<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; = charset=iso-8859-1"> <META content="MSHTML 6.00.2800.1264" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY> <DIV><FONT face=Arial>As stated in the PDF link provided:</FONT></DIV> <DIV><FONT face=Arial size=2>Range: 10% to 90%</FONT></DIV> <DIV><FONT face=Arial size=2>Typical EMC Deviation: = </FONT><U>+</U>3%</DIV> <DIV>Response Time: up to 20 seconds for 95% accuracy</DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial>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 <U>+</U>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 <U>+</U>3%" is typical = deviation - it may deviate more. And of course it takes up to 20 seconds to get 95% equilibration.</FONT></DIV> <DIV><FONT face=Arial></FONT> </DIV> <DIV><FONT face=Arial>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.</FONT></DIV> <DIV><FONT face=Arial></FONT> </DIV> <DIV><FONT face=Arial>These instruments are good for approximate RH in = non-extreme environments.</FONT></DIV> <DIV><FONT face=Arial></FONT> </DIV> <DIV><FONT face=Arial size=2><FONT size=3>Here is a link to a = description of the hygrometer that I use in my shop: </FONT><A href="http://www.pacer-ind.com/hygrometers/dh50.pdf">http://www.pacer-i= nd.com/hygrometers/dh50.pdf</A><FONT size=3>  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).</FONT></FONT></DIV> <DIV><FONT face=Arial></FONT> </DIV> <DIV><FONT face=Arial>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.</FONT></DIV> <DIV><FONT face=Arial></FONT> </DIV> <DIV><FONT face=Arial>Terry Farrell</FONT></DIV> <DIV><FONT face=Arial></FONT> </DIV> <DIV><FONT face=Arial size=2>----- Original Message ----- </FONT> <DIV><FONT face=Arial size=2>From: "Chris Gregg" <</FONT><A href="mailto:cdgregg@telus.net"><FONT face=Arial size=2>cdgregg@telus.net</FONT></A><FONT face=Arial = size=2>></FONT></DIV> <DIV><FONT face=Arial size=2>To: "Pianotech" <</FONT><A href="mailto:pianotech@ptg.org"><FONT face=Arial size=2>pianotech@ptg.org</FONT></A><FONT face=Arial = size=2>></FONT></DIV> <DIV><FONT face=Arial size=2>Sent: Wednesday, January 07, 2004 12:19 = AM</FONT></DIV> <DIV><FONT face=Arial size=2>Subject: Zero percent = humidity</FONT></DIV></DIV> <DIV><FONT face=Arial><BR><FONT size=2></FONT></FONT></DIV><FONT = face=Arial size=2>> <BR>> <BR>> I have a fairly accurate = hygrometer.  I bought it from a scientific <BR>> instrument supply company.  I = have been using it for the past year and have <BR>> been delighted with = the performance. A description of it can be seen at <BR>> </FONT><A href="http://www.hannacan.com/fiches_techniques/HI98601.pdf"><FONT = face=Arial size=2>http://www.hannacan.com/fiches_techniques/HI98601.pdf</FONT></A>= <BR><FONT face=Arial size=2>> Up here in the far North we have just been = going through a cold spell  with <BR>> an mass of Arctic air over us.  I = knew it was dry in some homes, have had <BR>> the humidity down to 5 to 8% at = times, however this is nothing compared to <BR>> some public buildings that = have music schools in them.  I was in one <BR>> yesterday that = recorded 2.7 percent in one room and this evening I was in a <BR>> building that = actually took the gauge down to 0% for a few moments.  I did <BR>> not = know this was possible, however I guess it is.  It must be like sitting = <BR>> right inside the furnace.  Some of the local piano salesmen tell me = they <BR>> sometimes hear things go crack on the showroom floor.  I = wonder why?  We <BR>> even have laminated boards that crack in this = part of the world.  Keeps us <BR>> busy though.  Install lots of Dampp = Chasers around this time of year.<BR>> <BR>> Chris<BR>> <BR>> = <BR>> _______________________________________________<BR>> pianotech list = info: </FONT><A href="https://www.moypiano.com/resources/#archives"><FONT = face=Arial size=2>https://www.moypiano.com/resources/#archives</FONT></A><BR><FON= T face=Arial size=2>> </FONT></BODY></HTML>