The extent of fouling of a spiral wound membrane module such as used in water treatment plants can be monitored using one or more sensors disposed between wraps of the membrane. The sensors, including electrodes, can communicate signals to a two-part computing device. A first part is located inside the pressure vessel in which the membrane module is disposed. The first part provides input signals and power to the sensors and receives sensor signals. A second part is located on the outside of the pressure vessel and communicates power to the first part via inductive coupling. The second part wirelessly receives the sensor signals from the first part and processes the signals to determine the extent of fouling of the membrane module.