Quick answer: A coating-thickness report is auditable when another inspector can reconstruct what was measured, where, with which checked instrument, what the individual readings were, and how the stated acceptance rule produced the conclusion. Averages alone cannot answer all of those questions.
A minimum field-record template
| Record | What to write down | Why it matters |
|---|---|---|
| Job and zone | Project, part ID, surface/zone, date and operator | Allows the area to be found again. |
| Measurement basis | Substrate, coating system, method, cited procedure and revision | Shows whether the method applies. |
| Instrument control | Gauge/probe model and serial, calibration status, reference or shim checks and adjustments | Makes the readings traceable to the equipment state. |
| Raw data | Spot map or coordinates and every retained reading with units | Permits recalculation and repeat visits. |
| Decision | Specified limits, sampling rule, calculated result, deviations and disposition | Separates measured facts from a pass/fail decision. |
Why an average is not enough
Suppose three readings are 117, 121 and 119 µm. Their mean is 119 µm, but without the specified limit, location plan and individual values a reviewer cannot judge the work. This is an illustrative arithmetic example, not a universal acceptance rule. Some project specifications also require spot or area calculations; record the data in the form that the cited document requires.
Handle unusual readings without rewriting history
- Keep the original reading and its location.
- Check the probe contact, surface condition and instrument verification; note the reason for any repeat measurement.
- Record both original and repeated values, then apply the agreed rule for inclusion or exclusion.
- If the pattern repeats, flag the zone for investigation rather than deleting inconvenient results.
Before issuing the report
Confirm that identifiers, units, gauge checks, raw readings, calculation and cited acceptance document agree. ASTM D7091 describes calibration, verification, adjustment and measurement practice; project limits must still come from the applicable specification or coating data sheet. For practical measurement decisions, see powder coating on steel and aluminum and paint over galvanized steel. Spot and area measurement explains why the sampling unit matters.
Frequently asked questions
Can gauge memory replace a report?
It can preserve readings, but the report still needs locations, conditions, instrument checks and the decision rule if those are not stored with the readings.
How long should records be kept?
Follow the contract and quality-system retention policy; there is no single retention period for all projects.
Technical source
Related instruments: DONGRU DR-A5 Automotive Paint Thickness Gauge · Request a quote