Could I use an AVO meter to test moisture content in Timber?

[Gerard Scanlan]

I think the title says it all. I usually only buy dried/seasoned timber and then leave it in my workshop for six months or longer before using it. However I recently met a woodturner who sources logs himself and he is only interested in highly figured pieces so he can supply me with with timber with more neutral grain patterns. The only problem is I have no way of judging when this timber, which feels damp to the touch ,will be ready for use. So I thought about buying a moisture meter. Then it occurred to me that an AVO meter might do the same thing. Is this a stupid question? i do not know yet. But I am soon to find out .

 

[DTR]

That's an interesting idea. Though I'd think that you'd need a moisture meter in the first place in order to calibrate the AVO.

 

[Gerard Scanlan]

I was planning to compare a piece of walnut that I have had for 4 years and is bone dry with the wet stuff and wait until the reading was the same. The previously acquired walnut was already seasoned when I got it so it my benchmark. I just thought if someone else had done this before they might be able to steer me in the right direction.

 

[thick_mike]

I guess the answer is...give it a go.

I think a standard multimeter only puts a 1 volt potential across the electrodes, so it may need a bit more to encourage a current to pass. There are meters for testing insulation (made by Megger for example), which put a voltage of 400volts across the electrodes, which may be more appropriate to the task...but they cost much more than a hygrometer.

As far as calibrating the device, you can take a piece of wood indoors and measure it every week or so. When the reading stops changing the wood is ready.

 

[SammyQ]

Mattias Wendle has already been there, done that. Try woodgears site. Sam

 

[thick_mike]

Mattias Wendle has already been there, done that. Try woodgears site. Sam

Cool! I love that guy's approach to problems.

Certainly cheaper than buying a megger!

 

[SammyQ]

Yup! All those bl**dy co**ectors seem to like them (AVO's/Meggers) as well as 073's (see other post about prices and fashion) Sam

 

[Eric The Viking]

Other multimeters are available

Check out Taylor, as an example of really well made AVO competitors, but the thing that's always put me off electrical moisture meters is the potential for error:

• Do you push the prods in to a known depth, exactly, every time?
• How's the battery?
• Does the wood's structure - density, grain, etc. make a difference?
• What's it been calibrated against?

I've not used them for wood, but I have chuckled when getting quotes for damp proofing. Watching some of the 'surveyors' at work has been interesting, and the results have been very variable indeed.

It would be really good to hear from someone who uses them a lot how they get on with them...

 

[thick_mike]

I assume whether you measure along or across the grain is important?

 

[Gerard Scanlan]

Wow Sam that wood gears site is fantastic. Mattias certainly has invented the wheel as far as answering my question.
Thanks for pointing me in his direction.

Gerard

 

[Eric The Viking]

The worst thing about Wandel is that his designs are really nice (to my eye, that is).

I could cope with him being an engineering genius, or very good at experimentation, but being a good designer is just too much. It isn't fair!

Seriously, he's one of those people who just make you grin from ear to ear, and It's so nice he's prepared to put all that stuff up on his site too.

E. :mrgreen: :mrgreen: :mrgreen:

 

[jimi43]

I assume whether you measure along or across the grain is important?

On my Protimeter it is important to measure the long grain...not across the grain with the two pins like this....

Calibration is where these things come in...to proof timber stock for sale. Relative readings...which is what I do all the time, can be done using any meter reading resistance...you can make a probe with two sharp pins next to each other banged into a piece of wood and soldered to the leads.

If you measure a known dry piece of a particular species and compare it with an unknown piece of the same species then you will get a fairly good indication of the relative moisture content.....and most importantly its progress in seasoning until no change is detected...when it will be as dry as it will get in the environment in which it is stored.

Jim

 

[SammyQ]

Gerard? You're welcome! Such information sharing is what this forum is all about; you take a little, give a little, Sam