A Century of Innovation: The History of Wood Moisture Meters

Wood moisture meters are an indispensable tool for woodworkers, floor installers, cabinetmakers, home inspectors, sawmill owners—really, anyone who wants to avoid moisture-related damage to their work.

And these tools have a century-long history.

Moisture meters started out as simple devices but quickly evolved to the pin-type and pinless moisture meters available today. Understanding this progression will help you as you shop for the right wood moisture meter for your purposes.

We’ll cover:

• The history of the moisture meter
• Which is better: pin or pinless meters?

Let’s find out how we got the sophisticated meters we have on the market today.

The history of the moisture meter

The ancestry of the wood moisture meter traces back to the very first moisture measurement devices developed in the 1920s.

These early meters didn’t physically resemble the meters we have today. They were called blinker-type meters, and measured the moisture levels by how often a light blinked—hence the name.

They capitalized on electrical properties in water, using electrical current to establish moisture content. Impurities in water allow it to conduct electricity, so the more electricity, the more moisture in the wood.¹ Higher amounts of moisture meant the wood needed to continue the drying process until it was drier and safer to use.

Technology advanced quickly on its heels.

Vacuum meters came next in the 1930s. These meters used a vacuum tube circuit to detect moisture.

Their process was similar to that of blinker-type meters, as they used the electrical resistance created by the presence or lack of moisture in the wood to determine the moisture content. High resistance indicated less moisture—low resistance meant higher moisture.²

The pin meter

Vacuum tube meters became the basis for the pin meter, which grew popular in the 1940s. Building upon the vacuum tube meters, pin meters had two or four electrodes that stuck into the wood and passed an electric current between them. The amount of resistance determined the moisture conditions of the wood.

Pin meters are still commonly used today. However, their circuitry now uses much more modern parts. Their mechanism is mostly unchanged, except that today’s meters only have two probes. Because they have been on the market for so long without updates, they are believed to be pretty reliable.

The pinless meter alternative

Around the same time pin meters were becoming popular, researchers were experimenting with another way to detect wood moisture, using dielectric properties. Basically, this method involved transmitting electric currents without the wood moisture being a conductor of the current.

Researchers used two different dielectric principles, and while both used radio waves to detect moisture, it resulted in two different methods of testing.

One of these types was power-loss testing. This testing determined the amount of moisture by how much electromagnetic energy was lost.

The other type was capacitance testing. This method measured how much energy could be stored, which equated to how much moisture was in the wood.

There were a number of pinless meters during the early 1900s. However, they fell out of favor because they were not believed to be very accurate.

However, that belief would change with more research…

The development of modern meters

20 years passed. Then, in the opening years of the 1960s, Delmer Wagner began working to develop the in-line meters, hoping to improve on the big, clunky vacuum tube meters used at the sawmill he worked at.

People didn’t think they were as accurate as the average pin meter, and some still weighed over ten pounds!

But in the 1990s, Wagner Meters changed that again. They started working on a better handheld solution even though this was a new market for them. They developed a handheld pinless meter that greatly improved on previous pinless styles.

This new design brought pinless meters to the forefront of the market. This new style used some of the same principles as capacitance and dielectric meters, renamed electromagnetic waves. These waves calculated the moisture in the wood without the need for pins. Wagner also made them more popular by designing them for woodworkers and flooring installers, instead of just for sawmills.³

In the 2000s, Wagner made their wood moisture meters digital (as opposed to the previous analog style), making them an even more powerful tool. Now, many pinless meters follow this basic design and method, allowing for far greater accuracy and ease of use. And because they have evolved so much, they are more accurate than pin meters, which have continued to use the same mechanisms since they were invented in the 1940s.

Even so, both continue to be sold. So which one is really better? Let’s look at the advantages and disadvantages of each to help you choose.

Which are better: pin or pinless meters?

The type of wood moisture meter that’s best for you will depend on your situation and needs. Here are some considerations to keep in mind as you evaluate your circumstances.

Let’s begin with the pin-type meters.

Pin meter advantages and disadvantages

Pin meters have several pros to them:

• Accurate depth readings. Pin meters only measure at the tips of the pins, so whatever depth they’re inserted at is exactly the depth you’ll get a measurement at. Pin meters can also be inserted at different depths, allowing you to get a picture of the moisture gradient in the wood. Pinless meters, on the other hand, generally have fixed depths.

