4 Placement for monitoring/testing
The QUESTemp should be placed at a height of 3.5 feet (1.1m) for standing individuals or
2 feet (.6m) for seated individuals. Tripod mounting is recommended to get the unit away
from anything that might block radiant heat or airflow. A 1/4"x20 threaded bushing on the
bottom of the instrument allows mounting to a standard photographic tripod. Do not stand
close to the unit during sampling.
Make sure that the wet bulb reservoir is filled with distilled water and that the cotton wick is
clean and fully wetted. After adding water or placing the unit in a new environment, allow
ten minutes for the globe and wet bulb readings to stabilize.
A series of dashes appear in the display if one of the following occur:
The Heat Index or Humidex is outside of its allowable range
The temperature is outside of its allowable range
A temperature sensor has failed
Natural Wet Bulb Thermometer
The natural wet bulb thermometer gives an indication of the effects of humidity on an
individual. Relative humidity and air flow are taken into account by measuring the amount
of evaporative cooling taking place at a thermometer covered with a moistened wick. The
QUESTemp uses a cotton wick immersed into a reservoir containing distilled water.
Ordinary tap water should not be used, 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.
Globe Thermometer
The globe thermometer gives an indication of the radiant heat exposure on an
individual due to either direct light 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.
As an option, a sensor array with a 6 inch diameter globe is available.
Dry Bulb Thermometer
The dry bulb thermometer measures the ambient air temperature. This measurement is
used in the outdoor WBGT calculation when a high solar radiant heat load may be
present. The series of white plates surrounding the sensor shield it from radiant heat.