I *think* this is the one Don McKechnie uses. (and I know he has a PC for it's findings...) I'm sure he'll post here in no time! :) On Mar 2, 2006, at 2:11 PM, Fred Sturm wrote: > 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 >
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