Hi all,
When testing your hygrometer with the salt test, how sensitive is the final humidity to the amount of water in the salt? Say the the salt is just a little dry versus just a little wet. How much difference in RH after everything stabilizes?

It is not that sensitive. But you cannot just add a few drops to a pile of salt and expect to the the correct reading, you need to make a paste of the salt kind of slushy. Just make sure you don't have a pile of slushy salt and then actual water not mixed in the salt.