I have been battling a CO2 mixer on a Wave/GE bioreactor S200EH. Running it at 5% CO2 it fluctuates up to 8% and down to 4% for short periods. These are calibrated every 6 months, adjusting the zero and span potentiometers while concentrations of 100% N2, 5% CO2 and 10% CO2 cal gas are sampled. Sometimes adjustment is needed but most cals are within tolerance.
I've replaced pumps, sensors, hoses, filters, orifices and entire modules. I've checked the gas supply (CO2 and Clean Air), Tested the mass flow controllers. Everything works great except the CO2 mixer.
Does anyone know what causes the fluctuations? More to the point, how do I fix it?
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