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Thread: Salinity reading keeps rising

  1. #1
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    Angry Salinity reading keeps rising

    Hello All,
    I wasn't sure where to post this as I have seen a lot of salinity probe issues here. Trouble is mine calibrates OK yet the reading constantly and slowly rises over the course of a day. I opened a ticket after I first noticed it. I followed the instructions the rep gave me and because my calibration solution was gone used a saltwater mix at 1.026sg which he said would work fine. He also assured me there was no need to condition or soak the probe for several hours or days.
    I did the manual calibration as instructed and everything looked fine the readings settled as they should have and the probe read 34.7 in the solution. I left it in the container for an hour and it rose almost 2 points. Now since I keep my tank at 1.026 I set the probe in the tank for a full day and now it is at 41.4. I only use RO/DI water and keep it topped off daily. There is no way the level is that high. I just double checked with my hydrometer and a refractometer which actually read 1.025. I am waiting on another reply from support.
    This is nuts. I got this system a little over a week ago and it has one nightmare after another starting with the 1 1/2 days it took for wifi setup. I know the probe will probably not be dead accurate but it would be a useful tool (if it was at least close) for tracking trends etc.
    For the cost of this system all I can say is I hope I didn't make a big mistake getting it.

  2. #2
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    Did you temperature match the calibration fluid to the tank? That could make an error, but it doesn't seem like it would keep rising unless you temperature was rising the whole time.

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    I got it pretty stable now. My temp swings about 1.3 degrees which is pretty tight compared to before I got the controller. The salinity does swing with the temperature and is extremely sensitive. My concern was the slow creep upwards after a day or so. I had to calibrate it in the tank to get it this stable. Neptune support said that would be OK because my salinity in the tank is 1.026 which is really close to the calibration fluid. I think temperature is key when trying to calibrate. It may not be laboratory accurate but I think it will work for me. I guess for future reference if I get any packets of cal fluid I will float them in the tank to equalize the temp. In what little documentation they give you they don't mention how critical temperature is.

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    Same problem here. Readings are creeping up steadily. After auto calibrating the probe, initial readings in the thank was 4.2ppt. after shaking the probe to let air out, reading was in the 32.0s ppt. (My house air degrees is around 76 to 77F, and my tank tank is around 75.3-76.3F. Calibration liquid packet was floated in main tank for about 10 min as suggested in some of the threads i see here randomly.) It's been 14 hours since, the readings are 42.0 now as we speak. I checked with my refractometer and the readings are 1.025ish specific gravity (just as it was 6 days ago. Pretty Stable). Probe is located in the top right corner of my tank.

    I am leaving it in as see how high will go, since I know my salinity levels are stable with the refractomer.

    Any suggestions?

  5. #5
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    I also come across this link concerning salinity. We are all mentioning the temperature in the tank and compare readings with our refractometers. But fact is that different refractometers are calibrated at different degrees. That makes a big difference in actual readings when comparing the two.

    https://reefapp.net/en/maintenance/c...unitconversion

  6. #6
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    Quote Originally Posted by 2mk View Post
    I also come across this link concerning salinity. We are all mentioning the temperature in the tank and compare readings with our refractometers. But fact is that different refractometers are calibrated at different degrees. That makes a big difference in actual readings when comparing the two.

    https://reefapp.net/en/maintenance/c...unitconversion
    Temp compensation (if selected and tuned properly) will eliminate that error between the two. Refractometer are not very temp dependent and the glass tends to cool the drop of water quickly enough to make it roughly neglegable.

    You might be an engineer if...You have no life and can prove it mathematically.

  7. #7
    Frequent Visitor 2mk's Avatar
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    Thank You for the explanation.

