Troubleshooting
© Rice Lake Weighing Systems
●
All Rights Reserved
9
5.0
Troubleshooting
If the system powers up and gives some type of stable digital readout that varies with the load
on the system, any system problems are probably caused by factors other than the load cells.
The load cells are often blamed for a malfunctioning system, but 90% of the time, the problem
lies elsewhere. Look for mechanical causes for your problem first.
If the system can be calibrated but doesn’t return to zero, loses calibration, or demonstrates
non-linearity or non-repeatability, see the following chart for possible causes and do the
following checks.
1. Check load cell mount for debris restricting load cell movement or debris between scale
and structure.
2. Check that tank/vessel and mounts are plumb, level, and square at critical areas.
3. Check all piping and conduit for connections which restrict vessel movement.
4. If check rods are used, loosen all connections to finger tight only for testing.
5. Check load cell cables for physical or water damage.
6. Check all electrical connections, especially in the junction box.
If the problem still is not found:
7. Check possible indicator malfunction by using a load cell simulator to input a known good
signal into the indicator.
8. Disconnect each load cell’s signal leads at the junction box and check individual load cell
outputs with a multimeter. Then check input/output impedances for comparison with load
cell manufacturer’s specifications.
If after all these checks the problem still cannot be isolated, reconnect all but one load cell.
Replace load cell with a load cell simulator. Alternate so that each load cell is individually
disconnected and replaced with a simulator. If there is a problem with a particular load cell, the
symptom should disappear when that load cell is disconnected and replaced with simulator.
Symptom
Possible Cause
No return to zero
Mechanical binding or debris in seals or under load cells May have lost
system calibration
Non-linearity
Thermal expansion or deflection under load causing binding or side load.
Non-repeatability
Loose load cell mount
Drifting caused by moisture
Load cell overload or shack damage
Mechanical binding
Lost calibration
Out of level or plumb
Moisture problem
Mechanical binding
Drifting readout
Moisture in junction box, cables or load cells
Mechanical binding
Table 5-1. Troubleshooting Chart
