Sensors
Natural Wet Bulb Thermometer
5
Sensors
Natural Wet Bulb Thermometer
The natural wet bulb thermometer
gives an indication of the effects of
humidity on an individual. Relative
humidity and wind speed are taken
into account by measuring the
amount of evaporative cooling taking
place at a thermometer covered with
a moistened wick.
A B C
A
. Globe thermometer
B
. Natural wet bulb
thermometer
C
. Dry bulb thermometer
Check Wick and Fill Natural Wet Bulb
The QUESTemp° Heat Stress Monitor uses a cotton wick immersed into a reservoir containing
distilled water.
DO NOT
use ordinary tap water, as the contaminants that are left behind after
evaporation will shorten the life of the wick and cause high readings. If the wick is discolored it
should be replaced. To
replace the wick
, slide the old wick off the top of the sensor. Place a
new wick over the sensor, making sure that the bottom of the wick is down in the reservoir.
Wick
Reservoir cover
Reservoir
Filling wet bulb reservoir
1.
Remove reservoir cover and fill with
distilled or de-ionized water.
2.
Replace reservoir cover.
Figure 1-4: Filling wet bulb reservoir
Globe Thermometer
The globe thermometer (left position) gives an indication of the radiant heat exposure on an
individual due to either direct sunlight or hot objects in the environment. This is accomplished by
placing a temperature sensor inside a blackened copper sphere and measuring the temperature
rise. The WBGT index is based on the response of a 6 inch diameter globe. The QUESTemp°
uses a 2-inch diameter globe for a faster response time. The temperature of the 2-inch globe is
correlated to match that of a 6 inch globe.
Sensors
