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Thread: Cond Probe

  1. #1
    Regular Vistor
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    Cond Probe

    Since installation, my conductivity probe has been reading hi between 42-43. I have recalibrated the probe a few times and made sure all bubbles are out. I reached out to the neptune support and they informed me that if my probe cables run next to power cables for any other equipment in the sump (I.e. skimmer, heater) it will throw off the reading. Considering that most aquarium setups are tight and people like to have their setups neat and tighty I find this a little had to understand. Has anyone else encountered this problem or heard of this?

  2. #2
    Frequent Contributor zombie's Avatar
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    That is a concern, but that likely isn't your problem. I would seperate it anyway but the main source of the error is probably temp error. One thing not stated clearly in the manual and often overlooked by support is that the calibration packet must exactly match tank temp during calibration or it can skew the reading by up to 10 ppt. What I do to achieve this is float the packet for 30 minutes in my sump. Lightly rinse off the probe in RODI and pat dry with a paper towel. Complete the dry step. Then open the top of the packet and use two magnets to hold it so the probe can go in but still touches tank water. Then let settle for 5 minutes for the wet step and hit complete (always manual calibration never auto).

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

  3. #3
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    Thank you, I will definitely try that. I know for a fact when I calibrated I did not have the packets at tank temp.

  4. #4
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    For example on the power cord interference. The week before last my previously steady reading started to gradually go down from 35 to 33 over the course of 7 days. At first I thought I might have a water leak but was unable to find one. Then during my weekend maintenance I noticed the power cord for my DC return pump was lying across the cord to my conductivity probe. I moved it and the readings went back to normal and are once again steady.

  5. #5
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    After neptune support recommended to relocate my cables, I did a test to see if I was receiving interference. I unplugged my return pump, skimmer and heater for an hour and saw no change my my results. Although I am currently working on a scheme of redesign for my sump cabinet and wire routing. I am not sure that the electric current could be the cause. I also literally just noticed when I was down in my cabinet planning, that my display has randomly dropped from 43.5 ppt to 32.5 ppt without me doing anything. I got excited so I tested the water with my refractometer and it’s at 35 ppt as normal. I know that the refractometer has some degree of error but could it be that much?

  6. #6
    Frequent Contributor zombie's Avatar
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    That random rapid change is probably bubbles in the cond probe. I would do a proper temp adjusted recalibration before changing water parameters.

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

  7. #7
    Regular Vistor
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    I ordered more calibrating solution, once it comes I will do a recalibration test as you described before. Hopefully it will correct the problem. Thank you guys for all the help.

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