Apex Salinity Probe Calibration

[mitch91175]

Was just thinking about something with the Apex salinity probe that I think would be a really good solution to getting accurate salinity readings. Why doesn't the Apex allow you to put in a "baseline calibration" for the probe that you read from another refractometer so you can get accurate salinity readings in Apex Fusion?

Wouldn't that make the whole calibration process unnecessary? For instance I know for a fact that my salinity is current 33.13ppt but my probe is reading it as 25.6ppt. Just seems like an oversight in my book for something that would be so easy to implement (at least I think so). Think about it, when in Fusion, you go to the probe and put in your actual salinity and the Apex adjust from there.

Am I completely off base with this assumption? I know that you can do so with the Alkatronic and other devices for dKH correction so why not with salinity and even pH as well on the Apex?

 

[glb]

That’s a great idea.

 

[TheHarold]

Was just thinking about something with the Apex salinity probe that I think would be a really good solution to getting accurate salinity readings. Why doesn't the Apex allow you to put in a "baseline calibration" for the probe that you read from another refractometer so you can get accurate salinity readings in Apex Fusion?

Wouldn't that make the whole calibration process unnecessary? For instance I know for a fact that my salinity is current 33.13ppt but my probe is reading it as 25.6ppt. Just seems like an oversight in my book for something that would be so easy to implement (at least I think so). Think about it, when in Fusion, you go to the probe and put in your actual salinity and the Apex adjust from there.

Am I completely off base with this assumption? I know that you can do so with the Alkatronic and other devices for dKH correction so why not with salinity and even pH as well on the Apex?

You can already do that somewhat, if your salinity is 35ppt you can just calibrate the probe IN your sump water to 35ppt. But yeah, they should absolutely allow a manual user input, or a reading "offset" like you can do with the temperature probe.

 

[APC]

Agree - lots of room for improvement with this probe specifically. Its a constant battle, and honestly I don't rely on it for accuracy at all. I am also having tons of problems with my APEX ATK auto top off system. It constantly errors out - and is totally unreliable. While my new Apex is an improvement over the original APEX that I had - all in all there is lots of room for improvement overall - and specifically with the salinity probe and the ATK.

 

[TheHarold]

Agree - lots of room for improvement with this probe specifically. Its a constant battle, and honestly I don't rely on it for accuracy at all. I am also having tons of problems with my APEX ATK auto top off system. It constantly errors out - and is totally unreliable. While my new Apex is an improvement over the original APEX that I had - all in all there is lots of room for improvement overall - and specifically with the salinity probe and the ATK.

I agree, after spending $800 on the apex, to have a probe that is BOTH unreliable and inaccurate is very annoying. If it was reliable that would be good enough for me, but after hours of troubleshooting and reading, it remains useless to me.

 

[mitch91175]

I am going to try to calibrate it using 35ppt solution to see if I can at least get it to be somewhat close. I don't rely on the readings either just helps give me a general idea of where my salinity is for the tank. Sad part is that I am more and more these days loosing faith in the Apex altogether. If I wasn't already so deep into it I would do something else honestly. Sad part is I have 2 - 2016 Apex with all the bells and whistles. First I had a bad PM2 module take down the whole system, then I had to invest in Google Wifi to get a better connect to Fusion, and now the probes just don't seems too reliable. I was dosing ozone based on the ORP probe reading but since have stopped using ozone altogether because I just cannot trust the probes in general.

Right now I have the pH in my CaRx controlling the pH in the chamber, but strongly considering going with a standalone Milwaukee controller instead.

 

[OceanMinded]

Wow this makes me want to stay away from Apex and I was just about to order one

 

[mitch91175]

Wow this makes me want to stay away from Apex and I was just about to order one

Definitely not saying stay away, but just be aware of what you are getting into. As you know all systems have their flaws.

 

[doughboy]

the conductivity probe issue is like the elephant in the room. every one who owns one have experienced the issue, but no one wants to talk about it. maybe so they can sell it later to someone who does not know. when I bought my apex (used), I was warned by the seller. likewise when I sold, I notified the buyer.

 

[mitch91175]

the conductivity probe issue is like the elephant in the room. every one who owns one have experienced the issue, but no one wants to talk about it. maybe so they can sell it later to someone who does not know.

Yeah I just deal with it too, lol. Besides, if your salinity is swinging like crazy, there are other issues.

 

[doughboy]

Yeah I just deal with it too, lol. Besides, if your salinity is swinging like crazy, there are other issues.

the swinging reading is a probe issue. So it can actually turn out worse if one actually trusts the (inaccurate) salinity reading and start making unnecessary changes. I know when I had the probe, the reading changes when outlets come on or off.

