Zero percent humidity

[Corte Swearingen]

Chris,

Hanna Instruments is a good organization that makes decent quality low-cost
instrumentation.  However, keep in mind that this instrument was really
designed for applications in which the humidity is above 10% RH.  In fact,
if you consider that the accuracy claim is 3% full-scale, that means even
at 10%RH, you can be off by plus or minus 3% - that's a 6% range of
inaccuracy at this low level of humidity.

I believe OSHA requires a minimum of 20% RH in public buildings (which is
still too low in my estimation) so I would almost assume that the
instrument you purchased is not working properly or maybe has a calibration
issue.  You may want to call Hanna and get their opinion.  They have good
customer service and should be able to take care of the problem.  If the
humidity was really down in the single digits in a public school like this,
it would be a very unhealthy environment indeed.

I have a hygrometer I purchased from Daigger Instruments (www.daigger.com)
and the lowest I have ever measured was around the 10-15% RH.  So again, my
opinion is to check with Hanna to see if there may be a problem with the
instrument you purchased.  If you can afford it, it is also a good idea to
get two hygrometers from two different manufacturers.  That way, one can
sort of act as a check for the other.  If they both read approximately the
same, your in good shape but if one is way off from the other, there is an
obvious problem.

Anyone else care to comment?

Corte Swearingen
Chicago


                                                                                                        
                      Chris Gregg                                                                       
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                      01/06/2004 11:19                                                                  
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I have a fairly accurate hygrometer.  I bought it from a scientific
instrument supply company.  I have been using it for the past year and have

been delighted with the performance. A description of it can be seen at
http://www.hannacan.com/fiches_techniques/HI98601.pdf
Up here in the far North we have just been going through a cold spell  with

an mass of Arctic air over us.  I knew it was dry in some homes, have had
the humidity down to 5 to 8% at times, however this is nothing compared to
some public buildings that have music schools in them.  I was in one
yesterday that recorded 2.7 percent in one room and this evening I was in a

building that actually took the gauge down to 0% for a few moments.  I did
not know this was possible, however I guess it is.  It must be like sitting

right inside the furnace.  Some of the local piano salesmen tell me they
sometimes hear things go crack on the showroom floor.  I wonder why?  We
even have laminated boards that crack in this part of the world.  Keeps us
busy though.  Install lots of Dampp Chasers around this time of year.

Chris


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