This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Dear List, 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. 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. 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. 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. 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. 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. 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. 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. Roger Wheelock Dampp-Chaser Corporation roger@dampp-chaser.com www.dampp-chaser.com ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/f2/14/4c/b6/attachment.htm ---------------------- multipart/alternative attachment--
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