Development and Testing of a Simple Carbon Dioxide Enrichment Controller for Growth Chambers
Proportional and proportional plus integral (PI) computer algorithms were implemented with a low cost pulse width modulated injection system to control CO2 in a 7.8 m3 growth chamber. Experimental studies with plants in the growth chamber showed that average CO2 concentrations over 12 h were within 3 and 1 mmol mol–1 of set point for the proportional and PI controllers, respectively. The positive offset in CO2 concentration found for the proportional control was attributed to sampled measurements and pulse width modulated CO2 injection, and discussion was presented on how true errors differ from measured error estimates for pulse width modulated injection with long sampling periods relative to injection periods.