Plantfog K 175 280 Manual

Principle

The Sling Psychrometer determines the Relative Humidity in % by measuring the effect of
evaporation of water on the display of a thermometer.
Two thermometers are surrounded by moving air ; one thermometer bulb is covered with a wet
wick. Evaporation of water from the wet wick reduces the temperature relative to the bulb of the dry
thermometer. The relative humidity is determined with the slide rule calculator on the back of the
instrument.
The lower the relative humidity of the surrounding air the larger the temperature difference will be
between dry and wet bulb.
Before starting a measuring cycle make sure that the wick is completely wetted and the dry bulb is
absolutely dry.

Taking a Reading

[1] Open the instrument by withdrawing the inner part from the frame.
[2] Thoroughly wet the wick by placing the exposed end under cold running water or
immersing it in water for some 30 seconds. This will wet both the exposed wick and the
spare wick coiled in the wick container. Do not use hot water – this may damage the
thermometer. The wick in the container will remain wet for some time so that you can
take readings for about 1 hour. Make sure that the dry bulb is absolutely dry..
[3] To take a reading pull out the inner part, turn it for 90 ° and rotate the thermometers.
[4] Rotate the thermometers for some 30 seconds with a rate of 2 to 3 turns per second
[5] Stop revolving the
instrument and take
note of
temperatures – wet
and
temperature;
be fast – the wet
thermometer tends
to adjust to room
temperature.
Compact Sling Psychrometer
both
dry