Sling or whirling psychrometer

The wick (free of grease and not contaminated by salt spray) must be moistened with distilled water, if this is not readily available, water from the condenser will generally be more suitable than ordinary fresh water. For preference the psychrometer observation is made to the windward side. Whirling or rotating the thermometers by hand at a controlled rate ensures the ventilation. Sling psychrometers lacking radiation shields for the thermometer bulbs should be shielded from direct insolation in some other way. Thermometers should be read at once after aspiration ceases because the wet-bulb temperature will begin to rise immediately, and the thermometers are likely to be subject to insolation effects. The wick should be changed regularly.