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Hygrometer

  • 1.  Hygrometer

    Posted 03-12-2018 12:20
    I'm looking for a hygrometer that is accurate below 5% MC. Anyone have a model that they are happy with? I will be putting it in my kiln.  In the meantime, I purchased the one below just to try it out. 
    ThanksEW8xCyvtSYWiHJF2XUvK_Hygrometer.jpg

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------


  • 2.  RE: Hygrometer

    Registered Piano Technician
    Posted 03-12-2018 13:38
      |   view attached
    I suppose it depends on the level of reliable accuracy that you want.  It challenges my  deep need for a sense of cosmic order to think that you would get the same results with the item you showed as you would with something considerably more expensive.  But I'm also a bit confused by your question, as you are asking about a hygrometer that would read 5% MC.  Hygromters read RH.   For 5% EMC you would need to maintain around 25%RH at 80 degrees.
    https://www.finewoodworking.com/FWNPDFfree/equilibrium-moisture-content-chart.pdf

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    David Skolnik
    Hastings-on-Hudson NY
    914-231-7565
    ------------------------------

    Attachment(s)



  • 3.  RE: Hygrometer

    Posted 03-12-2018 14:27
    That's what i'm doing now. Using a digital RH hygrometer along with a chart to guesstimate EMC. I'm also:  using a wood widget, Measuring wood weight, and using a moisture meter which only goes down to 6% unfortunately.
    Just looking for better scientific equipment, that perhaps someone else is using and are happy with. Like a review.
    -chris

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 4.  RE: Hygrometer

    Posted 03-12-2018 14:32
    Here's the moisture meter i'm using. Once 6% is reached it worthless. So, i end up only using it on firewood.

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 5.  RE: Hygrometer

    Member
    Posted 03-12-2018 20:00
    try lignomat excellent products with various types that can be used for different wood groups they offer moisture meters with built in wood temperature corrections so you do not need to use a conversion chart 
    I have a pin meter mini-ligno E/D  that can check moisture in lumber, veneer and fiberboard with a measuring range of 6-45%  for moisture value below 6% the meter will read 6.0 with a blinkingdecimal point   call 1-800-227-2105 or go to lignomat.com

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    James Kelly
    Pawleys Island SC
    843-325-4357
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  • 6.  RE: Hygrometer

    Posted 03-12-2018 21:55
    Chris,

    I have been all around robin hood's barn on this one...its a toughie.  The hygrometers are just not trustworthy enough to rely on exclusively. I have three of the digital kinds in the shop, and they give a range of readings depending on how old they are. I have a cheap analog one like the one you posted, and it always disagrees with all the other hygrometers...so I have no clue really what the RH in my shop is unless you say +/-20%.  You might ask, "why the cheap one"? And I would say at the temps and RH we need to read, in wet weather, the extreme ends of the scale are simply not trustworthy. If a hygrometer is going to be inaccurate, it might as well be a cheap one.   I never use the digital ones in the hot box, because high temps fry their digital brains. The moisture meters are completely  useless, for our needs, as they read to the center of a 3/4" board at +/-2%...which is huge. I never use mine at all.

    Instead, I triangulate. I bought a small bench top lab oven, lab thermometer, and ammo loader's grain scale to take accurate empirical MC measurements, throughout the drying process, of each individual board I rib. Associated with  the accurate oven dry samples, I have a Nossaman dial indicator  tool, which records the length of a piece of cross-grain spruce on the dial indicator. I calibrate this Nossaman tool for each board too, as its readings relative to MC are mobile too. Calibrating it is simple and takes no time at all when I'm taking oven dry samples from the box. Then I also measure the width of the board and compare that as it changes dimension, relative to the pieces I removed to oven dry.   I have a remote reading hygrometer in the box, but every time I look at it I say..."yeah right". I'll post a pic of the Nossaman style gauge if you think that would be useful.   



    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 7.  RE: Hygrometer

    Posted 03-13-2018 22:04
    Jim,
    I like the terminology "Triangulate" as that more accurately describes what I have been doing. 

    I have two wood samples one for inside the box and another for outside the box as a control.

    BTW, I have ditched the Hot Box per se. I have included in my arsenal an inexpensive closet dehumidifier I bought off of Amazon for $30.  I have reduced my electric bill quite a bit. Instead of hovering around 120 degree, it seems 80-90 is getting me in the zone. In fact, i had to back off today as at my last reading I was down to 1.2% EMC. 
    By accident, I think I discovered why 4% for compression boards. Using a steel bar with pins, I make divots in the soundboard before it goes in the box (again part of the triangulation method !) and I have noticed that below 4% there is not much more noticeable shrinkage.  I also have not noticed any damage occurring from going down to 1.2% either.  So maybe extreme accuracy is not needed.

