>This may seem like a flame, and it is not meant to be so.  However, if you
>have had your recording hygrothermograph recalibrated (and which springs
>replaced...?) after 4 years of use, you have 3+ years worth of less than
>accurate records.
>
>Recording hygrothermographs use a hair bundle (or sets of hair bundles) to
>respond to changes in %RH (temperature is recorded from bi-metalic strips
>and they tend to be very accurate) and major changes in relative humidity
>(winter=cold & dry; summer=warm & wet, etc.) in combination with acids and
>bases absorbed from the atmosphere (creating deliquescent salts) throw the
>hair bundles out of calibration.
>
>Hygrothermographs should be recalibrated after any significant change in
>the weather, otherwise their readings may not be dependable.
>
>It is largely for that reason that I began using data loggers nearly 10
>years ago; they are less likely to go out of calibration as the weather
>changes, and if the readings begin to drift, it is relatively easy to plug
>new numbers into the software to compensate for change.
>
>Jack C. Thompson
>Thompson Conservation Lab
>Portland, OR
>

Please share the brand name of your data loggers and place of purchase.
Thank you.

Kristi Alexander
Mgr. Collections
McClung Museum

>http://www.teleport.com/~tcl/index.html
>
>
>On Fri, 24 May 1996, Indianapolis Art Center wrote:
>
>> I use Abbeon Cal papers and pens--have had no trouble.  In fact, they just
>> had to replace the springs (after 4 yrs of use) for my 2 and recalibrate
>> them, and they only charged me $10 each plus shipping.
>>
>> I don't have their number handy, but if you have access to an 800 directory
>> you can probably find them.
>>
>> Julia Moore
>> Indianapolis Art Center
>>
>
>