Re: Looking for Temp and humidity sensors

[Pat Farrell <pfarrell@xxxxxxxxxx>]

B Fuhrmann wrote:

>>> Looking for commercially available Temperature and or Humidity Sensors.
>
> "Pat Farrell" <pfarrell@xxxxxxxxxx> wrote in message
>> Humidity is really just two temperatures, dry and wet.
>
> No, it is not.  You can measure it that way but why when there are direct
> sensors available.

Isn't the claim here that the one piece sensors, while available, are too
expensive?

Actually, you measure the dry and wet temperatures and calculate.

However, when I was an HVAC engineer, when we wanted a serious
measure of humidity, we used wet and dry temps. That was years
ago, maybe it reflected more pragmatic concerns.

>> Why not just get two temp sensors and a piece of cotton and some water?
>> The formula is trivial.
>
> Automating a wet bulb thermometer is not trivial.

Sure it is, get to temp sensors, put a cotton wick on one into a tank
of water. Put a float valve on the tank to control level of water in the
tank. Put a muffin fan blowing air across both sensors.
Measure and calculate. Periodically backflush the tank to clear
out the calcium and other scrud left over from the water.
Put in some algecide periodically, etc.

This is, of course, comp.home.automation, so you really
need computer sensors for the water temp, flow rate of both
water and air, etc.


--
Pat