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Thread: Salinity Probe Reading LOW

  1. #1
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    Salinity Probe Reading LOW

    Problem:
    My salinity probe is reading about ~29.8 while it should be closer to 35. The specific gravity of the tank water is 1.025 measured with multiple Milwaukee digital refractometers.

    Trouble Shooting:
    1) Cleaned probe using white distilled vinegar (full strength).
    2) Calibrated using 53000 ms/cm2 solution following the instruction from Neptune. I left the calibration solution packet in the sump for a couple of hours before calibration. Probe calibrates correctly and after calibration measure about 34.9 when left in the calibration solution.
    3) When I put it back in the tank, the reading settles to ~29.8
    4) To ensure it's not related to any stray voltage issue (I do have a grounding cable in the main tank, not in sump), I got some tank water in a plastic container and the prob measures the same 29.8.

    Background info:
    1) I do BRS 2 part Calcium (200 ml/day) & Alkalinity (240 ml/day) dosing using DOS and Magnesium manually (when needed).
    2) Use Tropic Marin Bio-Actif salt
    3) I have a temp. probe on the pm2 module and temp. compensation is set to 2.2

    I understand conductivity and specific gravity are two separate things but they don't seem to be even in the same ball park range.

    Any ideas?

    Thanks in advance.

  2. #2
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    how old is the probe could have passed its usable life span

  3. #3
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    I have been struggling for days with this exact issue. Today I have made a conclusion.
    Read the post #6 and #8 of this thread:
    https://forum.neptunesystems.com/sho...ation-Question

    My conclusion is this: Do not see the apex probe as a measuring tool but use it to monitor the fluctuation and make use of the alarm feature (with 10 minute delay). Use your calibrated digital refractometer (milwaukee MA887) for mixing water by first measuring the tank water first so that your newly mixed water will match the tank water.

  4. #4
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    This happened to me last month. Mine was reading fine sitting right at 35 (Salinity Option) when literally overnight it dropped to 27.X. I had the probe for over 4 years, so I just figured it had finally failed. I had calibrated it several times during its life. I ordered another and installed it this weekend. After installing and calibrating, this brand new Neptune Apex Conductivity Probe reads 27 and change. So maybe my old one wasn't bad. I then took readings with my optical refractometer calibrated with 35ppt solution and got a reading of 34ppt. I then I did the same with my Milwaukee Digital Refractometer and got a reading of 35ppt. This is very bizarre and disheartening. Do you think my PM2 is going tango-uniform? I'm running the current firmware with all modules current as well, and this has been for a while now.

  5. #5
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    p7willm really explained it well in his post#6 and 8 in that thread:
    https://forum.neptunesystems.com/sho...ation-Question

    Apex probe measures conductivity while refractometer and hydrometer measure density as there is no (easy) way to really measure salinity (part per thousand of salt).

    Maybe something changed the conductivity of water overnight but not density in your tank? As long as the probe reads 35 PPT in the calibration solution right after you finish the calibration, then the probe is no problem.

    Watch the BRS "Calibrate your Salinity Probe" video on youtube. Ryan suggests drying up the probe really good, shaking off the bubbles, and putting the temp probe in the same container where your calibration bag is in. His video is much more detailed than the procedures Apex provides.

    I trust my Milwaukee way more than the probe. The bubble trap and the interference issues make the apex probe UNRELIABLE. Shouldn't they have made it harder to trap bubble and used thicker wiring to eliminate interference? Neptune, when you have version 2 of these probes out, are we, customers who spent so much time messing with your probe, entitled for a FREE UPGRADE?

  6. #6
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    Are you still having these issues? I just got my Apex a week ago, and the first issue I started having was the conductivity probe reading low. When I calibrated it, it read 34.9. As soon as I put it into the sump, it then began to read 33ish. It slowly started falling, until it bottomed out around 29 and I decided I needed to do something. I searched every single forum, read close to 50 different posts about this issue and tried every fix from moving the wires, to putting it in a cup outside the tank, and I pretty much tried every single inch of my 125 gl tank/36 gl sump. It was still reading 29-32. This morning, I decided to fiddle with it some more. I tapped on it to remove the air bubbles, and a bunch came out. The reading didn't change though. So I completely inverted the probe and tada, several huge air bubbles came out. As soon as those large bubbles were released, my Apex jumped up to about 46!!! This meant my probe was incorrectly calibrated from the get go due to those extra air bubbles while it was in the 53ms solution. So, knowing 100% for sure that my tank is currently running at 35ppt, I did a MANUAL calibration in the main display. But before I did so, I ensured to invert the probe to remove those few larger air bubbles that wouldn't escape. The manual cal was a snap, and now I'm reading 34.9 and my refractometer is spot on with 35. I will most certainly purchase some calibration fluid and do a correct recalibration, but unit I can get my hands on some, this method will have to suffice!

