External ambient weather conditions — including temperature and relative humidity — can indeed influence the results of wood moisture readings. However, they do not affect pin and pinless wood moisture meters in the same way.
In this article, we’re going to go over the difference between pin and pinless meters, take a look at how each of these meters is affected by ambient weather conditions, examine how weather conditions impact wood moisture content, and end the article with some ‘best practices’ tips on how you can ensure that your moisture readings are as accurate as possible.
How pin wood moisture meters work
Pin-type moisture meters have two pins (or probes) that must penetrate the wood in order to test its moisture content. When the meter is turned on an electrical current flows between the two pins and the resistance is measured. An estimation of the moisture content of the wood is determined by the resistance.
Pin meter technology is based on the fact that water (with salts and impurities) is a great conductor of electricity while wood isn’t. Therefore, the drier the wood, the more resistance encountered.
Pin meters were the first type of moisture meter developed.
How do weather conditions affect the accuracy of pin-type meters?
With pin meters, the temperature of the wood being tested significantly affects the accuracy of the moisture content reading. This is because, as we just noted, pin meter technology is based on wood’s resistance to an electrical current. Well…
It turns out that warmer wood (warmer because its ambient environment is warmer) is a slightly better conductor of electricity than cooler wood. So, if you’re using a pin meter to test the moisture content of a piece of relatively warm wood, you could get a moisture content percentage that’s higher than what it really is.
On the other hand, very cool wood is a slightly less efficient conductor of electricity. Therefore, if you’re measuring the moisture content of wood that has been sitting in a very cool ambient environment, you could get a moisture content percentage that’s slightly lower than what it really is.
How pinless wood moisture meters work
Instead of pins, pinless wood moisture meters use an electromagnetic scanner to test wood moisture content. Because of this, they’re lightning fast to use. The meter’s scanner plate glides over the surface of the wood and allows a person to take multiple readings in the same amount of time it takes a person with a pin meter to take just one reading. Because pinless meters don’t damage the wood by poking holes in it they’re often used for measuring the moisture content of fine furniture and hardwood floors.
How do weather conditions affect the accuracy of pinless meters?
Unless the wood is frozen, pinless meters aren’t affected much by the temperature of the wood. This is because the technology behind pinless meters isn’t based on resistance. Therefore, unless you’ll be experiencing extremely cold temperatures, you don’t need to worry about weather conditions affecting the accuracy of pinless meters.
How weather conditions impact moisture content in wood
Now let’s talk more generally about how weather conditions impact wood moisture content.
Wood is a hygroscopic material. This means that it acts like a sponge. It’s able to absorb moisture from the environment and release moisture back into the environment. This process continues until the wood comes into balance with its ambient environment. This happens when the wood is no longer absorbing or releasing moisture.
Here’s how ambient weather conditions can affect the moisture content of wood…
Although this does depend on your geographical location, warmer weather conditions can mean lower relative humidity. This means that during the warmer months wood will release moisture into the environment. In other words, during warmer months in some locations, wood is drier.
During the wetter months, the higher relative humidity causes the wood to absorb moisture. This, of course, increases the wood’s moisture content.
For the sake of accuracy, these facts about wood are good to keep in mind when using either a pin or a pinless moisture meter.
Best Practices When Measuring Moisture Content During External Ambient Weather Conditions
There are a few best practices to follow in order to get the most accurate readings from your moisture meter…
1. Make sure you correctly specify which wood species you’re testing before you take a reading.
- This is because wood’s density and chemical makeup vary according to species. Pin-style meters are sensitive to wood’s chemical makeup while pinless meters are sensitive to wood density (also called ‘specific gravity’). Therefore, quality pin and pinless meters will always ask you to enter the wood species before taking a reading.
2. Make sure you wipe all water or surface moisture from the wood before taking a reading.
- Although certain high-end pinless meters do have the ability to “overlook” slight amounts of moisture on the surface of the wood, it’s still a good idea to thoroughly wipe the wood dry and then wait for about 30 minutes before taking a reading.
3. Make sure your meter is properly calibrated before taking a reading.
- Even the best meters will produce inaccurate readings if they’re not properly calibrated.
4. If you’re using a pin meter, make sure you correct for wood temperature.
- All quality pin wood moisture meters will come with temperature correction charts or adjustments which you’ll need to use if you want the most accurate readings.
5. If you’re using a pin meter, make sure you properly insert the pins into the wood.
- Improperly inserted pins can affect the accuracy of the reading. However, this can happen when the wood you’re trying to push the pins into is dense. In fact, pins can even bend or break. This is why it’s always a good idea to have spare pins on hand.
- Follow the manufacturer’s instructions on where to measure and with what grain orientation.
6. If you’re using a pinless meter, make sure the meter’s sensor plate isn’t damaged.
- A damaged scanning plate can affect the meter’s ability to have proper contact with the wood.
7. Make sure the meter’s batteries are fully charged.
- Low batteries can affect the accuracy of both pin and pinless meters.
8. Make sure your meter doesn’t have any water damage.
- If your meter isn’t dry or has any amount of water damage it probably won’t be able to provide accurate readings.
Weather Conditions Affect Accuracy
Ambient weather conditions can indeed affect the accuracy of moisture meters, both pin and pinless. However, as long as you understand the basics of wood as a hygroscopic material, your meter’s sensitivities, and follow the above mentioned best practices, you should be able to take accurate readings provided you use a quality moisture meter.
For more information on moisture meter accuracy and how to select a quality moisture meter, see: