and materials. It converts mechanical deformation into an electrical signal that can be recorded and analyzed for monitoring, testing, and control purposes.

Most common types are resistive (bonded metallic foil) strain gauges, semiconductor strain gauges, fiber Bragg grating (FBG) optical sensors, capacitive sensors, and piezoelectric sensors for dynamic measurements. Bonded foil gauges, developed in the late 1930s, consist of a patterned metal conductor adhered to a flexible backing; when the substrate deforms, the conductor’s electrical resistance changes. The relationship between resistance change and strain is characterized by the gauge factor. Readout is typically performed with a Wheatstone bridge and signal-conditioning electronics to provide amplification, temperature compensation, and filtering.

Applications include structural health monitoring of bridges and buildings, load and torque measurement in machinery, material testing in laboratories, aerospace and automotive component testing, and medical devices such as prosthetics and implants. Installation requires careful surface preparation, proper adhesive selection, and alignment to the principal strain direction; calibration and temperature compensation are often necessary to ensure accuracy.

Advantages of Dehnungsmelder include high sensitivity, suitability for long-term monitoring, and adaptability to various materials. Limitations can include temperature dependence, adhesive durability, limited range of measurable strains for some types, and vulnerability to environmental damage if not properly protected. Advances in fiber-optic and wireless sensor technology continue to expand their use in distributed and remote sensing applications.