Raise it up off the ground, and don't use anything porous to do so as that will hold moisture and throw off the reading. The sensor is on the bottom on the other side of the intake filter. Block its airflow or soak the area around it and it won't be accurate. BTW, i wouldn't put a humidifier within 2ft of a plant so you don't add moisture to its leaves causing burn from light magnification. But this question is 10month old, so you prob figured it out already