Polytec PSV-500, Hardware Manual

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A-1
A Optional Accessories
Appendix A: Optional Accessories
A.1 PSV-G-500 Geometry Scan Unit
A.1.1 Introduction
With the aid of the geometry scan unit you can determine the distance to the
object under investigation. If you make a geometry scan, within a few
milliseconds the system switches from the vibrometer laser to the geometry
laser and determines the exact distance to the object.
Measurement
principle
The distance measurement in the geometry scan unit is based on the transit
time technique. The distance is determined based on the time the light needs
to reach the object and to return from it.
Optimal
measurement
In the same way as it is with a vibrometry measurement, the detected
radiation is independent from the scattering characteristic of the surface and
the distance. To get an optimal measurement result you should use a diffuse
white surface in the close-up range (below 1.5 m) and a retro-reflective film at
longer distances.
NOTE!
If you use a retro-reflective film in the range below 1.5 m, the sensor can overload and affect
the measurement result. Therefore, use retro-reflective film only at distances longer than
1.5 m.
Generally, for a distance measurement no retro-reflective film is necessary. If
retro-reflective film is on the object under investigation, we recommend to set
the scan points onto the retro-reflective film or to cover the retro-reflective
film. If retro-reflective film is in the proximity of the scan points, the
measurement result can be falsified, although the geometry laser is not
pointed onto the retro-reflective film. Pay attention to the following information
when you carry out a distance measurement.
Object under investigation
Distance to the
object
Precautions
< 1.5 m Cover the retro-reflective film in any
case. With optically poorly reflective
surfaces treat the object with white
paper and carry out the distance
measurement.
≥ 1.5 m Carry out the distance measurement on
the retro-reflective film.