water hardness tester

[TimWilborne]

Key points:
Total dissolved solids (TDS) refers to a measure of all inorganic solids dissolved in the water. This means that it will measure ions that contribute to water hardness, tike calcium, but also those that do not, like sodium.

While conductivity is a convenient way to get an approximation of the hardness of water it does have the drawback of combining all ions in the measurement, including those that do not contribute to the water’s hardness.

http://www.globalw.com/support/hardness.html

Dan

I started to ask earlier before I realized how old the thread was...

Most ROs I've worked with use conductivity sensors to determine water quality, but they are water supplies for various industrial processes.

Are the TDS sensors mainly used for drinking water or what are some examples of when TDS sensors would be used in place of conductivity sensors?

Thanks
TW

 

[danw]

I can't answer your question about TDS vs conductivity. I've only dealt with conductivity, never TDS. HACH is a major player in the water instrumentation and their applications table from their glossy brochure for Power Generation lists both contacting and non-contact (presumably toroidal) conductivity instruments as their TDS instrument.

I suspect that TDS is just a calculation on conductivity. But the industrial conductivity meters that I've used have not had a TDS calculation.

Interestingly enough, HACH has what appears to be an industrial strength hardness instrument:

Dan

 

[the_msp]

We have a RO & polisher plant (DSS) where I work. It uses a conductivity meter. I will post the model number on monday...

 

[the_msp]

Apologies for the delay;

We use a Mettler Toledo probe and transmitter;

Transmitter - conductivity 7100e, price = 1723 Euros
Cable - price = 148 Euros
Sensor - INPro7002/1,2"TC-VP 3.1B, price = 1713 Euros

 

[rta53]

The original poster of this message wanted to know about instrumentation that would measure hardness and give an output. I hope she was able to get an answer somewhere else because none of the answers she was given here were correct. She wanted to know hardness and not TDS. While they are related they are not the same. The Hach SP510 is basically a setpoint switch that trips when hardness rises above the level of the reagents. It does not provide an analog output. Hardness instrumentation that actually gives a hardness reading and an analog output is very expensive. We're talking $9000.