Thank you, Wolfgang. Sounds like you have a great deal of experience and expertise with these matters!
My issue is not that the humidistats are inaccurate. It’s that they don’t match when they are out of their plastic bags. In the bags, with the same salt (plain old table salt) in roughly the same amount, with a few drops of water, they are reading exactly the same. Outside of the bags, in the music room that I’m trying to monitor, they are quite far off from one another. I would love to know some way of ascertaining which one is more accurate in the room. Since they are both within their claimed margin of error within the bag, I’m puzzled about how to assess their accuracy in the room itself.
Hope that makes sense!
Jonathan