Calibrate Your Wood Moisture Meter – Simple Steps
- Make sure the serial number on your On-Demand Calibrator (ODC) matches the serial number on your meter.
- Place the ODC on its legs on a non-metallic surface.
- Turn the meter on, then use the SPECIES/MATERIAL button to put your meter in CAL mode.
- Place the meter on the ODC, correctly “seating” the meter sensor pad firmly in the recessed area of the ODC. IMPORTANT: Failure to correctly and firmly “seat” the sensor pad in the recessed area will cause an inaccurate calibration.
- Verify the meter is seated correctly by moving the meter slightly up and down and then side to side.
- Apply light downward pressure and press the AUDIO button 3 times. The meter will begin to make a “beeping” sound which indicates it’s going through the calibration process.
- When the calibration procedure is completed, the meter will display the word LIFT. Immediately remove the meter from the ODC and hold the meter in the air approximately 5 seconds until the word DONE appears on the display.
- Press the ON/HOLD to return the meter to normal measuring mode.
“Confident Craftsmanship Comes from Careful Calibration”
Try saying that five times fast.
Luckily, as a professional working with wood products, you don’t need to say it so much as you need to make it a reality by taking moisture meter calibration seriously.
A meter that is out of calibration is as useful as a dull saw. Could you get some work done? Sure, but the results will be ugly.
A moisture meter that deviates from its calibration standard will deliver inaccurate results. That’s a fact. If you’re getting erroneous readings from a moisture meter, your woodworking and your reputation will suffer.
On one hand, it’s worth remembering that a high-quality moisture meter can stay calibrated for years. Absent some external factor that can cause physical damage to the meter, it’s not likely to become decalibrated.
On the other hand, woodworking is about precision. So it’s also worth understanding how to ensure the meter you’re using is calibrated and how to get recalibrated if it’s not.
What Havoc Can an Out of Calibration Meter Wreak?
A meter out of calibration can tell you your wood is ready to be fashioned into its end-use when it’s not. Once the final product is within the in-service environment, it will start to lose or gain moisture as it works to reach a point of equilibrium moisture content (EMC) with its surroundings. Then very bad things happen. Exactly what those bad things are will vary by end-use. Here are some all-too-common bad outcomes for different types of woodworkers.
Furniture and decorative woodwork: Overall project dimensions can change, making that round tabletop slightly oval, the legs askew, and flat surfaces warp and twist. Any wood door, whether for a cabinet or front of the house, can change size as it loses and gains moisture. When the changes are significant enough, doors get jammed or show gaps with their frames. These same size fluctuations can cause swelling or cracking in wood panels.
With woodworking, it’s all about the joints. Working with wood that’s not at the proper moisture level can result in weakened joints. Many joint types rely on the fact that the wood will expand slightly (slightly) in its in-service location. The expectation is the joints will tighten and strengthen as the wood swells. If this doesn’t happen because the wood was too wet when joined, then the entire piece is compromised.
Wood flooring installers: Flooring installers have an advantage because they are likely working in the in-service location. Furniture makers and luthiers have to make some educated guesses about future service conditions. Flooring installers avoid moisture-related failures by letting the wood acclimate to the surroundings. Yet the installer can’t know if the wood has acclimated without a calibrated moisture meter.
If the wood’s moisture content (MC) is too high when installed, it will shrink over time. This shrinkage can cause gaps between boards. If the wood’s MC is too low when installed, the wood’s expansion from absorbing moisture can cause cracks, cupping, or crowning.
Wood pallets: Wood pallets are used everywhere in shipping and warehousing. They ease storing and moving large quantities of goods. If the pallets’ moisture level hasn’t equilibrated, they might damage the products as they absorb or release moisture into the air. Organic goods, like produce or natural fabrics, are particularly susceptible to spoiling.
Indeed, wood pallets used in container shipping present the highest risk of moisture-related damage. Shipping containers are closed spaces, but they aren’t airtight. As they move from day to night and climate to climate, the air inside the shipping container is continually interacting with the outside air. That means temperatures and humidity are in constant flux.
Wood pallets that are too wet going into shipping have too much moisture to release into the air and into products being shipped. If the air temperature is cold enough, this moisture will appear as condensation. Often, condensation appears on the container’s ceiling and drops onto the goods below. Not good.
Luthiers: An acoustic wood instrument’s construction determines the quality of its tone and volume. Building a string instrument before the wood has acclimated can cause warping, cracking, and separation at the seams. All these deformities in the wood can change the body shape, the shape of the holes, how securely the top or bottom plate are secured to the sides, or the strength of the bridge. In addition to being unsightly and risking full destruction of the instrument if the moisture-related damage is severe, all these issues will impact sound quality.
