A belt weigher calibration report records the tests carried out, the conditions found and the results left after any work. Read the numbers alongside the test method, reference equipment, comments and limitations. There is no single set of percentages that makes every weightometer pass or fail.
What do as found and as left mean?
- As found: the result recorded before the relevant adjustment or work. Check whether cleaning or repair happened before this measurement.
- As left: the result recorded after the stated work, under the conditions tested.
- Change: the difference between recorded values or settings, as defined in that report. It is not automatically the percentage error in every tonne measured since the last visit.
A report may list raw readings, calibration factors, indicated error or a mixture of these. Identify what each column represents before comparing values. A changed setting is evidence that something was adjusted; its numerical change is not always a direct measure of material error.
How should I interpret zero and span?
Zero relates to the empty-belt reference. Span relates to the measurement response to an applied reference load. Read both with the units and method used. A zero percentage might use rated capacity, reference load or an instrument-specific basis; a span figure may describe a setting change or test error. Ask if the denominator is unclear. Our guide to zero, span and repeatability explains the distinction.
Do not assume belt speed and belt length are merely background details. They may be measured checks, stored settings or calculated results. Incorrect speed scaling or a wrong belt-length setting can affect measurement or calibration timing. The report should distinguish what was checked from what was changed.
What does repeatability tell me?
Repeatability describes how closely repeated results agree under comparable conditions. It does not establish accuracy by itself: a system can produce closely grouped results that are consistently biased. The report should identify the repeated test, reference and calculation used.
As a rule of thumb, repeat span runs should agree within about 0.1%. Poor repeatability can involve mechanics, sensors, electrical signals, operating conditions or the test arrangement; it does not identify one failed component.
Which percentages should trigger action?
Use the criteria stated for that installation and test. If they are missing, ask for clarification rather than applying a generic zero or span limit. A result outside the agreed criteria deserves assessment even if similar drift has happened before. A blank result means the outcome is unknown from that field, not that the equipment passed.
Example only: if a suitable material reference is 100.0 tonnes and the belt weigher records 101.0 tonnes for the same batch, the indicated error is (101.0 − 100.0) ÷ 100.0 × 100 = +1.0%. That figure is relative to the reference mass. Whether it is acceptable depends on the agreed requirements and the quality of the comparison.
What does the calibration method establish?
A test-weight or chain result describes performance against that reference. A controlled material test checks the system using conveyed material and an appropriate reference measurement. A good result applies to the tested conditions; it does not guarantee every future loading rate or operating state. See belt weigher calibration methods.
Routine servicing is not automatically legal-for-trade verification. If the tonnes determine a sale by weight, confirm the required approval, verification and documentation using National Measurement Institute guidance. Ask what service, calibration or verification scope the report actually covers.
How do comments and recommendations change the interpretation?
Read the work sequence. A large zero change after removing build-up means something different from an unexplained change on a clean installation. Notes about damaged idlers, restricted frame movement, moisture or an unreliable speed signal explain why a test may have been limited or follow-up work requested.
Separate completed repairs from recommendations. Assign responsibility and timing to unresolved work, especially where the report questions whether the measurement is fit for its intended purpose. Do not file the report as a clean bill of health solely because an as-left number looks small.
What should I compare between visits?
Compare like-for-like results, methods and units. Last visit’s as-left and this visit’s as-found can reveal change, but check for intervening repairs, settings changes, different references or different test conditions. AIMM helps retain the service history for assets we maintain.
A report cannot usually establish exactly when an error began or how it varied between visits. Avoid applying today’s error to months of production without a defensible investigation. Repeated recommendations, worsening results or an unexplained step change are reasons to discuss a plan.
Frequently asked questions
Does an out-of-tolerance result mean the weigher is broken?
Not necessarily. It means the recorded result did not meet the criteria applied. Determine the cause, consequence and required action; do not dismiss it as normal without assessment.
Does a blank repeatability field mean it passed?
No. Ask whether the test was performed, recorded elsewhere or omitted, and why.
When should I contact Accurate Industries?
Contact us if the percentage basis is unclear, results do not repeat, an important test was limited or a recommendation keeps returning. We can assess repair options and whether an upgrade would offer better value.
Need a manual for your equipment?
Talk to us about manuals for your equipment. Send the make, model, serial number and software version (a photo of the label is fine) and we’ll help you find the right document.
For help interpreting a report, contact Accurate Industries or ask about weightometer calibration and belt weigher servicing.