Chapter 7: Troubleshooting
Check Mechanical Components
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If proper excitation voltage is reaching the load cells, check the output
signal from each cell. If one cell has a particularly high or low dead-load
output it is suspect (the maximum output possible from any cell is 30
mV at 15 VDC excitation and loaded to gross capacity).
If any cell has an unusual signal, remove all load from that cell by raising
the platform. With the power still on, measure the output from the
suspect load cell. The “no load” zero output should be + 1.5% of the full
scale output. For example, if the excitation voltage is 15 VDC then the
full scale output is 30 mV. Therefore, the no load zero output should be
within + 0.45 mV. If the load cell is out of specification, replace it.
If a load cell fails any of the above test, replace it.
Check Mechanical
Components
Due to the simplicity of the 2888 Deckmate design, there are only a few
mechanical components to troubleshoot. Ensure that the platform has
freedom of movement and that the load cells are not resting against the
fixed bumpers. If the load cells are contacting the fixed bumpers with no
motion in the scale platform, check the following:
1. Is the platform level or rocking? Reshimming may be required.
2. Check the rocker pins for unusual wear. Replace any rocker pins that
are unevenly worn or have flattened bearing surfaces.
3. Examine the rocker pin receivers in the frame. If the bearing surface
is sunken, depressed, or unevenly worn, replace the frame.
4. If the fixed bumpers on the frame are excessively worn or damaged,
the entire frame will need to be replaced.
5. Inspect the platform and frame for any apparent physical damage.
Replace any platform or frame that is bent or contains broken welds.
6. Verify that the load cell overload gap is proper.
Note: Remove signal leads
from terminals to measure
output.
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