Glass Thermometer Accuracy

Discussion in 'General Discussions' started by Singhms, Jun 14, 2011.

  1. AmithS

    AmithS

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    Hi Everyone,

    How accurate are glass thermometers?

    I needed to purchase a 2nd thermometer so I went to the lfs. They had about 4 BOYU glass thermometers and when I looked at them each was showing a different temperature! +-1deg.

    So any way I bought the 1 I was most comfortable and then decided to test it against my current no name brand glass thermo!

    So what I have now is 2x glass thermos with 2x different readings apart by 1deg!

    So what does 1 do now, and what does 1 trust now?

    Calibrate them in some manner to know if it says 25deg its actually 23deg???

    What are your taughts?
     
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  3. azurekoi

    azurekoi Loaches & Gobies

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    Cheap glass thermometers are just that...Cheap...

    Most vary by a degree or two... Use them more as a guideline and maybe invest in a GOOD digital one later...
     
  4. TankMaster

    TankMaster Apistogramma Nerd

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    Okay, think about it. There's a piece of paper in that tube of glass telling you the approximate temperature. How accurate can the manufacturing process be to place that paper dead on every time?

    Glass thermometers from the same manufacturer will vary. I have 2 and they show me a difference of 1 degree.

    Not the most effective but it gives you an idea of the temperature.

    TM
     
  5. OP
    AmithS

    AmithS

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    I agree with your posts guys, as i said the all 4 BOYU glass thermos in store where different.

    So it leaves the next question in mind, how important is temperature? Is an indication sufficient?
     
  6. mxz

    mxz Uaru

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    I think accuracy would be important when breeding. Otherwise a general idea or +-1 variation would suffice.
     
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  7. azurekoi

    azurekoi Loaches & Gobies

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    I basicly trust a Glass thermometer to tell me my heater is working in winter....bout the best you can expect from it....lol
     
  8. Zoom

    Zoom Retired Moderator

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    As long as the murcury is within the 25-27 degree mark and the fish are happy... you are generally ok with most fish.
     
  9. richardnuss

    richardnuss

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    I agree with @Zoom, why do you need single degree accuracy? If you keep discus, make sure it is above 28C, if you are keeping a community, keep it between 25-27 (depending on fish requirements). You should be keeping the temp constant (within parameters) rather than at an exact temp all day every day. Again, look at nature, do you think fish stay at 1 temp all day every day, 365?

    For specific breeding - be more specific (spend the money and go digital) but as a fishkeeper, 2 thermometers should keep you in range?
     
    Last edited by a moderator: Oct 2, 2016
  10. TankMaster

    TankMaster Apistogramma Nerd

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    Nobody mentioned anything about how imperative single degree accuracy is.

    Thank you for your fish keeping lessons buddy but I would like to point out something.

    In your tank, the temperature is never constant! The tank dimensions affects this greatly. The bigger/taller/wider/longer the tank, there is more variation of temperature. Temps taken at different areas of the tank will give you around +/- 2 degree variations, with the warmest area being around the heater.

    The question was simple:

    And the answer is simple as well.

    Accuracy ranges from one manufacturer to the next and from one batch to the next. Even some digital thermometers are a bit shabby but the offset is so insignificant that you rather just trust the thermometer.

    For general fish keeping and even breeding, it works. No fuss :)

    Back in the old days when there was no digital thermometers, what do you think they used?

    Enough said :)
     
    Last edited by a moderator: Oct 2, 2016
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  11. Pezulu

    Pezulu

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    To resurrect an OLD thread...

    After seeing this thread I decided to test the accuracy of glass thermometers.
    All the thermometers were manufactured by the same company.
    All thermometers are quite expensive when compared to the cheaper variants that use a sucker to stick to the inside of the tank.
    All thermometers were bought from the same LFS.

    For the test I used 7 glass thermometers.
    They were placed about 1cm apart in the centre front portion of the same tank.
    Readings from each thermometer are shown.
    From L-R:
    1. 23°C
    2. 21°C
    3. 26°C
    4. 24°C
    5. 22°C
    6. 24.5°C
    7. 23°C

    20190503_093559.jpg

    20190503_114606.jpg
     
    Last edited: May 3, 2019
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  12. MariaS

    MariaS Moderator

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    That scary when you look at one saying 21 and the other 26

    No longer a 1 degree difference..
     
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  13. Reedfish

    Reedfish Moderator

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    @Pezulu,

    Interesting.

    I am assuming you checked that they were all the same temp reading before you put them in the tank?
    So not a calibration issue.
     
  14. Adrian Gatter

    Adrian Gatter

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    So #3 slipped through quality control at the factory? I'm guessing you get what you pay for.
     
  15. TheGrissom

    TheGrissom

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    All my tanks have those hook thermometers. I hardly look at them. When I do its mostly because I am working in the tank and the water feels too warm/cold and I just want to confirm that it isnt at a ridiculous temperature
     
  16. MariaS

    MariaS Moderator

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    We have actually resorted to the digital ones that stick to the glass as the pancakes up and down the glass kept knocking down the glass ones

    I still have some glass ones and occasionally, especially if im in doubt due to heat waves or very cold spells i pop two glass heaters in the tank for couple minutes to check the digital one against them and the digital ones have proven quite accurate so far
     
  17. BoelderBeestie

    BoelderBeestie

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    Digital probe all the way for me.
     
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  18. Reedfish

    Reedfish Moderator

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    My lungfish broke a few of the internal glass thermos
    So I also have one of the external digital thermo that stick to the glass.
     
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  19. MariaS

    MariaS Moderator

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    I find them the best so far
     
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  20. OP
    AmithS

    AmithS

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    I bought this Boyu fully submerged digital thermometer less than a year ago for about R100.

    Not very impressed.

    1. Does not show decimal point even though screen is large enough and it shows on the packaging. Digit space is blank and store never got back to me on why the digit is not displayed.
    2. Battery died about 2 weeks ago, so less than a year's worth of use. Battery can be replaced.
    3. And finally, I took out the thermometer today to get a replacement battery to see it's got moisture on the inside of the screen... so not sure how long it will last...

    20190512_112021.jpg
     
  21. OP
    AmithS

    AmithS

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    Accuracy for above, within 1 deg of my 2 glass thermometers...

    Although the reason I bought it was for the decimal point which doesn't work....
     

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