I would like to detect frost for my apple trees and thought I'd play around with arduino.
It turns out that you need to measure the Wet Bulb temperature.
As far as I see this is usually done wrapping the sensor in wet cloth.
Does anyone have any experience with such measurements/calculations? What's the easiest way to do this.
Is it possible to use a normal sensor like the BME280 and infer the wet bulb temperature using relative humidity, dry bulb temperature and maybe a wind meter?
As far as I see this is usually done wrapping the sensor in wet cloth.
Yes that is right.
Is it possible to use a normal sensor like the BME280 and infer the wet bulb temperature using relative humidity, dry bulb temperature
You can but the sensor will not be very accurate and this will reflect in the answer you get. I don’t know how accurate you need to be.
This is a link to the formula you need to use. Just manipulate them to make the subject of the equation equal to the value you want.
and maybe a wind meter?
No, you need a hot wire anemometer or a cup or ultrasonic anemometer for that. Note any humidity measurements must be shielded from the wind otherwise the results are not valid.
I suppose you could light fires and waft the warm air around with boards strapped to your arms. Like in that movie... can't remember the name. It was vines they were trying to protect from frost.
PaulRB:
I suppose you could light fires and waft the warm air around with boards strapped to your arms. Like in that movie... can't remember the name. It was vines they were trying to protect from frost.
Smudge pots were commonly used in the past, although I've never heard of anyone trying to stir the air with boards strapped to their arms. Google does turn up a lot of references to using large fans for frost protection.
A lot easier to turn on the irrigation and spray water onto the plants, although with an apple tree that might be difficult. Around here, the technique is commonly used for strawberry plants, and the news companies seem to love sending a reporter out to get pictures of a field of plants covered in ice.
Hi,
I think what you need to know is the "dew point" temperature.
The dew point is the temperature to which air must be cooled to become saturated with water vapor. When further cooled, the airborne water vapor will condense to form liquid water (dew). When air cools to its dew point through contact with a surface that is colder than the air, water will condense on the surface. When the temperature is below the freezing point of water, the dew point is called the frost point, as frost is formed rather than dew. The measurement of the dew point is related to humidity. A higher dew point means there will be more moisture in the air.
