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What is a donut load cell?

A donut load cell is a low-profile compression sensor with a central opening that allows a bolt, shaft, or other mechanical component to pass through the sensing element. This configuration is particularly useful when the force path must remain around a fastening point or structural member. The sensing element typically uses bonded strain gauges in a Wheatstone bridge circuit to convert small elastic deformation into an electrical signal proportional to the applied axial force.

The central aperture makes this type of sensor suitable for measuring loads directly around bolts and threaded assemblies. A bolt force sensor can be installed between two flat and parallel surfaces to monitor clamping force or verify preload during assembly. Proper alignment is important because the applied force should remain perpendicular to the sensing surface and distributed evenly across the active area. Bending moments, side loads, and uneven contact should be minimized to maintain measurement accuracy and repeatability.

A through hole load cell is commonly used in applications where conventional compression sensors cannot be positioned directly in the force path. Typical uses include bolt preload verification, fastener tension monitoring, press-fit testing, structural assembly validation, clamping force measurement, and overload monitoring for heavy industrial machinery. The through-hole configuration also allows engineers to integrate force measurement into existing mechanical structures without significantly changing the overall assembly.

For applications requiring a compact annular sensor, a washer type force sensor provides a practical solution for monitoring axial loads in confined spaces. Depending on the required capacity and operating environment, the sensing body can be manufactured from stainless steel or other suitable materials. A ring load cell can also be customized with different outer diameters, inner diameters, thicknesses, capacities, cable configurations, and electrical characteristics to match specific mechanical interfaces.

LCS provides standard and customized solutions for low-profile axial force measurement, with designs available for industrial automation, machinery testing, fastening systems, structural monitoring, and OEM equipment. Custom development can accommodate special dimensions, mounting requirements, rated capacities, and environmental conditions, helping customers integrate reliable force measurement directly into their existing mechanical assemblies.