salinity dilemma

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#1
The new Apex salinity probe says salt is high, my old swing arm says it is low... who to believe. Been using the swing arm for years. Ordered a refractometer..

Ug.
 
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#3
I use the tropic marin hydrometer to double check my hanna salinity meter sometimes.
 
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#4
I forgot the technicalities behind it but you have be careful to make sure you choose the right refractometer. I was told to use Red Sea's Seawater refractometer for this reason.
 
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#5
Actually the swing arm one can be suprisingly accurate and consistent if you rinse with fresh water to prevent salt build up for stoping it from swing freely. I would trust it over the prob as they are known to be problematic.
 

reefsUP2

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#6
Keep them maintained but always have something on hand to make sure it’s calibration is correct
 
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#7
The refractometer arrived today as well as the calibration solution, verified the refractometer read the same as the calibration solution. Calibrated the apex probe, then tested it in the same solution a few minutes later for the desired reading. Cool, threw it in the tank which I know was low, both the swing arm and refractometer read surprisingly close, 1.021 vs. 1.020.

Throw the probe in and it reads 1.035, wft. recalibrate again, still reads high. Off to the internet to do some research. Two things

1. Probe is sensitive to bubbles (knew that) AND probe is sensitive to electrical. The probe line was running over a power line

2. Also the calibration solution should be the same temp as the tank, float the calibration fluid in the tank, and then recalibrate.

The probe is now reading exactly the same as the refractometer.

Hope my struggles help someone else.


It is a new tank with no life in it.
 

drexel

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#11
What solution did you use to calibrate the probe? It shouldn't be the same 35ppt solution to test/calibrate a refractometer, it should be a conductivity solution like this. Also, it usually takes conductivity probes a couple days to settle in.
When buying a refractometer, look for one that measures seawater and not a brine solution. Veegee, DD Ocean, etc are all "seawater" refractometers. If you paid $50 or less for yours, it's probably not a good one. Tropic Marin glass hydrometers are great and swing arm hydrometers are horrible at reading proper salinity, as they only measure specific gravity, which is temp based.
Also, we should all be measuring (or referring to) salinity in parts per thousands, 35ppt, not specific gravity, 1.020 etc. Specific gravity is temperature related, thus the reading will actually be different based on your water temp, whereas salinity will always measure properly no matter what the temp is. The glass hydrometers will work better, as they are calibrated (usually) for 77 degrees, so one or two degrees doesn't throw it off much.
 
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#12
53 ms calibration solution, same as the 53,000 uMS from Neptune people. I'm not sure I understand why wouldn't want to use the same for both, if the solution matches the Neptune and gives me the expected reading. I didn't calibrate the refractometer, only validated it gave me the expected reading from the calibration solution.
 

drexel

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#15
53 ms calibration solution, same as the 53,000 uMS from Neptune people. I'm not sure I understand why wouldn't want to use the same for both, if the solution matches the Neptune and gives me the expected reading. I didn't calibrate the refractometer, only validated it gave me the expected reading from the calibration solution.
Solution for a conductivity probe is completely different than a solution for a refractometer. You can’t use one for the other, it doesn’t work that way.


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