When a weighing system misbehaves, the load cell is the first suspect. More often than not the cell is fine and the problem is how it was mounted. Side load, a check bolt that binds, a load button that is not centred, or a conduit that bypasses the sensor will all produce readings that look like a failing cell. Fixing the mounting fixes the system.
Side load is the usual suspect
A bending or shear-beam cell is designed to see force straight down its axis. Any sideways or eccentric load is read as error. A platform supported on one corner, a load applied off-centre, or a structure that flexes under load all push the cell sideways. The symptom is non-repeatable readings and a span that changes with where the weight sits, which is exactly how a "bad cell" presents.
| Symptom | Likely mounting cause |
|---|---|
| Reading varies with load position | Eccentric load, poor platform support |
| Zero shifts after each load | Binding check bolt or hard stop closing |
| Span drifts over weeks | Misaligned load button or debris under foot |
| Hysteresis on unload | Rigid conduit or bracket rubbing the cell |
The load button and loading washer
Many cells introduce load through a button or a loading washer that must sit square and centred. A washer on crooked, a button rubbing against a bracket, or a hard stop with a fraction of a millimetre of clearance that closes under load will all add a slow, load-dependent change that looks like creep. The load must pass through the designed introduction point, axially, with nothing bypassing the sensor.
Check bolts and conduit
Mounting bolts torqued unevenly put the cell into a permanent bend. A check bolt (the one that limits overload travel) adjusted too tight removes the cell's free movement and makes every reading wrong. A rigid conduit or cable gland tied off to the frame lets the structure carry part of the load, so the cell never sees it. Loosen, re-torque to the specified value, and make sure no rigid member short-circuits the sensor.
- Torque all mounts to the specified value, evenly.
- Confirm the load is applied axially through the load button.
- Check for debris under the load foot and a warped plate.
- Verify the excitation voltage at the cell terminals, not at the indicator.
A pre-commissioning check
Before trusting a new or repaired installation, log zero, apply a known load for the specified time, record the output, remove the load and record the recovered zero. Repeat a few times. If the recovered zero wanders or the span shifts with position, the fault is in the mounting, not the cell. A cell that is genuinely at fault usually has an overload history behind it; without one, look at what is touching the cell before ordering a replacement.
Sales Team