Harbor Freight Moisture Meter?

[Brody Goodwine]

Please, lets not make this a HF rant thread.

I purchased a HF moisture meter after reading quite a few reviews (plenty from woodworkers) stating that the meter works. For $12 it was worth a shot. I have had zero luck getting a reading in wood, and always wind up with 0% moisture no matter what wood I test, which of course isn't true. The meter is not DOA, as I always get a reading on my skin or if I dampen the wood. This is my 2nd meter to do this.

I'm starting to think it is user error on my part given the decent reviews, readings on my skin, and second unit to do the same thing.

I'm effectively just stabbing the wood with the two pins, so I'm not sure what I could goof up there. Advice?

[Brian Kent]

I think you can get $12 for it if you bring it to Harbor Freight.

[John Coloccia]

A good moisture meter costs hundreds, and sometimes thousands, of dollars. I'm not surprised that a $12 meter doesn't work well.Anyhow, are you sure you're in "wood" mode?

[Ronald Blue]

I have one and it has always worked for me. The pins do need to penetrate to get a reading. You might need to trim some off the end to get a reading. The wood obviously dries first on the outside. Let us know if you get it to work.

[Bill Davis]

Even high quality moisture meters have difficulty reading low MC wood and many have a minimum reading below which they will just not read.
Pin type moisture meters are basically measuring the electrical resistance between the pins and dry wood has a very high resistence - many megOhms and are therefore most inaccurate at low MC. My guess is that you are trying to measure out of that particular meter's range.

[Neil Brooks]

Even high quality moisture meters have difficulty reading low MC wood and many have a minimum reading below which they will just not read.
Pin type moisture meters are basically measuring the electrical resistance between the pins and dry wood has a very high resistence - many megOhms and are therefore most inaccurate at low MC. My guess is that you are trying to measure out of that particular meter's range.

I'm going to say "BINGO" to this one, but only based on my belief.

I have the earlier HF moisture meter -- not digital. I recently used it to check a WHOLE bunch of my lumber, AND some new stuff I'd recently bought.

Northern Colorado is very dry, though, and I know the last batch lived outside.

Nothing registered, except me

If you look at an Equilibrium Moisture Content Calculator, you find that it's very easy to have conditions where the wood is at an EMC below the low-reading end of the HF moisture meter.

All the stuff that was outside ... SHOULD BE below the (I think it's 7%) HF's range. Everything that's been in my shop for 6-24 months ... should ALSO be below, or just barely at, that range.

In fact, I'd have a difficult time finding wood, locally, without cutting it, myself, that WOULD register.

That's the conclusion I reached, anyway -- right, wrong, ridiculous, or otherwise.

Do the math on the EMC calculator, and see if it might explain your story, too.....

[Dave Lehnert]

I have the HF meter. I always thought the reading was high but have nothing to compare it to.

[Rob Holcomb]

I bought a Harborfreight moisture meter when I first set up my shop and used it quite a bit. It worked but as others have said, it measured high. I didn't know this at the time until I bought a Delmhorst J-Lite Pin-Type Moisture Meter and compared the two. The Delmhorst measured the moisture content on every board that I had to be 2-3% less than what the Harborfreight meter indicated. Not knowing which was giving me a more accurate reading, I borrowed meters from two other woodworking friends and theirs also indicated a 2-3% less value. So although the Harborfreight model works, it isn't as accurate as a more expensive model.

[Ken Whitney]

I bought the HF meter to monitor the drying of green wood turned bowls. It works, in that it reads progressively lower MC as time goes by, but I don't believe that the readings accurately reflect the moisture content. And it eventually stops reading when the bowl blanks reach a low enough moisture content, although I don't know what that is.

Not the worst $12 bucks I've spent.

[Brody Goodwine]

According to HF, the meter works in the 6-42% range.

Bill/Neil, I bet you are correct. That said per your link I should be at around 12.2%MC (garage temp ~55 and humidity ~65% - indiana), so not reading 12%MC when the meter supposedly read to 6% would be quite a bit of error (outside the 2% claimed). Again I understand this is a $12 HF tool, but if it was so far off I'm a little surprised by all the positive reviews.

