How exactly do you calibrate a thermometer?

[ChickDancer]

I've got five thermometers. Two are digital thermometer/hygrometers. They are the kind you get from Wal-mart for $8.

Then I've got three bulb-style thermometers. Two came with my LG incubators, and one is a cheap $1 bulb-style that came glued to a piece of plastic with the numbers on it.


ALL FIVE OF THEM have different readings. Worse than that, the two digital thermometers have a difference of 4 degrees inside of the same incubator! That's a HUGE difference!

So I might be cooking my eggs, or I might be slowing their development down. Either way, I've got to fix this so I have at least something I can rely on.

How exactly do you choose a thermometer with an "accurate temperature reading" to adjust the others? Which one of these things should I trust? How can I be sure of what the temperature REALLY is inside of these things? I've read Pete's guide to hatching both chicken eggs and goose eggs, but it never actually tells me how to CALIBRATE the thermometers. And I read other suggestions to "start with a thermometer with an accurate reading" but how do you know when you have found one of those?? How do you know what is REALLY accurate? And how do you calibrate one that isn't accurate?

 

[Granny Hatchet]

you cant, just pick the ones that are closest to each other. mama hens arent exact either. they calibrate the humidity using a thermometer. its hard to figure out. maybe if your really worried you could do a couple test eggs? the temps even vary inside the incubators .pick the two that are closest in temp. to each other and put the others in a drawer. good luck on your hatch.

 

[fried green eggs]

To calibrate means you can adjust them but, most can not be adjusted so, you just need to know how far off they are. I used a medical thermometer like the old glass ones you put under your tong. Fill a glass of water with small Ice cubes and water put the medical thermometer in the ice water and leave it for 5 mins. It should read 32 degrees F. Then fill a cup with 1/2 cup of table salt and add 1/4 cup of water to the salt. Put the cup in a zip-lock bag and put all of your thermometers in the bag - including the medical one you had tested in ice water. Seal the bag and let it sit on the counter over night or at least 8 to 12 hours. The humidity on the digital hygrometers should read 75% - if they don't make a note on a piece of tape as to how far they are off + or - from 75%. You will stick the tape on them so, you know how they read. Look at the thermometers and write down how far they are off + or - from what the medical one says the room temp is. That should help you to know what ones are better than others. I leave sticky tape with +4% and -2 degs or whatever on my digital thermometer/hygrometer so, I remember how to read them.

I went to my hardware store to get a really good accurate thermometer/hygrometer. They had all the different ones hanging up together in the store - I had to laugh, even the really expensive ones (hanging at the same level) didn't agree with each other. I went home without buying one. Figured the ones I had were fine.

 

[ChickDancer]

I figured you could "calibrate" the LG thermometers by nudging the glass tube up or down on the plastic sheet where the numbers are printed. The others I expected to do as you said and just record the differences.

It was just the whole method of finding an accurate thermometer that got me.

The two digital hydrometers do seem to agree on humidity though. So I'm not worried about that part being accurate. Plus I'v been hatching for four years using the same incubators, so I just know how many water trays need to be filled anyway. It's just that silly temperature reading I have to worry about.

 

[ChickDancer]

I'm trying something different for them. The two digital thermometers are about a year apart in age. And the older one has been in an incubator the whole time. So I put them both in the freezer. I left them in for about 1.5 hours, and finally got them to agree that my sister's poor freezer is a frigid 14 degrees. (And you thought Baskin Robbins ice cream was hard to scoop...)

But during their time in the freezer, they did NOT have batteries. I charged up a new pair and installed them immediately after taking the thermometers out of the freezer.

Now they are warming back up with freshly charged batteries in each of them (and the same brand and type now, too). One did start warming up a bit faster than the other, but that COULD be because it was taken out a few seconds before the second one.

But the fact that they both started out at 14 degrees immediately after installing batteries, means they agree on a temp at SOME point, and will hopefully continue to do so.

The bulb thermometers are now in there cooling down to that same chilly 14 degrees.

 

[ChickDancer]

Looking good so far.

Humidity is different, but in addition to warming up, they are drying off. When I removed them from the freezer, they both collected a LOT of condensation! So as they are warming up, the water is evaporating.

But high temps are the same, low temps are the same, high humidity was the same, and low humidity is the same.

 

[Granny Hatchet]

good work !! who said you cant calibrate? oh ya, that was me.

 

[blucoondawg]

I have skipped the digital thermometers because I didn't know what to trust I went to my local farm store and looked at the indoor and outdoor bulb thermometers they had quite an assortment. I noticed a few didn't read the same as all the others so I didn't buy them. I got a Taylor brand indoor thermometer all the Taylors seemed to have the same readings so I figure I can trust it.

 

[ChickDancer]

good work !!  who said you cant calibrate?  oh ya, that was me.

I'm just thinking of how electronic thermostats work and figured maybe the problem was related. An electric thermostat usually works by increasing or decreasing the distance between two metals. The warmer temperature increases their individual size until the two metals touch. Cooling them makes them smaller until they no longer touch. But I thought maybe over time under constant warm conditions, it takes MORE heat to get those metals to touch.

This is purely theoretical on my part, but it seems to be working. Right now they both read 72 degrees here in my bedroom. One has 46% humidity, and the other 47%. So I would say they are pretty darn close to actual temp and humidity, since they are FINALLY so incredibly close to each other.

Now to place them back into the incubator (same inc for both) and see what that reads...

 

[ChickDancer]

THIS is why I don't trust bulb thermometers. See the gaps?