Measurements
Wet Bulb Globe Temperature
8
Measurements
The QUESTemp
34 & 36 data logging area heat stress monitor directly senses the four
parameters: ambient or dry bulb temperature (DB), natural wet bulb temperature (WB), globe
temperature (G), and relative humidity (RH).
The QT
34/ 36 compute the Wet Bulb Globe Temperature (WBGT), stay times for three
possible indices (QT
36 only), and the Heat Index (HI) or the Canadian Humidex. Using inputs
on the side of the instrument, two additional sensor arrays can monitor up to three locations
simultaneously.
On the QUESTempº 36 model, you can measure air flow, in meters per second, by plugging an
optional hot wire anemometer sensor into a side jack on the unit.
Using Detection Management Software (DMS), you can determine the thermal comfort indices,
Predicted Mean Vote (PMV) and Predicted Percent Dissatisfied (PPD) (with the QUESTempº
36 model only).
Wet Bulb Globe Temperature
The WBGT is a weighted average of the three temperature sensors, a globe thermometer, a
wet bulb thermometer, and a dry-bulb thermometer, using the equations listed below.
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 workloads.
Stay Times/Rest Times (QTº36 only)
Stay times represent how long a worker should be able to safely work under heat stress
conditions (available on QUESTempº 36 only). Select one of the three indices for displaying
and printing from the unit: ACGIH Stay Times, NAVY PHEL’s, or EPRI Action Limits. (For
setup, refer to “Setup.” For detailed rest times refer to charts in Appendix B.)
Measurements