How accurate are thermometers?

[Anonymous]

I am just wondering since my thermometer reads 75 degrees and my heater needs to be set (to get the reading) to 79 degrees. When I set the heater to 76 the thermometer was about 73 degrees.

Are there thermometers that are more accurate than others or is the heater most likely to blame.

 

[Anonymous]

hi.
Not knowing what type/kind of therm or heater you have, I will blame the heater first. If the circulation is not good, you many have localized heating of the heater to the desired temperature, while your thermo is a few inch away, and see cooler temp.

 

[Anonymous]

The heater is a Won Brothers Pro 300W heater, and the thermometer is a very cheap glass w/suction cup design. (Red dye) Circulation is not great right now, but I am waiting for a new powerhead that will circulate 650gph which will correct that problem. The only circulation right now is a Turboflotor 1000 Multi with Aquabee pump. (125 gallon aquarium 72x18x22)

 

[Anonymous]

From what I understand, and IME, the the temp the Won heaters heat the water to has very little to do with the settings on the heater. One of the reasons for this is the way this heater ramps up to heating rather than a simple on and off activity. I have had 3 Won heaters and none of them have been accurate in terms of the numbers on the dial. I use a thermometer to judge the temp then mark the dial on the heater, then just make sure the dial is set to that mark.

RR

 

[MattM]

Check the circulation as 7ephors suggested, but the thermometer will be far more accurate than the heater. I've calibrated various cheap glass thermometers that customers have brought in using an expensive digital lab thermometer - the worst one was 1/4 degree off.

On the other hand, I've regularly seen aquarium heaters off by as much as 10 degrees. The dial on the heater is just a rough guesstimate. Ignore it and trust the thermometer.

 

[aakks]

Hey Matt, have you ever tested any of the cheap digital thermometers? I wonder how accurate these are compared with the glass ones.

Peter

 

[MattM]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by aakks:
<strong>Hey Matt, have you ever tested any of the cheap digital thermometers? I wonder how accurate these are compared with the glass ones.</strong><hr></blockquote>

The only one I've checked is the one we sell, the "Little Time & Temp" from Rainbow Lifegard. At $20+ I don't know if I'd call it "cheap", but it's accurate to about 0.1 degree.

 

[whusband]

maybe i'm just paraniod, but i put one sticker thermometer on the main tank and one on the sump. i like to have 2nd opinion

 

[Anonymous]

hi.
The resolution of the LTT may be 0.2 F, but to be realistic, anything less than $20 and use a thermoresistor is not going to give you that kind of accuracy. But for aqurarium purpose, it serves our purpose quit well.

Sometimes, we just get overboard with our strive for stability.

 

[Tangy1]

I double or triple the vote for redundancy. My Medusa Dual Temp controller was more than 5 degrees off. Unfortunately it was the only thermometer I had in my tank. Although nothing in my tank suffered any ill consequences, the chiller could have run a whole lot less.

I now keep a cheap floating therm. in the sump and 3 other press on therm. elsewhere on the tank and sump. They are all different brands but the are yielding around the same temp. The Medusa has been recalibrated and reads the same temp. as the rest of my therm.

 

[aakks]

The little time and temp is also the brand I've got. I've checked this with a glass thermometer before, and they matched up very close. I'm glad you had good luck with them too Matt!

I'll definately agree that second opinions are important. Even if most are accurate, you'll never know if you're the person who got a bum one unless you check it.

Peter

 

[Bubafat]

Why have redundancy if all of them are off? Might as well just get a thermometer and calibrate it using a large -10 to 120 degree C thermometer which is calibrated using boiling DI water and icewater.

Buba

 

[JohnD]

I have one of those "Little Time & Temp"s that Matt spoke about. I have calibrated my cheap Charlie glass thermometers with it and they are all right on the money.

Huz is right about a second opinion.

Super Cow, you are on the right track with getting more water flow. IMHO, that is your problem.

My $.02