Wish I could help you there. I just made my online purchase today from GQF for my thermometer/hygrometer combo. It will be my first one, so my knowledge level on the subject is just about nill.
However, on the hygrometer issue, Speckledhen has the most wonderful way to calibrate those. I'll pass this along and hope like heck I've gotten it right. If I haven't, I'm sure Cyn will be along soon to straighten us both out!
Take a large zip lock bag and place a dish of water and salt into the bag. The amount of salt should be such that the water added to it is the consistency of wet sand. If I remember right, Speckledhen said about a half cup of salt to a quarter cup of water...or was it the other way around...oh heck! Just make it the consistency of wet sand!
Place your hygrometer inside the zip lock bag along with the dish of water and salt and seal it up. Let that set undisturbed for about 12 hours. Your hygrometer
should read 75%. If it doesn't, if it reads, say 70%, then it's off by 5%. Therefore, any reading you have on it, you'll know to add 5% to the figure to get an accurate reading. Same holds true if it's showing 80% - just subtract the extra 5% in that case.
Cyn? Did I get it right??
As for thermometers....I've heard say that one can calibrate those with a good medical thermometer. Same basic principle as the hygrometer. Adjust your temp reading according to the reading on a quality medical thermometer. Be aware though, that there is a variance on all of these. Look on the package...it will say something like :Accurate to within +/- 3 degrees. Don't confuse that with the range reading. That's completely different. I think maybe the medical thermometers are far more precise than the typical household thermometers though.
I hope that helped a little...good luck on your incubating!
4 of them are the same type of device n one is different. Here are what they are reading (# 1 & 2 are the two new ones; #5 is the one thats a different type):
