You will probably have to experiment with it a bit to find the best place to make it most efficient. I wouldn't hang it at canopy level or beneath the canopy as that area is going to be the most humid of anywhere from the plant transpiring and from soil moisture evaporation. I would hang it about half way between the lights and the canopy but off to one side and out of the direct light and/or heat as those could affect its accuracy. Make sure you have good fan driven air movement to properly stirr the atmosphere within the growspace.