would the sht11 be good for measuring the air stream inside of "material dryers"???

laser-vector

i have been using the sht11 for some time now with many applications around our production site, and i must say i really enjoy using them.
however i have now been asked if i could use them in more places (and i mean a lot more places!!). We have a bunch of material dryers for drying plastic pellets prior to an injection molding process. so i was wondering what you guys think about using the sht* series sensors for taking semi-accurate measurements of the dryer's internal air stream.

the temperature in the dryer is typically at a constant 250 degrees Fahrenheit, and they run for days/weeks on end..

any input, suggestions, experience or sensor recommendations would be highly appreciated and considered for use in this project.

Thank you!!

kwinn

Hard to say how well it would work. 250 F is close to it's upper spec limit according to the data sheet. Might be worth while trying one out though.

Tracy Allen

It might be worth an email or call to Sensirion to ask the question. Their data sheets show the humidity accuracy as a function of humidity, but they don't AFAIK bracket that over temperature to the extremes. I have to assume that the graph is made at a moderate temperature and I wouldn't hazard a guess how it looks 250°F. Saturation vapor pressure of water at 250°F=121°C is quite high. If the beads are wet to begin with, you might see full saturation and a large error around the 100% point. As the beads dry, the evolution of water vapor might drop slowly, or it might drop like a rock. It would be worth the experiment to see. It begs the question of how accurate a reading is needed.

One thing is sure, the life of the sensor can be degraded by certain chemicals in the air stream. The Goretex cover can help somewhat, but it can become degraded too, and it does not stop vapors. The plastic beads might be benign, but applications such as drying concrete require special care.