Universal testing machines (UTMs) are essential for material qualification, structural research, and quality assurance. Interface load cells sit directly in series with the moving crosshead and the upper specimen grip of a UTM. A machine controller reads the load cell continuously within a closed feedback loop to regulate crosshead travel, maintain constant loading rates, or hold targeted force thresholds during stress relaxation evaluations. The transducer measures the specimen resistance as it deforms. The data acquisition system pairs this instantaneous force data with displacement data to measure elasticity, yield point, and ultimate tensile strength.