The proportioning test liquid can be used to measure induction ratio over a wide range of mixing ratios. The figure below shows the conductivity and a calibration curve for 1%, 3% and 6% solutions in tap water.
Linear regression of the above curve gives an R-value of 0,9995 which is almost identical to a straight line for which the R-value is 1,000. If the linear regression gives an R-value below 0,9800 it is advisable to do new calibration solutions.
The lower mixing ratio limit in this case is about 0,2%.
By using brackish or sea water the resolution will decrease. This must be checked from case to case. By measuring the conductivity of premix solution coming out from a system when released the induction ratio can be calculated by using the above calibration curve. The good R-value will give good precision in the measurement.