BAKER
INSTRUMENTS
Model
B6012/B6015
Compact Sling Psychrometers
Instruction Manual
Features
• Designed for portability (7.5" L x 1.5" dia.)
• Slide rule construction quickly converts temperature to relative humidity
• Built-in water reservoir holds sufficient water for several hours of testing
• Thin bulb design gives fast thermal response
• Non-mercury red spirit filled thermometers
• Thermometers constructed of shock-resistant glass; stems have deepetched numerals and 1" scale division for easy reading
• Temperature Range: -5 to 50°C / 25 to 120°F
• Accurate to within ±5% RH
Optional accessories: B6016 Spare Thermometer, °C
B6013 Spare Thermometer, °F
B6031 Replacement Wicks, 6 pack
Operating Instructions
Sling Psychrometers determine the % of Relative Humidity in the air by
measuring the evaporation of water in the surrounding air. Two thermometers
are placed in flowing air, one thermometer bulb being covered in a wet wick.
Evaporation from the wet bulb causes its temperature to be depressed relative
to that of the dry bulb. In dry air, evaporation will be rapid and the depression
will be greater, giving a low %RH reading. In humid air, there will be little
evaporation and the depression will be small, giving a high %RH reading. If
the air is completely saturated, no evaporation can take place so both the
wet and dry bulb thermometers will give the same reading, which equates to
100% RH. The RH% can be read off the Slide Rule calculator integrated into the
psychrometer or a standard Humidity Table can also be used.
Before Taking a Reading
Open the instrument by withdrawing the inner frame from he case.
Thoroughly wet the wick by placing the exposed end under cold running
water or immersing it in water for about 30 seconds. This will wet both the
exposed wick and the coiled in the wick container. Do NOT use hot water as it
may damage the thermometer. The wick will remain moist for several hours.
Always check that the wick is wet before taking any readings and ensure no
moisture remains on the dry bulb.
Taking a Reading
• Set the psychrometer at a right angle
• Hold the case and rotate the frame for 30 to 60 seconds at a speed of 2 to
3 revolutions per second
• Stop rotating the instrument and note the Wet Dry Bulb Temperatures
• Close the instrument and use the slide rule calculator to determine the %RH
Using the Slide Rule Calculator
When the Psychrometer is closed the Slide Rule can be used to calculate the
%Relative Humidity directly from the Wet and Dry Bulb Temperatures.
The Calculator has two scales, an Upper and Lower scale. The upper scale
should be used for dry bulb temperatures up to 70°F/ 20°C. On higher
temperatures the lower scale should be used.
Calculating the %RH reading
• Locate the Wet Bulb Temperature on the relevant scale
• By sliding the inner frame out of the case, align the Dry bulb temperature
with the Wet bulb temperature
• Read the % Relative Humidity from he centre scale at the location on the
arrow
Maintenance and Spare Parts
If the wick becomes worn or dirty it can be cut off and replaced with a wick
from the wick container. The wick container can be removed with a
twisting action and a new length of wick withdrawn.
Broken thermometers can be
replaced by removing the screw
at the rotating end of the frame.
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