The motor may not be rotating. Halt the measurement and check to confirm the motor is rotating properly.
When a load is applied to a rotating stepper motor, the waveform of the torque measured during synchronized rotation will contain ripples. However, if a step-out occurs, the detected torque will fluctuate dramatically. The SMC-2, SMT-2, and SS-*N all use this large fluctuation to identify a step-out. You can adjust step-out detection sensitivity to one of three ranges: Select #1 for highest sensitivity, #2 for moderate sensitivity, and #3 for lowest sensitivity. If you set the highest sensitivity, a ripple generated during synchronized rotation may be identified (erroneously) as a step-out, depending on the type of test motor. If this happens, change the sensitivity setting to a setting better suited to the motor and other conditions.