measuring water quality with Arduino (and Hydroponic)

Hi

I have monitoring system based on Arduino and Raspberry pi which I use to log data in various projects. mainly for schools.
I want to see if I can use simple Arduino code to create a tool for the children to explore and research quality of water in various locations.
The issue I look at now is conductivity, and I also have this sensor sensor
I have played with their code and with this public domain one
And I have looked at this page
I have made several readings (and accuracy is still not the issue)
Source Analog read Volt Microsiemens
Distilled 2 0.01 0.2
Tap 46 0.22 3.96
Fertilized 641 3.13 298.44

Ignoring currently the temperature

What I read does not fit with the table in
http://www.mbhes.com/conductivity_measurement.htm
Or I misunderstood
WHat I want to have at the end is Arduino with DIY sensor and temperature sensor and then we wil compare readings in class

rsegoly:
Hi

I have monitoring system based on Arduino and Raspberry pi which I use to log data in various projects. mainly for schools.
I want to see if I can use simple Arduino code to create a tool for the children to explore and research quality of water in various locations.
The issue I look at now is conductivity, and I also have this sensor sensor
I have played with their code and with this public domain one
And I have looked at this page
I have made several readings (and accuracy is still not the issue)
Source Analog read Volt Microsiemens
Distilled 2 0.01 0.2
Tap 46 0.22 3.96
Fertilized 641 3.13 298.44

Ignoring currently the temperature

What I read does not fit with the table in
http://www.mbhes.com/conductivity_measurement.htm
Or I misunderstood
WHat I want to have at the end is Arduino with DIY sensor and temperature sensor and then we wil compare readings in class

You have to have the temperature sensor connected, the MicroSiemens value needs the TempCoefficient.

 float CoefficientVolatge=(float)averageVoltage/TempCoefficient;

Chuck.

I understand the importance of temperature compensation but does the above measure values make sense?

rsegoly:
I understand the importance of temperature compensation but does the above measure values make sense?

Yes, Ignore the MicroSiemens Value, without callibration and Temperature compensations the MicroSiemens Value is useless.

The reference page for the Sensor show a value of

analog value: 43 and voltage of 209mV

Your example is 46 and 220mV

pretty close, until you calibrate the sensor and provide the temperature compensation the MicroSiemens Value is useless.

chuck.

Chuck
Which reference page?

rsegoly:
Chuck
Which reference page?

chuck.

LOL
This is the code I used
I have a place in Israel who want to use my system but they claimed they have level of 500 Siemens while my sensor showed something tlke 11.XXX SO i thought I am off track
I will be there today and see what actually they measure with their standalone sensorf

they were measuring PPM

If I have two different sensors from different vendors, they will have different readings because of size of electrode distance etc. Am I right?
So the code to use will always be unique for specific electrode or is just calibration?