Sensor for an alarm device, comprising at least: - a baseplate, - a cover, - a set of electronic components (3, 30) that can and are intended to be powered by an electrical power supply, the baseplate and the cover forming at least one housing (10, 10', 15, 15', 29, 29', 32) comprising the electronic components (3, 30) and/or said electrical power supply, the electronic components comprise an accelerometer and/or a magnetometer and/or a magneto resistive component, sensor for an alarm device characterized in that: the baseplate is composed of a first printed circuit in which said set of electronic components (3, 30) is incorporated, the first printed circuit comprises a first wall made of insulating material comprising a first outer face and a first assembling face opposite the first outer face, the first assembling face comprising at least one first cavity (10, 10') that can and is intended to at least partly receive said electrical power supply and that is open on a first rim of the first wall, the electronic components (3, 30) are incorporated at least partly in the first wall, the cover comprises a second wall comprising a second outer face and a second assembling face opposite the second outer face, the second assembling face comprising at least one second cavity (15, 15') that can and is intended to at least partly receive said electrical power supply and that is open on a second rim of the second wall, the first wall and the second wall are superposed and assembled with one another by the assembly of the first assembling face and the second assembling face by the assembling means (17, 17'), the first cavity (10, 10') and the second cavity (15, 15') are disposed facing one another to form at least one housing for receiving the electrical power supply comprising an access orifice provided with an overall rim of the assembly of the first and second walls (7, 12). - a baseplate, - a cover, - a set of electronic components (3, 30) that can and are intended to be powered by an electrical power supply, the baseplate and the cover forming at least one housing (10, 10', 15, 15', 29, 29', 32) comprising the electronic components (3, 30) and/or said electrical power supply, the baseplate is composed of a first printed circuit in which said set of electronic components (3, 30) is incorporated, the first printed circuit comprises a first wall made of insulating material comprising a first outer face and a first assembling face opposite the first outer face, the first assembling face comprising at least one first cavity (10, 10') that can and is intended to at least partly receive said electrical power supply and that is open on a first rim of the first wall, the electronic components (3, 30) are incorporated at least partly in the first wall, the cover comprises a second wall comprising a second outer face and a second assembling face opposite the second outer face, the second assembling face comprising at least one second cavity (15, 15') that can and is intended to at least partly receive said electrical power supply and that is open on a second rim of the second wall, the first wall and the second wall are superposed and assembled with one another by the assembly of the first assembling face and the second assembling face by the assembling means (17, 17'), the first cavity (10, 10') and the second cavity (15, 15') are disposed facing one another to form at least one housing for receiving the electrical power supply comprising an access orifice provided with an overall rim of the assembly of the first and second walls (7, 12).