In one aspect the present disclosure relates to a sensor for measuring at least one physical or chemical parameter of a cartridge filled with a liquid substance. In a further aspect the disclosure relates to a drug delivery device equipped with such a sensor, wherein the sensor includes a planar flexible foil having a first section and having a second section separated from the first section, at least one measurement electrode located on the flexible foil, wherein the flexible foil is wrappable into a wrapped configuration in which the foil forms at least a first wrap with an inner diameter that is equal to or larger than an outer diameter of the cartridge, wherein in the wrapped configuration the first section and the second section at least partially overlap, at least one fastener located in one of the first and second section and configured to attach to the other one of the first and second sections for keeping the flexible foil in the wrapped configuration.