Did you?

[Kenneth W. Burton]

On Thu, 14 Mar 1996, Vanderhoofven wrote:

> At 07:01 PM 3/13/96 -0700, you wrote:
> >Hi All,
> >
> >>I checked with the local newsroom to get info about relative humidity
> >>readings here in Dallas.  I was informed that the average in Feb. was about
> >>72% at midnight and 54% at 6:00 A.M.  According to the newspaper the rel
> >>hum. readings on Tuesday,  March 12 were 41% at midnight, 60% at 6 A.M.,
> >>33% at 11 A.M., 27% at 1 P.M. 25% at 3 P.M. and 44% at 6 P.M.
> >>
> >>F. Yonley
> >>
> >Did you use a compensation formula--i.e. the numbers above are for outside
> not inside. You must take these figures and adjust them for the temperature
> inside the building. I have the formula hiding in a filing cabinet somewhere
> but you probably could get
> >
> >it from the local weather office (try the airport).
> >
> >Even without adjustment your readings of 27% and 33% are below what
> Steinway would recommend.
> >
> >Regards, Don Rose drose@saskmaple.net
> >
> >
>
> Dear Don,
>
> What is the compensation formula?
>
> I use a digital hygrometer/thermometer that I got from Radio Shack to
> measure indoor temperature and relative humidity.  It works well for me.
>
> Also, what would Steinway recommend as to the low and high humidity levels
> that a piano should be subjected to?
>
> Sincerely,
>
>
> David A. Vanderhoofven
> dkvander@clandjop.com
> Joplin, Missouri, USA
> Associate Member, Piano Technicians Guild
> web page:  http://www.clandjop.com/~dkvander/
>
>
      David,

      I also own that Radio Shack digital hygrometer and have found
recently that it is quite inaccurate. It was reading about 7% too high in
the 30 to 40 range and completely hopeless below 30%
      I bought a sling psychrometer and use it constantly. You have to
twirl it for a minute and a half, then read the wet bulb and dry bulb
thermometers. A slide rule built into the instrument allows you to read
the relative humidity without having to dig out some charts.

      Ken Burton
     Calgary, Alberta