178-296 Mitutoyo SJ-210 and SJ-310 Low Force DetectorMitutoyo Surface Roughness Low Force Detector The Mitutoyo Surface Roughness Tester models SJ 210 & SJ 310 are both available in 2 different models, the Standard Force model and the Low Force model. The Standard Force model uses 4mN measuring force during the measurement. The Low Force model uses 0. 75mN measuring force during the measurement. This is a Standard Detector for the Low Force models, using only 0. 75mN measuring Force. Features include 0.