Beware Digital Thermometers are NOT Accurate

[Sandeep]

I've tested a bunch of coralife, marineland and off brand digital thermometers and almost none of them are accurate. Given the amount of money you invest in your tank, getting an accurate temp readout is critical. Do yourself a favour and get one of those laboratory grade 12" mercury thermometers (like the kind used in your high-school chemistry class). They can be purchased from scientific supply stores. My mercury thermometer runs from 0F to 200F.

 

Use your mercury thermometer to figure out how many degrees off your digital really is and then you can still use your digital thermometer knowing full well what the calibration difference in readings should be for the temp you want. So when my digital reads 86F I know it's really a perfect 78F. In testing the various digital thermometers I found them to vary by as much as 14F which is crazy.

 

Don't be cooking or freezing your corals looking at that digital readout and thinking it's accurate.

[ixTCxi]

can you show a picture of the mercury thermometers or a link ?

[masterbuilder]

I agree...I had one...for 1 whole hour before I took it back. Total waste of money. Those cheap "old fashion" type you get at any LFS work best. All of my "analog" type were less than 1 degree off matched up to a lab grade thermometer my wife brought home from the hospital lab.

[Mr. Fosi]

I had a digital that worked fine for a year, then suddenly started reading 7-8F in excess of actual temp. I thought my heater was going and replaced it before I thought to check the digital term with a $1 floating alcohol therm.

 

Two cheap alcohol terms are within 1F of the mercury therm I borrowed from my lab. Digital terms are garbage IMO.

[SPS20]

They are especially inaccurate when the batteries start going, IME. If you use a digital thermometer, and you suddenly start getting crazy readings, it is definitely a good idea to check it against another thermometer before you start tweaking your heater/chiller.

[Mr. Fosi]

^-- A lesson I learned a couple weeks ago.

[ixTCxi]

so is the one that stick on the tank with the suction cup good ?

[Mr. Fosi]

Those are what I have used for more than 10 years... Until I got the digital. Now that the digital did me wrong, I am back to the $1 suction cup alcohol thermometers.

[Duncan]

Those are what I have used for more than 10 years... Until I got the digital. Now that the digital did me wrong, I am back to the $1 suction cup alcohol thermometers.

 

yeah, nothin beats suction cup alcohol thermometer. some things are meant to be simple.

[eklikewhoa]

The digital one that came with my RK2 is pretty accurate....

[jm82792]

Well they are cheaper too I have a Celsius alcohol thermo very nice and accurate

[Scott Riemer]

I got me one of these:

 

http://www.professionalequipment.com/therm...l-thermometers/

 

It's been great. Plus, it's portable so I can test multiple tanks.

[ixTCxi]

digital thermo are good until its low on battery..

[SPS20]

In general, digital thermometers are a nice tool to have. Just get a little floating alcohol one as well, and float it in your sump. Any time you get a reading on the digi that you don't like, just grab the alcohol one and see if it agrees before you take any action.

 

I like redundancy, it takes alot of the doubt away.

[KoolFish]

Never had a problem with my Coralife Digital's but I do have the suction cup-merc therm. as a backup. So far they both give the same reading. Maybe I've been lucky!

[eklikewhoa]

I found that the Coralife one's where the worst.

[CorvetteJoe]

Wow, good stuff to know.

I have a coralife in the NC12 and some other random brand in the 75gal.

Both show me temps I like... but yeah, i wonder how "off" they may or may not be.

 

I think ill be picking up a regular old thermometer this week for sure!

[Mr. Fosi]

That's the brand that crapped out on me.

[TheCuban1040]

I got 3 of those Coralifes because they were only 4 bucks, I put all three on one tank and they all varied between 84 and 75. They seem to be precise enough, just not accurate.

[hollow]

Those are what I have used for more than 10 years... Until I got the digital. Now that the digital did me wrong, I am back to the $1 suction cup alcohol thermometers.

 

So something like this would be pretty accurate? thermometer

[Clayton07]

American Marine Pinpoint Wireless Temp Monitor is the only way to go. You can even have multiple sensors and one monitor. Thats my choice. Very reliable, very accurate, worth the money IMO.

[dan06277]

Thanks for the heads-up. I just put my regular thermometer back in my tank. Thankfully the RK II thermometer is reading about the same.

[SPS20]

So something like this would be pretty accurate? thermometer

 

Yup, those incredibly cheap little jobs are surprisingly accurate. But, they are a pain in the ass to read. I swear my vision gets a little bit worse every time I try to see the tiny lines on those things.

[HecticDialectics]

American Marine Pinpoint Wireless Temp Monitor is the only way to go. You can even have multiple sensors and one monitor. Thats my choice. Very reliable, very accurate, worth the money IMO.

 

 

Are you sure? I've always wondered about all of these. I'd imagine the probe thermometers like American Marine and the reef management computer probes (ie reefkeepers etc) are more accurate than the regular digitals, but anyone checked?

[hollow]

So which therm should I trust? Pinpoint wireless says 84 and alcohol therm says 82.