Using a conductivity sensor to determine TDS - The Planted Tank Forum
 
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post #1 of 3 (permalink) Old 02-17-2014, 03:24 AM Thread Starter
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Using a conductivity sensor to determine TDS

Good evening!

I have been thinking this over and it occurred to me that TDS is measured the same way salinity is via electric current to determine the amount of charged ions.

Now I have a conductivity meter that reads in us/cm. By doing some research it seems I should multiply this number by .67-.70 in freshwater to determine TDS (or 0.50 in saltwater).

I'm getting this info per this page: http://appslabs.com.au/salinity.htm

Am I right here? Or does a standard TDS meter not take a conductivity value and multiply it by this range?
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post #2 of 3 (permalink) Old 02-17-2014, 04:06 AM
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I am not sure how the TDS meter creates its read out, but you are right, it is testing for charged particles and we are pretending that this is all the dissolved solids. I remember reading somewhere that most TDS meters convert their test into a number that is the equivalent of all salt in the water, not a mix of ions.

I wonder if it is really important exactly what it is measuring?
The way I use test results is that I am comparing today's readings with the test results from last week, and the weeks before. If there are changing results, then I look further to see what is happening.

Do you have a TDS meter that you could compare the two sets of readings and see exactly how they are related?
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post #3 of 3 (permalink) Old 02-17-2014, 04:19 AM
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TDS meters ARE conductivity meters, just with the conversion factor added.


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