An electrode module for use in a diagnostic card for sensing at least one component concentration in a fluid sample, comprising: a substantially planar insulation layer; and a substantially planar metal conductor layer laminated to the insulator layer; the electrode module having a centrally located sensing region, a peripherally located contacting region and an intermediate heating region, the insulator layer in the sensing region having a number of throughgoing apertures (104A, 104B), a sensor membrane (105A, 105B) in each aperture for contact with the sample and for electrical contact with the conductor layer, characterized in that the conductor layer being divided into a corresponding number of conductor elements and a heater contact element (134A, 134B), each conductor element including a conductor path (133A, 133B) having a sensor end (132A, 132B) and an opposite contact pad end (131A, 131B), the sensor ends (132A, 132B) being located in the sensing region of the module and below one of the apertures respectively and the contact pad ends being located in the contact region, the heater contact element (134A, 134B) being electrically insulated from the conductor elements and surrounding the sensing region in the heating region, the heater contact element (134A, 134B) positioned in a connecting gap extending between the sensing and contact regions and the conductor paths extending through the connecting gap, wherein the conductor paths are tortuously long to reduce thermal conduction along the conductor paths, and wherein the conductor paths (133A, 133B) of the electrode array are long and thin to minimize lateral heat transport along such paths when the module is heated. a substantially planar insulation layer; and a substantially planar metal conductor layer laminated to the insulator layer; the electrode module having a centrally located sensing region, a peripherally located contacting region and an intermediate heating region, the insulator layer in the sensing region having a number of throughgoing apertures (104A, 104B), a sensor membrane (105A, 105B) in each aperture for contact with the sample and for electrical contact with the conductor layer, characterized in that the conductor layer being divided into a corresponding number of conductor elements and a heater contact element (134A, 134B), each conductor element including a conductor path (133A, 133B) having a sensor end (132A, 132B) and an opposite contact pad end (131A, 131B), the sensor ends (132A, 132B) being located in the sensing region of the module and below one of the apertures respectively and the contact pad ends being located in the contact region, the heater contact element (134A, 134B) being electrically insulated from the conductor elements and surrounding the sensing region in the heating region, the heater contact element (134A, 134B) positioned in a connecting gap extending between the sensing and contact regions and the conductor paths extending through the connecting gap, wherein the conductor paths are tortuously long to reduce thermal conduction along the conductor paths, and wherein the conductor paths (133A, 133B) of the electrode array are long and thin to minimize lateral heat transport along such paths when the module is heated.