Where do I place a hygrometer for best accuracy?

I have a humidifier next to my calatheas, and my hygrometer is on the wall about 2,5-4 meters away from the humidifier. Is it a good place or should it be placed nearer the humidifier and my calatheas to see a more exact result? I have my humidifier on for about 8 hours a day, and my hygrometer (where it is placed right now) shows 30-40 rh.