Exo Terra hygrometer vs. Hygrotherm

[Pyxiefan001]

So I bought an Exo Terra hygrometer (THIS ONE Amazon.com: Exo Terra Digital Hygrometer with Probe: Pet Supplies) so I can see the humidity in my Pyxie's exo box without having to flip through the Hygrotherm's monitors (even though I have everything set in there to maintain itself). The hygrometer seems to be either a bit off or more sensitive than the hygrotherm's sensor.

Both the hygrotherm sensor and ET "probe" are placed in the same location right next to one another, a couple of inches above the substrate, and well away from the humidifier itself to get the most accurate ambient readings. But both are giving me different readings. The hygrotherm is personally programmed to maintain the humidity around 80% (it will shut off the humidifier when it reaches said level. One example: the hygrotherm as I type reads 82% (the humidifier I have is a bit powerful, more on that below), and the ET hygrometer reads 87%. It does have 3 settings max, min, and what I suppose is ambient humidity. I keep it set to ambient of course. As I personally trust my hygrotherm to maintain parameters, I'm wondering if the hygrometer I have is a bit more sensitive than the hygrotherm sensor.

BTW the humidifier I'm using is a modified ultra sonic cool mist, from Walgreens. It does put out quite a bit of mist, obscuring view in the cage a bit. But, my enclosure being an exo terra, it has plenty of ventilation, none of which is closed off in anyway. It's got four screens on the top, and even extra vents below the doors. And my frog doesn't seem to be bother by it. I mainly want to know who/what to trust - my expensive and much adored hygrotherm that is digitally designed to maintain the (almost) exact parameters you program into it. . .or. . .my solo hygrotherm bought for only $13 from Amazon, which boasts rather mediocre reviews.

If it makes any difference here is my humidifier, and the work it does. I made this because I grew tired of the noise the ReptiFogger I originally bought annoyed the snot out of me.