What is a stroboscope?

A stroboscope is a source of flashing light that can be synchronized with any fast, repetitive motion so that a rapidly moving device seems to stand still, or to move slowly

Why use a stroboscope?

Stroboscopes are non-contact instruments,  which is a more sophisticated and safer method to measure speed. Typically used to measure the speed of rotation of motors, fans, pulleys, etc...

How a stroboscope works?

The digital stroboscope is a versatile flashing light source that is used to measure the speed of fast- moving objects or to produce the optical effect of stopping or slowing down high-speed motion for purposes of observation, analysis, or high-speed photography. The stroboscope emits a high- intensity, short-duration flash of light. The instrument features an electronic pulse generator that controls the flash rate, a line-operated power supply, and a light-emitting diode (LED) readout in flashes per minute. The light can be aimed at most moving objects, including those in otherwise inaccessible areas. When measuring the rotational speed of an object, set the flash rate initially to a higher setting than the estimated speed of the object. Then, slowly reduce the flash rate until the first single image appears. At this point, the strobe flash rate is equal to the rotational speed of the object, and the speed can be read directly from the digital display.

Illustration

Assume a white disk with a single black dot mounted on the shaft of an 1800-rpm motor. When the disk is rotating at 1800 rpm, it is impossible for the human eye to distinguish a single image and the dot will appear to be a blurred continuous circle. When illuminated by the flashing stroboscope light, synchronized to flash once every revolution of the disk (when the dot is at 3 o’clock, for example), the dot will be seen at this position - and only at this position - at a rate of 1800 times each minute. Thus, the dot will appear to “freeze” or stand still.

If the flash rate of the stroboscope is slowed to 1799 flashes per minute, the dot will be illuminated at a slightly different position each time the disc revolves, and the dot will appear to move slowly in the direction of rotation through 360° and arrive at its original position 1 minute later. A similar movement, but in a direction opposite the rotation of the dot, will be observed if the flash rate of the stroboscope is increased to 1801 fpm. If desired, the rate of apparent movement can be speeded up by further increases or decreases in the strobe flash rate.

When the image is stopped, the flash rate of the strobe equals the speed of the moving object. And since the flash rate is known the speed of the object is also known. Thus the stroboscope has a dual purpose of measuring speed and of apparently slowing down or stopping rapid motion for observation. The practical significance of the slow-motion effect is that, since it is the true copy of the high speed motion, all irregularities (vibration, torsion, chattering, whip) present in the high speed motion can be st udied.