SZG-441 handheld digital photoelectric tachometer, type a measurement range, high accuracy, versatility, ease of use of speed tables, measure the speed, line speed and frequency. And has recorded several functions. And the general non-contact hand-held digital tachometer than small, compact shape, feel better. When measured using a reflective marker affixed rotating object, the speed of the table aligned reflective markers visible point can be measured. Sense of the table with maximum, minimum alarm function, can store the last measured value and the maximum value of this measurement process, minimum.