Conair WSB - Manual (Page 84)

VERIFYING LOAD CELL FUNCTION
Most Problems are related to LOAD CELL function.
There are several ways to VERIFY that the load cells are functioning
properly. The slightest touch on the weigh bin should result in a
change in the readout. If this is not the case, something is wrong.
When the light touch is removed, the display should return to its
starting point. If this does not happen, something is interfering with
free movement of the cell or the bin. Make a careful inspection of
EVERYTHING around the load cells, the hanger bolts, the weigh bin tray
and the weigh bin. NOTHING should interfere with free movement.
NOTE: It is normal for load cell readout to drift several grams over
time and with different temperatures. Since all the component
dispenses are weighed by a single set of load cells, this drift
will affect all components equally and, therefore, the ratio of
the components will remain accurate. Empty weight is always
TARED so each dispense is accurately measured.
The following observations will verify proper load cell operation:
When the bin is empty, between cycles, the display should read near
zero. An error of several grams is not important since this empty
weight reading is "tared" from all dispense readings. The "empty
weight" readings should be consistently within 1 or 2 grams.
The addition of several pellets to the weigh bin should result in a
change in the readout. 1/10 of a gram is about four pellets, a gram
about forty. This should hold true when the weigh bin is full as well
as when it is empty.
Most load cell problems are caused by interference to the movement of
the load cell. The load cell must be free to respond to the weight of
a single pellet as well as free to move far enough to record full load
cell rated weight deflection.
If weight readout is very erratic check for damage to the load cell
wires. Check for a pinched wire in the connector.
An over-stressed load cell will read high. The top limit is ( 3100.0)
for a GB/WSB2xx and ( 22444) for GB/WSB4xx or GB/WSB9xx. A load cell
that was forced or pried upward to far will read ( 0.0).
We supply and replace load cells in matched sets and we always include
the mounting enclosures. You may remove the back plate from the
enclosure for visual inspection. It is not safe to remove the load
cell itself from the enclosure. To do so may stress the cell itself.
To operate with damaged load cells, see KEYPAD, *87, VOLUMETRIC.
To RECALIBRATE the LOAD CELLS, see the MAINTENANCE MANUAL.
For further information, see the next page, RAW SIGNAL READOUT,
and Following page, LOAD CELL plus WEIGH BIN TEST.
Page 85