Abstract: A concentration measurer for measuring the concentration of turbidities in object liquid by detecting the diffuse reflection light of a laser beam emitted to the object liquid, comprising a concentration detecting part formed by bundling a plurality of optical fibers for laser beam emission and a plurality of optical fibers for laser beam receiving. In this measurer, a body part having an emitter and a receiver for the laser beam and the concentration detecting part can be formed separately from each other, and the body part and the concentration detecting part can be connected by flexible optical fibers. By this measurer, a concentration up to a high turbidity concentration can be measured with high sensitivity and, when the concentration detecting part is formed separately from the body part, the concentration detecting part can be easily installed even in a restricted area and an adverse environment.

Abstract: A rotor movement warning device for use in a stepper motor has a stator provided with a plurality of windings and a rotor rotatably provided in associated with said stator. The rotor movement warning device includes a power source, a plurality of switching transistors provided in association with the plurality of windings, respectively, for controlling power supply from the power source to the windings, and a driving pulse producer for producing driving pulses to the plurality of switching transistors for effecting the rotation of the rotor. Further provided are detector for detecting, when the rotor stops, at least one switching transistor which is provided with the last driving pulse, and low frequency signal producer for producing low frequency signals which are applied to the switching transistor detected by the detector.