<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content="text/html; charset=windows-1252" = http-equiv=Content-Type> <META content="MSHTML 5.00.3019.2500" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT size=2>Dear List,</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>I offer the following in hopes of shedding some = light on relative humidity readings measured with inexpensive digital hygrometers = inside a piano when a Dampp-Chaser Climate Control System is operating.  I = will use the hygrometer we distribute as an example.  Please note = that we only distribute this hygrometer as a tool to use in showing a piano = owner the extremes of relative humidity he or she might experience in the = home.  We have never promoted it as a tool for technical or scientific = studies.  In our testing we use hygrometers that range in cost from approximately = $500 to $1500.  We believe that one needs to invest over $100 to get a = reasonable tool to use in testing System performance.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>We have switched hygrometer manufacturers and do = provide a slightly better hygrometer than we initially distributed.  = But even these are only moderately accurate, reasonably precise and the sensor = will drift significantly with time.  (This is simply the nature of the = inexpensive electronic sensor in these instruments.)  So kindly understand our intention was to provide a tool where you could show a piano owner a = 40-50% relative humidity swing had occurred when the hygrometer was left in = their home for a period of time.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>The other source of some confusion is in how the = Climate Control System operates.  The Humidistat contains an = electromechanical switch.  We measure the calibration of each switch in one of our = humidity controlled test rooms.  Here we bring the humidity up to about 65% = and down to about 30% very slowly over a 20-hour period.  Computers record = the upper and lower set point for each switch and our regular Humidistats now have = a six percent range with the average of the two set points falling between 42% = and 44% relative humidity.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>When a Climate Control System is functioning = within the piano the relative humidity rises and falls much faster = than the twenty hours of controlled humidity change the switch experienced = in our calibration test room.  The sensing band in the Humidistat is = slow to respond to a rapid increase in humidity, and = one observes "overshoot" where higher than expected relative humidity levels are recorded by a = hygrometer placed in the vicinity of the Humidistat.  We observe these in our = product development humidity controlled test rooms.  Here, however, we = are also measuring soundboard equilibrium moisture content.  What we = find is that we get good stabilization of the moisture level in the soundboard.  We use relative humidity as a surrogate for = moisture content in wood.  Unfortunately they do not always directly = correlate at any given point in time.  The soundboard tends to = equilibrate at constant moisture content while relative humidity is cycling in a = controllable, repeatable cycle.  The equilibration of soundboard moisture content = is the driving force for all our product development research, and this is = reflected by the pitch stability which our product can provide to the piano.  We discuss our product in terms of relative humidity, = only because it is a concept that a layperson can easily grasp.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>I am one who believes in under promising and over delivering.  I only recommend the hygrometer as a sales tool.  = I only claim the Climate Control System will help to provide pitch stability.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>Maintenance of pitch stability is directly dependent = on how confined the space is in which the Climate Control System = operates.  We have introduced a back side cover for vertical pianos that = provides better confinement.  We continue work on a grand undercover to = provide the same benefit.  We are pleased to have received patents last = year for both of these systems.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>We also continue work on a better Humidistat.  = We experiment with electronic sensors that respond quickly to avoid the "overshoot".  Unfortunately, the ones we have examined all = drift significantly.  (The electromechanical switch we now use does not = drift.) We cannot imagine a technician going in every year to replace a sensor = on a Humidistat.  We do monitor R&D on humidity sensors and hope = that the ideal unit will come along in the future.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>I would be happy to answer questions any of you = on the list might have if you would like to email me privately.  We at Dampp-Chaser are genuinely thankful for your interest in our products and appreciate the diversity of opinions offered in this forum.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>Roger Wheelock<BR>Dampp-Chaser Corporation<BR><A href="mailto:roger@dampp-chaser.com">roger@dampp-chaser.com</A><BR><A href="http://www.dampp-chaser.com">www.dampp-chaser.com</A><BR></FONT><= /DIV></BODY></HTML>