Was looking over at Sparkfun and trying to figure out if any of the temperature sensors support or distinguish between wet and dry temperature -- potential application is in a freezer or refrigerated storage. I'm also not 100% sure what the difference of wet vs dry temperature is and if you can derive that with a humidity sensor?



Temperature is a measure of the average thermal energy. A temp sensor will not tell you if we are talking a dry or wet bulb temp. The temperature is the same for both.

Wet or dry comes into play when you start thinking about how much thermal energy would be required to change the temperature of the air or how much condensation you will have if you lower the temperature of the air, etc.

To measure wet bulb, you need temperature and relative humidity. With those two sensors, you should have what you need.


It works the other way around: you use the wet bulb temperature to find relative humidity. I can't think of any direct use of wet bulb temperature.

The classic way to measure wet bulb temperature, is, well, using a wet bulb.

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The reservoir of a thermometer is kept wet by covering it with a wet wick. The water will evaporate and cause a temperature drop. The difference between dry bulb and wet bulb temperature is an indication for the air's humidity.

Electronic humidity sensors are mainly capacitive or resistive. Sensirion is a manufacturer of small sensors which combine temperature measurement with relative humidity measurement. They communicate with a microcontroller via I2C. Sensor size is just 3mm \$\times\$ 3mm.

enter image description here

While Sensirion mentions Conrad, Farnell, Newark and RS as distributors, availability may be a attention point.

Further reading:
Introduction to humidity
Choosing a Humidity Sensor: A Review of Three Technologies


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