HYDROMETER- To Measure Sea Water Salinity Levels

[Jumper]

Hi,

What will change with the salinity level? Is it the OHM or the Capacitance or any other physical factor?

What level of accuraccy and resolution are you looking for? Maybe you can start by providing the formulas for how the theory behind salinity and the factor you wish to measure.

How much will oxidation of the probes influence the value?
How will the water level on the probes influence?
Does temperature affect the physical factors?

Interesting project but I am not sure you can find a simple answer here without giving alot more background information about the theories behind this.

But if I have a deep look into the crystal ball I would say that a 12-bit ADC could be worth looking into, the 887 pic only has 10-bit.

[amgen]

Best Answer - Chosen by Asker

The average conductivity of sea water at 20degC and a salinity of 35g/kg is:
4.788 S/m (Siemens/meter)
http://www.kayelaby.npl.co.uk/general_ph…

The resistance is the reciprocal of the conductance, so:
R = 1/(4.788 S/m) = 0.2089 ohm/m <===ANSWER
at 20 degC and a salinity of 35g salt per kg water.

If you place two probes 1 meter apart in seawater under the stated conditions, the resistance will be 0.2089 ohm, according to the calculation and published conductance data.

• 10 months ago
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Asker's Rating:Asker's Commenterfect answer!
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looks like the readings move to the milliOhms once the water has some salt introduced, so you would have to work with op-amps to detect small changes in a certain range. Also mabye a reference to calculate from...such as .35 Ohms(some a/d reading) equals 200 PPM,parts/million.

that link seems broken, just a search for conductivity of salt water.

[Jumper]

http://www.reefcentral.com/forums/sh....php?t=1812946

So you might want to look at a AC solution.