PRECITEC CHRocodile C, Руководство по эксплуатации

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Measurements Start Up
4.1 Calibration Table
The CHRocodile C unit can store up to 8 different calibration tables corresponding to different optical
probes. In order to start measurement you need to download or select the calibration which
corresponds to the used optical probe (Cf. command $SEN in Appendix 1). Calibration table consists
in a look up table which gives the correspondence between the peak position (Barycenter data) and
the Altitude data.
The CHRocodile C is calibrated at factory with a certified calibration bench.
The calibration table depends on both spectrometer and optical probe. Consequently a calibration
table is specific to one set of CHRocodile C sensor (CHRocodile C unit + optical probe), it can’t be
used on another set even if you are using the same optical probe type (i.e same measuring range).
Fig 4-1: Example of calibration table for a single channel
4.2 Dark Acquisition
Even when there is no surface in the probe’s measurement range, the signal on the detector is not
zero. These non-zero values for each pixel on the detector is due to electronic dark and mostly to flare
corresponding to unwanted back-reflected light on optical lenses surfaces. This Dark signal which
limits the measurement dynamics of the sensor can be remove from the useful signal.
In order to eliminate the influence of this undesirable light, a dark reference is performed on the sensor
(Cf command DRK in Appendix 1). The Dark reference acquisition must be done when no object is in
the measurement range.