How Humidity Control Works?

“Is it possible to produce chambers with humidity control but no temperature control?”
Can you control only humidity? Not with any accuracy or repeatability. If you just want to get as dry or humid as possible, then skipping temperature control is acceptable.
But you still need to measure temperature to calculate relative humidity. Relative humidity is actually relative to the temperature. The higher the temperature, the more moisture the air can hold at a given temperature.
Relative humidity is the ratio of the amount of moisture in the air vs. how much it can hold. And herein lies the best reason to have temperature control: If the temperature changes, the relative humidity changes.
So a stable temperature helps ensure a stable humidity.