Conductivity can be used to compare the relative overall nutrient concentration of different brands, and to roughly verify the concentration claim made on the label.  This is done by measuring the conductivity value of the nutrient when diluted 100 fold (10ml into 1,000ml) with distilled water.  Hence, add the following volumes to 1,000ml of distilled water:

+  1-parts:  10ml of nutrient.

+  2-parts:  5ml of part ‘A’ + 5ml of part ‘B’.

+  3-parts:  Collect 10ml in accordance with the ratio of parts used to achieve a given formulation type e.g. 10ml of ‘bloom’ formulation may be comprised of 4ml part ‘A’ + 4ml part ‘B’ + 2ml part ‘C’.

Typically, the best 2 & 3-parts yield between 2.4 and 2.8mS (cF 24 to 28). Comparably, “slurry” type 1-part’s can far exceed 3.0mS (cF 30) - see Graph 3.2.

However, because the conductivity of different mineral salts varies, this method does contain a degree of error.  The error depends on how much the ratio of nutrient species in the different brands vary from each other, together with the type of mineral salts used.  For example, judging a PK additive against a full spectrum bloom formulation would not be a fair comparison because phosphorus shows relatively low activity with conductivity electrodes and therefore a conductivity measurement would under estimate the PK specification.  However, when comparing solutions of similar nature (e.g. bloom versus bloom), it is probably the easiest and quickest way of obtaining a good estimate of relative nutrient concentration.