Laboratory 4-Enviromental

(WBGT-Sling Psychrometer)

(lab assignment link)

 

Part I-WBGT

Wet Bulb (DRY Bulb) Globe Temperature Index (WBGT) (Cognitive/Psychomotor)

There are three temperatures to be measured:
Wet bulb,
Dry bulb,
Globe.

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Globe temperature measures the sun's radiation.
Wet bulb temperature measures humidity.
Dry bulb temperature measures air temperature.

All three temperatures are calculated to determine the Wet bulb, Globe Temperature (WBGT)
using the following formula: WBGT= 0.1 X DBT + 0.7 X WBT + GT x 0.2 you can calculate the WBGT.

In lab, you will be given the following information calculate the WBGT index AND to discuss the range and activity levels based on the results:

 

EXAMPLE if the following are measured:
Wet Bulb Temperature = 75 degrees
Dry Bulb Temperature = 95 degrees
Globe Bulb Temperature = 120;

Answer of WBGT = 86.

Ranges:

The following ranges indicate if it is safe to practice:

82-84.9 Alert for possible increase in index
85-87.9 Active practice curtailed (for un-acclimated athletes)
88-89.9 Active practice curtailed (all athletes-except most acclimated)
90+ All training stopped, team meetings/demonstrations held instead.

PART II -SLING PSYCHROMETER

The Sling Psychromter is composed of two thermometers, one with the ability to measure a wet bulb temperature, and one with the ability to measure a dry bulb temperature. By whirling the sling psychromoter for approx. 90 seconds, air is allow to venilate around both the dry bulb and the wet bulb. The dry bulb will measure the actual air temperature. The wet bulb is enclosed in a cloth wick which is constantly kept wet. When used correctly, the spinning motion of the psychromoter will cause air to strike the wet wick enclosed thermometer and measure the cooling of the bulb (due to evaporation) and determine how dry the air is. When measured together, the wet bulb and dry bulb can provide information on the relative humidity.

Directions on use of the Sling Psychrometer

This material is supplemental and does not take the place of lecture or lab sessions