An analyte sensor apparatus for implantation within a mammal, the analyte sensor apparatus comprising: an elongated base layer; a conductive layer disposed on the base layer and defining a plurality of working electrodes, counter electrodes and reference electrodes grouped together and positionally distributed within the conductive layer in a repeating pattern of units, each unit consisting of a working electrode, a counter electrode and a reference electrode; an analyte sensing layer disposed on the conductive layer; an analyte modulating layer disposed on the analyte sensing layer, wherein the analyte modulating layer comprises a composition that modulates the diffusion of an analyte diffusing through the analyte modulating layer; and a cover layer having an aperture so as to facilitate an analyte present in the mammal contacting and diffusing through the analyte modulating layer and contacting the analyte sensing layer; characterised in that: the electrodes are grouped in the units so that a first electrode in each unit is parallel to and disposed in a region proximal to a first edge of the elongated base layer; a second electrode in each unit is parallel to and disposed in a region proximal to an opposite edge of the elongated base layer; and a third electrode in each unit is disposed in a region of the elongated base layer that is between the first electrode and the second electrode; the electrodes are of a rectangular shape with their longer sides parallel to each other. an elongated base layer; a conductive layer disposed on the base layer and defining a plurality of working electrodes, counter electrodes and reference electrodes grouped together and positionally distributed within the conductive layer in a repeating pattern of units, each unit consisting of a working electrode, a counter electrode and a reference electrode; an analyte sensing layer disposed on the conductive layer; an analyte modulating layer disposed on the analyte sensing layer, wherein the analyte modulating layer comprises a composition that modulates the diffusion of an analyte diffusing through the analyte modulating layer; and a cover layer having an aperture so as to facilitate an analyte present in the mammal contacting and diffusing through the analyte modulating layer and contacting the analyte sensing layer; characterised in that: the electrodes are grouped in the units so that a first electrode in each unit is parallel to and disposed in a region proximal to a first edge of the elongated base layer; a second electrode in each unit is parallel to and disposed in a region proximal to an opposite edge of the elongated base layer; and a third electrode in each unit is disposed in a region of the elongated base layer that is between the first electrode and the second electrode; the electrodes are of a rectangular shape with their longer sides parallel to each other. the electrodes are grouped in the units so that a first electrode in each unit is parallel to and disposed in a region proximal to a first edge of the elongated base layer; a second electrode in each unit is parallel to and disposed in a region proximal to an opposite edge of the elongated base layer; and a third electrode in each unit is disposed in a region of the elongated base layer that is between the first electrode and the second electrode; the electrodes are of a rectangular shape with their longer sides parallel to each other.