Fred, Debbie & List, I can only echo Roger's endorsement. I have been using the Dickson DataLogger for some time and am very pleased with it. I have had three different models but the one I use all the time now is the TR320 which has the specs Roger mentioned, it is $229 but you need software and a cable to make charts and graphs to scare folks with, and that costs $79 and if you want to do recalibrations yourself that software is $249. All of which is extremely useful and has paid for itself many times over in Chris's world. I actually had the thrill recently of getting a university to alter their HVAC settings based on the data I supplied. The secretary in the 79 degree office is almost as grateful as the pianos in the hall that were toasting at 78 F and 7% rh. I've even measured, quite accurately I'm sure, at other venues, 3% recently. The TR320 also works at the piano as I am tuning, as I used to do with my Pianotek box, with its 2.5 digit LCD and BTW it will record up to 32,000 sample points over just about any duration you choose. I just wish it could dance. We'd have such a time me and my TR320. Chris Solliday it's late so go easy ----- Original Message ----- From: "Roger Wheelock" <roger@dampp-chaser.com> To: "College and University Technicians" <caut@ptg.org> Sent: Thursday, March 02, 2006 2:37 PM Subject: Re: [CAUT] Reading low humidity > Hi Fred, > > With Dickson units we see a fairly repeatable 1% RH drift per year downward > when compared to a US secondary standard hygrometer we use to calibrate our > humidistat switches. I am not sure of the direction of drift for all > sensors. My understanding is that airborne pollutants coat the plates in > the sensors, giving a variation in the reading with time. I believe most > sensors measure capacitance of the air between two small closely-spaced > plates. I think there are also some that measure resistance. > > Roger > > ----- Original Message ----- > From: "Fred Sturm" <fssturm@unm.edu> > To: "College and University Technicians" <caut@ptg.org> > Sent: Thursday, March 02, 2006 2:11 PM > Subject: Re: [CAUT] Reading low humidity > > > > Hi Roger, > > How much annual drift do you see on the Dickson? Is it always in a > > particular direction? Does that apply to any electronic sensor (direction > > of drift)? Is drift caused by "accumulation of crud" (sensor getting > > dirty, picking up air pollution, etc)? Or is there something else > > involved? I've got a bunch of other questions bubbling to the surface as > > well (how does an electronic sensor work in physical/electrical/chemical > > terms . . .), but any enlightenment you can provide along these lines > > would be most appreciated. > > Regards, > > Fred Sturm > > University of New Mexico > > fssturm@unm.edu > > On Mar 2, 2006, at 11:28 AM, Roger Wheelock wrote: > >> Hi Fred and Debbie, > >> > >> While this device is quite affordable, the spec. sheet lists the > >> relative humidity accuracy between 20-80% RH as +/- 3.5%, rising to +/- > >> 5% at the extremes. They also list annual drift at 1% and offer no > >> means (that I can see) for recalibration. The added cost over their > >> temperature-only data logger is $20. This cost differential means there > >> must be a low-end sensor for humidity, similar to a $25 hygrometer. > >> > >> By comparison a Dickson data logger is +/- 2% from 0-95% RH. These > >> drift downward 1% per year. They can be recalibrated. The bad news is > >> they cost about $270. > >> > >> Our experience is that performance improves with increasing price for > >> most electronic hygrometers and data loggers. We have yet to see one > >> that shouldn't be recalibrated annually. However, even when a unit > >> drifts, it can give accurate differences between two humidities. This > >> means that the reading will become less accurate over time but the > >> difference between a max. and min. reading will stay fairly constant. > >> > >> Roger > >> Dampp-Chaser Corp > > > > _______________________________________________ > > caut list info: https://www.moypiano.com/resources/#archives > > > > > _______________________________________________ > caut list info: https://www.moypiano.com/resources/#archives > >
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