Accurate temp. reading

[liusteven]

Randy,

I just got an acquacontroller and was wondering what is the most effective way to get an accurate reading? I have the big digital reading (life guard) but it was off 1 or 2 deg because I was testing it with a mercury thermometer...


Thanks

Steve

[Randy Holmes-Farley]

Is the aquacontroller adjustable?

Do any of them extend to 0 deg C? If so, you can make a crushed ice/RO water mixture and let it equilibrate. It should be very close to zero deg C (32 deg F).

[Salsini]

You adjust temp in the set up menu

from run mode to set up mode to temp set

[liusteven]

Thanks Randy and Salsini.... how long should I wait for the temp to go to O C.... 4-5 min?


Thanks

[liusteven]

OK.. the aquacontroller cannot go down to 0C... what else can I do?


Thanks

Steve

[Randy Holmes-Farley]

If you have a mercury thermometer that does, then you can calibrate it at zero (the ice) and 100 deg C (boiling water). If it reads OK, then use it to calibrate the controller in some water that both can read simultaneously. If it doesn't read correctly, then figure out an offset that works (hopefully as simple as "add 2 deg C to the mercury thermometer to get the correct value" or some such thing).

[liusteven]

OK will need to find a thermometer that goes to 0 - 100 C..

Thanks

[Randy Holmes-Farley]

Just checking at zero is a good first step. :)

[StephenS]

Just a thought could you put it in your mouth.

[Randy Holmes-Farley]

Yes, that is a good idea if you have a good oral thermometer as well. :)

[liusteven]

Randy,

I cannot find any thermometer that would go to OC.. maybe at a scientific store that would be expensive!

The Oral temp. these days start around 96 F so it is not close to temp that I want....

I have 3 readings from different thermometer..

1) Mecury thermometer (Cheap) is showing 82F
2) LifeGard Digital Temp ($22) is reading 80.5F
3) My aquacontroller is reading 81F

Not sure what I can do?

[Randy Holmes-Farley]

I don't know which might be accurate. I'd suggest that it doesn't really matter, but that may not be the answer you want. :D

If it were me, and I didn't have any other way to calibrate them, I'd assume that 2 and 3 are about right.

[liusteven]

Thanks Randy.. I guess I will have to live with it!


Thanks

steve

[tschopp]

If you have a good multimeter you can order a thermistor to measure the temperature. This thermister is accurate to 0.1C without calibration.

http://www.newark.com/NewarkWebCommerce/newark/en_US/support/search/searchResults.jsp?_dyncharset=ASCII&action=0&First=0&QText=44032&x=12&y=9

I typically order a cheaper, less accurate version and do a single point, ice bath calibration. This typically yields a sensor good to 0.02C. I have a mercury thermometer accurate to 0.01C to check the calibration.

Typical digital temp sensors are accurate to 2F. So I would bet money the real temp is in the 79 to 83 range and most likely it is in the 80 to 82 range.

You would need to encapsulate the thermistor to use it in water. I have used plastic tube about the size of a straw filled with silicone to protect the wires and thermistor.

[liusteven]

tschopp , thanks for the info...

[liusteven]

Randy,

I found a 0C thermometer and wanted to understand if temp. can dip below 0C with RO/Di water with Ice?


Thanks

[tschopp]

I have never seen an ice bath go below 0C. To make a good ice bath you need to have a container that is filled with crushed ice. Then you add water to fill the space between the ice. If you make an ice bath that does not have enough ice it will be warmer than 0C.

An accurate mercury thermometer will require a stem correction for the part of the thermometer that is outside the ice bath. Typically the ambient temperature outside the bath is warmer than 0C so this causes the thermometer to read higher than 0C and the correction will bring it back to 0C. Unless the room you are doing this in is less than 0C the thermometer should not read less than 0C. If I remember right a typical stem correction for us is around 0.1C. So unless you need really accurate results this will not matter.

A good mercury themometer can read low by a few degrees if the mercury seperates. Look for a small drop of mercury in the expansion chamber at the top of the thermometer. If you see any mercury in that you will need to heat the thermometer until the main column of mercury goes into that chamber. Then you shake it gently until the small drop rejoins the rest of the mercury. The thermometer will be good then. If you just have a cheap inaccurate thermometer add an offset based on the ice bath.

[Randy Holmes-Farley]

I found a 0C thermometer and wanted to understand if temp. can dip below 0C with RO/Di water with Ice?


Thanks, techopp, I agree. If you let it sit for a few minutes, it should be very close, and not below, 0 deg C.

[liusteven]

OK.. was very busy at work .. so I tested it today and found out that they mercury does not dip below 6C?? I did wait for 10min and then 20 min still did not move below the 6C...

I shook the mercury and then tried it and went to 4C and never went below that.. I do not think the mecury thermometer is off by 6C!!! because when the mercury thermometer is reading 82F my aquacontroller is reading 80F....

Thanks for all you help!

[Randy Holmes-Farley]

That's probably true. Other than getting a thermometer that you do trust (or can check in ice water and boiling water), I can't think of a good way to proceed.

[liusteven]

Thanks Randy...

[Randy Holmes-Farley]

You're welcome.

Happy reefing. :)

[Dag]

liusteven,

Did you ever find a good mercury thermometer? If so, can you recommend?