3M 46, 44 user manual Waterless Wetbulb, Computing Waterless wetbulb and wind speed

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.