The instrument includes a connector block (24) suitable for receiving a removable memory card (12), a printed circuit (20), a case including an opening (16) for insertion of the memory card, and contacts (48) for reprogramming the microcontroller (22). The reprogramming contacts (48) are disposed on the printed circuit (20) at a distance from terminals (26) for making contact with the memory card, in the space that the connector block (24) occupies on the printed circuit, and they are available from the inside volume of the connector block. The instrument is essentially lacking in any opening dedicated to accessing the reprogramming contacts, with access to these contacts being possible via the opening in the case and the inside volume of the connector block by inserting an insert (52) into the instrument instead of and replacing a memory card.