Conductivity probe consistency

[djbetterly]

So I've been running apex for some time, and until recently I've never had a problem with my conductivity probe. I've gotten to the point that I've completely isolated it from all other cables and the probe isn't even in the sump, its in the display tank. Everything was good, then suddenly I came home one day and it was ready between 32-33. Seemed odd, so I recalibrated. It calibrated to 35 just fine. Put it in the tank, immediately back to 32-33. I isolated the lines from everything, still 32-33. Decided to check my temp probe, that was off by a few degrees. After that the probe was reading fine for some time and now today, its back to 32-33 again. Right now its out drying out. I checked the temp, thats fine. THIS has become incredibly frustrating. I have no stray voltage, I've tested for that, I as well have a grounding probe. I'm kind of ranting, but I'm really really frustrated...

Also, is it me or does it seem there are a lot of topics about this lately. Is something up with the firmware?

[TimS]

Im having the same issues, my readings als the same as yours about 2 tot 3 PPM too low.

While in the first weeks all seemed fine. Mine dropped also out of nothing and never went up again.

[djbetterly]

What firmware are you running? I'm on 4.34_4F15
I re-calibrated again yesterday, seems a bit better but still about 1ppm too low. I'm amazed no other people have chimed in. Although there are a lot of posts recently regarding conductivity issues.


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[djbetterly]

Maybe I'll give support a ring next week. They are usually pretty good.


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[TimS]

What firmware are you running? I'm on 4.34_4F15
I re-calibrated again yesterday, seems a bit better but still about 1ppm too low. I'm amazed no other people have chimed in. Although there are a lot of posts recently regarding conductivity issues.


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Yes, this is the firmware I'm using.

I'm using a calibrated, hand made Germand hydrometer from Dupla Marin. It has an accuracy of 0.2 PPM! The Dupla tells me 35.0 PPM spot on, while my Apex probe tells me at this moment 33.0 PPM

So exactly 2 points difference.

For your information, this is the one I'm using:

http://reefbuilders.com/2014/05/08/u...ity-reference/

http://reefbuilders.com/2014/03/25/d...in-hydrometer/

I also went back with a sample of my water to my local tank store and they tested it with 2 other Dupla Hydrometers (with same results) and with the digital Hanna Checker module, also same figures.

I'm 100% positive those readings are correct and the conductivity probe is off. I have also a titanium grounding probe and I did test my tank water in a seperate cups too with no difference in reading.

Also my compensation is 2.2. but when I change that to 0 or any other number nothing changes in the way he reads the salt.

I have contacted support, they replied me once, I have replied to that, but not yet an response back.

[Alain B]

You might find some answer to your question here : https://www.dropbox.com/s/i18xl7dsam...eping.pdf?dl=0

[djbetterly]

That is definitely an in depth article. I have always understood that a refracts ether and a conductivity probe will never read the same. The issue I'm having is that the probe will calibrate fine and then one day randomly it will read 2-3ppm less for no reason. The only way I verify that nothing has changed is by comparing my previous refractometer readings to the reading taken the day the probe showed a drop in ppm. I do understand that micro bubbles could get into the probe at anytime but I shouldn't have to recalibrate that often.


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[Vimg840407]

great