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Thread: Salinity Probe in Close loop system reading inaccurate?

  1. #1
    Regular Vistor
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    Feb 2017
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    Malaysia
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    Question Salinity Probe in Close loop system reading inaccurate?

    Hi all. I installed my pH, ORP, and Cond probes in what are called straight-through cord-grip fittings in a PVC assembly where they sample water inside filter tubing. Just to share my experience with salinity probe reading.

    My current tank salinity reading is 30.50 ppt. (Yes it's a little low as my previous salinity refractometer was giving me inaccurate reading). As for this reading 30.50 i am sure it's accurate coz i measure it with Milwalkee Digital Refractory MA887 as well as the neptune apex as reading 30.40 ppt while i place the salinity probe in the sump area.

    The problem is when i put back the probe into pvc probe holder the reading changed to 44.00 ppt, previously i thought maybe there was some air bubble stucks in the pvc prove due to a restart in the probe pump which also pump water to 2 of my reactor. Then i took out the probe and put back into the water and then the reading goes back to 30 ppt which is accurate. I have tested this FOUR TIMES in total and get almost exactly 44 ppt whenever i put the probe into the pvb probe holder. I think the problem is not caused by air bubbles on the probe coz if that's the case i shouldn't be getting a consistence 44ppt everytime. Does anyone have any idea why is that so? Could it be the water flow in the pvc pipe causing an inaccurate reading to the conductivity probe? Because i have ORP & PH prove in the same area where i believe the reading is pretty accurate.

    Just hope to share the experience with others and hopefully get to find out an answer to this problem. Thank you in advance.


    BTW just for sharing.. for those who can't calibrate the cond probe accurately. I followed this video and managed to get a very accurate reading. You can check out the vids here at
    https://www.youtube.com/watch?v=6pxUb2-LaEo&t=168s . And also i use the neptune calibration fluid as i have tried other calibration fluid produce inaccurate reading.

    Salinity1.jpgSalinity2.jpg

  2. #2
    NSI Member
    Join Date
    Oct 2013
    Location
    Oxnard Ca
    Posts
    319
    I would guess that it has a lot to do with orientation and high flow through the plumbing.

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