SL 78-1994 "Determination of conductivity (ConductivityMeter method) " standard details the method of using ConductivityMeter to measure conductivity in water. The standard applies to the conductivity measurement of natural water samples, and points out the influence of possible interfering substances such as suspended solids, oils and greases in the sample on the measurement results. Methods to eliminate interference such as filtrate and extraction are proposed. The principle of the method is based on Ohm's law. The conductivity is calculated by measuring the resistance between electrodes in electrolysis solution. ConductivityMeter and thermostatic equipment with Accuracy not exceeding 1% are required to ensure the accuracy and repeatability of the measurement.