The internal wood pieces, like a brace or soundpost, will also be affected by humidity changes. Any shrinking or expanding due to moisture meddles with the instrument’s sound quality.
Even the wood’s weight can alter the sound. Wood made heavy from too much moisture can result in a sluggish sound, while too dry wood can make a tight sound. An excessively dry string instrument will also have problems projecting its sound.
A luthier’s biggest challenge is to remember that MC changes don’t need to be visible to alter the instrument’s sound.
What Does It Mean for a Wood Moisture Meter to Be “Calibrated?”
Let’s start with what it means to say a tool is “calibrated.” Calibration exists when the reading from a device with unknown accuracy falls within a specified range of the reading from a known standard.
For wood moisture meters, that standard is set by ASTM D4444 (Standard Test Method for Laboratory Standardization and Calibration of Hand-Held Moisture Meters). This standard outlines how to do the most accurate wood moisture test, the “oven-dry test.”
Understanding the Calibration Functions on a Handheld Meter
Meter companies often say their wood moisture meters have “built-in” calibration or “internal calibration.” It’s essential to understand what these terms mean.
All new meters are sent out from the factory already calibrated. That is, calibration is “built-in” the meter or the meter is said to have “internal” calibration. But of course, new meters come out of the factory calibrated and ready to use; it wouldn’t make much sense if they weren’t. These terms are also sometimes used by manufacturers to refer to a “built-in” or “internal” calibration test. That is, they refer to an internal function within the meter that tells you whether the meter is still calibrated. Many of these internal calibration check tests will even specify how far off the internal calibration is.
Yet “internal calibration” can be misleading in two ways. First, an internal calibration test uses an internal circuit as a reference point. Therefore, it’s prone to all the same risks for physical damage that may have caused the meter to de-calibrate in the first place. Also, an internal calibration circuit can not measure the initial stage of the sensing circuit, which in some meters is the part that’s most likely to get knocked out of calibration. A reliable calibration test requires an external, standardized reference point. That’s why most meter companies also sell tools you can use to perform an external calibration test.
For a pin meter, you need a moisture content standard (MCS) to conduct an external calibration test. An MCS is a small box with contacts or clips that’s been calibrated to a known value. Touch the pins of the meter to the contacts or clips. Then you compare the meter reading to the MCS’s known value. If it’s within a specified range, your meter is calibrated.
Conducting an external calibration test on a pinless meter requires a calibration verification block instead of an MCS. Otherwise, the process is similar. Place the meter on the block and take a reading. If the meter’s reading is within the acceptable range of the block’s known value, you’re good to go.
Yet the language about “internal calibration” or “built-in calibration” carries a greater risk. These terms may give the impression that the meter can calibrate itself. Nearly every moisture meter on the market needs to be sent back to the manufacturer to get recalibrated if it becomes decalibrated. That makes recalibration a costly process that can take weeks. It also means that you’d better have at least one other moisture meter — that is calibrated — to use in the interim.
Achieving True In-the-Field Calibration for Your Moisture Meter
In truth, there’s only one wood moisture meter line that allows you to calibrate the meter in the field: All of the meters in Wagner Meter’s range of Orion® Pinless Wood Moisture Meters come with an On-Demand Calibrator, an external tool that allows you to recalibrate the Orion meter.
On-site recalibration is a revolutionary breakthrough.
Use the On-Demand Calibrator whenever you suspect that your Orion wood moisture meter is out of calibration. Maybe you dropped your meter or it got tossed around in your truck, so you’re concerned. You can check whether it’s calibrated. Yet the On-Demand Calibrator works so quickly, it’s faster and easier simply to use it to calibrate your meter to Wagner’s superior factory accuracy standards.
It will take you less than 30 seconds to calibrate an Orion meter using the groundbreaking On-Demand Calibrator. This re-calibration tool is a small docking platform that provides an external, hard reference point. Exactly what’s needed to perform a reliable, accurate calibration. Now, there’s no reason to spend money to calibrate or put a meter temporarily out of service to get it calibrated.
Anyone seeking ISO certification can get a version of the On-Demand Calibrator that’s NIST-traceable.
The Orion line is the latest link in Wagner Meters’ chain of innovation dating back decades. Besides being the only moisture meter you can calibrate on-site, the Orion line provides users other advantages:
- High-speed readings let you take more measurements without losing time
- Dual-depth options that can measure shallower or deeper into the wood
- Improves data management by storing up to 100 readings — and the Orion 950 can deliver that data to a mobile app
- Calculates dew point and EMC for you
The Orion 950 Smart Pinless Wood Moisture Meter recently won the hardware category in the AWFS 2019 Visionary Awards. Judges evaluated products on their innovation, quality, practicality, user-friendliness, and production impact.
You can explore all the ways the Orion 950 is the most advanced wood moisture meter on the market here.