Here is a truly digital oxygen analyzer with analog and digital interfaces for control, display, and data-logging of oxygen and CO2 parameters.
The Oxigraf O2iR may be the chamber controller you need.
An error budget must be established for oxygen process control. Humidity changes can cause a large variation in the oxygen measurement. A hot, wet day relative humidity of 50% at 37ºC (99ºF) corresponds to an absolute humidity of 3.2%. Such a water vapor dilution would cause a variation from the cold, dry air oxygen concentration of 20.9 to 20.2%, a change of 0.7%. If 19.5% is to be the alarm value, then variations from all other sources must be substantially less than 0.7% (the difference between 19.5 and 20.2%).