Bosch Rexroth BODAS DSA/12 Instruction Manual page 33

Table 8: Speed sensor malfunction table
Malfunction Occurrence possible
Proto 0 km Operation
Sensor does x x
not supply
a signal
Sensor (x) x
supplies
incorrect or
no signal
x
x x
Possible cause
x Short circuit of the output signals
of the speed sensor by:
- Damage to the insulation in the
connected wiring harness.
x Humidity has entered the wiring
harness or the sensor.
The input resistances RPU and/or
RPD of the control unit are either
too large (high resistance) or too
small (low resistance).
x The ground line of the sensor is not
connected to the sensor ground of
the control unit.
There is a "potential shift" due to
different grounds between sensor
and higher-level control
Only for sensor operation outside
Rexroth components
- Air gap between the sensor and
the gear wheel/encoder wheel is
too large.
- Sensor is mechanically offset
laterally to the encoder wheel.
- Sensor is installed rotated by 90°
to the encoder wheel.
Troubleshooting | BODAS speed sensors
Remedy
The output stage includes a thermal short-circuit
limitation. This works as follows:
• If the output stage is overloaded by an output
current over the maximum specified 50 mA,
the output stage is deactivated. It becomes
high-impedance for 50 μs.
• From this moment until the output stage is
reactivated, the output level is exclusively
determined by the load at the output terminal
(pull-up/pull-down).
• After the 50 µs, the output stage is reactivated
to show the signal level (high or low) valid
at this moment.
• This shutdown process is repeated for as long as the
output stage is thermally overloaded.
• The time behavior of the shutdown results from the
temperature conditions on the output stage and
is dependent
– on the ambient temperature and cooling
– of the short circuit current
– on the signal path (ratio high/low frequency)
The output voltage in the event of a short circuit
depends on the (short-circuit) resistances present
at the output and can be calculated using the formulas
(see data sheet 95133 chapter "Output signals").
The seals of the wiring harness connector are
defective or the cable/sensor has been damaged.
Check whether the sensor is operated within its
"operating limits" and make sure that the input
resistances and the input capacitances of the
connected control unit are within the limits specified
in data sheet 95133.
Make sure that the ground of the sensor is connected
to the respective ground of the control unit with a low
resistance. Measure the connection.
With the information in the data sheet, check the
correct installation of the sensor as well as the air gap
between the sensor and the gear wheel/encoder wheel.
RE 95290-01-B/2021-09-13, Bosch Rexroth AG
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