The invention discloses a seven-
electrode conductivity sensor with a novel structure. In the invention, seven platinized film ring electrodes are arranged at the inner wall of the
honeycomb duct of a conductance
cell up and down; a cylindrical bore penetrating through the duct wall of the
honeycomb duct is arranged in a ring groove at the inner wall of the
honeycomb duct corresponding to each ring
electrode, and the cylindrical bore is internally provided with platinized film inner
layers; the platinized film inner layer at the inner port of the cylindrical bore is connected with the platinized film ring
electrode, and the platinized film inner layer at the outer port of the cylindrical bore forms a thickened platinized film
welding ring; the thickened platinized film
welding ring is welded with one end of a
platinum lead wire at the outside of the honeycomb duct, and the other end of the
platinum lead wire is welded with a
copper conductor which is connected with a
signal conversion circuit in the pressure-proof watertight shell of the sensor; and elastic sealing
grease is casted into the cylindrical bore penetrating through the duct wall of the honeycomb duct, thus the
platinum lead wire is prevented from being directly welded on the
quartz duct wall of the honeycomb duct, the sealing property of the honeycomb duct and the stability of the sensor are improved, and the advantages of high precision, convenient field usage and the like of the sensor are fully expressed.