Module 4 · Tools & Equipment
4.6 How to Avoid False Readings
7 min read
Every instrument in the kit measures a proxy for what you want to know, and every proxy can be produced by something else. This lesson collects the false readings in one place, because a beginner who knows how their tools lie is more useful than one with a better meter and no suspicion.
Learning objectives
By the end of this lesson you will be able to:
- Identify the common causes of false readings for each instrument.
- Apply cross-checking routines that expose a false reading.
- Explain why a single instrument can never be sufficient.
- Report readings with the caveats their limitations require.
Key terms
- False positive
- An instrument indicating moisture where there is little or none.
- False negative
- An instrument failing to indicate moisture that is present — often because it is deeper than the tool reaches.
- Cross-checking
- Confirming an indication with a different instrument or method that fails differently.
- Foil-backed plasterboard
- Plasterboard with a metallised vapour-control backing. Reads as saturated on a pinless meter regardless of moisture.
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Read the rest of Tools & Equipment
Module 1 is open to everyone. The remaining six modules — building science, each damp mechanism in depth, meters and thermal imaging, the full inspection method, and report writing — are free too. We just ask for an email so you can pick up where you left off, and so we can send your certificate when you finish.