    The new analog gauges arrived today. For some reason  I thought they were 8" in diameter.
    They were not.
    They are tiny little 2" diameter gauges.  But they are nicely made, and they are "certified" accurate too. Again, i got two. One for inside, the other for outside the box. 

    The other gauge i use is the widget. I think mine is a Gravagne design. I like the idea that the wood tells you what the EMC is.  Of course getting it calibrated is the trick.

    So, yes what is the Nossaman tool you were referring too?
    -chris
    #caveman


     


    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 8.  RE: Hygrometer

    Posted 03-13-2018 23:22
      |   view attached
    Here it is...a crossgrain sample of spruce 8mm thick, set in a channel, so it can move across the cross grain part of the panel. It is glued in the channel only at the end opposite the indicator. A small piece of maple or something hard is glued at the indicator contact so it does not dent  as the board moves. For his own gauge,Ron, determined the length of the crossgrain piece, by oven drying, that would give .010"/1% emc, close to target EMC of 5.5-6%. Accuracy over a large swing of EMC%'s is not that accurate, because the wood movement seems to be non-linear, at different %'s . I didn't make the calcs that Ron did, because I didn't find it accurate at EMC's other than my 5.5-6-5% target area. So mine is only set to indicate when the gauge is at target EMC%. 

    On my own gauge I don't trust the calibration season to season, as I have found it disagreed with oven dry samples. Instead, I have this gauge in the box with the drying board. When I pull out a piece of the board to oven dry, I note the reading on the gauge and post a sticky note showing the indicator reading/temp/oven dried emc of the sample just oven dried. I find that the gauge is quite reactive to temp...something in the indicator or something, expands when it warms up, so the indicator reading must be taken at a particular temp.

    Like I said, all the evidence is somewhat ambiguous, so I use 3 different techniques to try and triangulate in on what's going on. 

    Regarding your 1.2%...assuming that you are getting a reasonably accurate reading, once Jude Revely and I were comparing our Nossaman gauges in his hot box to see it they agreed (they didn't). His expensive humidistat flipped out over a long weekend and really dried everything way down past where I'd ever want to go. The gauge was ruined...it never returned even close to its original calibration, and movement of the sample board relative to its original dimension was reduced, indicating to me, that the sample had passed the point of cellular failure, and lost a fair amount of its previous elasticity.  Its interesting to see this level of destruction, by mistake, while its being read by a dial indicator.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 9.  RE: Hygrometer

    Registered Piano Technician
    Posted 03-15-2018 22:35
    Chris said:
    The new analog gauges arrived today. For some reason I thought they were 8" in diameter.
    They were not. They are tiny little 2" diameter gauges.

    Please allow this extremely brief tangent to an interesting discussion, but did anyone else read the above from Chris and think: Spinal Tap?

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    David Skolnik
    Hastings-on-Hudson NY
    914-231-7565
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  • 10.  RE: Hygrometer

    Registered Piano Technician
    Posted 03-17-2018 11:36
    David,

    Thank you for the attachment link. 
    Just want to point out that according to the chart, 5.0 EMC would
    happen at 25% RH and 100 degrees F, not 80 degrees. 
    Quite a handy reference. Easier than finding it in Hoadley books. 
    Interesting that there is nothing noted between 4.6 & 5.0 EMC,
    which means those would have to be extrapolated at roughly 23% RH
    and a warm temperature. I have a few moisture meters and it is very
    difficult to get accurate readings below 6% on them. The price doesn't 
    really seem to matter that much. I wonder how they determined it before
    the advent of these electronic devices. Just used math, I guess. 

    I also seem to remember reading that various species have different
    retention, and so density and cellular composition would also be factors
    contributing to EMC. Can't seem to locate that now. 





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    Dave Conte
    Owner
    North Richland Hills TX
    817-581-7321
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  • 11.  RE: Hygrometer

    Posted 03-14-2018 09:28
      |   view attached
    My hotbox setup includes a professional quality hydro-thermometer (Pace Industries DH50 - updated model is their DH500) to monitor temperature and relative humidity, a reptile terrarium thermostat to manually control temperature, four or five Damp-Chaser rods for heat, a Radio Shack 120V computer fan to keep the air circulating and the US Forest Service charts for wood moisture content based on equilibrium temperature and relative humidity. I keep my hot box slightly vented to allow excess water vapor to escape and I tap a tack into one corner of the panel and make mark on the other side across wood grain and monitor distance to determine when equilibrium conditions have been achieved. Seems pretty darn fool-proof to me. I have tried using the wood expansion meter/gauge-type thing out of curiosity and found it to be somewhat erratic. Moisture meters are useless at low MC conditions. Why fool with what works? IMHO, the key is to use a quality instrument for measuring temperature and relative humidity. The one I use comes with a traceable calibration certificate from the National Institute of Standards and Technology. Even with this level of data certainty, it is only accurate to within +/- 2% RH. You really need that level of certainty to determine MC accurately enough for our work. A $10 hygrometer is, at best, for home use - not for professional use.

