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Proton Products SL mini and SLR mini Series Speed and Length Gauges Instruction Manual - issue 1s
This parameter is highly-dependent on object
material, object distance to the centre of the depth-
of-field and object speed.
For example, a metal or matt-plastic surface moving
at 100 m/minute may return a SNR > 1000, but the
SNR for a translucent plastic object may be much
lower.
The signal-to-noise ratio must exceed 80 for a
consistent and reliable speed reading.
The DC level depends on the amount of light
received from the object and must be between 10%
and 90% for correct operation; it is held at around
30% by an automatic gain controller (AGC).
The AGC may be saturated by highly reflective (e.g.
flat, metallic) surfaces resulting in the DC level
exceeding 100%; in this case tilt the gauge (pitch,
angle ≠ 0) to reduce the received light and bring
the DC level below 90%.
Very narrow or low-reflectivity objects might not
reflect sufficient light for the DC level to reach 10%;
maximise the signal by locating the object as close
to the stand-off distance (i.e. centre of the depth-of-
field).
Highly-reflective, uneven or fast-moving objects
may result in saturation and clipping of the received
oscillating light signal.
Signal amplitudes below 80% will not incur
saturation, whilst an Automatic Gain Controller
(AGC) will accommodate signal amplitude between
80 and 99%. Signal amplitudes above 99% will still
yield measurements but at a substantially degraded
Good Reading rate.
Maintain the signal amplitude at below 80% by
tilting the gauge (pitch, angle ≠ 0) to reduce the
received light.
For use by Proton Products authorized service
personnel only.
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