I have an older model hovabator that you set temps. yourself with a thermometer. Been getting extremely poor hatch rates and suspected temp. problems but was unable to fine tune it. Ordered a 1588 with factory set temp. and set one batch of 42 eggs. Of those, 20 weren't fertile/or duds at day 14. Of the remainder, 21 out of 22 hatched right on schedule at 21 days. Since it was obvious that the 1588 was maintaining correct temp. very well, I put my 2 thermometers that came with the incubators in at mid egg level sitting on the turner. I went and bought a sack load of thermometers and have been marking the correct readings obtained when placed in the incubator, on them. Not one read correctly by the way. As an example, of the 2 that came with the hovabators, the first one read 102.5 and the other read 98 when place in the 99.5 degree 1588 hovabotor. I have just hatched 100% of viable eggs in the old incubator using one of the thermometers calibrated by the 1588! I used the thermometer that reads 98 for 99.5 since it was the one I was using for my previous failed hatches. Turns out I was cooking my eggs before. I now have lots of calibrated thermometers and know that my hatches will work if I am careful to maintain the same conditions each time. As to humidity, I don't bother with a hygrometer. I don't add water until lock down and then I fill the troughs with hot water and forget about it. I do keep a space heater in the bathroom with them. The heater maintains the room at 85 degrees.