strain sensor applications

Embedment vibrating-wire strain gauges usually give the most reliable long-term results. They’re self-contained, with the coil and wire sealed inside, so they handle the high-pH environment and initial curing heat better than resistive foil. Mount them on a small rebar cage before the pour, and make sure the flanges are properly tied to avoid floating. For large pours, a rosette pattern of three gauges oriented at 0°, 45°, and 90° lets you resolve principal strains without guesswork.

Spot-weld installation is the standard choice if you have a portable spot welder. For thinner steel or locations where welding isn’t allowed, a two-part cold-cure adhesive can also bond a foil gauge directly to prepared steel. Surface prep is critical either way: grind to white metal, degrease with acetone, and apply a protective coating immediately after installation. Kingmach includes a chemical-resistant cover film and a stainless steel shim in the kit for this purpose.

Yes, you can use a completion module or a precision resistor to build a Wheatstone bridge externally. Most full-bridge sensors output in mV/V, which any voltage-reading logger can handle with a stable excitation supply. For a quarter-bridge foil gauge, you would add three completion resistors. If you want to skip the wiring effort, choose a vibrating-wire sensor and a logger with a built-in vibrating-wire interface—those read frequency directly via the coil without needing a bridge completion.

It’s less about the gauge and more about the mechanical protection. A bare gauge with a thin cover can survive if the crew knows to avoid it, but on a busy site a welded steel box cover with a cable gland is much safer. After that, the splice point between the gauge leadwire and the extension cable often causes trouble. Encapsulating the splice in a epoxy-filled junction box or using pre-molded splice kits keeps moisture and tension out. When these steps are followed, multi-year survival rates exceed 90% in our experience.

Most strain gauges include a temperature coefficient, so they expand or contract even without load. Vibrating-wire gauges usually embed a thermistor for direct temperature correction. For foil gauges, you can wire a dummy gauge on an unloaded piece of the same material and connect it in the opposite bridge arm. The key is to match the thermal expansion of the dummy to the parent material—otherwise, you’ll introduce a false apparent strain. In practice, many users just monitor temperature separately and subtract the estimated thermal strain using the known coefficient of expansion for steel or concrete.