# How accurate is a HF cen tech moisture meter

Posted By HDRock, Nov 1, 2012 at 4:00 AM

1. #1

### HDRock Minister of Fire 2. NULL

Oct 25, 2012
2,239
859
Loc:
Grand Blanc, Mi
2. #2

### blades Minister of Fire 2. NULL

Nov 23, 2008
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681
Loc:
WI, Milw
Replace battery. mine works fine. you need less than 20 % for epa stove. 15 to 17 better . surface moisture is going to be higher on what you checked due to ambient conditions. take a split and resplit it then check across grain in middle of fresh split area.

3. #3

### rdust Minister of Fire 2. NULL

Feb 9, 2009
4,340
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Loc:
Michigan
25% on a meter is fine for an EPA stove.

Our moisture content guru posted this some time again.
drfera said:
There are different ways of expressing moisture content, which don't at all have to do with the method of determining them. The EPA test loads are Douglas fir that is between 16 and 20% wet-basis. That is expressed by taking the weight of the water present and dividing it by the weight of the entire split. Your moisture meter is calibrated for Doug fir as well, but the calculations done by the chip inside of it (or the width of the scale divisions if you are using an analog meter) are done using the dry-basis method of expressing moisture content. That is expressed by taking the weight of the water and dividing it by the weight of the dry fiber that would be present in the wood after all the water has been theoretically driven out (as would be done in a 215Âº oven in a lab).

Naturally, you get very different numbers, and this effect grows increasing more substantial as MC rises. It's a mathematical thing, and has nothing to do with the actual wood, which always has the same amount of water in it.

If you want a real easy way to convert dry-basis meter readings to the wet-basis used by the EPA tests, just divide the number on the meter by that same number plus 100, and you will get the correct wet-basis MC every time.

For example, the meter says the wood is 25% MC. Add 100 to 25, then divide that number (125) by the original reading. 25/125 = 20% MC wet-basis. The high end of the EPA test range... perfect for you stove.
In another case, the meter says the wood is 19% MC. Add 100 to 19, then divide that number (119) by the original reading. 19/119 = 16% MC wet-basis. The low end of the EPA test range... perfect for your stove.

As far as a definite cutoff number, I don't believe it exists. The way you load the stove, the type of wood, the way the wood is split, the amount of coals in there, the internal stove temps, the timing and size of wood additions, the strength of your draft.... all things that can and sometimes do have a more profound effect on the burn then just MC and draft opening. For me, the theoretical cutoff is 25% MC wet-basis (33% MC on the meter). That's 5% more water in the wood than the maximum allowable MC in the EPA test loads. Above that, you will likely have a progressively harder time burning your wood without micro-managing the stove.​

4. #4

### HDRock Minister of Fire 2. NULL

Oct 25, 2012
2,239
859
Loc:
Grand Blanc, Mi
Thanks for the input.
Sorry ,I should have done it sooner, but, I have added this to my signature:
Non EPA, Fire View Stove , very similar to my avatar.
Let me clarify, The wood I am burning checked at 19%.on the bark side,a fresh split on the same piece was 15%.
I guess you guys would call my stove a smoke dragon ? Is that right ?

5. #5

### Jags Moderate Moderator 2. NULL Staff Member

Aug 2, 2006
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Loc:
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Yes...but...a cool looking one.

Hmmm...the large window is suspicious. Are you sure that the stove is not possibly EPA phase 1 cert.?

6. #6

### DanCorcoran Minister of Fire 2. NULL

Jan 5, 2010
2,203
363
Loc:
Richmond, VA
I've always read to put the pins in parallel to the grain, not across it. And if you begin to get peculiar readings with the HF meter, just change the batteries.