Just switched over from Reef Keeper and 3 mon. old ORP has odd readings

[Delmo]

I have a BRS ORP probe about 3 months old, it was reading around 400 on average with the RK and now switching it over to the Apex it is reading about 80. (from 50, two days ago and now 80)
Does the 2 week settle in period need to happen again before I think something is wrong with it?
Stupid question: Why doesn't Apex allow for the common calibration solution to be used and calibrated by?

[zombie]

Unless you let the tip dry out, there shouldnt be a settling period. That low of a reading is indicative of a poor connection (make sure the bnc connector isnt corroded and its seated well) or a damaged probe.

For your last question, I have no idea. Aquamaniac is the guy to ask about that.

[jonmos75]

I have used BRS & Neptune ORP probes and both gave different reading....and each time I removed and swapped them they would start at a lower value and then climb up over a 1-2 weeks and then would settle into a patten opposite of my pH probe...

Remember with ORP probes it is not all about a certain number value it is about a trend....

[aquamanic]

Why doesn't Apex allow for the common calibration solution to be used and calibrated by?

The Neptune ORP measurement is more accurate. Similar to pH probes where you have a 2 point calibration so you can get slope and offset, the ORP probe requires two different mV solutions - 263mV and 86mV. You can't buy those (or if you could, then you don't need the quinhydrone). But with pH solutions and quinhydrone you can make ORP calibration solutions with the appropriate mV.

[Delmo]

Unless you let the tip dry out, there shouldnt be a settling period. That low of a reading is indicative of a poor connection (make sure the bnc connector isnt corroded and its seated well) or a damaged probe.

The Probe never left the water, I just physically switched the plug from the RKE over to the new Apex...(it was currently steady between 396-402)
I'll give it a little while, but I guess I might be wrong about the probe needing to settle, maybe the Apex just needs time to settle into the new relationship.
As long as it does settle, I won't care so much as what is, but what the tide is doing.
Thanks Everyone.

And.... Where is everyone getting there Quinhydrone for calibrating? (I know I probably don't need to, but it's kinda like that crooked picture on the wall behind your Boss' desk.)

[aquamanic]

Where is everyone getting there Quinhydrone for calibrating?

You shouldn't need to calibrate it but if you want to straighten that picture.....http://www.pulseinstruments.net/orp2...yaccurate.aspx

Marine Depot used to carry one...
http://www.marinedepot.com/Octopus_p...FITECL-vi.html

[Delmo]

Thanks Aquamaniac.
I realize this is probably an old argument, but it seems that Neptune would rather people not calibrate their probes (because it's obviously cost prohibitive for the majority) than to make a calibration point on the Apex made for the $1.95 calibration fluid?
Is a 1 point calibration worse than none?
Just thinking out loud here.
After all, if the number is not that important and the trend is...
I think I might actually still have some quinhydrone laying around in a box somewhere from my Octopus 3000 days. Does it have an expiration?

[Delmo]

My BRS probe never came around and danced around 50, so I installed the Neptune orp probe and it started at 250 and steadily climbed to 550 over a week. My ozone shut off at 405 and that was a couple weeks ago. It is currently mirroring my pH (opposite rise and fall) and staying between 420 and 450. I wonder if I should reset my high limit to 460 on my ozone or if I should calibrate the darn thing. Corals look happy. Any advice?

[zombie]

Id just change the high limit. Way easier then trying to source quinhydrone.

[Alain B]

My BRS probe never came around and danced around 50, so I installed the Neptune orp probe and it started at 250 and steadily climbed to 550 over a week. My ozone shut off at 405 and that was a couple weeks ago. It is currently mirroring my pH (opposite rise and fall) and staying between 420 and 450. I wonder if I should reset my high limit to 460 on my ozone or if I should calibrate the darn thing. Corals look happy. Any advice?

ORP of sea water is around 450 , any excess could be detrimental .

[zombie]

ORP of sea water is around 450 , any excess could be detrimental .

Assuming the orp without calibration is accurate. Without calibration, the measured value vs actual value could have an error of +-100mV.

[aquamanic]

Instead of calibrating it, just get yourself some of the 400mv solution used to calibrate other probes. Maybe your LFS or club has some - you just need a thimble of it. Stick your ORP probe in there and it should read 400 if it's calibrated and not dirty.

[Delmo]

I have a few packets left over from previous setup. That seems like it should be able to tell me a ballpark error factor. Good thinking, thanks. I'll let you guys know.

[Delmo]

Ok, so I actually didn't have the 400mv packets... I went ahead and got the Sensorex calibration kit....
So right before calibration was reading 445 and right after is 315. So, thanks Apex, for that. I fugured it just had a high shift to its brand new factory calibration. So now my ozone will kick back in.

[Terence]

ORP probes will also get dirty and drift high. My experience has been that they will drift high and then stop drifting. Once you clean them they will drop down again and slowly creep up over a few weeks and then stop again. For this reason, and also because I was lazy, I always just adjusted everything to account for the higher value.

Might not have been the "recommended" way to go but always did me right. And I was running light ozone too.