Function Of Stroboscope
Cris Luczak
A stroboscope, also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. It consists of either a rotating disk with slots or holes or a lamp such as a flashtube which produces brief repetitive flashes of light. Usually, the rate of the stroboscope is adjustable to different frequencies. When a rotating or vibrating object is observed with the stroboscope at its vibration frequency (or a submultiple of it), it appears stationary. Thus stroboscopes are also used to measure frequency.
The principle is used for the study of rotating, reciprocating, oscillating or vibrating objects. Machine parts and vibrating string are common examples. A stroboscope used to set the ignition timing of internal combustion engines is called a timing light.
In its simplest mechanical form, a stroboscope can be a rotating cylinder (or bowl with a raised edge) with evenly spaced holes or slots placed in the line of sight between the observer and the moving object. The observer looks through the holes/slots on the near and far side at the same time, with the slots/holes moving in opposite directions. When the holes/slots are aligned on opposite sides, the object is visible to the observer.
Alternately, a single moving hole or slot can be used with a fixed/stationary hole or slot. The stationary hole or slot limits the light to a single viewing path and reduces glare from light passing through other parts of the moving hole/slot.
The rotational speed is adjusted so that it becomes synchronised with the movement of the observed system, which seems to slow and stop. The illusion is caused by temporal aliasing, commonly known as the stroboscopic effect.
In electronic versions, the perforated disc is replaced by a lamp capable of emitting brief and rapid flashes of light. Typically a gas-discharge or solid-state lamp is used, because they are capable of emitting light nearly instantly when power is applied, and extinguishing just as fast when the power is removed.
By comparison, incandescent lamps have a brief warm-up when energized, followed by a cool-down period when power is removed. These delays result in smearing and blurring of detail of objects partially illuminated during the warm-up and cool-down periods. For most applications, incandescent lamps are too slow for clear stroboscopic effects. Yet when operated from an AC source they are mostly fast enough to cause audible hum (at double mains frequency) on optical audio playback such as on film projection.
The frequency of the flash is adjusted so that it is an equal to, or a unit fraction of the object's cyclic speed, at which point the object is seen to be either stationary or moving slowly backward or forward, depending on the flash frequency.
Neon lamps or light-emitting diodes are commonly used for low-intensity strobe applications. Neon lamps were more common before the development of solid-state electronics, but are being replaced by LEDs in most low-intensity strobe applications.
Xenon flash lamps are used for medium- and high-intensity strobe applications. Sufficiently rapid or bright flashing may require active cooling such as forced-air or water cooling to prevent the xenon flash lamp from melting.
As well as having important applications for scientific research, the earliest inventions received immediate popular success as methods for producing moving pictures, and the principle was used for numerous toys. Other early pioneers employed rotating mirrors, or vibrating mirrors known as mirror galvanometers.
Harold Eugene Edgerton ("Doc" Edgerton) employed a flashing lamp to study machine parts in motion.[2] General Radio Corporation then went on to produce this device in the form of their "Strobotac", an early example of a commercially successful stroboscope.[3]
Stroboscopes play an important role in the study of stresses on machinery in motion, and in many other forms of research. Bright stroboscopes are able to overpower ambient lighting and make stop-motion effects apparent without the need for dark ambient operating conditions.
In medicine, stroboscopes are used to view the vocal cords for the diagnosis of conditions that have produced dysphonia (hoarseness). The patient hums or speaks into a microphone which in turn activates the stroboscope at either the same or a slightly different frequency. The light source and a camera are positioned by endoscopy.
Another application of the stroboscope can be seen on many gramophone turntables. The edge of the platter has marks at specific intervals so that when viewed under fluorescent lighting powered at mains frequency, provided the platter is rotating at the correct speed, the marks appear to be stationary. This will not work well under incandescent lighting, as incandescent bulbs do not significantly strobe. For this reason, some turntables have a neon bulb or LED next to the platter. The LED must be driven by a half wave rectifier from the mains transformer, or by an oscillator.
Flashing lamp strobes have also been adapted as a lighting effect for discotheques and night clubs where they give the impression of dancing in slow motion. The strobe rate of these devices is typically not very precise or very fast, because entertainment applications do not usually require a high degree of performance.
