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WetBulb Globe Temperature
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WetBulb Globe Temperature
The WBGT is a weighted average of the three temperature sensors using the following
formulas:
• WBGT (indoor) = 0.7WB + 0.3G (denoted as “WBGTi” on the display)
• WBGT (outdoor) = 0.7WB + 0.2G + 0.1DB (denoted as “WBGTo” on the display)
The resulting WBGT values can then be compared to indices of work-rest regimens
(stay times) based upon work loads.
Stay Times/Rest Times (QTº46 only)
Stay times represent how long a worker should be able to safely work under heat
stress conditions. Select one of four indices for displaying and printing from the
unit: ACGIH Stay Times, NAVY PHEL’s, U.S. Navy/Marine Corp. Ashore Flag
Conditions, or EPRI Action Limits. Refer to Appendix B for more information on the
indices.
Heat Index/Humidex
The Heat Index is determined using the dry bulb temperature and relative humidity.
Based upon charts available from the U.S. National Weather Service, Heat Index
represents how an average person feels relative to climate conditions. For a given
temperature, the higher the humidity, the higher the heat index.
The Heat Index is defined over a temperature range of 70°F - 120°F (21°C - 49°C) and
a relative humidity range of 30% - 99%. Outside of this range, the instrument will
show dashes in the display for the Heat Index.
The Humidex, used primarily in Canada, works on the same concept as the Heat
Index. The values are slightly different. The Humidex is defined over a temperature
range of 70°F - 109°F (21°C - 43°C) and a relative humidity range of 20% - 99%.
Outside of this range, the instrument will show dashes in the display for the Humidex.
Airflow
The QUESTemp° 46 measures airflow if Quest’s Air Probe accessory is used. The
Air Probe uses an omni-directional anemometer sensor that measures air flow
between 0 and 20 meters per second in 0.1m/s increments. Please see “Airflow
Functionality”, page 21 for more details.