Hair bundles for hygrothermographs

Helen McPherson <hmcpherson [at] slv__vic__gov__au> writes

>We have a range of drum hygrothermographs ( thermohygrographs in our
>part of the world), including battery and clockwork models, Nikkei,
>Sato Sigma, Izuzu, Ogawa Seiki and Michromech. Depending on the
>machine location, they run on 7 and 31 day cycles. The machines are
>recalibrated using an electronic hygrometer, each time the charts
>are changed. The hygrometer is recalibrated inhouse every 12 months.

We were advised by a manufacturer to clean the hairs occasionally
(e.g. annually if in a clean environment, more frequently if dust is
a problem) using a swab dipped in ethyl alcohol or industrial
methylated spirits and taking care not to stretch the hairs by
pressing on them.

We have used this method and found that there did not seem to be any
change in response. The effect of moving the thermohygrograph for
cleaning was more noticeable than the cleaning. Regular calibration
is still needed, of course.

Richard and Helena Jaeschke


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                  Conservation DistList Instance 16:25
                Distributed: Wednesday, October 2, 2002
                       Message Id: cdl-16-25-003
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