Re: Boiler TDS and Conductivity ?

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Posted by Jenny on April 13, 2000 at 18:14:53:

In Reply to: Boiler TDS and Conductivity ? posted by mike on April 13, 2000 at 08:35:25:

: How does Boiler TDS relate to Conductivity ?
: I know you can't haver conductivity without TDS, or can you ?
: Also, why would you want to check both TDS & conductivity in
: your boiler water ?

: Any help greatly appreciated.

TDS and Conductivity are directly related. When TDS increases Conductivity increases. The reverse is also true. These two, however, are not proportional to each other.
Since conductivity is the opposite (or mathematical inverse) of resistance, the higher the conducitivity the greater the ability for current to flow through the fluid. This is a result of ionic particles dissolved within the fluid or solution. That means that these particles have a charge, positive or negative associated with them. The greater the number of dissolved particles, hence TDS, the greater the conducitivity and this then means a larger current can flow (for a constant voltage source e.g. the battery in the TDS or conducitivity meter) through the solution.
So technically, no, you can't have one without the other.
Now, pure water is highly polar, so I'm not sure that you can't say it acts as a ideal resistor, but for our purposes we will. So then, chemically pure water (nothing but H2O) would have zero TDS and zero conducitivity.
Since I don't have a chart with me that shows values for TDS and conductivity I can only guess right now. I think at say 3500 micromhos
conductivity, TDS (in ppm) is lower. I measure boiler water TDS by measuring the conducivity and relating the two. I've done it so long that now I only work with conductivity and know where the numbers should be. I perform other seperate tests in ppm. It's just what I do. Other people measure boiler water in ppm.
There is no need to measure TDS and then turn around and measure conductivity since they tell you the same thing. The funny thing is, if you use a meter to measure TDS how do you think its actually measuring the TDS?

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