Vintage Bendix Model 594 Hygro-Thermograph Humidity Air Temperature Recorder, US $59.99 – Picture 0

Vintage Bendix Model 594 Hygro-Thermograph Humidity Air Temperature Recorder, US $59.99 – Picture 1

Vintage Bendix Model 594 Hygro-Thermograph Humidity Air Temperature Recorder, US $59.99 – Picture 2

Vintage Bendix Model 594 Hygro-Thermograph Humidity Air Temperature Recorder, US $59.99 – Picture 3

Vintage Bendix Model 594 Hygro-thermograph Humidity Air Temperature Recorder

US $59.99

Chula Vista, California, United States
Jan 30th

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HYGRO-THERMOGRAPH RECORDING RELATIVE HUMIDITY AIR TEMPERATURE Model 594 The Bendix Corporation Friez Instrument Division Baltimore, Maryland Temperature and relative humidity (RH) are major considerations for any collection as some materials are particularly susceptible to damage from extremes, or too rapid fluctuations, in either value. Established museums, collections and archives, use a variety of HVAC (heating, ventilation, and air conditioning) equipment, as well as sophisticated monitoring instruments, to maintain their collection environments. Many will recognize this type of instrument from visits to museums or galleries, where they can be spotted tucked away in corners. The Bendix hygrothermograph is still being made, though its maker is now called Belfort Instrument. The heart of the instrument is a mechanical clock housed in a brass cylinder. Instead of turning hands across a dial, however, this clock turns itself. The cylinder can be set to complete a rotation in either one day or one week. This instrument incorporates a replaceable chart that is clipped around the cylinder. A hygro-thermograph chart typically features two scales, one for recording temperature, the other relative humidity. As the cylinder rotates, each scale is marked by an inked pen. These are actuated by mechanisms that react to atmospheric changes. Temperature is recorded using a still-common method—a bimetallic strip whose deflection changes according to the difference in the thermal expansion of two different metals (usually steel and copper or a copper alloy) that have been joined along their length. In 1783, Horace-Benedict de Saussure introduced his new method for measuring humidity with a classical flourish: a putto playing with another’s hair. The second pen, tracking humidity, is actuated by hair—specifically human hair that has been treated to remove moisture and natural oils. This treated hair will vary in length between 2 and 2.5% across the range of relative humidity. This simple, accurate, and reliable way of recording RH remains relatively unchanged since it was first introduced in the eighteenth century by the Swiss philosopher Horace-Benedict de Saussure in his Essais sur l’Hygrometry (1783). It is remarkable, though, that these simple and robust hygrothermographs still have a well-established place in many institutions. They are among the survivors or a generation of instruments that traced data in ink, or smoked paper, against a rotating drum.

Condition:	Used: An item that has been used previously. The item may have some signs of cosmetic wear, but is fully operational and functions as intended. This item may be a floor model or store return that has been used. See the seller’s listing for full details and description of any imperfections. ...	Brand	Bendix
MPN	Model 594
Model	Model 594
Country of Manufacture	United States