# Digital thermometer recommendations please



## BarryH (3 Mar 2020)

I have three of the Risepro digital thermometers and each one shows a different temperature. They vary by as much as 2 degrees. I think most of the basic digital ones like the Risepro are pretty much the same and just have different brand names printed on them.

Does anyone have a recommendation for a digital thermometer that is "reasonably" accurate? Not even sure if there is such a thing available.


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## alto (3 Mar 2020)

There are individually certified thermometers but I generally just choose the “average “ thermometer in the group - I just look for trends in tank temps, or sudden shifts, check that tap vs tank is within a few degrees (change water should be cooler rather than warmer)

(I presently use a digital cooking thermometer and just check tank temp vs heater setting - I can tell the difference between a couple degree F by hand touch anyway)


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## ian_m (4 Mar 2020)

After going through numerous "digital thermometers" including some quite expensive ones, this is what generally happened them all eventually.





I have used one of these for last couple of years. Doesn't cost much, doesn't need battery and works fine. This is a JBL one, about £5 odd from a popular auction site.


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## BarryH (4 Mar 2020)

Thanks for the replies, really appreciated.


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## dw1305 (4 Mar 2020)

Hi all, 





alto said:


> I can tell the difference between a couple degree F by hand touch anyway





ian_m said:


> I have used one of these for last couple of years. Doesn't cost much, doesn't need battery and works fine.


Same <"for me">.

cheers Darrel


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## Akmaliano (4 Mar 2020)

used one of these for years without any problems. changed the battery maybe once in 5 yrs


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## BarryH (4 Mar 2020)

Thanks for the reply, those are the ones I'm using now but with the Risepro brand logo on them. Put three in a small tank of water and get three completely different readings, varying by well over two degrees.


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## ian_m (4 Mar 2020)

The best digital one I did have, was similar to the above with a remote water proof probe. Came from RS and before aquarium use, was officially supposed to be used at work, but I used it to measure cave temperatures (8'C water is bloomin cold to get into).

It eventually failed as where the cable went into the tank it cracked and crumbled presumably due to being attacked by UV light from my lights.


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## mort (4 Mar 2020)

I use glass thermometers as well but most of the aquarium ones I've come across will still be out by a degree or two. When I get them I fill up a glass with water and add lots of ice, pop the thermometer in, take a reading, and after a few minutes it should be 0c. Most of the time the thermometer still reads 1 or 2c but I know how much it's out and just mentally adjust in my head when I read it. I'm not that fussed about being 100% accurate as long as it stays above my set minimum.
If you are buying it from a shop then it's worth having a look through them to see which one is most likely accurate as you will probably get a range of reading on even the same model.


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## frederick thompson (4 Mar 2020)

Akmaliano said:


> used one of these for years without any problems. changed the battery maybe once in 5 yrs
> 
> View attachment 132122


I have five of the same ones. On my koi pond and qt grow on set up. Two are permanently outside on the pond. And one in filter house. And two on grow on qt.
Had them 4 years now. Cheap as chips.
And done good.
Fred

Sent from my SM-G960F using Tapatalk


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## Wookii (5 Mar 2020)

BarryH said:


> I have three of the Risepro digital thermometers and each one shows a different temperature. They vary by as much as 2 degrees. I think most of the basic digital ones like the Risepro are pretty much the same and just have different brand names printed on them.
> 
> Does anyone have a recommendation for a digital thermometer that is "reasonably" accurate? Not even sure if there is such a thing available.



It might be more than you want to spend, but I can thoroughly recommend the Inkbird controllers:

https://www.amazon.co.uk/gp/product/B07Q2M1CDS/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1

The benefit of a controller rather than just a straight thermometer is that it'll help protect your tank from heater failure - it'll switch it off if the heater tries to cook your tank, or it'll sound an alarm if you heater fails completely and your temperature starts to drop. With the wi-fi version you can also control it, and check the temperature, from your phone and receive alerts whilst away from the house.


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## BarryH (6 Mar 2020)

Wookii said:


> It might be more than you want to spend, but I can thoroughly recommend the Inkbird controllers:
> 
> https://www.amazon.co.uk/gp/product/B07Q2M1CDS/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1



Thanks for the link, I'll take a look at the Inkbird controller.

At the minute I've started using one of the cooking type thermometers that Alto mentioned above. At least it's portable and I can also use it to check the buckets when I do a water change. It's also the one that reads nearest to the JBL glass thermometer.


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## jaypeecee (6 Mar 2020)

Hi @BarryH 

I have an InkBird ITC-308. Good piece of kit. A bit fiddly setting it up initially but well worth it.

