I tested the dials I bought with the salt test. Get a soda bottle cap, fill it with table salt. wet the salt, but you don't want water standing on top of it. Put that and the hygrometer in a zip lock bag and zip it shut. In 6 hours, it should read 75%. so whatever it reads you'll know what to add or subrtact. Like for mine, one was reading 85% the other was reading 70%. so what that first one reads, I know it's actually 10% less, the other one, it's 5% more than what it reads. I wrote it on each one, so I don't have to trust this memory of mine to remember, LOL
putting them both in with the built in one, they were really close, but the built in one wasn't even close when I did it
I have a freestanding unit in the same room as the incubator that does not have a bulb on it. Would that work for this, just wondering if it would or if I still need to purchase the kind with the bulb attachment.