Posted by: lcowie | November 16, 2010

Learn About Psychometrics

During your BPI training class, you should learn about psychometrics. Psychometrics refers to dry bulb temperature (DBT) and wet bulb temperature (WBT). The WBT is a thermometer whose sensing bulb is covered with a wet sock evaporating into a rapid stream of air. It is a smart way of detecting relative humidity in the air, by means of evaporation.

A sling psychrometer is basically two thermometers in one. One thermometer has a dry bulb and the other has a wet bulb. They call it a sling psychrometer because you are going to sling it around, or whirl it around. The wet bulb (or latent heat part) captures evaporation, while the dry bulb (sensible heat) has no reason to change. You are measuring the amount of humidity in the air. Lower humidity means more evaporation, which means more energy pulled from the air, which means lower WBT. The wet bulb temperature will be lower than the dry bulb temperature, unless the relative humidity is 100%. The bigger the difference between the wet bulb and the dry bulb, the less humidity in the air.

Leave a comment if you have any thoughts, questions, or stories about the sling psychrometer.

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