Jestersix

Quicker way to calibrate Apex salinity probe?

Chromis

Chromis

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I took Terence’s advice from a recent Neptune video and moved my Apex salinity probe from where it was sitting near the output of my skimmer to somewhere *not* in a deluge of micro bubbles, and guess what, now the salinity readings are steady (they vary slightly with temp).

My Q: is there an easy way to calibrate the probe without dealing with the high/low salinity calibration solutions? I was hoping there is something similar to the temp probe (where you just enter the temp you think the probe should be reading)?
 
Well if you keep your tank near standard you can just calibrate salinity probe using tank water ... easy peasy ...

PS I’m sure you already know but if you keep salinity probe at an angle with bubble escape hole up results are pretty consistent.
 
Plankton said:
Well if you keep your tank near standard you can just calibrate salinity probe using tank water ... easy peasy ...

PS I’m sure you already know but if you keep salinity probe at an angle with bubble escape hole up results are pretty consistent.
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I didn’t know about this tip, thanks!

Yea I’m thinking about just letting my tank salinity reach 35ppt (which is approximately the 53k uS calibration sample salinity according to a BRS video) and then calibrating to the tank water. Though 35ppt from an optical measurement (Milwaukee meter) might not equal 35ppt from electrical probe measurement, might be close enough.
 
This is what I do, way easier and better than using calibration solutions. It doesn’t matter that salinity by refraction isn’t exactly the same as by conductance in this case; they are all just estimates with assumptions anyway.

The point is you get your tank where you want it to 35 ppt by Milwaukee then do the calibration telling Apex that you are using the 53,000 uS calibration solution. You need to take it out to take a dry reading (I blow it off with a computer duster) as the first step but otherwise completely straightforward.

Since the conductivity probe is crazy unreliable it is nice that it‘s easy to recalibrate.
 
+1 on calibrating in the tank itself. Pretending it is calibration fluid.
Works fairly well once you do that.

@Vhuang168
I have tested for stray voltage, and tried with/without a grounding plug, and it made no difference.
So while stray voltage could cause additional problem, I am pretty confident it is not my problem.
Interesting thought about EMI though.
The probe cable appears to be coaxial, and sensor is under water.
But the cable does pass through this huge mess of unshielded power cords.
IMG_0664.jpg
 
rygh said:
+1 on calibrating in the tank itself. Pretending it is calibration fluid.
Works fairly well once you do that.

@Vhuang168
I have tested for stray voltage, and tried with/without a grounding plug, and it made no difference.
So while stray voltage could cause additional problem, I am pretty confident it is not my problem.
Interesting thought about EMI though.
The probe cable appears to be coaxial, and sensor is under water.
But the cable does pass through this huge mess of unshielded power cords.
View attachment 27651
Click to expand...
I would call that a rat’s nest of cables, but I don’t think a rat could fit through that hole with all the cables in the way lol
 
Chromis said:
Have you tried plotting salinity vs equipment power use trends to see if there is any correlation?
Click to expand...
That would show up in the logs, so it is not that simple.

But I am wondering if it tracks a certain piece of equipment added or removed, or when I move wires around.
Because the failure is more that every once in a while, it just decides to shift quite a ways.
Like it will be registering 35.0, +/-0.2 for months, then shift to say 38.5, then stay there, +/-0.2.

Not really a big deal anymore.
When it goes wonky, which is fairly rare, I double check with refractometer, and just re-calibrate to tank water.
 
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