CPR Thermal Imaging & Moisture Meters 3 — Questions and Answers
Question 1: A pin-type moisture meter uses which principle to measure moisture content?
- Capacitance change in a dielectric field
- Electrical resistance between two probes (Correct answer)
- Microwave signal attenuation through the material
- Infrared reflectance off the surface
Correct answer: Electrical resistance between two probes
Pin-type meters measure the electrical resistance between two probes — water conducts electricity, so higher moisture content lowers resistance and raises the meter reading.
Question 2: Which moisture meter type is BEST suited for quickly scanning large areas of hardwood flooring without surface damage?
- Invasive pin meter with insulated probes
- Pinless (non-invasive) capacitance meter (Correct answer)
- Thermo-hygrometer with surface probe
- Psychrometric calculator
Correct answer: Pinless (non-invasive) capacitance meter
Pinless capacitance meters scan large areas quickly and non-destructively by measuring changes in the electromagnetic field caused by moisture below the surface.
Question 3: What is the generally accepted equilibrium moisture content (EMC) range for kiln-dried hardwood flooring to be considered dry in the US?
- 1–3%
- 6–9% (Correct answer)
- 12–16%
- 18–20%
Correct answer: 6–9%
In the US, kiln-dried hardwood flooring typically has an EMC of 6–9%, and readings within this range are considered acceptable for dry, stable conditions.
Question 4: A moisture meter reading of 28% on a gypsum drywall reference scale indicates:
- The material is within acceptable dryness standards
- Elevated moisture that warrants further investigation (Correct answer)
- The drywall must be removed immediately without further testing
- A normal reading for freshly installed drywall
Correct answer: Elevated moisture that warrants further investigation
A reading of 28% on the gypsum reference scale is significantly elevated and warrants further investigation with confirmatory tools such as a thermo-hygrometer or invasive probing.
Question 5: When measuring moisture in concrete slabs, which method is considered the MOST accurate by ASTM F2170?
- Pin-type meter on the surface
- Pinless meter at maximum depth setting
- In-situ relative humidity (RH) probe in a drilled hole (Correct answer)
- Calcium chloride (anhydrous) surface test
Correct answer: In-situ relative humidity (RH) probe in a drilled hole
ASTM F2170 recognizes in-situ RH probes inserted into drilled holes at 40% slab depth as the most accurate method for assessing concrete moisture conditions.
Question 6: Which factor can cause a pinless moisture meter to give a FALSE HIGH reading on wood flooring?
- Low ambient humidity in the room
- A metal fastener or pipe beneath the surface (Correct answer)
- Using the incorrect species correction setting
- Scanning too slowly across the floor
Correct answer: A metal fastener or pipe beneath the surface
Metal fasteners, pipes, or foil-backed underlayment beneath the surface can interfere with the capacitance field and cause a pinless meter to display falsely elevated readings.
Question 7: Insulated pin probes on a moisture meter are used to:
- Prevent electrical shock to the operator during testing
- Measure moisture at a specific depth rather than the surface (Correct answer)
- Increase the sensitivity range of the meter
- Allow testing in materials with high salt content
Correct answer: Measure moisture at a specific depth rather than the surface
Insulated probes have coatings that prevent contact with the wood except at the pin tips, allowing the meter to measure resistance — and therefore moisture — at a specific depth.
CPR Thermal Imaging & Moisture Meters 3
A pin-type moisture meter uses which principle to measure moisture content?