S.G and Salinity
- Thread starter ColinAbi
- Start date
ColinAbi
Hola
Ok thanks.
Not a big deal, but "Typical Surface Ocean Value" of NSW is "34-36 ppt salinity; sg = 1.025-1.027."
http://reefkeeping.com/issues/2004-05/rhf/
So if you're digital refractometer shows 32-33 ppt but your hydrometer reads SG of 1.025, one of them is off.
Again, not a big deal, but with non-digital refractometer, you can get .35 ppm salinity calibration fluid to make sure refractometer is accurate. Since non-digital refractometer is almost as easy to use as a hydrometer, and you can check the refractometer's accuracy as often as you like for a few cents a pop, not sure why anyone would opt for digital refractometer or hydrometer? But to each his own.
Oh, and if anyone is thing of getting a non-digital refractometer, bee-vare, bee-vare the Red Sea refractometer. IME, it has to be recalibrated after each and every use -- otherwise, it shows readings off by 4 to 6 ppm salinity.
Ta,
Mike
http://reefkeeping.com/issues/2004-05/rhf/
So if you're digital refractometer shows 32-33 ppt but your hydrometer reads SG of 1.025, one of them is off.
Again, not a big deal, but with non-digital refractometer, you can get .35 ppm salinity calibration fluid to make sure refractometer is accurate. Since non-digital refractometer is almost as easy to use as a hydrometer, and you can check the refractometer's accuracy as often as you like for a few cents a pop, not sure why anyone would opt for digital refractometer or hydrometer? But to each his own.
Oh, and if anyone is thing of getting a non-digital refractometer, bee-vare, bee-vare the Red Sea refractometer. IME, it has to be recalibrated after each and every use -- otherwise, it shows readings off by 4 to 6 ppm salinity.
Ta,
Mike
ColinAbi
Hola
Actually, the digital refractometer (milwaukee )reads ppt, SG and one other one I forgot what it was. I recalibrated it with the solution it came with. I press sg and it says 1.025 , I press the ppt and it says 32- 33.
BigJohnny
Active member
SG is dependent on temperature, salinity in ppt is not. Your s.g. can vary with the same ppt reading. You can definitely have 33 ppt 1.025 s.g. since measuring temperature is significantly less than NSW, and rounding is involved. Also 1 ppt is a lot less of a change then .001 s.g. under the same conditions.
I use the same refractometer and shoot for 35 ppt. This ends up reading 1.026 in my house and when I have calibrated my refractometer moments prior in the same room/temperature.
Also make sure you let your calibration fluid and sample sit for 3 mins to get the same temperature as the sensor itself before taking a measurement.
I use the same refractometer and shoot for 35 ppt. This ends up reading 1.026 in my house and when I have calibrated my refractometer moments prior in the same room/temperature.
Also make sure you let your calibration fluid and sample sit for 3 mins to get the same temperature as the sensor itself before taking a measurement.
ColinAbi
Hola
Thanks for the tips. Next time I will let the solution sit .
Great chart, thanks.Here's a chart showing Salinity v SG. It looks to me like your meter is working fine...
JMorris271
New member
PSU Whatever that means
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ColinAbi
Hola
Yep, that's what it was lol.
JMorris271
New member
psu.......Practical Salinity Unit
The Practical Salinity Scale defines salinity in terms of the conductivity ratio of a sample to that of a solution of 32.4356 g of KCl at 15°C in a 1 kg solution. A sample of seawater at 15°C with a conductivity equal to this KCl solution has a salinity of exactly 35 practical salinity units (psu).
as per Google
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JMorris271
New member
dup. sorry
ColinAbi
Hola
Thanks for the explanation, I think if I remember correctly, I was also getting 32-33 for the psu.
Refractive index = "also called index of refraction, measure of the bending of a ray of light when passing from one medium into another. If i is the angle of incidence of a ray in vacuum (angle between the incoming ray and the perpendicular to the surface of a medium, called the normal; see figure) and r is the angle of refraction (angle between the ray in the medium and the normal), the refractive index n is defined as the ratio of the sine of the angle of incidence to the sine of the angle of refraction; i.e., n = sin i / sin r. Refractive index is also equal to the velocity c of light of a given wavelength in empty space divided by its velocity v in a substance, or n = c/v."
http://www.britannica.com/science/refractive-index
"The Practical Salinity Scale defines salinity in terms of the conductivity ratio of a sample to that of a solution of 32.4356 g of KCl at 15°C in a 1 kg solution. A sample of seawater at 15°C with a conductivity equal to this KCl solution has a salinity of exactly 35 practical salinity units (psu).
as per Google "
Post # 11 above.
It's fine if you want to delve into the refractive index and the practical salinity scale to measure the salinity of your water.
But for me, a store-bought refractometer, and calibration fluid, is sufficient.
Just saying,
Mike
http://www.britannica.com/science/refractive-index
"The Practical Salinity Scale defines salinity in terms of the conductivity ratio of a sample to that of a solution of 32.4356 g of KCl at 15°C in a 1 kg solution. A sample of seawater at 15°C with a conductivity equal to this KCl solution has a salinity of exactly 35 practical salinity units (psu).
as per Google "
Post # 11 above.
It's fine if you want to delve into the refractive index and the practical salinity scale to measure the salinity of your water.
But for me, a store-bought refractometer, and calibration fluid, is sufficient.
Just saying,
Mike
JMorris271
New member
Thanks Mike. I feel so much better knowing you feel it's fine.
I use a store bought meter and that fluid as well. myself.
