Wood temperature is another important factor affecting the accuracy of moisture meters. As wood temperature increases, moisture content rises. As wood temperature decreases, the moisture content falls.

Moisture meters are highly sensitive to changes in wood temperature. Since meters are calibrated to 70° F, any wood temperature above or below 70° F requires the user to adjust the readings plus or minus 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 a user does not adjust his meter for those fluctuations, he could end up with inaccurate readings and a costly error.

Consider the floor installer who’s trying to install hardwood flooring at 6% MC. He’s not going to want to install it at 8% or 9% MC. But that’s what could happen if he fails to adjust his meter for changes in wood temperature. In this example, even a 2% or 3% difference in the reading can be problematic for someone requiring accuracy from his meter.

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%), one piece between (11%-20%), and one piece (greater than 20%).
  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.
  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.