Over the years, I have accumulated several aquarium digital thermometers. They are notoriously inaccurate. It is not uncommon for them to be +/-2C or worse. You could consider getting something like this:

https://thermometer.co.uk/food-thermometers/1320-thermastick-pocket-thermometers.html

Using this, you can then 'calibrate' your other thermometers. My cheapo thermometers all carry a Post-It Note saying things like 'reads 1.5C high', for example.

JPC


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## Andrew Butler (6 Mar 2020)

Wookii said:


> It might be more than you want to spend, but I can thoroughly recommend the Inkbird controllers:





BarryH said:


> Thanks for the link, I'll take a look at the Inkbird controller.





jaypeecee said:


> I have an InkBird ITC-308. Good piece of kit. A bit fiddly setting it up initially but well worth it.


It doesn't mean it reads accurate though is the problem; there is the option to calibrate on the majority of these controllers which is a big plus but you still need something to calibrate it against. 
Elitech make pretty much the same thing as InkBird and is what the majority of Marine enthusiasts use is one shape or another (and they're cheaper) you can either buy you own and make a system or buy a version like the InkBird linked above or I've found in recent years they've brought one out in a nice tidy box which you can take apart, fiddle around with and drill some holes to fix it inside your cabinet and in my opinion is just tidier.
Still a case of finding something to calibrate it against in the first place


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## BarryH (6 Mar 2020)

Andrew Butler said:


> It doesn't mean it reads accurate though is the problem; there is the option to calibrate on the majority of these controllers which is a big plus but you still need something to calibrate it against.



That was the reason I changed to the cooking style one. Using only the one thermometer at least I can get a bit of consistency, if it's out, it'll be out by the same amount every time. It would still be great to have something accurate that I could calibrate it against though.


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## Andrew Butler (6 Mar 2020)

BarryH said:


> It would still be great to have something accurate that I could calibrate it against though.





mort said:


> I use glass thermometers as well but most of the aquarium ones I've come across will still be out by a degree or two. When I get them I fill up a glass with water and add lots of ice, pop the thermometer in, take a reading, and after a few minutes it should be 0c.


I believe what @mort says to be true as a calibration method but I'd imagine an upper reference would be useful too.
Even the best devices require calibration but they are carried out by specialists similar to how a set of scales would be calibrated (only using a very different technique)


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## ian_m (6 Mar 2020)

This is the standard picture rolled out to indicate precision vs accuracy.

Expensive and calibrated thermometers are accurate and precise(top left picture). All readings tend to indicate correct temperature and different thermometers all read virtually the same, but they cost.

Cheap digital thermometers can be precise BUT are more than often inaccurate (both right hand pictures) ie they all read the same'ish value but it is the wrong value. This is sorted by calibrating the thermometer.

Most glass based thermometers tend to be accurate but imprecise due to manufacturing tolerances, though often the spread of errors may be considerably better than a digital thermometer. (bottom left picture).


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## jaypeecee (6 Mar 2020)

Hi Folks,

I use a Hanna HI-98501 food thermometer as my reference. It has an accuracy of +/- 0.2C and a resolution of 0.1C over the temperature range that I'm interested in. I use it to calibrate my InkBird ITC-308. Here is a link:

https://www.hannainstruments.co.uk/hi-98501-checktemp-electronic-thermometer.html#specifications

JPC


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## Matt @ ScapeEasy (6 Mar 2020)

This is probably slightly random but the inaccuracy of thermometer was really enough to like when my young son was ill and the thermometer we had bought to test his temperature (on good recommendation) didn’t show anything up. When we eventually ended up in A&E, they were able to “recalibrate” our expectations.
This does remind me that humans can quite readily detect a difference of 0.5 degrees celcius between two water sources so if you’re wanting a thermometer e.g. for water changes, the answer is to use what your parents gave you


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## BarryH (6 Mar 2020)

ian_m said:


> Expensive and calibrated thermometers are accurate and precise. All readings tend to indicate correct temperature and different thermometers all read virtually the same, but they cost.



Thanks for the reply Ian. What are the "expensive and calibrated thermometers"? Possibly the same as the ones used in hospitals or labs?


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## ian_m (7 Mar 2020)

Yes hospitals and labs will be calibrated as accuracy and repeatability is key.

As for fish keeping, +-1 'C (or more will be fine), fish won't mind.

Personally I would stick with a liquid in glass thermometer designed for fish tank use. It will have been designed for limited tank water range, so liable to be more accurate than a general purpose large range thermometer (ie -20 to +90 for instance). Also big plus no batteries required, all adding to the KISS of fish keeping (Keep It Simple Stupid).


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