Draft Sensors; Short Circuit In Draft Sensor Line - Valtra 6000 Workshop Manual

32. Electro---hydraulic power lift
A
View A
U
U SIGNAL
SUPPLY
Figure 5. Draft sensor
1. Pressure resistant grease

Draft sensors

The draft sensors act as mounting bolts for the lower links. The
sensors convert draft forces into electrical signals.
The draft sensors are housed in tubes manufactured from a
special steel. Inside the sensor there is a carrier wave elec-
tronics unit, a signal amplifier, and a transformer which pro-
duces a magnetic field at the measuring point.
The draft force causes a shearing stress on the sensor and this
changes the magnetic properties of the metal, which causes
a variation in the voltage in the transformer secondary
U = 9,5 ---10,5 V (DC)
SUPPLY
U = 2,5 ---7,5 V (DC) (draft max. --- push max.)
SIGNAL
(signal voltage is 5 V when the lower links are unloaded).
The draft pins must be changed if they are damaged. If the
sensor lead is damaged it can be repaired using three pin
connectors.
Note!
Draft sensor 31287410, 40 kN (6200 ---6900)
Draft sensor 33303900, 60 kN (8050 ---8750)
1. 1. 1994
1. 8. 1998
1
Measuring the draft sensor internal volt-
ages
See page 320/13.

Short circuit in draft sensor line

--- Short circuit in the supply line causes deadlock of the whole
system (current breaks also in the selector panel A2E ). If this
short circuit is only momentary, the system starts normally
with the lift/lower switch. If the short circuit is sustained, the
power lift remains locked.
--- Short circuit in the signal line causes the lifting reaction on
the lower links during the short. The system returns automati-
cally to the normal function after the short circuit ("ghost lifts").
--- Contact between the supply and signal lines causes the full
lowering reaction on the lower links during the short circuit.
Note! The draft sensor internal build ---up has been changed.
At the same time, the sensor coverings have been changed.
The earlier sensor fits with the new coverings. The new sensor
cannot be fitted with the earlier covers but they must be
changed. The new cover can be used inplace with the earlier
covers after changing the sheet metal cover.
293
Model Code Page
6000-- 8400 320
45 Nm
7