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Load cell corner error is a position-dependent weighing error: the same load gives different readings when moved across a platform. Before changing a junction-box adjustment, establish whether the difference is repeatable and whether the platform can transfer force freely to its supports. Electrical trimming cannot reliably correct a deck rubbing against a ramp or a mounting assembly that changes contact as the load moves.
Map the load cell corner error before adjusting it
Mark the test locations on a drawing or photograph and use the same reference load at each location. Follow the scale's approved test procedure for load size and placement. Total platform capacity does not establish a safe load at every corner; a concentrated load can overstress one support or part of the deck.
Record the unloaded indication, then the reading at the centre and each specified off-centre position. Return to the reference position during the sequence. Repeat in a different order where the procedure permits. This helps separate a position effect from a drift that happened while the load was being moved.
| Pattern in the record | What it suggests checking | What it does not prove |
|---|---|---|
| One position is consistently different | That support's mount, wiring and contribution to the summed output. | That the sensor below that corner is necessarily damaged. |
| The result changes with test order | Return to zero, settling, drift and movement of mechanical contacts. | A fixed sensitivity difference that can simply be trimmed away. |
| The discrepancy grows as load increases | Deck deflection, clearances and the response across the working range. | That a trim made with one light test load will remain valid. |
| All positions shift over time | Changing zero, temperature, excitation or the reference condition. | A purely spatial corner error. |
Record the actual reference load and readings rather than just writing "corner passed". If a fixture is used to place the load, include its weight and ensure it is supported in the same way at every test location. Stop if the placement is unsafe or the load distribution cannot be established.
Look for a changing mechanical contact
Inspect the gap to ramps, guards, stops and surrounding steelwork. Check debris below the platform and the condition of each foundation point. Under load, an apparently clear deck may deflect into a fixed object. A restraint can also carry a changing portion of the weighing force if it is incorrectly positioned or preloaded.
At the sensor, inspect seating, loading pieces and the specified orientation. For a compression column such as the MV-LC0030, the bearing geometry and capacity-specific dimensions must fit the assembly. Similar capacity does not make an improvised loading cup suitable. Do not add shims or change restraint clearances without the mounting design and an approved safe work method.
Do not aim for identical unloaded millivolt readings from every support. The empty platform may not distribute its weight equally. Compare changes produced by a controlled load, using the documented sensitivity, excitation and mechanical layout. An unequal reaction can be physically correct.
Check the junction box without erasing the baseline
Save the existing trim positions or configuration and identify each channel by its physical location. Inspect terminations, cable damage and signs of moisture. A changing connection resistance or leakage path can make an adjustment appear successful at one moment and fail later.
Only qualified personnel should disconnect or test the electrical circuit, using the instrument instructions and the site's isolation procedure. Do not remove a load-bearing sensor to compare channels until the structure has been unloaded and independently supported under an approved method. Individual electrical readings are useful, but their collection must not alter the mechanical support condition unknowingly.
When trimming is justified
Trimming becomes appropriate when the mechanical installation is sound, the signals are stable and the remaining position error can be corrected by the system's documented balancing method. Excitation trimming, signal trimming and individual digital-channel calibration are not interchangeable procedures. Use the instructions for the installed box and indicator rather than a generic direction for turning a potentiometer.
A large adjustment requirement should prompt another compatibility check. Confirm capacities, sensitivities, wiring and the exact replacement version. An adjustment at its limit can leave little room for later correction and may indicate that an unsuitable component has been introduced.
After balancing, recheck the centre indication and span because the combined response may have changed. Repeat the position map, increasing and decreasing load checks and return to zero. The acceptance limit should already be defined for this scale; no universal corner-error percentage is implied here.
Send the readings that distinguish an adjustment from a replacement
For a METRAVON enquiry, provide the platform drawing, sensor models and capacities, junction-box and indicator details, and the position map before adjustment. Include photographs of the mounts and any recent replacement parts. The replacement assessment explains the additional evidence needed if one sensor remains suspect.
A request for "four matching sensors" without the installation and electrical details can repeat the original problem. Use the contact page to send the test record together with the hardware information, and state whether the enquiry concerns a new platform or correction of an existing scale.
Questions during corner testing
Q1. Can normal production loads replace a controlled position test?
They can reveal a problem, but differences in load magnitude, contact area and placement make diagnosis difficult. Use a controlled reference and defined positions for comparison. If only a process-based verification is feasible, document its limitations instead of calling it an equivalent corner calibration.
Q2. Must a single-point platform be adjusted like a four-cell platform?
No. A single-point design does not have four independent support channels to balance. Check its permitted platform dimensions, mounting surfaces and off-centre loading conditions. A four-channel junction-box trimming procedure cannot correct a single-point installation that exceeds its mechanical specification.
Summary
Preserve the position-dependent readings, correct changing contacts and confirm stable channel behaviour before trimming. Accept the result only after the same positions and relevant loads have been retested. A balanced centre reading alone does not demonstrate a platform that weighs consistently across its usable surface.
