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KF5JRV > TECHNI 08.08.16 16:18l 38 Lines 2365 Bytes #999 (0) @ WW
BID : 7318_KF5JRV
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Subj: The Dragoyle Evaporimeter
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Sent: 160808/1117Z 7318@KF5JRV.#NWAR.AR.USA.NA BPQK1.4.65
The Dragoyle Evaporimeter
Evaporimeters determined the rate of air evaporation from a wet surface to the
atmosphere, which is another way of measuring air humidity. Not only were
evaporimeters used to study conditions of the atmosphere, but they also became
useful for early forms of 'climate control'. The "Dragoyle" Air Tester in the measures
evaporation from a wet cloth that is kept damp from water contained within the
object. The decreasing level of water over a period of hours or days was used to
calculate the rate of air evaporation.
The Dragoyle, which is designed to look like a curious dragon-like creature,
measured the "air-comfort" of workplaces such as factories, workshops, and
offices. The principles behind this evaporimeter were first developed by the
Scottish mathematician and physicist Sir John Leslie (1766-1832). By 1925 the
instrument was packaged and sold as the Dragoyle in America. 'Air comfort' was
determined by measuring the combined effects of temperature, humidity, and
air-circulation.
The Dragoyle is made from a sealed glass piece consisting of a large bulb,
which features as the head of the Dragoyle, with a long tube that resembles
the creature's tongue. A millimeter of coloured liquid rests in the 'tongue'
tube and the large bulb of glass is covered with a piece of
fabric. The ends of the fabric are suspended like a wick in an internal
reservoir of water and the wet cloth creates temperature and pressure
differences as the water evaporates. The bead of liquid inside the
Dragoyle's 'tongue' moves to equalize the pressure between the two sections of
the glass vessel, causing the creature's head to rock back and forth. These
movements or 'strokes' are counted by the minute and indicate how humidity and
air circulation might be adjusted for a more comfortable work environment.
Depending of the rate of 'strokes' per minute, temperature or draughts could
be better regulated. By the early twentieth century, it was recognized that
metabolic processes within the worker's body significantly affected closed or
confined spaces such as the factory and that better indoor conditions improved
the efficiency of the worker. The ideal conditions for the sedentary worker
differed from those standing or involved in more physical activity, as
described in the Dragoyle instruction booklet.
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