Hi, Inside the older damppchaser controllers you will find a honeywell humidistat. It relies on a plastic film of some kind that expands and contracts and operates a mechanical switch. I have no details regarding aging, perhaps we have a honeywell connection somewhere on this list? At 09:40 AM 2/7/99 -0500, you wrote: >Bdshull@AOL.COM wrote: >> >> Jim, thanks for your note. I need to put a system in my own Steinway upright >> (has the cast duplex bar) - Grandma brought it from Missouri to Pasadena in >> 1909, and now its in my house - I hate to tune it (my associate did for my >> birthday, first tuning in about 10 years), and a Damppchaser is the way to go. >> Great piano when in tune. >> >> About Damppchaser systems: Now that the humidistats on some of these systems >> are getting along in years, are they showing signs of malfunction? The pianos >> we have discussed have systems 15-20 years old and they are very stable, but I >> wonder if anyone has studied these older systems. I have several old >> humidistats and think I will set up an older system in my old Steinway, set a >> Radio Shack or Damppchaser humidity gauge in it for a week and check its high >> and low readings. Not real accurate but it should tell something. Maybe >> the folks at Damppchaser have a pretty good idea of their longevity. Should >> we begin replacing systems after a time? >> >> Bill Shull >> University of Redlands, La Sierra University >> 25826 Davis Way >> Loma Linda, CA 92354 >> (909) 796-4226 > > > >I suspect that there is not much to the humidistat. In the early 80's I >was an engineer and did some work that required monitoring of humidity. > >The device we used looked like a rear window defogger, only about 2" X >2". It had a fine wire in a zig-zag pattern that covered one side of the >device. The electrical resistance of the wire was proportional to the >humidity. If the humidity changed, so did the resistance of the wire. >The resistance change was monitored by an electonic circuit that >controlled an analog meter to indicate humidity changes. > >I bet the humidistat uses a similar arrangement. At the two extremes of >the desired humidity window, a switch (it could be a relay or an >electronic switch)is activated to turn on the heater bar or the >humidifier. > >I feel certain that very few of the humidistats are no longer >functional. At worst, they may be a little out of calibration, but as >long as the humidity remains somewhat constant, you won't notice. > >If things seem ok....if the piano is holding its pitch....the system is >ok. >-- > >Frank Cahill >Associate Member, Piano Technicians Guild >Northern Va > > Regards, Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T. Tuner for the Saskatchewan Centre of the Arts drose@dlcwest.com http://www.dlcwest.com/~drose/ 3004 Grant Rd. REGINA, SK S4S 5G7 306-352-3620 or 1-888-29t-uner
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