Microsiemens to PPM

[kevinpo]

Hi Randy,
I have a conductivity solution that is 84 microsiemens @77F/25C. What should it read in PPM? I want to calibrate a low range TDS meter with it.

TIA,
Kevin

[Randy Holmes-Farley]

It is not necessarily a 1:1 correlation. :D

It might be 40.38 ppm or 38.04 ppm or 50.50 ppm depending on how you define ppm. :lol:

For most purposes, you can pick whichever units you like.

This article should help (see Table 2):

What is TDS?
http://www.reefkeeping.com/issues/2004-04/rhf/feature/index.htm

[kevinpo]

The solution is Sodium chloride does that mean the meter should read 38.04 ppm? It is a Hanna meter (0-999 range) and Hanna solution.

Regards,
Kevin
PS: I read the article and now know more but maybe not enough :)

[Randy Holmes-Farley]

No, it makes no difference at all what is in the liquid. It all depends on what standard you choose to use. Like deg F vs deg C.

IOW, saying the water has a conductivity of 84 uS/cm is an unambiguous statement. Saying the water has a TDS of 38 ppm is ambiguous, just as 38 degrees is ambiguous.