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Proscan 2200 (Chromatic Sensor) User Manual V.4.0
Once the sensor has been changed, replace the nose cone. Select the appropriate sensor via
the Tools/Sensor Selection menu in the Proscan 2200 software.
5.0
Dark Referencing
5.1. Acquiring the dark signal
The dark signal of the sensor is generated by undesirable back-reflections on the optical
surfaces inside the sensor. This signal must be measured and saved to the non-volatile
memory so that it can be subtracted from the measured signal. The level of the dark signal
depends on the sampling rate and on the LED brightness.
A dark signal acquisition is performed during adjustment by the manufacturer, but must be
repeated at regular intervals.
5.2. Recommendation
The dark signal acquisition procedure should preferably be performed at least a quarter of an
hour after switching the sensor on, in order to ensure that sensor has reached thermal
equilibrium.
Dark signal measurement may be launched by pressing the “Dark” button on the sensor front
panel. This operation may take a few dozens of seconds, as the sensor measures and saves
the dark signal at all pre-set frequencies successively.
In order to perform a dark signal acquisition, it is essential to have no object within the
measurement field, or even better, to blank off the light beam by applying a piece of paper
over the tip of the optical
pen
.
•
Press the “Dark” button on the front
panel of the sensor.
•
The “Intensity” and “Measure” Led
indicators
•
on the front panel blink on and off in
green alternatively, to indicate that
the operation is in progress.
•
Keep the optical pen tip blanked off.
When measurement is done, the 3
LED indicators blink on and off
simultaneously, and their colour
indicates the result of the operation.
Green
if the level of the acquired dark signal is satisfactory at all rates
Orange
if the dark signal level is too high at low rates, but it is still possible to measure at
higher rates
Red
if the dark signal level is too high at all rates.
The piece of paper can now be removed and the sensor can be used in the normal way.