  7. #7
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    When you did the manual calibration, what solution level you use? I don't remember it gives a choice of 35ppt (whatever ms it is). Did it allow you to change unit to PPT and manually enter a number?

    Good idea to keep the probe upside down.

  8. #8
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    I don't know about other Apex version, but on the new Apex, it defaulted to '53,000 us' which is basically 1.026. I only did this because I was tired of seeing a BS reading, so really I had nothing to lose. I took the probe out of the tank, dried it off. Then it's just 2 steps in the manual calibration process. Just make sure when you put the probe in the tank to completely invert the probe for a few secs to get the remaining air bubbles out. Then I set it upright in the tank and finished the calibration. It immediately went to 34.9 when it was finished.

  9. #9
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    YOU ARE GENIUS! Right, 53ms is 35PPT which is 1.026. If you know your tank water is 1.026, then use it to calibrate and tip the probe upside down!
    Apex needs to address the bubble trapping and wiring interference problem.
    HELLO NEPTUNE!!! Give us version 2 of your probe for free!

  10. #10
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    They should at least update their automatic calibration procedures to include IN THE STEPS to purge the probe of air bubbles. The manual that I was using online mentioned this in a NOTE. The note is AFTER the calibration process. So I didn't even notice the "shake probe to purge air bubbles" note until my cat knocked over the remainder of the cal solution. Hopefully others can benefit from this tip instead of wasting money on new probes, etc.

  11. #11
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    Do a reset first on the apex if you can't get it to calibrate, guys. Dip the probe upside down into your known 35PPT solution (or tank water) where your temp probe is. Don't spend money buying those calibration solution (if you do, BRS is cheap with free shipping).
    You need Milwaukee. That is the only thing I trust.
    And I finally got my probe agree with my Milwaukee!
    And 53000mS is 1.026 SG is 35 PPT.

  12. #12
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    Mine is stuck on 27.4. Calibration is correct since it is at 35. But when I put in my sump it is 27.4. Unless there isnt enough salt in my tank (refrac says 34) there is something wrong with this probe. I mixed 40ppt of saltwater solution in a small container and the probe still said 28ppt.

  13. #13
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    I have this problem also recalibrated twice still got the same result refract says 1.025 ?

  14. #14
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    Quote Originally Posted by derekc View Post
    Dip the probe upside down into your known 35PPT solution (or tank water) where your temp probe is. Don't spend money buying those calibration solution
    This is bogus info. 35PPT solution or refractometer calibration fluids are not suitable to calibrate a conductivity probe. The only acceptable solution is one specifically made to be used for calibration of conductivity. For normal saltwater use, the probe must be calibrated with 53000 microSeimens solution.

    From a sticky posted here on the forum:

    Refractometer calibration fluids and conductivity calibration solutions are not the same. Use the proper calibration solution.

    In general, you cannot use calibration solution meant for calibrating a saltwater refractometer to calibrate a conductivity probe (and vice versa). While there are a couple of calibration solutions available which are labeled as being suitable for both uses, I've found the results of using them to be inconsistent. I strongly recommend that only the Neptune 53mS calibration solution be used to calibrate a Neptune conductivity probe. It has always given me good results.
    Please do not send me PMs with technical questions or requesting assistance - use the forums for Apex help. PM me ONLY if the matter is of a private or personal nature. Thanks.

  15. #15
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    Quote Originally Posted by RussM View Post
    This is bogus info. 35PPT solution or refractometer calibration fluids are not suitable to calibrate a conductivity probe. The only acceptable solution is one specifically made to be used for calibration of conductivity. For normal saltwater use, the probe must be calibrated with 53000 microSeimens solution.

    From a sticky posted here on the forum:

    Refractometer calibration fluids and conductivity calibration solutions are not the same. Use the proper calibration solution.

