Monarch Instrument Nova-Strobe PBL - Manual (Page 8)

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to take into account tangential velocity (rotational speed) – the further
away the rotating point is from the center axis the faster the tangential
velocity and the worse the blur appears to be – it is always the same
number of degrees of rotation but the physical length of the blur gets
bigger as the point moves faster. The strobe adjusts the width of the pulse
automatically to keep the degree of rotation visible constant.
There are two methods of adjusting the fl ash pulse width and hence the
brightness and consequently the blur.
1.2.1 Degree of Rotation Adjustment
The fi rst method is to adjust the fl ash pulse width for degree of
rotation visible (blur). The user can set this from 0.2 to 14 degrees
out of 360. The higher the setting the brighter the strobe appears to
be but the more blurred the target is. Optimal setting to stop motion
is 1.8 to 3.6°. The number of degrees is a proportional amount
and remains constant as the fl ash rate increases or decreases. The
strobe automatically calculates how wide the pulse width should
be at different fl ash rates to keep the blur constant – the faster the
fl ash rate the narrower the pulse width. The pulse width equals:
(setting in degrees/360) x (1/fl ash rate in Hz).
Thus the blur remains constant no matter what the fl ash rate*.
1.2.2 Pulse Duration Adjustment
The second method is to adjust the fl ash pulse width to a fi xed
number of microseconds. Here the user sets the fl ash pulse width
in microseconds not degrees. As the fl ash rate increases the pulse
width stays the same and the image will get brighter and more
blurred as the fl ash width remains constant*. The degree of rotation
visible changes to keep the pulse width of the fl ash constant*.
*Note: There are two limits maintained by the strobe – the pulse
can never be greater than 3000 µs nor can it exceed 14° of rotation.