Does anyone have the formula to convert microseimens to TDS. I can approximate it but never saw the actual formula.

Take a look at this web site. http://www.sensorex.com/support/education/conductivity_education.html
Hope this helps

You could also try onlineconversion.com

Not all TDS meters are the same. It depends on if your TDS meter is TDS as NaCl, KCl, CaCO3, or 442. Each chemical has a different curve.

Rule of thumb: Conductivity = TDS x 2

This is pretty close for ppm of KCl and CaCO3 (49-50 ppm TDS = 100 conductivity). It is a little high for NaCl (~47 ppm TDS = 100 conductivity). And is a little low for 442 (~62 ppm TDS = 100 conductivity).

The calibration solution you use should list the ppm value, which solution the calibration solution is made of (KCl, NaCl, CaCO3, 442), and the corresponding conductivity value. If you need exact numbers, let me know. I will post something on my website (I can not attach a file to this reply).

Florian,
If you could post it that would be great. My wife (she is a hospital biomed) is in charge of the acutes and there is some discrepancy between the calculated values between the HYDRA,MyronL ,90DX and the Ameriwater RO. My call is just to compare apples to apples and not use so many different meters, but!!
Thanks

Well TechManager. I tried to reply to tell you that I posted the documents on my website. But, RenalWeb wont let me post my website to tell you where to find them without paying an advertising fee. So, its on my website, in the Dialysis section, and then click on Dialysis Water issues. You will see 2 documents (one graph and one table) labeled Water Conductivity vs TDS. I hope you can find it.

Also, HM Digital has a conductivity probe that will display conductivity in uS/cm, TDS in ppm NaCl, TDS in ppm KCl, and TDS in ppm 442...4 measurements in one probe...and it is only $72. You can find it at http://www.wet-international.com/products_ind.asp?itemI...t=WATER+CONDITIONING

You can use one probe to compare to all of your other instruments.

This might help in answering some questions...


http://www.lenntech.com/unit-conversion-calculator/tds_engels.htm