Conductivity anomaly

LC8Sumi · Jan 20, 2020

Hello!

I was wondering if it's normal that my conductivity probe needs recalibration every 1-2 weeks as the measured value will otherwise drift downwards?

So in other words, it reports that the salinity is dropping (let's say 0.1 PSU / day), while it is not?

Cheers

Brew12 · Jan 20, 2020

LC8Sumi said:
Hello!

I was wondering if it's normal that my conductivity probe needs recalibration every 1-2 weeks as the measured value will otherwise drift downwards?

So in other words, it reports that the salinity is dropping (let's say 0.1 PSU / day), while it is not?

Cheers

Are you sure its not? My tank does that fairly consistently.

LC8Sumi · Jan 20, 2020

Brew12 said:
Are you sure its not? My tank does that fairly consistently.

I am. Because if I pull the probe and recalibrate it, it then goes back to where it should be. It just seems odd, that it needs to be recalibrated every 1-2 weeks

ScottB · Jan 20, 2020

Mine seems to drift all over the place but slowly. I only use it as an alarm to let me know if my ATO sticks open/closed.

I bother to recalibrate a couple times a year.

Brew12 · Jan 20, 2020

LC8Sumi said:
I am. Because if I pull the probe and recalibrate it, it then goes back to where it should be. It just seems odd, that it needs to be recalibrated every 1-2 weeks

How are you cleaning it?

LC8Sumi · Jan 20, 2020

Brew12 said:
How are you cleaning it?

I’m not cleaning it in the 1-2 week timeframe. When doing a recalibration I soak it in citric acid for 5 mins, then rinse it off with rodi. But this time (after 8 days it was reading 1ppt below) I just recalibrated it, because there was nearly no buildup/biofiom on it yet.

Brew12 · Jan 20, 2020

LC8Sumi said:
I’m not cleaning it in the 1-2 week timeframe. When doing a recalibration I soak it in citric acid for 5 mins, then rinse it off with rodi. But this time (after 8 days it was reading 1ppt below) I just recalibrated it, because there was nearly no buildup/biofiom on it yet.

I soak mine in citric acid for a few hours every month or two which is when I recalibrate. I'm wondering if the 5 minute bath isn't long enough.

LC8Sumi · Jan 20, 2020

Brew12 said:
I soak mine in citric acid for a few hours every month or two which is when I recalibrate. I'm wondering if the 5 minute bath isn't long enough.

It might not be, although the probe seems to be clean after it. Anyway, it’s still drifting 1 ppt / 1.5 week, which is strange and suggests that the probe is faulty

Brew12 · Jan 20, 2020

LC8Sumi said:
It might not be, although the probe seems to be clean after it. Anyway, it’s still drifting 1 ppt / 1.5 week, which is strange and suggests that the probe is faulty

Next time it drifts around 1psu I would let it soak for 2 hours and put it back in the tank without recalibrating. If it gets close to the original reading then it's a cleaning issue. If it stays 1ppt low then I would agree that it is a probe issue.

LC8Sumi · Jan 20, 2020

Brew12 said:
Next time it drifts around 1psu I would let it soak for 2 hours and put it back in the tank without recalibrating. If it gets close to the original reading then it's a cleaning issue. If it stays 1ppt low then I would agree that it is a probe issue.

Good idea! Will try that

Vinny@GHLUSA · Jan 20, 2020

The most common causes of probe drifting is due to a leak of electrical current from some other piece of equipment. We've seen several cases where some heaters, flow pumps and even return pumps leaking current which is picked up by the conductivity probe and shows up as skewed values.

In pumps themselves, if their motor blocks were not isolated well enough, it may eventually cause an electrical leak. Other causes could be power cables running alongside the probe cable which cause electrical noise.

A recent case here shows how one user was able to resolve his issue with drifting probe values.
In the end the probe was not at fault.

Salinity Probe Drift

Hi, I have been running my Profilux 4 since Jan. this year. Everything works OK except the following. My slainity probe (conductivity probe) readings drift so fast in thease days. It was almost OK until couple of weeks ago. It suddenly drifts downward from 34.0 psu to 31.2 psu within a...

forum.aquariumcomputer.com

LC8Sumi · Jan 20, 2020

Vinny@GHLUSA said:
The most common causes of probe drifting is due to a leak of electrical current from some other piece of equipment. We've seen several cases where some heaters, flow pumps and even return pumps leaking current which is picked up by the conductivity probe and shows up as skewed values.

In pumps themselves, if their motor blocks were not isolated well enough, it may eventually cause an electrical leak. Other causes could be power cables running alongside the probe cable which cause electrical noise.

A recent case here shows how one user was able to resolve his issue with drifting probe values.
In the end the probe was not at fault.

Salinity Probe Drift

Hi, I have been running my Profilux 4 since Jan. this year. Everything works OK except the following. My slainity probe (conductivity probe) readings drift so fast in thease days. It was almost OK until couple of weeks ago. It suddenly drifts downward from 34.0 psu to 31.2 psu within a...

forum.aquariumcomputer.com

Thanks. I have a grounding probe. Also the wires are running the same way before/during/after the calibration & normal use. The values aren’t jumping around, that one would expect during signal pickup, it is just constantly drifting downwards as days go by.

edit: interestingly enough, I also have a royal exclusive skimmer pump, although an AC one and not a DC one. Will investigate if that might be the issue! Although I’m not using a converter as I have 230V 50Hz AC