Rice Lake RL9000TWM-HT Series - Manual (Page 8)

5. 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 fi rst.
If the system can be calibrated but doesn’t return to zero, loses calibration, or demon-
strates 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 be-
tween
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 fi nger 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 specifi cations.
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
Non-Linearity
Non-Repeatability
Lost Calibration
Drifting Readout
Mechanical binding of debris in seals or under load cells; may
have lost system calibration
Thermal expansion or deflection under load causing binding
or side load
Loose load cell mount; drifting caused by moisture, load cell
overload or shock damage; mechanical binding
Out of level or plumb; moisture problem; mechanical binding
Moisture in junction box, cables, or load cell; mechanical binding
4. Junction Box Connections, Adjustments & Calibration
1. Refer to junction box manual for trimming details.
2. Refer to indicator manual for system calibration details.
6