Waste of time, been there done that. I added a humidistat in bathroom onto existing fan. In spring/summer/autumn worked fine, have shower fan runs, fan eventually turns off. However in winter when the bathroom temperature is lower the fan just comes on all the time. Change setting then fan doesn't work rest of year.
Sorted by buying an expensive (over £100 I think) VentAxia fan that has a temperature compensated humidistat and that worked wonderfully as expected all year round. Also had a timed override, which I connected to a chorded momentary action pull switch, so that if someone dropped a non humid smelly in the bathroom the fan could chew it away !!!!!