The MIGHTY STROBE X-1 provides all essential features of a stroboscope in a lightweight body weighing only 900 g (battery included) that can be operated with one hand. The high brightness, high intensity 15 W output makes this single unit ideal for revolution counting of motors and other rotating equipment, inspecting rapidly rotating or moving bodies, and for photographic applications.
This small, lightweight body is capable of producing very large intensity. The matt-finish reflector delivers uniform light that illuminates an area 60 cm in diameter at a distance of 1 m. Further, it can be used effectively for visual inspections of steel rolling mills, or for production inspection of wide printing presses, etc.
The intensity can be switched between high, medium, and low according to the requirement, ensuring that the light is not too bright.
A stroboscope's flash duration corresponds to a camera's shutter speed. When compared to LED strobes, the MIGHTY STROBE X-1 has an exceptionally fast shutter speed of 2.4 s, producing stationary images of extraordinary clarity.
In addition to the wide-ranging flash frequency of 30 - 36,000 FPM for the internal oscillation emitter, and 0 - 36,000 FPM for the external signal trigger emitter, the unit is also equipped with an output jack for an external flash signal. Moreover, the unit can be connected to a proximity sensor or photoelectric sensor for tachometer use (30 - 120000 RPM). The flash phase and time delay angle functions are ideal for research applications, and the battery-operated design allows the unit to be used anywhere.
With an easy 2 h charge using the AC adapter included, the unit can be used for up to 4 h on its L (low) intensity setting, and up to 1.5 h continuously even on its H (high) intensity setting. There is also no need to interrupt your work, as the unit can be used while it is being charged.
Harold Edgerton, as a very young man, was intrigued when he saw that lightning flashes made rain drops appear stationary in the air. This discovery marked the beginning of the history of modern stroboscopes. Today, stroboscopes are used not just to measure and observe rotation and motion, but in optical shutters for products incorporating computers and fulfill various functions in industry and in our daily lives.
Sugawara's stroboscopes use xenon flashlamps developed and manufactured in-house. Drawing on the know-how accumulated over many years, Sugawara evaluates each part used in its products, including capacitors, to ensure high product reliability.
Sugawara offers a wide array of stroboscopes, ranging from general-purpose portable products to larger models for use in production lines and laboratories. The flash duration provided by these products ranges from an extremely short 40 nsec to as long as 2 msec.
The dax offers powerful features for both diagnostic inspection and speed measurements. Lightweight and bright with flash rates to 20,000 flashes per minute and an accuracy of 0.004% of setting, these strobes are comfortable to hold and easy to operate.
Using a Nova-Pro handheld stroboscope from Monarch Instrument, V-TEK Associates demonstrates resonant frequencies inherent in machine vibration analysis. By matching the rotation frequency of the MVAT6-01 the strobe flashing virtually slows or stops motion of the rotor. This also captures the cantilever beam which is moving in resonant harmonics with the machine vibration.
View this select set of stroboscopic visualization and test measurement instruments for an array of industry applications. Features such as Phase Delay, Virtual RPM, Phase Shift, Laser Tachometer, and Strobe Synchronization.
The Nova-Pro Infrared Stroboscope is used with a FASTEC high-speed camera to capture ultra-slow motion, high definition videos of insect and wildlife behavior in their real-world habitats. The infrared LEDs brightly illuminate the area being filmed without the disturbing effects of standard visible light.
By means of extremely short flash impulses the HELIO-STROB master allows the observation of very rapid processes with the naked eye.
It provides pin sharp images of the apparently stationary object: the "stroboscopic effect".
All functional adjustments can comfortably be set via the touch panel and the twist knob.
When analysing fast processes such as rotation or vibration the standard features "slow motion" and "position" (phase shifting) put even the smallest detail into perspective. The finely graduated dimmer function allows an adjustment of the light intensity and thus enables fatigue-free observation to the smallest detail.
The flash frequency can either be controlled by the accurate internal trigger, by an external trigger or even by mains synchronous triggering.
Thanks to the integrated prescaler external impulses are processed up to a frequency of 8000 Hz*.
Proximity switches and optical sensors can directly be connected to the stroboscope.