Hygrothermographs

I think that in the hygrothermograph selection matter there are many
problems, and its necessary to think very well prior to deciding
what model we will buy:  Storage space to measure, number of
stations needed, the environment--too dry or too humid, too
variable, etc--, and specially calibration and time that we decide
to expend in the post-study of data.

I don't know your models, but I think that the hair
hygrothermographs are similar. At the National Library, in the past
we observed:

    *   High time consumed in the study
    *   High number of observer errors--it's very difficult decide
        between the lines
    *   they need calibration--Once every two months or more,
        especially in too dry environments
    *   Low accuracy out of 35 to 80% RH levels.

The dataloggers can be of help to conservators. There are many
models in the market. In Spain we can meet different models:
Hanwell, Testo and SmartReader. All can work with in a simple
computer. There are very expensive, but more cheap than the hair
hygrothermographs. The software can do simple statistical
calculation--mean, average, max. min, etc.--but it's possible to
export the data to other statistical programs, e.g. Lotus, Excel,
etc. However, I believe than only the Hanwell system can do easy and
reliable calibration.

Now, in the National library, we use the Hanwell dataloggers. We
have two models: Humbug autonomous system, similar to the
SmartReader (5 monitors) and Hanwell Radio telemetry, 14 monitors,
in my own opinion the best.

We can read measurements in real time. The measurement is
transmitted to the computer by low power UHF radio. No installation
costs, and very good graphics, however I think that Hanwell need
improve its statistics software.

The calibration and adjustment is very easy, with 3 different
salts: Novasina Sensor Check SC-75, SC-53 and SC-33.

If you need more information, contact

    Hanwell instruments Ltd.,
    Queensgate House, 48 Queen Street
    Exeter, Devon, EX4 3 SR, UK
    +44 1 392 496 810
    Fax: +44 1 392 426 291

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                  Conservation DistList Instance 12:11
                   Distributed: Friday, July 17, 1998
                       Message Id: cdl-12-11-004
                                  ***