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Measuring element | FWA 43xx / FWA 44xx | 27
Robert Bosch GmbH 1 690 326 006 2008-8-25
en
CCD camera11.5
CCD cameraFig. 32:
Functional diagram11.5.1
1 Downfall diode (Infrared)
2 Downfall pendulum
3 Infrared-downfall beam
4 CCD lines for camber beam
5 Sign beam assumed opposite from MWA
6 Sign diode
7 Objective
8 Sign beam assumed opposite to MWA
Function11.5.2
The heart of CCD camera builds the CCD camera
R
line designed in 30 degree angle (Single lined).
The evaluation is black / white.
R
The resolution is 2048 Pixel. R
In order to achieve the required accuracy, all 2048 R
pixels are evaluated and the illumination differences
between each pixel are considered.
Measuring principle11.5.3
Each CCD camera has a tilted CCD line (Sensor) and
R
two dispatch diodes.
Sign LED (LED = light emitting diode) is shown in
R
the direction opposite to the camera. It indicates
an infrared beam on the opposite CCD line which is
invisible to the human eye.
The circular motion of a camera is automatically
R
identified by the beam coming form the opposite
direction.
The second diode is found above the camera and is
R
illuminated by the pendulum on CCD line.
The tilt of camera is represented on its own CCD
R
line using the pendulum swing.
The diodes are quickly switched-on and again
R
switched-off in succession for determining the angle.
This happens in a specific time system.
Dark shots (Ambient light) and light shots (LED) are
R
undertaken during each measuring. The fixed time
system results from the exposure times and the
necessity is to be synchronised with opposite LED.
The determined images are digitally transferred to
R
the measuring processor which, with the help of
calibre data achieve absolute angle. The calibre data
is automatically stored in the camera. After every
switch-on, the measuring processor gets this data
from the camera. After fitting in the bracket, still this
mounting is corrected (Zero correction).
A measuring cycle comprises of four measuring
R
images and lasts for approx. half a second. Thereby
each LED is shortly turned on.
Depending on the position of the wheel and
R
the MWA connected to that and its camera, the
respective camber values are resulted from that.
Opening angle:11.5.4
The camera has an opening angle of + / - 23 degree.
R
Thus it enables to execute the standardised sign R
difference angle measurement by 20 degrees alone
using MWA without electronic turn-tilt plate.
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