    As of this moment ( about 26 hours after calibration) my readings are as follows:
    ORP 262
    pH 7.32
    Salt 49.40 (it keep going up)
    Tmp 75.5



    My salinity keeps going up. Again, I checked my salinity with a refractometer and my readings came out to be 1.025 s (I even calibrated my refractometer with calibration liquid, and it proves to be correct), which equate to:

    Salinity at 75.5°F

    Conductivity 70.7 mS/cm
    Salinity PSU 49.4 (≈ 49.4 ppt)
    Density 1.0345 g/cm³
    Specific gravity 1.0374

    Are these conversions correct? Is the 49.4 number in the Apex equals to "ppt" - salinity or "mS/cm" conductivity? Please help.

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    It is in ppt.

    What did it read in calibration fluid?

    Did you shake out bubbles while calibrating?

    What does it read in a cup of tank water outside of the tank?


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  9. #9
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    Apologize for the late reply. I was too excited that the calibration was successful that I did not read any readings at all and assumed it was good to go. Then again, nothing about it was mentioned in the instructions.

    I did wiggle the probe in the packet a bit before starting.

    It read the same as it was in the tank during water change two days ago. I have since took the probe off line for drying to re-calibrate again.

    Is the calibration liquid reusable? No other liquid went in it when i used it, and sealed again with tape after use.

  10. #10
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    The calibration packet should be okay for another attempt and be close enough.

    Don't spend a bunch of time drying it out. Just rinse it in ro and pat it dry with a paper towel. Gets better calibration and takes way less effort.

    You might be an engineer if...You have no life and can prove it mathematically.

  11. #11
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    Thanks. I will try that again tonight. Is there such a thing that the probe can go bad by calibrating too many times or doing it the wrong way?

    also when manual calibrate, What is the value to set for temp compensation? How do I determine this value?

  12. #12
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    Quote Originally Posted by 2mk View Post
    Thanks. I will try that again tonight. Is there such a thing that the probe can go bad by calibrating too many times or doing it the wrong way?

    also when manual calibrate, What is the value to set for temp compensation? How do I determine this value?
    You can't calibrate too many times. You could do it thousands of time and cause zero damage.

    Start at 2.2 for temp compensation, and the closer your tank is to 77F during calibration (the packet needs to match exactly) then the easier tuning the temp compensation value will be. Basically just watch the graph over a few days and see if cond stays relatively constant (+- 0.3 ppt at most) as temperature changes. If they increase together too much, increase the number 0.1. If they move opposite directions too much, reduce by 0.1.

    You might be an engineer if...You have no life and can prove it mathematically.

  13. #13
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    Before trying what you suggested above, I did an auto calibration with the tank water as mention by MarkA above, since i don't want to really waste the remaining calibration liquid. My tank water was around 1.025sg from refractometer reading. Display reading was 34.9 ppt right after successful calibration @ 75.7 F , 7.46ph, and 294 ORP. It's been 2 days since and the stable appearing salinity has been creeping up slowly. Can you tell me if I got it working this time? Please see graph below. Or maybe I should do a Temp Comp calibration with the tank water to make it more accurate?

    panel.jpgsalt3.jpgsalt2.jpgsalt.jpg


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    2mk,
    I set my temp compensation to 2.2 and it has been pretty stable. My SG is about 1.25 and the probe (which read in ppt) averages about 35.5ppt. All in all it is,for me, quite accurate. After I fussed with it for so long I just left it alone and go more by the graph to guage the average salinity over time. So for a few months now my average is fine. It makes some pretty scary swings when I top off and when the temp swings. If you keep up with top offs and your heater control is "tight" give it a week and check the average on the graph. Also plot the temp graph with for a few days worth of time and you will see what I mean about how sensitive it is. I do have some new calibration fluid but have not attempted any more calibrations as it agrees with my refractometer and hydrometer.