    In general, you cannot use calibration solution meant for calibrating a saltwater refractometer to calibrate a conductivity probe (and vice versa). While there are a couple of calibration solutions available which are labeled as being suitable for both uses, I've found the results of using them to be inconsistent. I strongly recommend that only the Neptune 53mS calibration solution be used to calibrate a Neptune conductivity probe. It has always given me good results.
    This might be true however sometime ago I was having a serious problem with calibrating the probe and contacted Neptune support. They wanted me to calibrate the probe again and I ran out of their solution the only thing I had was my calibration solution for my refractometer and they said that it was fine. So take what you want from that.

  16. #16
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    Quote Originally Posted by marksw View Post
    This might be true however sometime ago I was having a serious problem with calibrating the probe and contacted Neptune support. They wanted me to calibrate the probe again and I ran out of their solution the only thing I had was my calibration solution for my refractometer and they said that it was fine. So take what you want from that.
    I doubt that a support tech specifically said that you can use refractometer calibration solution. You might want to review that helpdesk ticket.
    Please do not send me PMs with technical questions or requesting assistance - use the forums for Apex help. PM me ONLY if the matter is of a private or personal nature. Thanks.

  17. #17
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    Quote Originally Posted by RussM View Post
    I doubt that a support tech specifically said that you can use refractometer calibration solution. You might want to review that helpdesk ticket.
    Here is the copy of the support ticket :

    Hi Victor,
    Unfortunately I ran out of your connectivity solution. Can I use Pinpoint brand I do have that available? If not is there anything else I can do in the meantime?
    Thanks
    Show quoted text






    Hi ,


    Is it 53mS Solution? If yes, then yes



    Please let us know if you have any other questions, or need any additional clarification.


    Please Reference Ticket: http://support.neptunesystems.com/helpdesk/tickets/



    Thank you,


    Neptune Systems Support Team

    -------------------------------------

    Victor Loeza Jr
    Agent, Technical Support
    T: 408-779-4090

    Neptune Systems







  18. #18
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    This is also a quote for the BRS website :

    PINPOINT Salinity Calibration Fluid is 53.0 mS standardized fluid for calibrating PINPOINT Salinity Monitors as well as refractometers. PINPOINT Salinity Calibration Fluid calibrates to sg 1.026 or 35ppt.

  19. #19
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    Here is a troubleshooting tip from Neptune support which fixed my probe readings by resetting the PM2 :

    Follow the steps. You're basically failing the test on purpose first so it resets it to defaults. then you're basically doing it all over again to calibrate with default settings. Steps here.





    Follow the steps below and send us your results.


    1. Remove the Cond Probe from your PM2.
    2. Remove the temp probe from your PM2. (If ANY)
    3. Then go through the calibration again.
    4. Aquacontroller Display : SETUP> COND SETUP
    5. Set the Temp Comp to 0.0.
    6. Click on COND CALIBRATE
    7. Fail purposefully (GO THROUGH THE MENUS RAPIDLY).
    8. It will reset to Defaults by clicking on SAVE, OK, SAVE, Etc.
    9. Now Plug the Cond probe into your PM2
    10. Now go to SETUP> COND SETUP> COND RANGE > SALINITY



    Make sure the cond probe is plugged all the way in. Go to SETUP> COND SETUP> COND CALIBRATE.


    1. It will say 'Dry Settling' This is the Dry Phase. Hold the cond probe out in the air for a minute and wait 1 minute. Then click OK
    2. Now select your solution. use the up and down arrows to select 53000 then click OK
    3. Then place the cond probe in the bag of solution. Keep it there for about 2 minutes then press OK.
    4. It'll save and bring you back out to the menu. Click HOME and you're all done.
    5. Keep the probe in the bag of solution and what does the cond probe read? It should read 34.9 or 35 ish.


    If it read 34.9-35.0 in the solution the probe is capable of reading accurately and is operating.

