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Author Topic: Non-Digital Hygrometer  (Read 656 times)

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Offline Denny

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Non-Digital Hygrometer
« on: April 26, 2017, 11:02:08 am »
Hey folks I'm looking to buy another non-digital hygrometer and am having a hard time finding one for sale. My old one was made by Taylor and although they still make non-digital hygrometers, they no longer make any in my temperature range. So looking around online for alternatives and I can't seem to find anyone making or selling these old-school hygrometers.  Searching the forum here it seems like all the advice is to just get a digital one but... *DanG I just feel more comfortable with some mercury in some glass tubes.  I actually have a really nice digital hygrometer made by Omega, its there RH200A model, but I want the old mercury thermometer type so I can hang in one of my kilns and let it there overnight\few hours.  I still have one good Taylor hygrometer, at one time I had 4 or 5 of em, but over the years they gradually got destroyed. Anyways.....  anyone have any leads on where to buy one, please holler. ;D
Thank ya kindly...

Offline Denny

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Re: Non-Digital Hygrometer
« Reply #1 on: May 04, 2017, 11:14:17 am »
Well I think I looked everywhere and no one makes a mercury filled hygrometer in my temp range. Most just go up to 120 degrees. Hard to believe there's an unfilled market in this day and age.  And my Omega RH200a ... is outta calibration, and this is one of the reasons why I don't like digital hygrometers.

How bout I make my own ? They're just thermometers right ? Just that one thermometer has a wick and water tray for it.  Why can't I just buy two high temp thermometers, duct tape and binder twine em to a board, staple on a water tray, add a wick and BAM... I got my old-school hygrometer.

I have like four or five different digital hygrometers and they're all outta wack.

I'm really blown away that no one sells these anymore.

For you guys who use the digital ones, how do they hold up when drying acidic red oak ? Can you leave em in the kiln for hours ? 

Offline GeneWengert-WoodDoc

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Re: Non-Digital Hygrometer
« Reply #2 on: May 05, 2017, 07:41:00 am »
Commmercial dry kilns use electronic thermometers, often tied into a computerized system.  The sensors will give at least 10 to 20 years of service unless physically damaged.  The sensor, such as a platinum resistance bulb, has no moving parts, so it cannot get out of calibration.  It uses a three wire system in order to cancel out any effects of long wires.  So, the only issue possible is the electronics of the display.  Most of the kilns have no problem with the system for many years.  Calibration is checked electronically today.  In the old days, we did calibration with a bucket of hot water that was well stirred.

Your issues with loss of calibration in several units is perplexing.  If you put all the sensors in the same place (Such as a plastic bag and then wrapped in insulation so the temperature is the same and not changing), do they read the same?  What sort of errors do you see?  Do you think the errors are in the connecting wires or with the display?
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline Denny

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Re: Non-Digital Hygrometer
« Reply #3 on: May 05, 2017, 09:27:57 am »
I don"t suspect any of my eight kiln controllers to be out of calibration, they all use RTDs. Although I must say that my controllers have to be about 20 years old and the kilns are almost 40 years old and while I do my best to maintain everything, the insulation is getting older every day and I'm sure there's air leaks along seams and other unforeseen seal issues, but for the most part my controllers match my hygrometer.  Why do I still use a hygrometer ?  Well I don't really. I only use it occasionally, I'll hang it in the kiln to make sure everything is where its supposed to be. I'm drying 150,000 ft of dead green, soaking wet, 90% MC red and white oaks in these kilns I like the assurance the my controllers are reading correctly. We've had these old Taylor mercury filled hygrometers for at least 17 years and now I'm down to one left. So... I figured I'd hop online and grab a spare one... and to my surprise, no one makes em anymore.

And I'll have to count the amount of digital hygrometers that I have, but off the top of my head, I got 3 or 4 of em and none of seem to match each others readings. My Omega, which is a beautiful and expensive piece of equipment is not even close to reading RH correctly(it reads the temp perfect tho).  All these digital hygrometers I have were bought and broken by the previous kiln operator. I've always used the mercury filled Taylor hygrometers.  So this all leads up to me being suspicious of digital. Its just nice to see that mercury ya know...

Oh and one more thing, at one point I ran 17 kilns for my company and 9 of those kilns used the old gas filled bulbs. I've calibrated a few of those in my time, stirring it hot and cold water buckets. Ah the memories LOL.  I had Foxboro brand kiln controllers with the gas filled bulbs. Nothing digital at all on those old Foxboro's.  And speaking of old-school gas-filled temp sensors, I have a brand new one that I dont need if anyone out there is looking for this hard to find part.

Offline K-Guy

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Re: Non-Digital Hygrometer
« Reply #4 on: May 26, 2017, 02:18:18 pm »
Well I think I looked everywhere and no one makes a mercury filled hygrometer in my temp range. Most just go up to 120 degrees. Hard to believe there's an unfilled market in this day and age.  And my Omega RH200a ... is outta calibration, and this is one of the reasons why I don't like digital hygrometers.

How bout I make my own ? They're just thermometers right ? Just that one thermometer has a wick and water tray for it.  Why can't I just buy two high temp thermometers, duct tape and binder twine em to a board, staple on a water tray, add a wick and BAM... I got my old-school hygrometer.

I have like four or five different digital hygrometers and they're all outta wack.

I'm really blown away that no one sells these anymore.

For you guys who use the digital ones, how do they hold up when drying acidic red oak ? Can you leave em in the kiln for hours ?
Denny
Nyle sells them, they read up to 220f for $242.00 each. They are lab instruments.

Offline Kbeitz

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Re: Non-Digital Hygrometer
« Reply #5 on: July 01, 2017, 02:44:28 pm »
First place I look for anything in E bay. 
Remember it all new stock almost every week.
Collector and builder of many things.
I have a
machine shop
Wood work shop
And a Weld shop
And now a saw mill
and a bunch of new forum friends.