# Methods of measuring constantly high air humidity

How can I measure still air in 90-100% RH range with constant 25°C temperature?

• I've no idea. All psychrometer concepts I know about need a sufficient amount of air flow. If you are not willing to supply that, then I'm left without knowing a method. It will be interesting if someone can suggest a still-air concept. Better still, one that has useful accuracy (not an easy thing to achieve) for the narrow range you are discussing. Do you know of any commercial devices that work without air flow?
– jonk
Sep 17 '21 at 18:15
• This sounds physically hard – maybe investigate the properties of a microwave cavity oscillator, where the moisture changes $\varepsilon_r$, maybe? Sep 17 '21 at 18:59
• Can we use a tiny fan to blow air slowly to the sensor? Sep 18 '21 at 0:41