Zero percent humidity

[Farrell]

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As stated in the PDF link provided:
Range: 10% to 90%
Typical EMC Deviation: +3%
Response Time: up to 20 seconds for 95% accuracy

This means that below 10% RH, the unit may be way off. If you look at a =
graph of the accuracy of these instruments, you will find that one =
having a "typical EMC deviation of +3%" will actually be better than =
that in the middle of its range, and worse at the extremes ("typical" =
may be more like 10% deviation near the extremes of the spec range), and =
way worse beyond its extremes. The "typical EMC deviation of +3%" is =
typical deviation - it may deviate more. And of course it takes up to 20 =
seconds to get 95% equilibration.

So, what all that means is any readings down at 5 to 8% is gibberish. A =
reading of 2.7% is super gibberish, and a reading of zero for a few =
seconds is ultra gibberish.

These instruments are good for approximate RH in non-extreme =
environments.

Here is a link to a description of the hygrometer that I use in my shop: =
http://www.pacer-ind.com/hygrometers/dh50.pdf  I paid about $300 for it =
and its specs are only a little better than the specs for your =
instrument. However, the 2% RH accuracy is assured within the spec =
range, and "typical" testing shows it to be within about 0.5% accuracy =
(the company sent me test data of my specific instrument).

I guess the point being here, don't expect a free lunch - including the =
world of hygrometers. Don't read too much into the numeric display of =
those little inexpensive hygrometers - they are handy to document =
whether it is "dry" or "humid" in an environment - and even if it is a =
bit dryer today than yesterday, but don't put any money on their =
ultimate accuracy - especially as one approaches their spec range, and =
certainly not when it suggests RH is outside its spec range.

Terry Farrell

----- Original Message -----=20
From: "Chris Gregg" <cdgregg@telus.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: Wednesday, January 07, 2004 12:19 AM
Subject: Zero percent humidity


>=20
>=20
> I have a fairly accurate hygrometer.  I bought it from a scientific=20
> instrument supply company.  I have been using it for the past year and =
have=20
> been delighted with the performance. A description of it can be seen =
at=20
> http://www.hannacan.com/fiches_techniques/HI98601.pdf
> Up here in the far North we have just been going through a cold spell  =
with=20
> an mass of Arctic air over us.  I knew it was dry in some homes, have =
had=20
> the humidity down to 5 to 8% at times, however this is nothing =
compared to=20
> some public buildings that have music schools in them.  I was in one=20
> yesterday that recorded 2.7 percent in one room and this evening I was =
in a=20
> building that actually took the gauge down to 0% for a few moments.  I =
did=20
> not know this was possible, however I guess it is.  It must be like =
sitting=20
> right inside the furnace.  Some of the local piano salesmen tell me =
they=20
> sometimes hear things go crack on the showroom floor.  I wonder why?  =
We=20
> even have laminated boards that crack in this part of the world.  =
Keeps us=20
> busy though.  Install lots of Dampp Chasers around this time of year.
>=20
> Chris
>=20
>=20
> _______________________________________________
> pianotech list info: https://www.moypiano.com/resources/#archives
> 
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