Conductivity vs Digital Refractometer vs ATI Results

KenO

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I have 2 setups a 60 gallon cube and my main setup which consists of a 250 gallon and a 130 gallon both plumbed into a sump (~150 gallon) and 2 - 40 gallon breeder tanks plumbed into the same sump. When I sent in my water samples to ATI both showed low Salinity; Main Setup: 32.32 PSU and 60 Cube: 32.71 PSU. Below is the results for the Main Setup. I can post the 60 Cube if needed.

ATI Results Main Setup:
Tank 1.png


GHL P4 Conductivity Reading at the time I collected the water sample to ship. Reading was 49.5ms


IMG_2548.png

Conversion Table
PPT Conversion.png


So I am using a Milwaukee MA887 Digital Seawater Refractometer which was showing a reading of 1.026 at the time I collected the sample.

So what I am trying to determine what my SG, PPT, PSU or ms level really is. Looking at the data above I would say the ATI results and the conductivity meter look really close.

Here is what I have done. I took a sample of my water to a friend's place. Now he has a brand new Hanna Digital refractometer. We calibrated it with the 35ppt solution that came with the meter. It showed my water to be at 1.024 ok so low. Seems to agree with the data above. When I got home I tested my water and the Milwaukee showed 1.026. So I calibrated it using my RO/DI water and took a reading. The Milwaukee meter showed 1.028. Ok the level went up vs down as expected. So I'm suspecting my Milwaukee meter is off. So I made up a solution as per Randy's recipe using the Morton salt. 3.65 grams of salt and 96.35 grams of RO/DI water. I didn't take a picture of the water when I measured it but I did take a picture of the salt on the scale. I measured the sample and got 1.027. Which is within the error range of the meter which is .002. So based on the DIY solution my meter doesn't look to be that far off? I'm not sure.

IMG_2539.jpeg


So I decided to recalibrate my conductivity probes on both of my GHL P4's. I let the bottle of the 50ms solution sit in the tank water for a couple of hours and did the calibration. I have 2 - P4's on different tanks and recalibrated the other conductivity probe after letting the solution sit for an hour in that tank. One tank runs at 78.2 degrees and the other around 79 degrees. Both calibrated without an issue.

So here is where I need some help. I took the DIY solution I used to test the Milwaukee meter and I have a packet of Neptune's 53ms solution. I placed both of them in the sump to temp acclimate. The DIY solution I made per Randy's recipe, can that be used to test the conductivity probe? I suspect not since when I put the conductivity probe in the DIY solution it jumped to around 57ms. I rinsed off the probe and tested the 53ms solution. It registered 53ms on the P4. I then took the Neptune conductivity solution and let it temp acclimate on my other setup and it too read 53ms. Based on this data, I feel the conductivity probes on the P4's seem pretty accurate.

So at this point I am suspecting my salinity level in the tanks are low. I previously had a Neptune Apex and didn't trust the conductivity probe since I couldn't ever get it to calibrate correctly. The GHL conductivity probe has a different design vs the Apex conductivity. Based on the testing, I am suspecting the conductivity probe on the GHL P4 seems to be more accurate. So I had started to raise my salinity slowly. So anybody else out there have input based on this data or their own data? It is confusing since the Milwaukee meter with the Randy DIY solution seems to be close. One thing I still need to check is to make sure the GHL temp probes on the both setups are displaying the temp correctly.

Thoughts and/or inputs? Let me know.
 

GoVols

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Thought:

The Milwaukee has been known to read about .2 off for a pretty good while.
You can't calibrate to .35, you zero it out with RO/DI.

We had a discussion about it on Randy forum some years back.

The Vee Gee STX-3 is what I use, and Randy gives the Pinpoint conducive meter high regards.
 
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KenO

KenO

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Thought:

The Milwaukee has been known to read about .2 off for a pretty good while.
You can't calibrate to .35, you zero it out with RO/DI.

We had a discussion about it on Randy forum some years back.

The Vee Gee STX-3 is what I use, and Randy gives the Pinpoint conducive meter high regards.
Yes you have to use RO/DI water to calibrate it. I was using the diy solution to test accuracy, which I’ve done over the years using Randy’s diy recipe. The meter had been working well for years. I’ve had it now for 7-8 years, and it’s been reliable for me up to now. Like all of us as we get old our calibration drifts lol. I will most likely get a conductivity meter going forward. I will look at the one Randy likes.
 
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