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A load cell accuracy specification describes the sensing component under stated test conditions. Scale accuracy concerns the result after that component has been installed under a platform, tank or fixture and connected to its electronics. The distinction matters when buying equipment: a tight sensor error limit does not cover forces from connected pipes, a binding platform or incorrect indicator settings. Ask which performance is included in the quotation and how it will be verified after installation.
Put the weighing requirement into the quotation
Write the result the operator needs before selecting the cell. State maximum gross load, smallest working load or batch, permitted error and the point at which a reading will be accepted. A settled inventory reading is a different task from stopping a feeder while material is still falling. Name the receiving device too: local indicator, PLC or production record.
A specification such as "accurate to one display division" is incomplete until the division size, load range and test conditions are defined. Adding digits to an indicator does not demonstrate the same improvement in the measured weight. Keep the display increment separate from the acceptance limit and from the uncertainty of the reference used to test it.
For a replacement project, provide the existing acceptance records as well as the old sensor nameplate. They show the performance the installed machine previously achieved. If no such record exists, ask for a proposed installed test rather than assuming a new cell will restore an undocumented accuracy claim.
| Order detail | What to state | Handover proof |
|---|---|---|
| Working range | The loads or batch sizes at which the result will be used. | Test results at relevant loads, with any untested region identified. |
| Load position | Where material, containers or vehicles can load the structure. | Repeated checks at the agreed positions, not just at the centre. |
| Time of reading | Whether weighing occurs during motion or after a defined settling condition. | The same timing and filter settings used for the acceptance test. |
| Final output | The unit and destination of the value used for process decisions. | Agreement between the reference result and the final receiving system. |
Scale accuracy vs load cell accuracy: ask for the right evidence
A datasheet, a serial-number calibration report and an installed-system test answer different questions. The datasheet describes a model or configuration. A calibration report can describe the tested unit, method and results. Neither automatically includes the pipework, loading surfaces, cable extensions or software scaling added at the customer's site.
For example, the METRAVON MV-LC0190 lists a total error reference of +/-0.2% F.S. That is not a promise of +/-0.2% of every displayed reading from a completed fixture. The selected capacity and the fixture's own effects matter. The separate load cell accuracy guide explains the percentage bases and how to investigate contributions to error.
The MV-LC0030 lists a nominal 2 mV/V output and a 10-500 t capacity range. Those data help select a bridge input and support capacity; they do not state the permissible error of a finished truck scale. Require the proposed capacity-specific drawing and a description of how the loading pieces will fit. A sensor calibration cannot compensate for a platform that intermittently bears against a fixed stop.
For a vessel using MV-WM0006 modules, the scale supplier must also account for the mechanical assembly and connected services. Changing a pipe support can change the indicated weight without altering any sensor specification. Assign responsibility for these installation interfaces before the purchase order is released.
Agree who will prove the assembled scale
Split acceptance into checks that can be completed before dispatch and checks that need the actual site. Identification, dimensions and electrical configuration can be inspected before installation. Pipe forces, foundation behaviour and the final PLC value need the completed system. A supplier's bench test should not silently replace a site test that was necessary to the purchase decision.
Specify who provides reference loads, safe access, lifting arrangements and the person authorized to adjust calibration. Agree how reference uncertainty will be considered when a result is near the permitted error. Avoid adopting a test-load percentage from another machine's manual: the correct method depends on the equipment, intended use and applicable requirements.
Record results before adjustments, then repeat the agreed checks afterwards. Include increasing and decreasing loads, repeatability and appropriate eccentric loading. If the site cannot test the whole working range, identify the verified range and any separately justified substitution method. Do not label an extrapolated region as directly tested. The calibration procedure gives a practical sequence for preserving this evidence.
Send METRAVON the required weighing result, support drawing and existing instrument details through the enquiry page. Ask the quotation to distinguish the sensor specification from the installed performance to be demonstrated, and identify any site work excluded from supply.
Questions before accepting an accuracy claim
Q1. Can a component certificate establish approval for commercial transactions?
No such approval should be inferred from a generic calibration certificate. Requirements depend on the equipment, application and jurisdiction. Obtain the applicable documentation for the actual assembled configuration and have the responsible local metrology authority or qualified specialist confirm what is required before using it for regulated transactions.
Q2. If the local display passes, can the controller value be accepted without testing?
Not when the controller value determines the transaction, batch or alarm. Check the transfer at relevant points, including unit conversion, scaling and update behaviour. A correctly calibrated indicator can still feed an incorrectly configured analog input or a misinterpreted digital value.
Q3. What if the agreed test fails after installation?
Keep the failed result and test conditions, then locate the discrepancy before changing the contract limit or calibration. Mechanical correction, instrument configuration and sensor replacement are different remedies. Repeat the affected tests after the correction; a signed delivery note is not evidence that the weighing requirement was met.
Summary
Buy the required weighing result with a defined scope and acceptance method. Use the load cell specification to select a component, and use installed tests to establish what the scale can deliver. Keeping those two commitments separate makes quotations comparable and avoids disputes at commissioning.
