Moisture Meter

[Joe]

I came across an article in an old Fine Woodworking issue recently (I inherited some a while back) with instructions as to how to make your own meter. I didn't study it closely but I don't think it's too complicated. The article doesn't seem to be in the FW online archive though - perhaps they'd put it on there if asked.

Joel

 

[Anonymous]

Now you have me thinking if I have made a mistake buying a pin type meter :roll:

Cheers

Mike

I may have imagined it ( I often do :? ) but I thoght I saw somewhere that you got a more accurate reading by knocking a couple of panel pins in the wood and then use the pins of the meter to take the reading from those.

 

[DaveL]

I may have imagined it ( I often do :? ) but I thoght I saw somewhere that you got a more accurate reading by knocking a couple of panel pins in the wood and then use the pins of the meter to take the reading from those.

I have read that this is good if you are air drying boards on a rack. By using the panel pins and leaving them you always measure in the same place.

 

[Anonymous]

I may have imagined it ( I often do :? ) but I thoght I saw somewhere that you got a more accurate reading by knocking a couple of panel pins in the wood and then use the pins of the meter to take the reading from those.

I have read that this is good if you are air drying boards on a rack. By using the panel pins and leaving them you always measure in the same place.

Thanks for the confirmation.

 

[Mike.C]

MDF HAKA wrote,

DaveL wrote:
MDF_HAKA wrote:
I may have imagined it ( I often do ) but I thoght I saw somewhere that you got a more accurate reading by knocking a couple of panel pins in the wood and then use the pins of the meter to take the reading from those.

I have read that this is good if you are air drying boards on a rack. By using the panel pins and leaving them you always measure in the same place.


Thanks for the confirmation.
_________________
rgds

Steve

So you do not need to check to a depth of 5mm a number of times along the length of the board?

Cheers

Mike

 

[tnimble]

From the WoodWeb link a page back:

Preferred Procedure for Use of Pin-Type Meters
1) Turn meter on and check that battery has ample power. (See calibration discussion on page 4.)

* All meters have a button or switch to check that the battery is OK. If check does not show that battery has required amount of power, replace battery with a fresh one.

* If meter has adjustment knob/screw, turn to bring the needle or digital readout to the position recommended by meter manufacturer.

2) Select a location to make the MC measurement.

* For lumber, the location should be at least 1 foot from the end of piece and about the middle of the wide face of the board.

* If measuring pieces of molding, turnings or other products less than 4 feet in length, select a location in about the middle of the piece.

* For piled lumber, readings may be taken on the edge or narrow face of the board. However, remember the edge pieces may not represent the MC of the interior pieces. Readings taken from the end grain of boards will not usually represent the average MC of the piece.

3) Position the pins on the wood surface with needles parallel to the grain. (A few meters require the pins to be across the grain; check the instruction book.)

* Having the pins parallel to the grain is important when the MC is above 15% MC. For readings below 15% MC, pin alignment is not very critical.

4) Force the pins into the wood---How deep?

* When using meters with pins mounted in meter case, (pins usually 3/8-inch long, uninsulated) DO NOT hammer or pound on case. Apply only hand pressure. Try to push pins to their full length into the wood. For oak, hickory and other dense woods, force pins as deep as possible without striking the meter.

* Meters with electrodes (pins) attached by cables typically have some type of hammer to drive longer pins (usually 1-inch long, insulated except at tip) to desired depth in wood.

* To determine the average MC of the piece, drive insulated pins 1/5 to 1/4 of the thickness of the piece. Example: for 4/4 lumber, drive to 1/4-inch depth; for 8/4 lumber, drive to 1/2-inch depth.

* To determine if moisture gradients exist, take readings at different depths from surface to core. A shell wetter than the core would indicate moisture regain after kiln drying.

* To determine core MC of the piece, drive pin tips to center of piece.

5) Read current MC values and record

* If meter readings drift, use the reading taken immediately after electrode reaches desired depth in piece.

6) Take MC readings at more than 1 location per piece.

* To give indication of MC variation, if any, along the length or width of the piece.

* To help locate wet pockets in piece.

7) Make temperature corrections if lumber temperature is below 60o F or above 90o F.

* Meters are usually calibrated for 70-80 degrees F. If lumber is above or below this temperature by 20 degrees F or more, corrections should be made. Correction tables are available from the meter manufacturer and many general wood drying reference books. Readings at room temperature are usually best.

* Some meters have provisions for presetting temperature correction on meter. If the meter has this feature, use it.

