Vintage Wilson Warden Hair Hygrograph

This is a very nice, small, Vintage Wilson Warden Hair Hygrograph in a black cast casing with laquered brass drum and internal base. It dates to approximately 1920-1940. 

• In pretty good condition, with a few surface scuffs and scratches in the paintwork commensurate with age and use.
• The black paintwork has faded with age.
• It will need chart paper and a pen.
• The brass Wilson, Warden & Co label, which would have been attached to the inner base, is missing. 
• The timer movement works well, ticking and keeping time satisfactorily.
• I’m not sure how accurate the hygrograph is at measuring the humidity.
• Wilson Warden is Stamped in the base

It was previously owned by the A.W.E (UK Atomic Weapons Establishment) Electrical Standards Department.

Maximum Approximate Size (WHD): 29 x  18 x 23 cm

A hair hygrograph is a chart recorder which records the humidity (or dew point) over time. It works by using the principle that a human or horse hair changes length depending on the level of humidity in the air.

The difference in hair length is only 2.5% between humidities of 0-100%. A hair hygrograph is, therefore, a very sensitive piece of equipment! On this instrument the ‘hair’ is located in the open chimney at the side of the recorder. The contraction and expansion of the hair is conveyed to the recorder arm, which charts the readings over time.

All in all this represents a scarce opportunity to obtain one of these instruments for use or to add to your collection. Please click on the following link for more meteorological and weather instruments.