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Vintage Negretti And Zambra Hair Hygrograph R30401

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Vintage Negretti And Zambra Hair Hygrograph R30401

This is a very nice, small, Vintage Negretti And Zambra Hair Hygrograph R30401 in a black cast casing. It dates to approximately 1930-1950. The R series numbering started with R101 in 1920: R standing for ‘Recording.’

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.

Vintage Negretti And Zambra Hair Hygrograph R30401
Vintage Negretti And Zambra Hair Hygrograph R30401

In very good working condition, with a few surface scuffs and scratches in the paintwork commensurate with age and use. It may need a new pen.


  • Negretti and Zambra Badge
  • Measures Percentage Relative Humidity
  • Serial Number: R30401
  • Range 10/ 100%
  • Reg.No. 698680

The timer movement works well, ticking and keeping time satisfactorily. I’m not sure how accurate the hygrograph is at measuring the humidity.

All in all this represents a scarce opportunity to obtain one of these instruments for use or to add to your collection.

Some Trivia For You

Negretti & Zambra was founded in 1850 by Henry Negretti and Joseph Zambra. The company has a world renown reputation for producing some of the finest quality scientific, meteorological, and optical instrumentation. In fact, so good that they were appointed instrument makers for the Royal Observatory, British Admiralty and members of the British Royal Family; including Queen Victoria.

Negretti was acquired by Meggitt Holdings in 1985. 


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