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Waterless Wetbulb
7
Measurements
The QUESTemp° 44/46 data logging area heat stress monitor directly senses three
parameters: dry bulb temperature (DB), globe temperature (G), and relative humidity
(RH).
It computes the wet bulb (WB), the Wet Bulb Globe Temperature (WBGT), stay times
for four possible indices, 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 46 model, you can measure airflow, in meters per second, by
plugging an optional hot wire anemometer sensor into a side jack on the unit.
Determine thermal comfort indices, Predicted Mean Vote (PMV) and Predicted Percent
Dissatisfied (PPD), using Detection Management Software (DMS).
Waterless Wetbulb
The Waterless Wetbulb is an estimated measurement using the % of Relative
Humidity, Dry Bulb Temperature, and Globe Bulb Temperature to determine
the psychrometric wetbulb. The psychrometric wetbulb value is adjusted
based on airflow to provide the waterless wetbulb estimate.
Computing Waterless wetbulb and wind speed
When computing the waterless wetbulb, you can increase accuracy by setting
the airflow to the current environments wind speed. The recommended
airflow setting for an indoor environment is 0.3 m/s unless otherwise
determined with an air-probe measurement (available only on the QTº46
model). The recommended setting for outdoor environment is 2.0 m/s.
NOTE: To convert wind speed from miles/hour to meters/sec use the
following formula:
• Miles/hour * .447 = meters/sec. (Example: If the average
wind speed is 5mph, then enter 5*.447 = 2.2 meters/sec.)
If you are using the QUESTempº46 with the Air Probe attached, you would
not set the airflow setting. (It will automatically calculate with the current
reading.)
Please see “Setup for Waterless Wetbulb measurement” on page 11 for
details on setting the Airflow.
Measurements