Abstract: A measuring cell for measuring electrical conductivity of liquids having a bore which in operation is contacted by a liquid, the conductivity of which is to be measured and a plurality of electrodes spaced along the bore and forming part of the bore surface, the electrodes being of coaxial annular form and including a first and a fourth electrode which constitute current electrodes for connection to a controllable AC current supply, a second and third electrode between the current electrodes and constituting voltage electrodes for connection to a high input impedance amplifier provided with means for employing the amplifier output to control the AC current supply to maintain sensibly constant the voltage at the voltage electrodes and a fifth electrode of annular form coaxial with the first to fourth electrodes and for connection to the first electrode by way of a buffer amplifier presenting a high impedance to the first electrode and a low impedance to the fifth electrode and located on the side of the first