OWL Energy and RH

Slightly random question: has anyone done a tear down on an Owl energy monitor? I’m interested in what RH sensor it uses. Have been running one alongside an emonTH for a few weeks and the owl is reading about 10% below the TH. Am thinking of buying a couple of salt-based RH calibration cells to check accuracy, anyone else tried this?

There was some discussion on calibrating the humidity sensor on the old forums.