Hello Don and List, While I would be the first to say these data loggers are certainly affordable and easy to use, their accuracy can be highly variable. We have found that manufactures of data loggers often "inflate" their relative humidity accuracy specification and do not discuss instrument drift with time. It seems fairly ironic having an instrument that reads to 0.1% RH when the accuracy specification is +/- 3% (Model TW-USB-2) or +/- 4.5% (Model TW-USB-RT). We recommend investing in a data logger that has +/- 2% accuracy or better, and then have it calibrated annually. This Dickson model has been a workhorse for us over the years. http://www.dicksondata.com/product/model_TP125.php Roger ----- Original Message ----- From: "Don Mannino" <DMannino at kawaius.com> To: <grahampianos at yahoo.com>; <caut at ptg.org> Sent: Tuesday, January 06, 2009 10:53 AM Subject: Re: [CAUT] HVAC information - Data Loggers Perhaps someone has already mentioned this and I missed it, but I have come across a great tool for diagnosing and illustrating environmental issues. It is a relatively inexpensive and small data logger. http://www.thermoworks.com/products/logger/usb_loggers.html I like the TW-USB-2, which costs $82 and is quite accurate. You install a small program with USB drivers in your computer, then plug in the data logger. You tell it through the software how often you want to take measurements, and when to start measuring. You then take the data logger out of the computer, and place it in the room you want to check. It's only a few inches long, so can be taped under a piano easily. After whatever length of time you want recorded, you plug the logger back into the computer and it makes a very nice graph of the temperature and humidity levels. This can be printed. It seems to me that this kind of a tool would be a great aid in illustrating how severe the conditions are, and armed with this chart and some backup materials related to humidity levels and piano soundboards, you would be better prepared to discuss the need for better controls in a building. I attached a PDF of one of the charts, a measurement of the overnight conditions in our Shigeru Kawai showroom here in California. You can just see the temperature and humidity bump up at the very end when I picked it up and carried it to my office to download the readings in the morning. Don Mannino
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