Hygrometer accuracy

[MiniatureOrchids]

Hey all, tricky question for you. What hygrometers do you use to track humidity in your terrariums?

Reason I ask is that I bought a reasonably cheap hygrometer on Amazon, and we've been using it for 6-12 months. It often said that the humidity was > 90% despite moss etc feeling a bit dry. Last week, I ordered a new Hygrometer (with a wired probe) and it was reading about 20% lower than our original one, which indicates that all the time we thought the humidity was in the 90s, it was probably in the 70s.

So, after a bit of googling, I tried the salt test last night. I put a bottle cap of salt with some water, along with the hygrometers, into a sealed container for 12 hours. In theory, the humidity should stabilise at 75% and you can get an idea of the hygrometer's accuracy and then compensate when reading it.

But now, the hygrometers (which are in the tupperware tub with the salt) are saying 72% and 74% respectively. The latter reading is the one that was showing as 99% previously.

So it seems like they're both approximately correct around the 75% mark, but diverge dramatically once humidity increases.

So what does one have to do to get an accurate meter? Should I stick with an analogue meter instead? Any recommended and well-respected brands to try? It's no good trying to keep a humid environment for the orchids and moss if we think it's at 90%+ and actually it's at 70% - or vice versa!!!