  20. #20
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    I am really confused by this probe. I purchased a 2016 Apex and calibrated it out of the box according to the initial instructions. After calibration, it immediately read ~35ppt no problem, only to drop to 20ppt over night. I heard this take time to break in sometimes so I let it go, it then crept up slowly over the course of the week to around 38ppt. I then ordered more calibration solution and followed the exact methodology from the BRS video. I thoroughly dried the probe over night. When reconnecting it, I routed its wire in a completely separate path from everything else (on the opposite side of my stand), to eliminate any possible interference... I floated my solution in the same water source as my temp probe. I set the temp compenstation to 2.2. I then did the manual calibration. I put the probe in the water and it read around 34ppt, which seemed about right based on my SG and temperature. Great. But then it crept down again below 32 and I started getting notifications. Last night, I decided to try moving the probe to a new location in the sump. It was in the return chamber, so I put it between my baffles where I get good flow but no turbulence or bubbles. Boom, it went right to 34.2 which is dead-accurate. Then I wake up this morning and it's at 32.8 again. There is an ATO on the system, so these fluctuations don't make sense.

    I'm a little disappointed by this probe, and it's a big reason I was willing to shell out the extra cash on the new model. I don't mind if the accuracy is a problem, but I do mind that it can't seem to remain stable. What good is it if I can't even rely on it to stay within a reasonable margin of error so I can set up appropriate notifications?

    Any help would be greatly appreciated.

  21. #21
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    I'm honestly not following how using perfect salinity tank water to calibrate a probe that monitors tank water salinity can be wrong.

    So it measures conductivity. Perhaps the conductivity of perfect 35ppm freshly mixed salt water is not the same as the conductivity of the calibration solution. I'm not monitoring for fluctuations in cal solution, I'm monitoring for deviations from perfect tank water.

    If the consensus is to trust our refractometers, and not the probe, then convince me of a reason calibrating to our refractometer is a bad idea.

  22. #22
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    How do I manually calibrate the conductivity probe?

  23. #23
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    Quote Originally Posted by pranalli View Post
    I am really confused by this probe. I purchased a 2016 Apex and calibrated it out of the box according to the initial instructions. After calibration, it immediately read ~35ppt no problem, only to drop to 20ppt over night. I heard this take time to break in sometimes so I let it go, it then crept up slowly over the course of the week to around 38ppt. I then ordered more calibration solution and followed the exact methodology from the BRS video. I thoroughly dried the probe over night. When reconnecting it, I routed its wire in a completely separate path from everything else (on the opposite side of my stand), to eliminate any possible interference... I floated my solution in the same water source as my temp probe. I set the temp compenstation to 2.2. I then did the manual calibration. I put the probe in the water and it read around 34ppt, which seemed about right based on my SG and temperature. Great. But then it crept down again below 32 and I started getting notifications. Last night, I decided to try moving the probe to a new location in the sump. It was in the return chamber, so I put it between my baffles where I get good flow but no turbulence or bubbles. Boom, it went right to 34.2 which is dead-accurate. Then I wake up this morning and it's at 32.8 again. There is an ATO on the system, so these fluctuations don't make sense.

    I'm a little disappointed by this probe, and it's a big reason I was willing to shell out the extra cash on the new model. I don't mind if the accuracy is a problem, but I do mind that it can't seem to remain stable. What good is it if I can't even rely on it to stay within a reasonable margin of error so I can set up appropriate notifications?

    Any help would be greatly appreciated.
    Sounds to me like you are getting air bubbles deep inside the probe. I have to turn my probe upside down while still under water to release all of the air about once or twice a month in order to maintain a stable reading.


    Sent from my iPhone using Tapatalk

  24. #24
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    Quote Originally Posted by c.kenney1989 View Post
    Sounds to me like you are getting air bubbles deep inside the probe. I have to turn my probe upside down while still under water to release all of the air about once or twice a month in order to maintain a stable reading.


    Sent from my iPhone using Tapatalk
    That's fine if you don't have to then take the probe back out of the water to insert it into a probe holder. This Salinity probe issue is ridiculous and Neptune should step up and address it. I have just wasted 4 more packs of calibration solution and countless hours of my time only to get garbage readings again in the mid 40's. I have tested my water with both my Milwaukee MA877 as well as my Red Sea refractometer and my salinity is 35ppt. I have tried everything that has already been discussed in this thread and others as well as following the steps from the BRS video and still no luck. I am beyond upset right now. If there was another decent controller option out there I would buy it.

  25. #25
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    When manually calibration what should the probe settle at when dry and then when in the solution?


    Sent from my iPhone using Tapatalk

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