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    Quote Originally Posted by MarkA View Post
    2mk,
    I set my temp compensation to 2.2 and it has been pretty stable. My SG is about 1.25 and the probe (which read in ppt) averages about 35.5ppt. All in all it is,for me, quite accurate. After I fussed with it for so long I just left it alone and go more by the graph to guage the average salinity over time. So for a few months now my average is fine. It makes some pretty scary swings when I top off and when the temp swings. If you keep up with top offs and your heater control is "tight" give it a week and check the average on the graph. Also plot the temp graph with for a few days worth of time and you will see what I mean about how sensitive it is. I do have some new calibration fluid but have not attempted any more calibrations as it agrees with my refractometer and hydrometer.
    Very insightful and helpful information. Eversince the last calibration mentioned on my last post, my salinity are more statble now but still a bit higher than what refractometer indicates. Please graph below. The first major dip you see see in the graph was my a 20% water change 3 days ago. The second major dip was when I manually topped off the tank to accommodate my refugium pump water level (3 cups). The fourth increase was due adjusting Temp Compensation to 2.2. And finally, the last dip is due to adjusting Temp Comp back to 0.0. My reading right now is at 37.0 ppt. Would you consider these readings normal now? Or should I recalibrate with tank water? (I only have my used calibration fluid).
    What temperature did you calibrate it at?

    2017-12-19.jpg
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    If you have a reasonably accurate scale it's actually better to use randy holmes farley salinity calibration solution with table salt in a pinch. It's more consistent in Cl levels and is more accurate than you can get with a refractometer.

    You might be an engineer if...You have no life and can prove it mathematically.

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    Quote Originally Posted by zombie View Post
    If you have a reasonably accurate scale it's actually better to use randy holmes farley salinity calibration solution with table salt in a pinch. It's more consistent in Cl levels and is more accurate than you can get with a refractometer. If you just want a baseline at 35ppt for now and want to calibrate later with proper solution, you can just calibrate in the tank temporarily.

    You might be an engineer if...You have no life and can prove it mathematically.


    You might be an engineer if...You have no life and can prove it mathematically.

  18. #18
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    Quote Originally Posted by zombie View Post
    If you have a reasonably accurate scale it's actually better to use randy holmes farley salinity calibration solution with table salt in a pinch. It's more consistent in Cl levels and is more accurate than you can get with a refractometer.

    You might be an engineer if...You have no life and can prove it mathematically.
    Are you suggesting making you own salinity 53.0 calibration fluid? Is it possible and how?
    When You're a NOOB, You need lots of help all the time

  19. #19
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    Quote Originally Posted by 2mk View Post
    Are you suggesting making you own salinity 53.0 calibration fluid? Is it possible and how?
    Yep. Randy has recipes for conductivity, salinity, and SG that you only need RODI, table salt, and a decent scale.

    http://reefkeeping.com/issues/2004-06/rhf/index.php

    You might be an engineer if...You have no life and can prove it mathematically.

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    Quote Originally Posted by zombie View Post
    Yep. Randy has recipes for conductivity, salinity, and SG that you only need RODI, table salt, and a decent scale.

    http://reefkeeping.com/issues/2004-06/rhf/index.php

    You might be an engineer if...You have no life and can prove it mathematically.
    Thanks. Your answers never ceases to amaze me.
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  21. #21
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    parameters2017-09-19.jpg I think my numbers are more stable now. So far I have not recalibrated the salinity probe. As a lot of people have pointed out, especially Zombie in multiple threads, Temperature is very important during calibration. Even more so after calibration. My temperature was going haywire due to a clogged chiller during the past 2 days. Once I have corrected the temperature problem, salinity became more stable and predictable. It might also have to do with the break in period that Zombie mention in past post directed at me concerning the slowly creeping up temperature. I will observe a bit more and report back for all to see the thread in coming future.

    Thanks all that pitched in to my ais.
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    Thanks for this thread, I am also having issues with my conductivity and PH probes since setting up my Apex a month ago. I originally calibrated as per the getting started guide which did not mention temperature stabilisation so I didn’t include that step. I have just picked up a pH 7 and pH 10 solution and are waiting for the conductivity solution to re-calibrate.

    At the moment my pH reads a little low and swings between 8.05 and 8.2, correlating with and lagging temperature changes (i.e. as temp rises pH also rises a short time later, as temp falls pH falls a little time later). My testing indicates pH is closer to 8.4 (API kit). Hopefully re-calibrating with a temperate matched solution will improve this.

