Checks, verification and calibration: know the difference

Scope: follow the named procedure

Manufacturers sometimes use “calibration” for a user-accessible reset or offset operation. Read what the procedure actually does, the required conditions and the stated result. Do not assume that a menu item creates a traceable calibration certificate.

This guide uses Protimeter MMS3 Manual Rev3-1 and the Bosch GMS 120-27 UK English online manual as examples. Bosch’s wall-scanner example is separate from the moisture-meter discussion. Their button sequences and acceptance values must not be transferred to other tools.

Four activities to distinguish

Terminology varies. Name the actual activity in the record rather than using “calibrated” as a blanket description.

What the MMS3 example shows

Section 4.7j of the MMS3 manual separates non-invasive offset calibration from pin moisture calibration verification. The pin check and the pinless procedure have different setup conditions. Following the wrong setup can invalidate the intended check. Consult that section for the full instructions rather than substituting a generic online reset sequence. Manual.

The same manual’s safety section says its accuracy specifications are valid for one year after calibration and calls for recalibration after that period. This is a statement about this manual and instrument, not a universal annual rule for every moisture meter. Generic marketing advice about occasional calibration does not override the applicable model instructions.

A successful pin check does not by itself validate the humidity probe or the non-invasive search function. Keep the mode and check result together in your records.

A wall scanner is a separate example

For the GMS 120-27, Bosch describes manual recalibration for a particular condition: a metal indication with persistently high amplitude when there is no metal near the tool. The recalibration page specifies setup conditions and the procedure. The error page also distinguishes temperature, interference and contact problems.

This is not an instruction to recalibrate whenever a real wall produces an inconvenient result. First identify the symptom and consult the correct manual. A successful recalibration also does not turn a non-response into proof of a service-free drilling position.

A practical pre-use and post-concern record

1. Identify the instrument, probe/accessories and mode to be used.
2. Inspect and clean the relevant surfaces as the maker specifies; check for damage and power problems.
3. Allow any specified environmental stabilisation, then perform the applicable reference or built-in check.
4. Record the date, procedure, conditions and exact result. Retain a calibration certificate reference where one exists.
5. If a check fails, repeat only as the manual permits and investigate the cause. Do not silently continue because subsequent readings look plausible.
6. After a drop, damage, unusual drift or a failed check, follow the maker’s service advice and consider whether earlier results need review.

The last step is our record-management recommendation, not a claim that a particular incident always changes accuracy. Mark affected observations as uncertain until the issue is resolved.

Limits and next steps

A meter can pass its instrument check while being unsuitable for the material or mode selected. Conversely, two methods can disagree because they sample different regions or use different scales. Review pin and pinless methods and measurement units before treating disagreement as a calibration fault.

Use the wall CSV or timber and floor CSV to preserve the procedure and result. Neither blank template is itself a certificate or evidence that any check was carried out.