For the hygrometer in my still airs I use 2 cheap ones from ebay but am considering getting a more expensive one. The thing is I watch the air bubbles and adjust so the number is only a starting point. I kind of think using my ebay one is like using a scaled that is not zeroed out to find out how much weight a child gains in a month. Sure the actual starting and ending weight may not be spot on but the change in weight should be close. So I set the humidity to make the cheapy model say 45% then every 7 days I candle air bubbles and adjust the humidity up or down based on the air bubble getting bigger. For lockdown I typically increase the humidity by 5-10 degrees. For by ebay cheapies they register the lockdown humidity at 70% until a chick hatches and wow then it shoots up to 90% for at least 30 minutes.