Wood Temperature Test

Wood temperature is another important factor that can affect the accuracy of some moisture meters. As wood temperature increases, moisture meters can read higher even if the moisture content has not changed. As wood temperature decreases, the moisture meter can read lower.

Pin-type moisture meters in particular are highly sensitive to changes in wood temperature. Since these meters are typically calibrated to 70° F, any wood temperature significantly different than 70° F would require the user to adjust the readings to ensure accuracy. The rationale behind the Wood Temperature Test is to determine if a meter is highly sensitive to wood temperature fluctuations, thereby affecting its accuracy.

Real-World Scenarios

Many pin meter manufacturers include temperature conversion charts in their manuals. Typically, temperature conversion charts are difficult to read. In the real-world, most people probably are not going to want to take the extra time it takes to figure out how to read these charts to correct their readings. As a result, if a meter is highly sensitive to wood temperature fluctuations and the user does not make any adjustments to account for this, inaccurate readings could be the result.

Consider the floor installer who’s trying to install hardwood flooring at 6% MC. The idea, of course, would be to avoid installing at 8% or 9% MC, and yet that’s exactly what could happen if no adjustments are made to account for wood temperature. In this example, even a 2% or 3% difference in readings could be problematic for someone requiring accurate moisture measurement.

Wood Temperature Test Procedures

Refrigerator

1. Take three pieces of Douglas fir, one piece between (5%-10%) labeled C1A, one piece between (11%-20%) labeled C1B, and one piece (greater than 20%) labeled C1C.
2. With each meter, take a reading of each of these pieces at room temperature and record both the meter reading and the wood temperature.
3. Drill a hole in the C1B sample to monitor the wood’s core temperature with thermocouples.
4. Place the wood in the refrigerator for 1 hour.
5. Record the wood temperature and take a reading of the first piece with each meter. Record.
6. Repeat step 5 with each piece of wood.
7. Allow the wood to equilibrate to room temperature for one hour.

Note: The wood samples will remain wrapped during this test.

Microwave/RH Chamber

1. Take three pieces of Douglas fir, one piece between (5%-10%) and label it W1A, one piece between (11%-20%) and label it W1B, and one piece (greater than 20%) and label it W1C.
2. With each meter, take a reading of each of these pieces at room temperature and record both the meter reading and the wood temperature.
3. Place the first piece of wood in the microwave for 30 seconds.
4. Take a reading of the ambient RH.
5. Place the first piece of wood in the RH chamber at the ambient RH for 10 minutes at 112 degrees F.
6. Record the surface temperature of the wood, and record each reading for %MC.
7. Repeat steps 2-6 with the next piece of wood and the next group of meters, so that every meter reads at least 1 piece of wood.