A customer recently approached ADM Instrument Engineering to resolve inconsistent measurement readings in their weighbridge.

The customer’s weighbridge gave different weight measurement readings from each of its load cells. Efforts taken to rectify the problem by adjusting the potentiometers in the control box were unsuccessful.

ADM found that the weighbridge had not been levelled correctly during installation, leading to the inaccurate readings.

A fundamental rule with any weighing scale is that it must be Straight, Plumb and Level. Unless all the surfaces supporting the load cells are perfectly level, the weighing system will not function correctly. Remedies include packing the foundation using shims beneath the load cell assemblies.

However, ADM also recommends inspecting the weighbridge first to ensure the Straight, Plumb and Level rule. In addition to being rigid, the connections between modules should meet the manufacturer's specifications.

Load cell base plates are often incorrectly aligned, causing eccentric or side loading of the load cell. Observing the Straight, Plumb and Level rule will correct this problem.

Before packing up the foundation with shims, the weighbridge owner should place 4.5 to 6.8 tonnes of test weight over each load cell and record the actual weight. The test should be repeated and the results compared; an analysis will show certain corners (load cells) may have consistently lower weights than others.

These are load cell supports that need packing up with the shims. Once the shims are inserted beneath the load cell supports on the low output load cells, the test should be repeated until all the load cells provide consistent weight readings.