Different thermometers are showing different temps? Is this bad?

[Tanichca]

The incubator is a brand new hovabator 1602N with a fan, on day 20. There are two digital thermometers and one mercury thermometers in the bator. The digitals show 97.6 and 99, respectively, and the mercury one shows 105!! Is this bad? Normal? Should I be worried? There are several eggs that are pipped, will the temperature hurt them or the un pipped eggs?

 

[HEChicken]

First, yes, it is not good to have thermometers you can't trust. Unfortunately, digital thermometers are notoriously unreliable and I would ditch them. By mercury, are you sure it is truly a mercury thermometer (which are almost impossible to buy any more) or do you just mean it is an analog thermometer, that reads temperature much as the mercury ones used to do?

I would be more likely to trust the analog, and in that case 105 is definitely not good. However even all analog thermometers are not created equal.

It is important to calibrate both thermometer and hygrometer prior to starting a hatch. Hygrometers are easy doing the salt test, but thermometers are more problematic. The unscientific method I used to calibrate mine was as follows:

I went to Walmart and looked at their $1 analog thermometers that read like the mercury ones used to. They had about 20 on the rack and most of them read 75. A few read higher or lower than that. I concluded that the law of probability dictated that Walmart had its thermostat set to 75, and those reading that temp were accurate. I bought one, brought it home and set it on my house thermostat (which I hoped read accurately). Within hours it read the same. So I decided it was reading accurately enough and since then have used it exclusively for incubating. Prior to doing this, I had up to 5 thermometers, every one of them with a different reading, and my hatches were terrible. Since I bought the $1 thermometer that is accurate, my hatches have been in the 90-100% range.