 

[OceanMinded]

Why is this still an issue though? If it’s the probe it’s self why wouldn’t Neptune go with a better one? Or why wouldn’t they fix this problem ? It seems like so many people are spending so much money for this aquarium controller but virtually no one talks about this issue. Salinity monitoring was one of the key features that almost sold me on the apex. Obviously there are many other benefits but seriously? Why even go with the regular when you can get the EL for much less and without the extra baggage they doesn’t even work

 

[spifftempo]

**DISCLAIMER** I WORK FOR NEPTUNE SYSTEMS. I AM SHARING MY OWN PERSONAL EXPERIENCE AS A HOBBYIST WITH THE SALINITY PROBE, THEN PROVIDING SOME GUIDANCE ON ITS USE AND FUNCTION**

My probe works great. I haven't calibrated it in over 6 months, it matches my natural seawater refractometer all the time (and I calibrate the refractometer before every use). I have temperature compensation set to 2.4% and never see any affects of temperature on my probe.

The key to this probe is PLACEMENT. It needs some flow (so the water cannot be stagnant) and it cannot have any micro-bubble build up on it. For me, I mounted it in my return pump chamber on my Reefer 170. It is on the back side of my return pump and the probe is mounted at a slight angle to prevent any micro-bubble build up. This works for me. I have seen some people point a small power head (like a Koralia Nano 240) to provide flow and knock off any air bubbles that may accumulate on the probe.

The second thing I would mention is the probe is fragile. It breaks easily if dropped, knocked on the side of the sump ect. If you take the probe out of your sump and you hear anything in the probe rattling when you shake it, then it is broken and will cause erratic readings.

Here are some screen shots of my salinity probe graph and the probe mounted it my sump- nothing really all that special. I have graphed it against temperature and you can see the affects of temperature are fairly minor. In a period of a week my salinity has been 34.1 +/- .2 pr or so. That's a about 1.0256 to 1.0259 SG.

As I said, temperature only has a minor affect on my salinity measurements and I achieve this by using the temperature compensation feature used on the Apex. You can see I had a couple of colder days and my salinity was lower during that time, but not by much. I arrived at a 2.4% compensation factor after a period of a couple weeks of testing. I started with the 2.0% Neptune Systems recommendation, but was still seeing some pretty large affects of temperature on the probe over periods of couple days. I then moved it down to 1.8%, recalibrated and saw an even larger affect of temperature. So I went up to 2.2%, recalibrated and saw less of an affect but still enough to warranted some further adjusting. I went to 2.4%, recalibrated- got this behavior and was happy and left it alone.

Now, I'm not trying to say that some of you experience some real problems with your salinity probe and those aren't valid complaints. I hope just to illustrate here the probe works and can work very reliably. If you are experiencing issues with your probe I suggest the following:

1. Rule out that it isn't something in the tank. Place the probe in a cup of water for 10-15 minutes, do the numbers stay fairly stable? If so and the numbers are erratic in the tank, then you have stray voltage in the tank, EMI, but more likely air-bubble build up. If not, then see (4) below.
2. Rule out stray voltage and a possible device in the aquarium creating a noisy EMI environment. EMI is common with high-end DC pumps (think ABYZZ) or low end AC pumps. To determine the offending device, turn everything off in aquarium do the salinity number stabilize? If so, then turn one device on at time, starting with your return pump. Let it run for a minute or two, then take a look at your salinity readings. If you see your numbers become erratic, then the device you just turned on is either causing an EMI field or it has introduced some stray voltage into your tank. Moving the probe can help to mitigate the issue of EMI. With stray voltage, its typically recommended the offending device should be replaced. A grounding probe is a solution, but is really just a band-aide.
3. If you see a slow and steady rise or fall of your salinity probe over a period of days, then that is the slow build up of micro-bubbles over time. Try finding another place in your tank, place the probe at an angle, point a small power ect.
4. If you take the probe out of water and just shake and you hear ANYTHING other than water draining out of the probe, then the probe is broken and needs to be replaced.
5 Make sure the probe is well seated into the Apex Base Unit. If it is not fully seated, then you can expect erratic readings.

All of the issues above cause erratic readings and deal with precision. Precision, in my opinion, in this case is the more important matter regarding this probe. The second part of the equation is ACCURACY. Inaccurate readings are typically due to errors or oversights in the calibration process. The process itself is really quite simple.

1. Place the calibration solution in tank to bring to tank temperature.
2. Set the temperature compensation value to 2.0% . (Here I have it set to 2.4%, which I detailed how I arrived at that above, this may not be the best TC for your aquarium).

