Mechanical meters often rely on such things as horse hair, pieces of wood
and similar organic things to indicate humidity. For accurate results use a
wet and dry bulb system with a psychrometric chart.

N-

I agree. However, I have an inexpensive version of the wet-dry system that may
be as bad as the horse hair. It consists of two thermometers with one having a
wick attached to the bulb, fed by a water reservoir. It has a conversion
matrix printed on the mounting plate. Comparing with several other sources
suchas electronic guages and TV weather reports, it tends to be ten to twenty
percent off.

The electronic humidity guages may only be within five percent, but that is
much better than some of the alternatives.

Fred