I'd be okay if it read 0 on anything below 8 or so, but if i'm at 12% and it reads 0 I'd like to know the difference between 8% and 12%.

I'll cut down a thicker piece and try it on the center of a board then report back. Given the unit works by conductance (thanks Bill) should I try to scuff up the pins a bit with the hope of better conduction?

[Brody Goodwine]

Well, i just ran outside to stab a few items in the elements. No rain for about 5 days here.

Old stump - 14%
Wood Ladder Under Soffit - 11%
Rotten MDF Under Soffit - 10%

So i guess Bill/Neil are correct, but how far off do those numbers seem? I'd expect much higher IMO.

It would be interesting to see a back to back comparison vs a higher quality meter.

[Neil Brooks]

Brody:

The (cool) thing about equilibrium moisture content is that -- by definition -- it means the wood has reached the moisture content that it will STAY at, given the humidity and temperature of the "room."

So ... high, low, or accurate, you CAN use the HF meter to do the IMPORTANT thing: figure out when the MC (moisture content) has leveled off.

That's really the key, particularly if you're building projects that will live in similar conditions, rather than shipping a dresser from the rain forest to the dessert, or vice versa.

'Zat make sense ?

[Charles McElroy]

I bought a General that did the exact same thing. Finally, just before I took it back I put a new battery in it. Worked great ever after.

[Brody Goodwine]

Neil, the problem is that I really don't dry any lumber. I live in an old historic neighborhood where a large garage is uncommon, and frankly I'm just not that prolific yet to need the volume. Therefore my main use would be the make a quick spot-check of some lumber prior to machining it, so I really want the number, not the trend. I fully understand the trend being most important if you were drying lumber. I'd like to know 8% vs 12%MC, but IMO the meter reads 0% at both of those points unless some pretty damp items laying outside (see above) were at 10-14%

[Bill Davis]

Brody - The gold standard for accurate MC measurement is the to use the ovendry (OD) method. I have used this many times and use it to check my moisture meter. here is a summary but note it is more cumbersome than the convenience of a meter, and likely more expensive because of the cost of a scale to weigh the wood sample that has sufficient resolution and accuracy.

The standard method of determining the relationship of water in wood is to:

1. weigh a wood sample before drying to obtain the combined weight of the woodand water;
2. dry the wood sample in an oven at 103 ±2° Centigrade (100°C = boiling point of water) for (approximately) 24 hours;
3. re-weigh the wood sample;
4. repeat steps 2 and 3 until the current weight equals the previous weight (the wood sample is now ovendry (OD), sometimes referred to as bone dry);
5. apply Equation 2 for determining % MC of the wood.

Equation 2: % MC = (weight of wood before drying - OD weight) ÷ OD weight

From the equation above, when the water weighs more than the wood, the % MC will be greater than 100. The OD weight is not a natural state for wood, and the sample must be weighed immediately after being removed from the oven. Because wood is a hygroscopic material (meaning that it readily takes up and retains moisture), it is impossible to prevent moisture from entering dry wood. As soon as the OD sample is exposed to the air, it will start to take in moisture from the air.

For a reliable result the sample piece of wood should weigh 100g or more and you must weigh it with an accuracy of +/- 0.1g or with a precision of 0.1% of the weight of the wood sample .

I use a small kitchen type electric toaster oven with an accurate thermometer measuring the internal temperature because I found the oven dial to be very inaccurate. I use a weigh scale that weighs up to 5500g with a resolution of 0.1g and I use sample wood pieces that weigh in excess of 100g. I use a weight standard to calibrate the scale each time because true weight is not reliable otherwise for my cheap scale.
Toaster oven $50
Weigh Scale $250
5000g Weight Standard $70
Calculator $20
Electricity $??
Time $??

So I use my MC meter most of the time. But I can verify it by following the gold standard proceedure above.