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Tested 3 of my hygrometers outside with current humidity/temp. The abbeon I bought from e bay is used and off by about 19% it reads 60 % and the hygroset reads 47% and radio shack at 41 % Current temp is 41% humidity 77 F. How do I go about recalibrating the abbeon ?? thank you . I really appreciate the advice !!

Take a look at this thread, Ernie:

viewtopic.php?f=10101&t=51980

You can buy a gadget that will measure the actual RH in your space (a psychrometer).

Or, you can buy some potassium carbonate (cheap on the internet), put some of that in a tray, saturate it with water, and lock the solution in an airtight bin or ziplock bag with the hygrometer being calibrated. You leave it overnight. The air inside the bag settles to an RH of just over 43%. If the hygrometer says something different from 43%, you turn a little screw to adjust the dial indicator.

Here's another useful thread:http://www.anzlf.com/viewtopic.php?t=6123

The first post in the thread describes calibrating two Abbeon hygrometers using the potassium carbonate method.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I bought an Abbeon from eBay that was busted. Ambient read a value. Used a dehumidifier to lower the humidity by 15% according to sling psych, and the Abbeon had the same reading. The eBay seller accepted the return so I got my money back. Bought a new one instead.

Ernie if you want to send me the Abbeon and the others if they are adjustable and mechanical and not digital and I'm happy to calibrate them for you and send them back.

We have several lab quality glorified, motorized wet bulb testers that we use annually for ours.

It is concerning to me that the Abbeon is that far off though. Makes me wonder if it's been either tampered with or if it's broken. Our Abbeons are never more than a couple of percent off each year.

Regarding the radio shack if it's a digital digitals are notorious for having "range" issues. What I mean is that they can be pretty accurate for a while in a desired range such as say 40 - 50%. But out side that range they are often way off meaning 15% or more off. That might explain why it read so high at your place but was seemingly accurate with the weather reports outside. Just a thought.

Ok I used the ambient outside humidity as a guide 34% rt now. The radio shlock digital iis 25 yrs old and had the exact reading as the local weather app. The abbeon ,came from placerville ca. it is accurate inside the home and concurs with the radio shack . The hygroset reads too high outside but fine inside.

Hesh let me do some more testing . and I will l take up your offer.

You bet.

The Abbeon-branded Lufft hygrometers are screw-adjusted for humidity and spring tension adjusted for temperature. The humidity adjustment screws are either accessed through the cut-outs at the 6 o'clock position on the case, or from the 3 or 9 o'clock positions. We've found that salt calibration using the Bovida-style packets seem to work pretty well, but we use salt solutions with equilibrium RH close to or in the 40%-50% range to avoid the larger errors seen with common sodium chloride calibration.

The older of our two Abbeon-labeled hygrometers was a mess when it arrived. At full humidity calibration screw adjustment, the hygrometer was still reading about 10% high, so we made the decision to service it ourselves. After full disassembly, cautious cleaning, judicious lubrication, and adjustment of the tensioner/adjuster, we were able to bring the hygrometer to +/- 0 with calibration screw adjustment.

By the way, Abbeon will calibrate your hygrometer, but suggests that the user can do the job as accurately as they can with salt calibration. Calibration service with postage and handling is about $70 if I recall correctly.

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For the times they are a changin'

- Bob Dylan

Woodie, how do you open the case? The used one I bought needs to be cleaned and oiled. But the case has no obvious fasteners.

Yep and they are pretty quick too. I've sent mine there on the west coast IIRC before I learned how to do it myself.

They also have or had two levels of calibration services. One was with-in 3-5% or so and they also have a more refined level that they described as using a national standard for a tighter dial-in. It's been ten years since I sent to them so I may be off on the details but I'm quite certain that they had two levels of service available.

My experiences with them were good.

The only initially difficult thing about calibrating a hygrometer that has a calibration adjustment is learning to reliably do wet bulb testing and getting the stuff or device to do it. After that it's kind of a science class all over again and fun.

We spent over 5 hours on the task; at our shop rate, that is well over the cost of two new, properly calibrated units. I would strongly recommend against doing this yourself, as it is difficult work done with improvised tools, and with no guarantee of success. Sending it out to Abbeon for assessment and possibly repair and calibration might be a reasonable option, but a better one would be to eBay the present unit and replace with one that is as new or very close to it.

The rear cover plate is made of thin formed and tempered sheet brass, and may be removed by levering the edge of the plate out of the formed channel on the rear edge of the case, starting at the small semicircular cutouts seen to divide the rim of the cover plate into what are essentially metal tabs (to be inserted into the channel rolled into the rear edge of the case). Once the rear cover plate is removed, the mechanism is fully exposed for cleaning and servicing. Reinstalling the rear cover plate is somewhat more difficult than removal, and you should expect to mar both case and cover plate in the process (although in use, any damage is nicely hidden...but you will of course know that it is there). A special tool for rear case cover removal undoubtedly exists, but still only gets you into the case, leaving the harder part of the job to be done after rebuilding the actual mechanism.

If not in possession of special skills in the rebuilding of complex, fiddly bits of machinery, I would avoid the task entirely. Mr. Morelli mentioned a similarity with the rebuilding of a multi-barrel vintage auto racing carburetor, while I saw some similarity to a drive system rebuild I once talked myself into doing on a 1960's era European industrial sewing machine. Neither of us feel the least bit inclined to subject ourselves to those tasks again, and the rebuilding of a Lufft hygrometer without the required special tools (the case cracker in particular) and spare bits and pieces seems to me to fall in that same category of 'once was more than enough - never again.'

Finally, if the appearance of your fingernails are of any concern to you, that alone suggests avoiding the task described. The horrified look on the face of my nail technician when I reported in for hygrometer-related nail repairs was likely similar to my own when presented with the bill.

_________________
For the times they are a changin'

- Bob Dylan

Thank you too woodie and hesh for the detailed explanations of the inner workings of the abbeon. I had no clue ?

I opened up my Cole Parmer (abbeon) hygrometer that came in from eBay last week. It was originally about 20% off the RH and the inside looked quite dusty. I was afraid it might be too far gone. I blew it out with compressed air and calibrated it, but thought I would open it up to inspect it more closely. Took me about 30 minutes with a small flat blade screwdriver to pry up a bit more than half of the brass rim and then the back was easily pryed out. No fingernail damage.

I was surprised how few parts make up the hygrometer. A bit of string, a couple of pivots and a small coiled spring. The original compressed air cleaning actually did an adequate job of cleaning it. Added a bit of light oil to the pivots and closed it up. I sealed the back with 3 small metal screws to aid in future disassembly. It seems to be working well now.