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Measurements Start Up
4.1
Calibration Table
The CHRocodile CLS unit can store up to 5 different calibration tables corresponding to different
Optical Heads. In order to start measurement you need to download or select the calibration which
correspond to the used Optical Head (Cf. section 5.2 in user manual). Calibration table consists in a
Look Up Table which give the correspondence between the peak position (Barycenter data) and the
Altitude data.
The global calibration table contains 192 single calibration tables for each of the 192 points (or
channel) in the line. Consequently, each channel are calibrated independently at factory.
The calibration table depends on both spectrometer and optical head. Consequently a calibration table
is specific to one set of CHRocodile CLS sensor (CHRocodile CLS unit + Optical Head), it can’t be
used on another set even if you are using the same optical head 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. This 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.
