Auto-Diagnosis Menu (Wbewbe 4120 D4120 /13); Msr - Bosch WBE 4120 Instructions De Réparation

en 52 | WBE 4120 / WBE 4120 D / WBE 4120 DT | Auto-diagnosis menu (WBE 4120 /WBE 4120 D)
6. Auto-diagnosis menu
(WBE 4120 /WBE 4120 D)
On every Bosch balancing machine, you can find an
auto-diagnosis menu that you can use during the assis-
tance in order to check the machine very carefully.
6.1

Msr

The first step in the test menu is checking the pick-ups;
this procedure, that will be analysed in details later on,
is fundamental to identify any sensor problem.
BALANCING SYSTEM
The tool that is used to measure the wheel unbalance
has a mechanic system based on a lever at 1°degree.
The piezoelectric sensors which are in the lower part of
the shaft, at its sides, detect vibrations by converting
the strength into electric tension.
Abb. 2: Position of the piezoelectric sensors
TENSIONS
The piezoelectric sensors, according to where they are,
receive a different stress and weight. In fact, the inter-
nal one, in the left side of the shaft, is excited less than
the external one. So we can say that the ratio between
them is 1.6, that is, the tension measured by the exter-
nal pick-up is 1.6 times higher than the tension meas-
ured by the internal pick-up.
Abb. 3: Stress spread on the shaft
PHASE ANGLE
In general, we use the word phase to identify a particu-
lar moment during a periodical phenomenon (in this
case it is the electrical signal generated by the pick-up
during the launch of the wheel). When we consider two
signals (generated by the internal and the external pick-
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up), we can say that there is a phase angle between
them which means that there is a difference between
the tensions. For instance, in this picture, if the black
signal represents the tension of the external pick-up
and the red signal represents the tension of the internal
pick-up, we can say that the tensions are opposite, that
is, that the difference is 180°. The crests of a signal are
lined up with the troughs of the other and vice versa.
Abb. 4: Ratio between the tensions measured by the pick-ups
To enter the test menu press "SET" until the notice
"TST" appears on the left display and then press "MM/
INCH" (1.5s Max). Now the display will show the notice
"Msr".
If you press + DISTANCE, you will see on the displays
both the values in sequence read by the pick-up during
the last launch and the phase angle shown in degrees.
In order to monitor if the pick-ups work correctly, follow
these instructions:
14. mount a test wheel on the machine (14-15" of iron)
and balance it perfectly;
15. apply a single test weight outside (for example
100g) and make a test launch.
At the end, check the values: the tension value of the
internal pick-up must be always less than the tension
value of the external pick-up. The internal one must go
between 1.2 and 1.8.
As you can see from the picture below, to calculate the
phase angle, you must divide the external pick-up value
by the internal one. In this way, you can get the ratio
(603 / 384 = 1,57).
Left Display Right Display Description
Msr
ex.: 384
ex.: 603
ex.: 179 ex.: 580
ex.: 2
NOTES FOR THE ASSISTANCE:
Bosch Automotive Service Solutions GmbH
Press "+" DISTANCE to roll down
the menu
1° value shown: tension
measured by internal pick-up
2° value shown: tension
measured by external pick-up
3° value shown: angle of difference
of phase
4° value: rounded off ratio be-
tween the pick-ups