This Bendix Friez 566-2 psychrometer dates from 1960. It is a simple wet bulb hygrometer where the wet bulb is aspirated by an internal battery-powered electric fan (3 D-cell batteries). Water is applied manually to the wet bulb wick, I use a plastic squeeze bottle with a needle spout. The thermometers range from 10 F to 100 F, though a Celsius model was also manufactured. The manual contains relative humidity and dew point tables that appear to be based on Marvin's tables (see the Miscellaneous Downloads section of this website). Belfort Instruments continues to sell this model on their website.

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