I got mine a few days ago, tested it for 2 days on a empty tub and then tested it with aspen in it. I set the probe from the hydrofarm thermostat on the inside of the tub above the hottest area and put that to around 93 .. I then put the aspen and layer it on top of the probe. I then put the acurite probe on top of the aspen and it hits around 91.

so far so good..