The conductivity of a solution depends on the concentration of dissolved ions (and their charge and mobility). pH is the concentration of dissolved hydrogen + ions. So just knowing the pH of a solution is not enough information to make any statements about the conductivity. A strong base has very few hydrogen ions but is still highly conductive due to other ions.
I have tried using a sensor and test on a few solution with different pH value and it seems that it does not have any significant change. I have assume that the sensor is not sensitive to the conductivity.
I tried to do an impedance test on those different solution and it could be seen that that is significant change and I would like to know why and the relation of impedance and pH value.
If I want to test for a given sensor to be only sensitive to impedance, is there other thing I have to test for (e.g conductivity and etc)?
The most sensitive test of the PH is conductivity, the better an insulator the liquid is , the lower the number of free ions are present. We used to test de-ionised water to a level of better then 2 micro-mhos for use in a heat exchanger system (boiling away at a power density of 1 KW/sq cm) , any thing higher caused corrosion due to the water's chemical action due to the free ions.
Frank