    ------------------------------
    Terry Farrell
    Farrell Piano Service, Inc.
    Brandon, Florida
    terry@farrellpiano.com
    813-684-3505
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  • 12.  RE: Hygrometer

    Posted 03-15-2018 22:02
    Thanks for the suggestions y'all, helped a lot.

    Terry, you are right, good equipment makes the difference. The key element is the Lab certification. I went to their website for products they certify. It turns out that technology has advanced to the degree that you can get the same degree of accuracy with products in the $100 range. I upgraded from the reptile terrarium thermostat, as I found a model similar online that has a wider range -4 degrees F to 225 degrees F for about the same cost. I also decided to get a data logger for ovens, what the heck might as well have some fun with it. 

    Jims ideas were interesting too. Being you own lab may have advantages. But I know if I bought a Lab oven, it would probably get use once or twice and then start collecting dust. 
    Thanks again.

    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 13.  RE: Hygrometer

    Registered Piano Technician
    Posted 03-16-2018 16:34
    So...how did they do this 150 years ago?

    Pwg

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    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
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  • 14.  RE: Hygrometer

    Registered Piano Technician
    Posted 03-20-2018 12:04

    Chris,

    the cheap manual hair strand hygrometer you posted can be surprisingly accurate (only for RH, of course) if it can be calibrated by adjusting a screw on the back of the unit, which is often the case.

    I have an expensive german digital hygrometer (and the conservatory here has another one), and if I compare them to each other, they are within +/- 2% from each other. That is, if they are calibrated, which is a pain - we have to send them to Germany for that.

    The hair strand hygrometer get thrown off quite fast, but the calibration method is a breeze: 1) put it inside a damp (bordering on soaking) towel for 30 minutes, then adjust the screw until it reads 97%.

    Doing that, and measuring it against these expensive meters, it lands inside +/- 5%, which I think is quite remarkable.



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    Patrick Wingren, RPT
    Jakobstad, Finland
    0035844-5288048
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  • 15.  RE: Hygrometer

    Posted 03-20-2018 22:27
    I agree Patrick. I purchased two, one for inside the box and when for the room. I'm finding them quite reliable.

    I upgrade my thermostat to a digital temperature controller. This thing is fantastic!!! It has added a higher degree of accuracy. It keeps the hot box at the same temp within 3 degrees (low to high). Only took about 10 minutes to wire it up and put into service. It was only $15 and wow is the thing sensitive.


    ------------------------------
    A hunter's drumbeat steers the stampeding herd,
    His belly growls in hunger to what he sees.
    The mammoth aware blows his mighty trumpet,
    But alas, the caveman tickles the ivories.

    chernobieffpiano.com
    865-986-7720
    ------------------------------



  • 16.  RE: Hygrometer

    Posted 03-21-2018 08:46
    is it a thermostat?  specs? manufacturer?

    I'm somewhat mystified about something you said earlier in the thread. You said you had started using a dehumidifier instead of heater bars (or other heat source).  In my earlier experiments, no dehumdifier I could find, especially not a cheapo one, could extract moisture from air that was drier than 40 or 50%...which in my own experiments made them useless in a soundboard conditiining chamber. Are you using a dehudifier?...looks from the temp on your box, that you are still heating the box in the tried and true method.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 17.  RE: Hygrometer

    Posted 03-21-2018 09:17
    Dang it Jim good question.
    First the mfg is Bayite. It's a tempurature controller. Specs -4 degrees to 220 defrees F.
    It's 110v at 10 amps. Admittedly it's on a 20 amp circuit. I have a neighbor that is a professional electrician, he said it's fine.
    I have a cheapo closet dehumidifier, that IS collecting water. I look at it as an extra way to remove moisture out of the box, the same way a vent would. It's inconclusive at the moment, but it appears I'm operating at a slightly lower temp to maintain the RH I'm targeting with it.
    -chris





  • 18.  RE: Hygrometer

    Registered Piano Technician
    Posted 03-21-2018 12:51
    FYI, here's a reference sheet which lists chemical salts used to calibrate RH gauges.  They are the primary standards used in the labs.  For example, sodium chloride (table salt) solution gives a reference point at 75%RH while lithium chloride gives a reference around 11%RH.  

        https://www.omega.com/temperature/Z/pdf/z103.pdf

    The accuracy of hygrometer sensors drift with time, and most have strong dependencies on the ambient temperature.  The latter is why portable industrial digital RH gauges incorporate a temperature sensor as well: to correct the RH sensor for its temperature dependency.


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    John Rhodes
    Vancouver WA
    360-721-0728
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