• Surface moisture doesn’t affect them if they have insulated pins. If your pin meter has insulated pins, only the tips take a moisture reading. When inserted into the wood, you don’t have to worry about surface moisture skewing the reading.

• They’re better than other types at measuring rough wood, uneven wood, or curved wood. No matter the surface, pin meters still give a reading as accurate as anywhere else. Pinless meters, on the other, require a flat, smooth surface for an accurate reading.

• They’re less expensive. On the whole, pin meters usually have a lower price tag than pinless meters. This makes them an ideal budget option for a new woodworker who still wants a solid moisture measurement.

While they have a number of good things going for them, pin meters also have their share of downsides:

• They’re sensitive to wood temperature. The accuracy of a pin meter is affected by the temperature, especially when the temperature heads toward extremes. Higher-end pin meters have temperature correction charts, which make up for this problem. But most do not, which leaves you on your own. Guesswork is rarely accurate in this case.
• They leave pinholes in the wood. To obtain a moisture reading, pin meters have to be physically stuck into the wood (which may require a hammer probe). This makes holes in the wood.And, since it’s advisable to take multiple readings across the wood for a more accurate picture, you’ll end up with multiple sets of small holes across the piece of wood.The seat of a rocking chair? Not pretty. A tabletop? Unappealing.
• The pins can snap off easily. This is true especially if the pins are longer or the wood is hard, such as oak. When the pins snap off, you first have to reinstall the pins, which can be annoying if you’re in a hurry or don’t have any with you. And if the pins break off consistently enough, you’ll have to purchase more. Sometimes, the pins can even break off inside the wood. That turns an easy moisture check into a complicated problem.

• They aren’t the best for large projects. Getting a reading with a pin meter takes significantly longer than with a pinless because you have to insert the pins properly, which can be difficult with hardwood. If you’re using a large amount of wood, having to take a lot of readings like that can be frustrating.

With this comprehensive view of pin meters, let’s turn now to pinless meters.

Pinless meters advantages and disadvantages

Here are the advantages of using a pinless meter:

• You can take dual-depth readings. Like we said earlier, pin meters can only read exactly where the pin tips are. With a pinless meter, you can switch between two different depths without withdrawing pins. This is really handy when you need meter readings at a second depth. Most dual-depth pinless meters read at ¼ inch and ¾ inch.

• They take far less time to get a reading. Getting multiple readings across the wood is as simple as moving the meter along the wood’s surface. You can pick up many readings in just a few seconds.

• They’re more accurate. Third-party studies indicate that pinless meters tend to be more accurate on the whole than pin meters. Also, consider this, with a pinless meter, you won’t be tempted to take shortcuts to reduce the time it takes for a reading—the readings are already quick and easy to take! On top of these things, many pinless meters have calibration ability, which enables the meter to be reset, improving accuracy.

These are their disadvantages:

• They’re not ideal for curved, rough, or uneven surfaces, or surfaces that are too small to cover the entire sensor pad (think thin chair legs or rungs). Attempting to take measurements on these types of surfaces can result in inaccurate readings.

• They’re affected by standing water or surface moisture. This refers to wood with visible water droplets on its surface. If the wood was sitting in the rain or fell in water, you’ll need to wipe it dry before using a pinless meter, or the reading may be affected.

Now that we’ve gone over the pros and cons of both pin and pinless wood moisture meters, here’s the question—which one is better?

Generally, pinless are preferred by professionals in the industry because they are more accurate, faster, and easier.

What’s more, at the writing of this article, many come with technological features not available on pin meters. Some examples are EMC (equilibrium moisture content) calculators or sensors that detect ambient relative humidity.

That being said, a pin meter may still work best for your situation. It’s important to go through the advantages and disadvantages of each type of meter and choose one based on your situation.

A long legacy

Wood moisture meters have come a long way from their humble beginnings in the 1920s. They’ve gone from big, cumbersome tools to sleek handheld devices. And they’ve increased from slow-time results to quick results.

Whether you decide to go with a pin meter or a pinless meter for your projects, know that the meter you are choosing is the product of 100 years of testing, researching, and experimenting.

When are you choosing your wood moisture meter?

1. Morgan, Tony, “History of Wood Moisture Meters,” Wagner Meters, March 12, 2024. (↑)
2. Ibid. (↑)
3. Ibid. (↑)