Is it time for a new temp probe?

[reefknight]

So when I recently started using my ~3yr old ACIII I noticed that the temp reading was off. I always keep a glass thermometer around to check "wacky" readings by the ACIII. Noticed that it was off by about 4 degrees F. So I adjusted it via the calibration setting. Noticed that it happened again about a week later following a power outage. Figured that it had lost its memory during the outage. This morning it emails me at 4AM to tell me that the temp is 90F! I jump out of bed and look at the glass thermo, 79F. Attempted to adjust the calibration setting and its as low as it will go. Also when watching the display the temp rapidly changes, increase & decrease.

I figure I already know the answer, but wanted to check with others on this before shelling out the cash to PA for a new one. Is it the probe thats gone bad? The pH & ORP probes seem to be holding fine, so I'm thinking its probably not an interference issue, right? Thoughts are welcomed.

THanks

 

[Deleted member 143833]

Normally, temp probes fail either going high (about 120) or low (about 20). If the temp probe is jumping around it could be a probe going bad but I don't think so.

On a side note; calibrating to a glass thermometer is a lost cause; by doing that you likely have the probe further out of calibration (unless the glass thermometer is NIST calibrated).

Things to check:

* Does the probe appear damaged; if water is able to get into the probe then it can cause randon radings

* Do you have float switches? Disconnect them from the controller and verify they are not leaking current into the controller.

You can always just replace the temp probe and see of the problem goes away; that is the best solution if you can do that; remember, new probe should be calibrated.

Note about calibration; the calibration offset shoud be small .5-1.5 degrees. I assume you are using calibration and not temperature offset; the 2 are different.

 

[reefknight]

Ken, Thnak you for your assistance. To answer your questions;

Probe appears to be fine. Cap is sealed, no seperation that I can detect.

I do not have float switches or a break out box connected to my ACIII. My ATO is a Tunze Osmomlator. Located a chamber before my probes.

I use a glass thermometer as I've found them to be more accurate than any of the digital ones that I have used in the past, such as the Coralife Digital. Had four of them and they all read differently. I'm currently looking to purchase a NIST calibrated thermometer for instances such as these.

As far as calibration, I use Menu>Setup>Temp probe>Temp Calibration.....Currently that scale on mine reads from 90.1-124.9F. I don't believe that I have ever seen the offset option on my ACIII. Is this in a hidden menu or am I missing something?

To give you a layout of the sump it is as such;
Drain/skimmer> baffles/heater> return/ATO <Fuge/ probes

 

[reefknight]

Ordered a new probe and installed it. The temp is now reading 68F.

Really?!?!

Any assistance is greatly appreciated. Also recieved my new skimmer today, broken. Having a lovely day, thanks all.

 

[Deleted member 143833]

Ordered a new probe and installed it. The temp is now reading 68F.

Really?!?!

Any assistance is greatly appreciated. Also recieved my new skimmer today, broken. Having a lovely day, thanks all.

Reset your calibration; if you calibrated with a bad probe the temp offste could be way off. Normally the offset would be no greater than .5-1 degree.