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Thread: Thermometer accuracy

  1. #1
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    Default Thermometer accuracy

    WARNING: I'm about to rant!

    So I'm trying to set up a second tank for QT/Grow out and decided to buy a cheap probe type external thermometer. I set up this tank with the original equipment which was sitting in my garage for over 25 years, so I wanted to check that the heater was still working correctly. To my surprise, the heater not only still works, but keeps the temperature at 28C which is where I set it over 25 years ago!!!!!!

    I thought I better check the accuracy of this new thermometer so I put it in my display tank which has the InkBird ITC-308 controller in it. Well........

    The temperature differential was over 3 degrees!!!!! I thought to myself, what a piece of $h!t. Then I got to thinking. How accurate is the InkBird. It turns out the InkBird was the one that was off. I used an old liquid photography thermometer that I use to set the developer temp and I know for a fact that is accurate to within 1 degrees Celsius and sure enough, the new cheap thermometer was the accurate one and the InkBird was the one that was out.

    I know the InkBird was accurate when I first bought it, but over time it seems to have lost it's calibration. So, after calibrating, it now reads the same as the cheaper probe thermometer.

    The only good thing to come out of this is I now know why some of my discus were hiding and not eating as voraciously as before. Their behavior has change over the last couple of weeks or so.

    Actually, another thing I learnt was that it's true that if you want to curb discus aggression, lower the temperature. My lot have been oddly behaving themselves.

    End of rant.

  2. #2
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    Hey Spidy, Is your accurate thermometer a mercury one? IMHO, I think those are pretty accurate.

    At least the Inkbird can be calibrated!

    https://www.iddba.org/training-mater....aspx?ext=.pdf

  3. #3
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    Quote Originally Posted by Rebel View Post
    Hey Spidy, Is your accurate thermometer a mercury one? IMHO, I think those are pretty accurate.

    At least the Inkbird can be calibrated!

    https://www.iddba.org/training-mater....aspx?ext=.pdf
    It's a newer "blue liquid" non toxic type that are considered as accurate but less toxic. I used the liquid thermometer to check the accuracy of the two digital ones.

  4. #4
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    Quote Originally Posted by Spidy View Post

    Actually, another thing I learnt was that it's true that if you want to curb discus aggression, lower the temperature. My lot have been oddly behaving themselves.
    I would just as quickly unlearn it if i were you. Making your Discus feel unwell due to inappropriate conditions is a terrible idea.

    Ado
    Whatever

  5. #5
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    Quote Originally Posted by Spidy View Post
    It's a newer "blue liquid" non toxic type that are considered as accurate but less toxic. I used the liquid thermometer to check the accuracy of the two digital ones.
    I never know which 'gold standard' to use when I compare thermometers. It's important to know that your reference standard is absolutely accurate.

    For discus, I hope you've seen this
    https://www.youtube.com/watch?v=VXe3VKh7qF8


  6. #6
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    My filter (Fluval G3) has built in temp monitoring. Once a week or so I compare this to my digital stick thermometer. They are always within 0.1C of each other.

    It is always best to test your testers once in a while !!!
    Whatever

  7. #7
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    Ado, Rebel, it was not intentional and wouldn't do it normally, but it happens to be true. All the discus were being "quiet". I noticed the change in behavior but didn't put two and two together until last night. And Rebel, yes, great vid.

  8. #8
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    Quote Originally Posted by Rebel View Post
    I never know which 'gold standard' to use when I compare thermometers. It's important to know that your reference standard is absolutely accurate.
    A man with a watch knows what time it is. A man with two watches is never sure.
    Last edited by Neon Tetra; 14-09-18 at 02:24 PM.

  9. #9
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    Quote Originally Posted by Neon Tetra View Post
    A man with a watch knows what time it is. A man with two watches is never sure.
    I think that 'A man with a watch thinks he knows what time it is' is more accurate.
    Whatever

  10. #10
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    I use a digital temperature laser IR gun to check temps on my tanks now... I've used all sorts of temp gauges in the past and none seemed that accurate when comparing multiple side by side. This thing is pretty accurate as far as I can tell, and takes about a second to check the tank temp. Don't really need to know 24/7 anyway. So a ball park with a thermometer is good enough and one of these when accuracy is needed (and its quick, so i can check temps of water coming from tap when filling tanks...).

    Cost me about 15-20 bux from Aldi when it was there, but can be had in a fair few places for the same price.
    "The stuff I buy is a bit pricey however it is as dry as a nuns nasty" - BigDaddyAdo

  11. #11
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    @indir, I just ordered one of them yellow numbers.

  12. #12
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    Quote Originally Posted by indir View Post
    I use a digital temperature laser IR gun to check temps on my tanks now... I've used all sorts of temp gauges in the past and none seemed that accurate when comparing multiple side by side. This thing is pretty accurate as far as I can tell, and takes about a second to check the tank temp. Don't really need to know 24/7 anyway. So a ball park with a thermometer is good enough and one of these when accuracy is needed (and its quick, so i can check temps of water coming from tap when filling tanks...).

    Cost me about 15-20 bux from Aldi when it was there, but can be had in a fair few places for the same price.
    The problem with these guns is that they do not measure the temperature through water. They measure at the glass surface, or if pointing directly into the tank, the water's surface. Many people think that they are measuring the point of where the laser falls, i.e. on a piece of driftwood for example. This is not the case.

  13. #13
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    Once I get mine, I will do a comparison with various surfaces and my other aquarium thermometers.

  14. #14
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    Yes good point Spidy. I've not found any real variation between glass temp and water temp unless i had the dryer running for a while in the laundry (where my rack is set up) which causes condensation on the glass often. But this would be easy enough to solve by pointing at the surface of the water anyway, no? Thermometers generally measure the area of water that surrounds them/their probe anyway so there shouldn't be a large enough difference between areas of the tank to make a difference to where the temp (in tank) is taken IMO.
    "The stuff I buy is a bit pricey however it is as dry as a nuns nasty" - BigDaddyAdo

  15. #15
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    Quote Originally Posted by indir View Post
    Yes good point Spidy. I've not found any real variation between glass temp and water temp unless i had the dryer running for a while in the laundry (where my rack is set up) which causes condensation on the glass often. But this would be easy enough to solve by pointing at the surface of the water anyway, no? Thermometers generally measure the area of water that surrounds them/their probe anyway so there shouldn't be a large enough difference between areas of the tank to make a difference to where the temp (in tank) is taken IMO.
    Totally agree with what you're saying however consider this scenario. You have a big tank, say 6 foot long and only one heater. Your water flow is poor and you think where you placed your thermometer is in a good place to measure the average temp of the tank. The reading your internal thermometer gives you will be off whatever reading you get from pointing a laser thermometer at your glass as your glass will have an equalised temp.

    I'm probably splitting hairs here but I feel I had to bring this point up as a lot of people think the reading they get from one of these thermometers is the actual temperature of the spot they're aiming at, where in actual fact, it isn't.

    In my case, I placed both probes (the InkBird and the external thermometer) very near each other without them actually touching. And even then, they're still both out about half a degree from my liquid filled thermometer anyway.

    Nothing is ever easy in this hobby.

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