Ran across a thread on this forum from August 2005 and haven't figured out how to make a reply in it yet. I also searched long for a direct relationship between Salinity and Conductivity to no avail, and finally worked out the relationship myself with less than 100% confidence in the result. 90% plus maybe, but would appreciate critical comment. An Excel spreadsheet can be downloaded (110KBytes) at:
http://www.sensordev.com/PSU_vs_Conductivity.xls
The bulk of the sheet is just to illustrate how the relationship was determined. There's a small calculator at the left middle that will crank out values across the range of 2 to 42 PSU (practical salinity units, a unitless number, go figure). Note also that it's based on comparison with a KCl standard solution, which is part of what bothers me. KCl and NaCl do not have the same conductivity vs. concentration curves, nor the same response to temperature changes. My unconfirmed hope is that the folks who derived the PSU scale based their results on empirical measurements of the KCl standard ratios with NaCl dominated seawater, which I believe would get around the differences.
http://www.sensordev.com/PSU_vs_Conductivity.xls
The bulk of the sheet is just to illustrate how the relationship was determined. There's a small calculator at the left middle that will crank out values across the range of 2 to 42 PSU (practical salinity units, a unitless number, go figure). Note also that it's based on comparison with a KCl standard solution, which is part of what bothers me. KCl and NaCl do not have the same conductivity vs. concentration curves, nor the same response to temperature changes. My unconfirmed hope is that the folks who derived the PSU scale based their results on empirical measurements of the KCl standard ratios with NaCl dominated seawater, which I believe would get around the differences.
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