This is similar to the Flag approach to weather forecasting: If the flag is wet, it is raining; if the flag is dry, it is clear; if the flag is moving, it is windy; if the flag is moving very fast; it is very windy; and if the flag is stiff, then it is freezing.And why does your council think you need such equipment?
Shirt off = hot, sweater on = cold
biscuit dissolves in atmosphere = very humid
biscuit stays nice and crisp = low humidity!
Simple approach - no need for machine that sounds very delicate!