EC / TDS Readers

[LiveRockRob]

Hi All,

I just received my COM-100 reader to test my RO/DI water. I haven't accuired the RO/DI unit yet, but I would like to test TDS / EC of my tap watter against what britta is filtering.

I also purchased a "calibration standard" - jar with solution that states 1000ppm, but it also has values for alternative metods written down.

Ok, my question is that within the manual you are able to switch it over from the following modes:

A. EC with KCI temp coefficient
B. EC with 442 temp coefficient
C. EC with NaCI temp coefficient

D. TDS with KCI conversion factor and temp coefficient
E. TDS with 442 conversion factor and temp coefficient
F. TDS with NaCI conversion factor and temp coefficient

Q1
What is the prefered mode for EC?
Q2
What is the prefered mode for TDS?
Q3
The manual states that one should use calibration standard that is in range of the values you are measuring. Since I think the values will be up to 500ppm for tap and 0 for RO/DI, should I buy a new calibration standard and not use the 1000ppm?

Thanks for the help.

LiveRockRob