Check Out Procedure
Scale readings on the scale head display do not return reliably to zero, or
drift, or test weights give different values based on their placement on the
This test is
done by using Scale
(click to go to test using a
a "stretched" cell cannot return to same "resting" value
returns a non-linear response
throughout its range.
non load-cell failure due to
couplers, tight electrical/hydraulic
The SEARCH FOR BAD
LOADCELL(S) should include tests for
HYSTERESIS and LINEARITY.
Multiple loadcell scales should be tested at each cell location.
A. SINGLE LOADCELL Scales:
1. Note scale tare reading.
2. Lift up on scale, then
release. Note reading.
3. Load down scale, remove
load. Note reading.
Readings which do not
return to tare within a few counts, may indicate a 'sprung' cell (one that
has been mechanically over stressed) or there may be a mechanical bind i.e.
bad scale bearings or binding electrical and/or pneumatic hoses.
B. MULTIPLE LOADCELL
If after pulling and
pushing the scale using the SINGLE CELL test (above), the readings do not
return to the tare value, ISOLATE the faulty cell by:
Pulling and/or pushing at
each cell location - the bad cell will be worst at returning to zero.
If a cell is in doubt,
perform the Hysteresis test while testing the loadcell
signal values with a voltmeter.
See instructions for testing by looking at loadcell
signals with a voltmeter.
If possible, apply stresses
as close as possible to the cell being evaluated.
A. SINGLE LOADCELL Scale
readings should be taken at several points in its load range. Non-linearity
can be caused by sprung cells, but it can also be caused by bad mechanical
pivots, binding due to incorrectly routed electrical or pneumatic lines, or
other mechanical connections to the scale which do not permit free movement.
B. MULTIPLE LOADCELL
scales should be tested as in single cell systems. Additional testing by
tensing and compressing cells at each point, may show up problems not found
by normal loading from a central point. A properly balanced scale, should
read correctly, regardless of which loadcell is stressed. Un-even results
between different cell locations are a strong indicator of a problem with a