* The meter, including the electrode pins, should be at room temperature if at all possible.

8) Make species correction as needed.

* Some meters have provisions for presetting species or species groups on meter. If the meter has this feature, use it.

* Species corrections are usually very slight (1% MC or less) for most North American woods; corrections may be greater for some tropical woods. Correction tables are available from the meter manufacturer and many general wood drying reference books. Most meters sold in the U. S. are factory calibrated for Douglas-fir or for Southern pine, so no correction is needed when used on these species.

9) Turn off meter when finished taking readings.

I just can't see how doing that would not have a severe impact on the usability of the lumber. And the reason I've not (yet) bought a pin type meter. I also haven't bought a pin less type meter for I find them very expensive. They cost around 300 to 575 pound and up that the few stored that sell them.

 

[Mike.C]

tnimble wrote,

I just can't see how doing that would not have a severe impact on the usability of the lumber. And the reason I've not (yet) bought a pin type meter. I also haven't bought a pin less type meter for I find them very expensive. They cost around 300 to 575 pound and up that the few stored that sell them.

tnimble I can see what you mean, and part of me has to agree with what you are saying, but on the other hand it seems that other members are using them and getting by. The trouble is I cannot get any info from anyone who uses one regally, so I suppose I will have to wait and see how good or bad the holes look when I get mine. As for the pin less type, I have even less info on them.

Very frustrating

Cheers

Mike

 

[beech1948]

You might have a look at these if you have not already

http://www.woodweb.com/knowledge_base/Pin_and_pinless_moisture_meters.html

http://www.decoratingdirect.co.uk/viewprod/e/EHPCT33/

http://www.electrophysics.co.uk/index.htm

http://www.woodcraft.com/family.aspx?FamilyID=4308

https://www.ukworkshop.co.uk/forums/viewtopic.php?p=58942&sid=b152899bb4df669ef83fcefe55434b7a

http://www.wmsconsulting.co.uk/moisture_meters.htm

Hope this is enough. I have a Wagner ls220

regards
Alan

 

[beech1948]

oops mine is an MMC220

Sorry.
Alan

 

[ivan]

I was under the impression that very cheap meters are not of absolute accuracy but are fairly consistent. Thus good for a series of checks to see if timber is still adjusting to its surroundings, but not very good at acurate % measure of a given species.

I understand that cheaper 'pro' meters have a table of species so you can correct the meter reading; the US models presumably list a lot of American species?

 

[tnimble]

Very frustrating

Indeed.



I've done quite a bit of reading on the pinless meters. It seems that the ability to be able to have an SG correction on the meter is not that important. As long as you have an table you're set. Having the input on the meter can be handy so you don't have to correct all readings by say +1.7%

Electrophysics CT33:
Range: 0% - 30%
Readout: Analogue 1% scale
Scan depth: 25mm
SG Correction Method: Manual
SG Range: 0.2 to 1.0 (range of included table)
Sample & Hold: No
Price: £160 (inv vat)

Electrophysics CT100:
Range: 0% - 30%
Readout: LCD 1% increments
Scan depth: 25mm
SG Correction Method: Internal (dial knob)
SG Correction Range: 0.4 to 0.8
Sample & Hold: No
Price: £189 (inc vat)

Wagner MMC205:
Range: 5% - 20%
Readout: LCD 1% increments
Scan depth: 19mm
SG Correction Method: Internal (push button)
SG Correction Range: 0.3 to 0.7
Sample & Hold: No
Price: £130 (inc vat and postage from amazon)

Wagner MMC210:
Range: 5% - 30%
Readout: LCD 0.1% increments
Scan depth: 19mm
SG Correction Method: Internal (push button)
SG Correction Range: 0.3 to 0.7
Sample & Hold: Yes
Price: £180 (inc vat and postage from amazon)

Wagner MMC220:
Range: 5% - 30%
Readout: LCD 0.1% increments
Scan depth: 19mm
SG Correction Method: Internal (push button)
SG Correction Range: 0.2 to 1.0
Sample & Hold: Yes
Price: £200 (inc vat and postage from amazon)



If you're happy to correct the readings manually the MMC210 will be just as fine as the MMC220. If you don't need to know the MC in 0.1% accuracy the MMC205, CT100 or CT33 will all be fine.

The Wagner MMC205 from amazon seems to be the most price efficient choice. Next up would be the CT33 followed by the MMC210 which might be functionally in favor above the CT33.


