Acurite Thermometer/Hygrometer Question

I have one of these measuring my temps/humidity but I have stumbled upon an issue. Does anyone know where the sensor is for the hygrometer? Is it in the probe or is it in the display portion? My device is reading a humidity of 84% and I've had fans blowing in the vents all day long and the lowest it got down to was around 70%. I was wondering if perhaps it is much dryer in the enclosure than I originally thought and the humidity sensor is on the display box somewhere and reading ambient levels outside the enclosure (the display is outside the tank with a separate thermometer measuring the cool end)?

Also, I have my probe adhered to the bottom surface of the enclosure. Should I pull it up and just lay it on top of the substrate (cypress mulch)?

humidity sensor is on the unit itself (display portion), on the back near the bottom. I just lay mind on the substrate on the cool side. Cypress mulch retains some moisture, you may want to stick it an inch or so above the substrate. Get the 3M velcro tabs, or find a suction cup that will hold it up. Though my boa decided she doesn't like hers on the side of the tank, I think she comes out of her hide just to knock it down.

Edit: On another note, why cypress mulch? From what I have read about it, its prone to mold and should be replaced weekly (though that's if it's sprayed every day). My ball sheds fine on aspen.

Cypress mulch is naturally more resistant to mold growth and mildew and I don't have to spray it, it is humid enough.