WOW! That's acrare thing indeed.

[atoll]

2 digital temperature readings the same from 2 different items of equipment. The lit one is my D-D temperature controller with probe in the sump the other a cheap thermometer with probe in the tank both reading identical. I have had digital thermometers that were over 1c out. I check them against an accurate liquid thermometer and they are both spot on.
One probe is in the sump the other in my DT, double insurance with alarm.

 

[kittenbritches]

I've even dipped two of the identical black ones and had one consistently reading 1.5-2° higher than the other.

I triple-check, too.

 

[atoll]

I've even dipped two of the identical black ones and had one consistently reading 1.5-2° higher than the other.

I triple-check, too.

This is the problem esp when the manufacturers claim accuracy that isn't there. So many people take manufacturers specifications as true without double or as you say triple checking. I checked both mine against a highly accurate liquid thermometer and both check out as accurate.
I had a wel regarded temperature controller that read 1.5c over the actual temperature. It's oK if you know that and can set your temperature accordingly but why should you have to. I would urge anybody reading this to double check their tanks temperature against a known accurate thermometer rather than just relying on what you read off a scale or digital read out, you just might be surprised. Many thermometers and temperature controllers state an accuracy of + or - 1c.
My cheap thermometer cost me just £2-45p about $3 I guess yet it reads the same as my much more expensive temperature controller which am very pleased about.

 

[kittenbritches]

This is the problem esp when the manufacturers claim accuracy that isn't there. So many people take manufacturers specifications as true without double or as you say triple checking. I checked both mine against a highly accurate liquid thermometer and both check out as accurate.
I had a wel regarded temperature controller that read 1.5c over the actual temperature. It's oK if you know that and can set your temperature accordingly but why should you have to. I would urge anybody reading this to double check their tanks temperature against a known accurate thermometer rather than just relying on what you read off a scale or digital read out, you just might be surprised. Many thermometers and temperature controllers state an accuracy of + or - 1c.
My cheap thermometer cost me just £2-45p about $3 I guess yet it reads the same as my much more expensive temperature controller which am very pleased about.

Oh absolutely. In the case of the cheap black ones, the inaccurate one wasn't even consistently off — it varied between 1-2° at temperatures all between that range, so if I was relying on it, I couldn't even adjust for the discrepancy.

I checked them against room temperature and tank temperature as well.

We rely so heavily on devices and digital readings, in my opinion, it is folly to not cross-check or otherwise verify readings before trusting them!

I do this when testing water parameters, too.

 

[Joe31415]

I've even dipped two of the identical black ones and had one consistently reading 1.5-2° higher than the other.

Those black ones are awful. I have three or four of them (some bought, some came free with something else (heater maybe)). I put all of them in the tank with all the probes next to each other and from highest to lowest I had something like a 2 or 3 degree spread.
I just use them in short term quarantine tanks. And before I use them, I'll usually put the probe in my DT for a little while and make a note of what it reads. It doesn't really matter if it says 76 or 81 or something in between, as long as I remember what it says and try to maintain that temp in the QT.
I'll also toss them in buckets of water I'm heating for a water change when my main concern is 'is the water warm enough yet' and less concerned about the exact temp.

 

[kittenbritches]

I'll also toss them in buckets of water I'm heating for a water change when my main concern is 'is the water warm enough yet'

That's all I use mine for, too.

 

[X-37B]

This is why I use an old mercury lab thermometer. It has been accurate for over 30 years.
I had a digital in a nano 5 years ago and it was horrible at +4°f.
But as long as I knew the real temp I just adjusted it according to the mercury stick.
I had an Apex when I setup my 120 but never used it and sold it.
The temp probe was dead on to my mercury stick for what its worth.