# Digital thermometer variation in temperatures



## Chris82 (Sep 16, 2015)

Hi guys,

I have a couple of different digital thermometers and the variation can be anywhere upto +/- 2 degrees. I want to be able to use a digital thermometer so I can be accurate when incubating some python eggs. This amount of variation can obviously be detrimental. 

What digital thermometers do you use and how do you know that the temperature being displayed is that temp?

Any brands to stay away from or any that are great and are a must have?

thanks 

chris


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## MatE (Sep 16, 2015)

I only use the cheap ones of fleabay.They have a stainless probe end.I think it comes down to how accurate your thermostat can be.I use 4 x 25w party globes not heat cords or mats as I reckon they have better heat transfer as there not insulated.I rarely see a .2 of a degree difference in temps.

Just my observations.


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## ronhalling (Sep 16, 2015)

Hey Chris i use an infra-red thermometer i got from 1 of our sponsors that is accurate to within +/- .03 deg C and put a tag on my hard wired thermometers in the enclosures to tell me what variation there is (if any) for the 1 being used, sometimes there can be quite a bit of difference between what the thermostat reads and what the thermometer reads, this way by tagging each 1 i know that the accuracy is between +/- .03 deg C for all by adding or subtracting any variation. Hope this helps to answer your enquiry  ...........................Ron


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## Sdaji (Sep 16, 2015)

I find that most thermometers are very precise, but also most types are quite inaccurate (yes, there's a big difference between precise and accurate  In this case it's an important difference). For incubators I always either test a few and get an accurate one (which will also be precise, because they all are) or I calibrate it using a group of thermometers, and tag them like Ron described.

In my first season incubating snake eggs, back in the 90s, I bought myself an expensive, fancy digital thermometer. Unfortunately it was about 4 degrees out, so I had my eggs incubating at about 35 degrees, which killed them all, and I only worked out why afterwards. Since then I've been pretty careful with thermometers.

In general, you get slightly better accuracy with more expensive thermometers, but not really enough to make it worthwhile, especially if you can be bothered calibrating them yourself.


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## Wallo (Sep 16, 2015)

i have always used the URS/iPetz Mini Digital Thermometer and never had an issue - i have a few and they are all dead on


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## Chris82 (Sep 16, 2015)

Sdaji said:


> I find that most thermometers are very precise, but also most types are quite inaccurate (yes, there's a big difference between precise and accurate  In this case it's an important difference). For incubators I always either test a few and get an accurate one (which will also be precise, because they all are) or I calibrate it using a group of thermometers, and tag them like Ron described.
> 
> In my first season incubating snake eggs, back in the 90s, I bought myself an expensive, fancy digital thermometer. Unfortunately it was about 4 degrees out, so I had my eggs incubating at about 35 degrees, which killed them all, and I only worked out why afterwards. Since then I've been pretty careful with thermometers.
> 
> In general, you get slightly better accuracy with more expensive thermometers, but not really enough to make it worthwhile, especially if you can be bothered calibrating them yourself.



thanks all all for your input. This is what I don't want to happen within the incubator having the temp too high. So for an example if I have three different brands of thermometer, they're all placed in the exact spot but they all read differently. How then do I know which is the accurate reading so I can adjust the thermostat up/down to the temp I need? How do I calibrate a thermometer and can they all be calibrated?


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## cement (Sep 16, 2015)

Why not just use the average temp from all three?
I always check the incubator with a couple and if theres any difference, its never more then a degree or two I just go off the average.
For the actual snakes, a degree or 5 difference wont make any difference , if they have a gradient they'll just suit themselves, which is exactly what you want for them anyway.


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## ronhalling (Sep 17, 2015)

Hey Chris, i might not have explained it the best, what i meant was i use the infra-red temp gun to get the temp from inside the enclosure then if there is any variation between that and the hard wired digital thermometer i tag the hard wired thermometer with what the variation is, that way all my hard wired 1s can be as accurate as the infra-red gun once the variation is taken into account.  ....................Ron


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## Sdaji (Sep 17, 2015)

ronhalling said:


> Hey Chris, i might not have explained it the best, what i meant was i use the infra-red temp gun to get the temp from inside the enclosure then if there is any variation between that and the hard wired digital thermometer i tag the hard wired thermometer with what the variation is, that way all my hard wired 1s can be as accurate as the infra-red gun once the variation is taken into account.  ....................Ron



If you're using your infrared thermometer to calibrate all your other thermometers, make sure your infrared is accurate and you're using it correctly. Measuring different objects of the same temperature will give different temperatures with an infrared thermometer (put a piece of polished metal, a piece of wood and a piece of glass next to each other in the same room, let them come to the same temperature, then measure them! They'll be very different). Infrared thermometers also come out of calibration on their own over time, while digital (thermistor) and liquid (mercury/alcohol etc.) thermometers generally hold their calibration indefinitely.


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## ronhalling (Sep 18, 2015)

Sdaji said:


> If you're using your infrared thermometer to calibrate all your other thermometers, make sure your infrared is accurate and you're using it correctly. Measuring different objects of the same temperature will give different temperatures with an infrared thermometer (put a piece of polished metal, a piece of wood and a piece of glass next to each other in the same room, let them come to the same temperature, then measure them! They'll be very different). Infrared thermometers also come out of calibration on their own over time, while digital (thermistor) and liquid (mercury/alcohol etc.) thermometers generally hold their calibration indefinitely.



Everything you have said is very true, and i thank you for pointing that out to the general membership as it can be a big trap for new players, yes mine has been calibrated down to +/- .03 deg C using the professional incubators at a chook farm a friend owns. Thanks for your reply mate it could be very helpful to new members.  ............................Ron


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## Chris82 (Sep 18, 2015)

These are all good tips guys and I thankyou all for your input. You mentioned thermistor digital thermometers. Is this a particular brand? I think I'll go out and buy a mercury/alcohol one just so I can get a better idea of what the digital ones may or may not be out by. I do also have an infrared but as mentioned above it may well be out. I've checked and this one cannot be calibrated!


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## Sdaji (Sep 18, 2015)

Chris82 said:


> These are all good tips guys and I thankyou all for your input. You mentioned thermistor digital thermometers. Is this a particular brand? I think I'll go out and buy a mercury/alcohol one just so I can get a better idea of what the digital ones may or may not be out by. I do also have an infrared but as mentioned above it may well be out. I've checked and this one cannot be calibrated!



Thermistors are basically two pieces of wire twisted together. A current runs through them and the electrical properties of the current change depending on the temperature of the wires at the exact point they are touching at. It is the way pretty much all of the electrical ("digital") thermometers work (an infrared is just as digital as a digital, and both measurements are analog simply converted into a digital display).

If you pull apart the probe of a digital thermometer, you'll see that there are two wires running along the cord, and they contact in the end of the probe. That's the exact point where the temperature is being taken, that is the thermistor. Most of the modern thermostats use a thermistor too, which simply operates as a thermometer. Back in the old days before the fancy gadgets were available we used old style thermostats with mechanical gas bellows, or spring and mercury tilt switch mechanisms. I'm sure there still a fair few IMIT thermostats with gas bellows in enclosures, and maybe some old Honeywell ones with the mercury tilt switches too. Hehe, sorry, I'm getting a bit distracted by nostalgia!

Mercury and alcohol thermometers aren't really any more accurate or precise than digital ones, and are a little more difficult to read (obviously they are analog). Thermistors are pretty reliable gadgets, and these days are really cheap.


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