Ravas RPW-310-EL Operator's Manual page 18

Not linear
Instability With no load it
is most of the
time humidity,
bad connection
or component r
bad shield.
Check cables
The potentiometers
with which we calibrate
the output of the load
cells, are mechanical
parts therefore, higher
risk components
Check if it is load cells
or indicator
Check cable
Check for humidity
Check the indicator.
Check cables. In
warehouse and lift
truck the cable is
working all the time
when following the
lifting movement. It
may be worn or
damaged. Changing
temperatures and
chemicals have an
effect on the lifetime of
a cable.
The potentiometers
with which we calibrate
the output of the load
cells are mechanical
parts and are sensitive
to humidity, shocks
and vibration.
Measure resistance with ohm meter between wires
and load cell body. Do this with the other load cells
disconnected from indicator. No resistance is allowed.
The load cells should have +/- 350 ohm between the
signal wires: yellow and green, and excitation wires,
black and red.
Bad connections will cause changes when moving the
scale.
Bend and move the cable briskly especially where the
cable is moving continuously while lifting. While doing
so, look at the display to see if it reacts to the
movements.
Move the board and but pressure with fingers on the
potentiometers while looking at the display to see if it
reacts. Do not touch the contact itself.
Load cells or indicator are very rarely the cause of this
problem. Easiest way to check is by changing the
indicator temporarily. If problem is not solved when
changing the indicator, the problem is the load cell,
cable or mechanics
Very rarely the cause. Maybe in a lift truck.
Check for water marks on the indicator board or load
cell connections (potentiometers).
Sometimes the indicator will show a weight when the
load cells are disconnected. If you do this and the
indicator becomes more stable, it is most likely
elsewhere in the system.
Check visually for traces of oxidation. If found, heating
the solder contacts can solve the problem.
Bad connections will cause changes when moving the
scale.
Bend and move the cable briskly especially where the
cable is moving continuously when lifting. While doing
so, look at the display to see if it reacts to the
movements.
Move the board and but pressure with fingers on the
potentiometers while looking at the display to see if it
reacts. Do not touch the contact itself.
18