Chinese ???

[Sunset Machine]

Yep, you must dry the depth mic off with a clean rag or paper towel between measurements. No floating oil either. The other thing to avoid is the edge where the water creeps up the sides of the trough. So far I've seen no need to average the measurements - everything was very repeatable the ONE time I tried this using clay dams and plastic tubing. In that case I referenced from a machined surface instead of the worn ways. That may have been a blunder. Wanting to check it and having no level, I'm driven by need, so to say...