Drift is dangerous because it is gradual
A chamber that fails outright is an obvious problem with an obvious response. A chamber that is two degrees off, or holding twelve percent less humidity than it reports, produces a trial that looks completed and is quietly not comparable to the one before it.
Look for a gradient, not an average
Single-point measurement at the sensor position will confirm what the controller already believes. The useful question is whether conditions are uniform across the growing space. Position within the chamber becomes a hidden experimental variable the moment it is not.
Multi-point verification across shelves and across the chamber depth is how you find this.
Humidity and temperature are coupled
Relative humidity depends on temperature, so a temperature control problem presents as a humidity problem and vice versa. Diagnosing them separately leads to chasing the wrong system. Both need to be measured together before drawing conclusions.
Lighting affects thermal load
Lighting is a significant heat source inside the chamber. Degraded output means less heat as well as less light, which shifts the balance the refrigeration system was set up for. A chamber that has drifted since a lamp change is usually telling you about thermal load rather than about a control fault.
Check the programme is executing as written
Programmes get modified over years by different people. Before diagnosing hardware, confirm that what the controller is actually executing matches what the current protocol says it should be. This is a surprisingly frequent root cause and costs nothing to check.
Schedule maintenance between trials
Chamber maintenance carried out mid-trial is disruptive at best and invalidating at worst. Give your service provider your trial calendar and let the work fall into the gaps. It is a straightforward conversation that avoids a genuinely expensive problem.
