| Electronics > Projects, Designs, and Technical Stuff |
| Measure 100% of CO2 inside a chamber |
| << < (4/4) |
| Dave_PT:
@CatalinaWOW Thank you! The idea is, since the CO2 gas is expensive, open the exhaust valve and the normal air valve (this one connected to an air compressor) and let run for a while to ensure that inside the chamber there is no "CO2". Then close the exhaust valve and start the compression of air inside until reach the calculated pressure. Then close the air valve and open the CO2 until it reached the calculated pressure too and close the CO2 valve. To maintain the pressure of CO2 (to compensate the material absorption) I will need do some electronic control and create a hysteresis. For example, when the pressure fall below 1.9bar I "stop" the experience and inject more CO2, until reach the 2bar pressure. The pressure, temperature, humidity and electronic state of each valve will always be part of the continuous logging and more detailed calculations are made after the experiment ends. @ehughes Thank you. For reasons that I can't control, the time slot for testing aren't too big. So I need to develop this (with some level of accuracy) and assembly it in place in a weekend. But I will read about your suggestion to better know this technique. |
| SiliconWizard:
--- Quote from: Dave_PT on March 28, 2019, 07:42:38 pm ---The interior of the chamber can reach 90% of humidity and can be heated to 70 ° C. --- End quote --- The sensor you picked so far would not cut it then. Its operating temperature range is -20°C to +50°C apparently, so I wouldn't count too much on its behavior at 70°C. As said above, it's a wheatstone bridge basically and the characteristic output at 3V ref. voltage is given on the first graph (mV vs. %CO2 if I get it correctly). Given its nature, I guess it would require calibration as well. Its rated "sensitivity" (around 0.5mV/%CO2) is just given as a ballpark value and should be calibrated. Getting a reliable measurement of just a couple % difference at around 100% CO2 will be extremely challenging for most sensors as well IMO. The sound speed idea looks interesting but the "pretty easy to do"... not so sure. I've thought of some "air quality" sensors (some are rather accurate for CO2 measurement but usually optimized for low CO2 concentration so typically under 5-10%CO2) so... not an option. |
| Dave_PT:
@SiliconWizard Thanks. After some discussion and study, I think that THIS is the way to have success. |
| Navigation |
| Message Index |
| Previous page |