All the SG correction tables for all the Wagner Meters seem to be exchangeble / the same. This means the MMC210 and MMC220 can measure the same species. Even the MMC205 can do them all. The only thing is that when an correction index is outside of the range supported by the meter you have to do the correction manually.

I don't know if the SG correction library CD that comes with the MMC220 is the same as that comes with the MMC210 and/or MMC205. If it does you can just get the MMC205 if you're happy to manually correct for some species.

Can anybody that ones the MMC205 veryfy this?

 

[tnimble]

Just to let know. I purchased the Wagner MMC210 from Amazon back in april. The meter is very excellent. And I just received an about 50 euro refund from Amazon on the order.

 

[Tusses]

Ive had the timber check for about 8 years now.

seems very consitent, even after this time - and still on the same battery ???

 

[RogerM]

Not sure whether this is worthy of a potential gloat. Just bought this Wagner L607 on Ebay for £27.50. Price on WM Supplies is £245 + VAT so hoping I've got a bargain.

 

[chipchaser]

Has anyone built the "Shop-made moisture meter" described in the July 1985 issue of Fine Woodworking?

As Joe posted on page 2 of this thread, it doesn't look too complicated but there appear to be a couple of loose ends and it would be nice to know whether it worked before investing time into making it

Regards

Graham

 

[johnnyb]

one of the best selling meters is from protimeter. the surveymaster would be best for timber i think. these are mostly used by architects and use both the pin method and the radio freq method they also have tables of woods and their cmpensation values. i use one everyday and they are pro tools and very robust. spares are also available and the have a calibration device with them. also hammer probes as an optional extra. my feeling is the pin method is the most accurate on timber everytime and gives an exact reading of the moisture between the points. the radio method is less exacting but if your working on materials other than timber is very useful. equilibrium relative humidity would give an exact amount but could leave a large hole in your timbber! you would also require the protimeter mms which also has temp and rh measurement. would a few percent make any difference to cabinetmakers?

 

[Rich]

I am very much in favour of technology and gadgets, I can't get enough of them, but how would our predecessors have known the moisture content and when the timber was ready for usage, were there any signs to look for or was it trial and error? looking at the famous Chippendale and sheraton furniture the craftsmen must have had some way of knowing rather than trusting to luck, don't you think?

Regards,

Rich.

 

[Ironballs]

They would have done so Rich, but then they also didn't have damp-proofed, dry, warm centrally heated homes. Many is the piece of seemingly stable antique furniture that has cracked once it has been in a modern house for a while. I store timber in the garage but it has to come into the house for a period before I machine it, a moisture meter would take out some of my guess work

 

[Rich]

Thanks for the reply, IB, I think I understand what you say even though you use a meter there is still guesswork involved, but how would the shipwrights in the time of Henry V111 have got on, they needed oak like there was no tomorrow when the spanish armada was coming, they must have had to use it green, in such a hurry, I'm not trying to distract from the thread but the old boys must have known something that we don't.

Regards,

Rich.

 

[chipchaser]

Ironballs is on the money with regard to temperature and humidity before the almost universal adoption of central heating. As well as furniture there is plenty of historic timber wall panelling which was in good order until damaged by the over warm and dry environment available from the C20th. As a child, it was not unusual to see condensation and Jack Frost “drawing” on windows in cold weather. This was sheer luxury after we moved from the hole in the road and the cardboard box :lol:

14% moisture content was probably safe for joinery timber before the central heating era but the Victorians probably used a lower moisture content in high quality work. In the late 60’s we were told to specify 12% or less in constantly heated buildings. Thomas Chippendale, I think, used Mahogany and similar stable hardwoods in quite small sections which would have been dried by rule of thumb to moisture contents known to be safe. I read that he also laminated 3 plies of thin timber from which he cut fretwork for chair backs.

Moisture meters were developed in the 1920’s but mediaeval carpenters knew about seasoned timber. Although green Oak was used for timber framing LF Salzman in his “Building in England Down to 1540” provides evidence of seasoned timber:

http://i455.photobucket.com/albums/qq27 ... xtract.jpg

Some of which was imported:

http://i455.photobucket.com/albums/qq27 ... xtract.jpg

I don’t know about ships but as they sat in water being built of green oak was probably of little importance. Henry the Eighth’s problem was supply of oak as it was being used by other industries. There is a record of an Ironmaster in the Forest of Dean being fined £20,00 for using Oak that should have been reserved for shipbuilding for fuelling his furnaces.

Regards

Graham