This Opto-electronic Sensor Series A1S is ready for various applications with smooth or profiled targets: a dot of paint on a shaft is adequate to start measurements. Likewise, a fan blade, a screw head, a slot or cam will serve. Function does not depend on the target material, there being no load or reaction to the object. In addition, It is Easy and quick to use, especially in connection with the portable tachometers C118 or C156.