Water Supply Issues

[AliciaS]

Question received by mill personnel:
We are currently using a Dry bulb/Wet bulb setup in in our kilns but are constantly having trouble with water supply issues. Is there a reliable electronic RH sensor that can take the stress of being in a dry kiln environment?

[TimothyD]

That is an interesting concept.  I have a couple follow up questions:
Would an RH Sensor, providing %RH and temperature be sufficient to replace a Dry Bulb/Wet Bulb setup?
What would be the maximum temperature that the RH Sensor might need to operate in?
What RH levels might the RH sensor be exposed to during a typical charge? 

Knowing this data, would allow me to investigate a solution.

Tim

[MichaelM]

There is a discussion of relative humidity measurement at https://en.wikipedia.org/wiki/Hygrometer

The wet-bulb is commonly used in kilns because of the chemicals in the atmosphere and the temperature.

Other sensors rely on resistance or capacitance and the materials generally don't work at high temperature.  Not in the wiki reference are ir sensors - water vapor attenuates the ir waves.  These are probably the most accurate, but the electronics are temperature sensitive.  Expensive too.

The resistance device that has been used in kilns is a cellulose wafer place between two electrodes.

The humble dry/wet bulb is robust and inexpensive.  The sensor (the sock) is easily changed when contaminated.

As to the original question - I would be curious what the water supply issue is.  This would seem easier to solve that figuring out a new sensor. 

[TimothyD]

Great points, Mike!
We use an RH sensor in one of our other products, but it's normal operating range is only up to 140 F in the higher humidity range, and this is a rather high end sensor.