    My conductivity reads a little high, as my refractometer shows a solid 1.024. Today at the time I took the refractometer reading the temp was 25.2 and the Apex read salinity at 36 ppt - should be closer to 34 ppt. It also bounces between 35.5 and 36.5, sometimes correlated with and lagging a temperature change. It also occasionally dives and then spikes, sometimes to 36.4 or so, sometimes to 36.8. The dive/spikes are typically caused by the chiller kicking in and dropping the temp from 26.5 to 25.2, but also occur when I do a tank clean. I currently have the temp comp set to 2.2 but I do see some inverse salinity changes compared to temperature changes so may need to try dropping this a little.

    I am not sure whether to recalibrate when I get my new solution or play around with it a little first before I do that. All my probes are located in the sump inlet of my Red Sea Reefer 250, above (and in) my Marine Pure balls, in a quite stable and air bubble free environment.

    Any suggestions or other thoughts would be greatly appreciated.

  23. #23
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    Quote Originally Posted by Tastee View Post
    Thanks for this thread, I am also having issues with my conductivity and PH probes since setting up my Apex a month ago. I originally calibrated as per the getting started guide which did not mention temperature stabilisation so I didn’t include that step. I have just picked up a pH 7 and pH 10 solution and are waiting for the conductivity solution to re-calibrate.

    At the moment my pH reads a little low and swings between 8.05 and 8.2, correlating with and lagging temperature changes (i.e. as temp rises pH also rises a short time later, as temp falls pH falls a little time later). My testing indicates pH is closer to 8.4 (API kit). Hopefully re-calibrating with a temperate matched solution will improve this.

    My conductivity reads a little high, as my refractometer shows a solid 1.024. Today at the time I took the refractometer reading the temp was 25.2 and the Apex read salinity at 36 ppt - should be closer to 34 ppt. It also bounces between 35.5 and 36.5, sometimes correlated with and lagging a temperature change. It also occasionally dives and then spikes, sometimes to 36.4 or so, sometimes to 36.8. The dive/spikes are typically caused by the chiller kicking in and dropping the temp from 26.5 to 25.2, but also occur when I do a tank clean. I currently have the temp comp set to 2.2 but I do see some inverse salinity changes compared to temperature changes so may need to try dropping this a little.

    I am not sure whether to recalibrate when I get my new solution or play around with it a little first before I do that. All my probes are located in the sump inlet of my Red Sea Reefer 250, above (and in) my Marine Pure balls, in a quite stable and air bubble free environment.

    Any suggestions or other thoughts would be greatly appreciated.
    One thing of note for your decision. If your tank is at 77F/25C during calibration, the calibration and temp compensation become independent (because the compensation is always 0ppt at 77F). If you can't do that, I would dial in the temp compensation value first and then recalibrate to minimize error from the TC change.

    You might be an engineer if...You have no life and can prove it mathematically.

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    Zombie, do you mind me playing that back to ensure I understand the point you are making?

    If I can recalibrate when the tank is 77F/25C then the Temp Comp number is irrelevant and it is safe to recalibrate. I can then tune the temp comp factor after so that I don’t see inverse or correlated swings so often.

    If I can’t do this at a 77F/25C temp then I need to ensure I tune the temp comp numbers first.

    Did I understand you correctly?
    Sounds like the first option is the preferred one.

    Thanks, Brad.

  25. #25
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    Quote Originally Posted by Tastee View Post
    Zombie, do you mind me playing that back to ensure I understand the point you are making?

    If I can recalibrate when the tank is 77F/25C then the Temp Comp number is irrelevant and it is safe to recalibrate. I can then tune the temp comp factor after so that I don’t see inverse or correlated swings so often.

    If I can’t do this at a 77F/25C temp then I need to ensure I tune the temp comp numbers first.

    Did I understand you correctly?
    Sounds like the first option is the preferred one.

    Thanks, Brad.
    Exactly.

    You might be an engineer if...You have no life and can prove it mathematically.

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