3. I prefer a manual calibration, but that's just because at my heart I am a old school "Control Freak"
4. Take the probe out of water dry it- just give it a couple shakes.
5. Wait for the value to settle at the dry value and click OK
6. Open up the calibration solution and place the probe in the calibration solution. Leave the solution in the water during the calibration
7. Hold the bag at a 30-45 degree angle in the water with the probe angled as well
8. Give the probe a couple twirls in the bag and maybe a tap or two. This releases any air bubbles that may be on the probe.
9. Let the probe sit for a bit and settle.
10. Select OK after you don't see the settling number change with +/-2 units for 10 seconds. Really if there are not any air bubbles and the solution is staying the same temperature as the tank water, then this shouldn't take more than 30-45 seconds to settle.
11. After calibration the probe should read 34.9-35.1. Those numbers indicate an accurate calibration. If you don't get those measurements in the solution, then the calibration was not accurate.

Reading over this post, its pretty long-winded, but I hope it helped provide some details of how the probe can work reliably. I encourage you to contact our support team if you are having trouble with you salinity measurements after following some of the tips here.

Thanks for all your feedback everyone. It is appreciated.

- Paul

 

[doughboy]

Since the probe is designed for use in reef aquarium, then it should work with any reef equipment, no exceptions.
I think the suggestion to provide a way to specify fixed offset value is a good suggestion and should not be hard or impossible to do.

 

[n2585722]

Since the probe is designed for use in reef aquarium, then it should work with any reef equipment, no exceptions.
I think the suggestion to provide a way to specify fixed offset value is a good suggestion and should not be hard or impossible to do.

You are asking for an impossible task. I am an electronics technician and I have seen some strange interferrence issues over the years. If the items are made by the same manufacturer then there is a good chance there will be no issue. One company has no control over what another one will do. They have a habit of changing things over time. So even it they tested something with everything when in the development phase there is nothing to stop the other company form changing the way their product is made down the road.

Also the salinity probe is a conductivity probe. Anything that effects the conductivity of the water will change the reading of the probe. Air bubbles will do it by removing surface area of the electrodes lowereing the reading. Live tank inhabitants that get between the electrodes can have either effect. Also items added to the water can change conductivity and not necessarily change the salinity. These are issues that all conductivity probes will have regardless of company.

 

[doughboy]

You are asking for an impossible task. I am an electronics technician and I have seen some strange interferrence issues over the years. If the items are made by the same manufacturer then there is a good chance there will be no issue. One company has no control over what another one will do. They have a habit of changing things over time. So even it they tested something with everything when in the development phase there is nothing to stop the other company form changing the way their product is made down the road.

Also the salinity probe is a conductivity probe. Anything that effects the conductivity of the water will change the reading of the probe. Air bubbles will do it by removing surface area of the electrodes lowereing the reading. Live tank inhabitants that get between the electrodes can have either effect. Also items added to the water can change conductivity and not necessarily change the salinity. These are issues that all conductivity probes will have regardless of company.

hmm, I think the suggested solution can be phrased better. It was not my suggestion, but I concur with the suggestion.
You can calibrate the probe outside of the sump, but when installed in the sump, interference offsets the reading. The suggestion is to merely add an offset value to make the reading as calibrated. Yes it is a simple solution. I have built diy controller (refer to diy thread in RC) with conductivity probe so I know exactly what can and cannot be done.

 

[n2585722]

hmm, I think the suggested solution can be phrased better. It was not my suggestion, but I concur with the suggestion.
You can calibrate the probe outside of the sump, but when installed in the sump, interference offsets the reading. The suggestion is to merely add an offset value to make the reading as calibrated. Yes it is a simple solution. I have built diy controller (refer to diy thread in RC) with conductivity probe so I know exactly what can and cannot be done.

I was not aware that the Apex would not allow you to change the calibration set point form 35. Is this the issue? I do not have an Apex. The controller I do have will let you change the set point to any value you want to calibrate it too, within reason. If this is the case it should be changeable.

 

[doughboy]

Its not just the set point, its manually entering an offset value to the set point.
also there are ways to filter out readings in firmware to retain only valid readings.

 

[DivingTheWorld]

You can already do that somewhat, if your salinity is 35ppt you can just calibrate the probe IN your sump water to 35ppt. But yeah, they should absolutely allow a manual user input, or a reading "offset" like you can do with the temperature probe.

I've been doing this for years. I love the Apex, but the salinity probe is a pain... I use it only as a backup. When I calibrate, I use my proven hydrometer to verify my tank is 35.0, then calibrate the probe in my sump. It seems to work pretty good this way and calibration is much easier.

 

[TheHarold]

I've been doing this for years. I love the Apex, but the salinity probe is a pain... I use it only as a backup. When I calibrate, I use my proven hydrometer to verify my tank is 35.0, then calibrate the probe in my sump. It seems to work pretty good this way and calibration is much easier.

Yep! I have a miluakee digital refractometer as well as standard solutions to confirm its accuracy. That is what I go by. So when my actual ppt is confirmed to be 35, I just calibrate it in the sump. I am thinking that there is electrical interference in the tank stand or other factors that make the universal calibration fluid not so universal.