Dampp-Chaser hygrometer specs

[John Ross]

Hi Roger,
If a person has a psychomotor, is there a way to change the hygrometer to 
agree. That way, we could check and calibrate them, periodically?
Regards,
John M. Ross
Windsor, Nova Scotia, Canada
jrpiano@win.eastlink.ca
----- Original Message ----- 
From: "Roger Wheelock" <roger@dampp-chaser.com>
To: "Pianotech" <pianotech@ptg.org>; "College and University Technicians" 
<caut@ptg.org>
Cc: "Becky Baldwin" <becky@dampp-chaser.com>
Sent: Tuesday, January 25, 2005 2:01 PM
Subject: Dampp-Chaser hygrometer specs


> Hello list,
>
> I have received a few inquiries regarding the accuracy of Dampp-Chaser 
> hygrometers.  Customers have purchased the units in quantity, set them all 
> up to run side by side, and then have become concerned about the results. 
> We contacted the manufacturer in Sweden and they verified the following 
> information.
>
> Measuring range:  20-95%RH
> Accuracy within 50-70%RH: +/- 3%RH
> Accuracy outside 50-70%RH: +/- 5%RH
>
> I find that these specs are typical for hygrometers priced similarly to 
> ours.  Unfortunately, 42% RH could be read anywhere from 37%RH to 47%RH 
> when read with these instruments.  We believe, however, that the 
> instruments do measure changes in relative humidity quite accurately.  We 
> had hoped technicians would use them to show piano owners the variations 
> in the piano's environment (maximum versus minimum readings) rather than 
> use them as scientific instruments.  I use either data loggers or high end 
> ($1500 plus) hygrometers in my research.  The old saying, you get what you 
> pay for, is really true for hygrometers.
>
> Another thing I occasionally do is find myself questioning the reading 
> only to realize a little later that it was set on either the max. or min. 
> I feel pretty dumb when I figure this out, but thought I would pass it 
> along just in case.
>
> Thanks,
>
> Roger
>
>
>
>
>
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