Abstract: The transaction data are acquired, developed and stored by a processing device located in direct proximity to measuring instruments, which includes a control processor (H) and a storage module (S). The data are stored in a non-volatile and redundant media (3, 4) and under the control of a control element (5). Queries to be performed are transmitted thereto by control processor (H) by means of a transmission channel (L) and of a buffer memory (8). The data of these queries are written and read into the storage media via a memory (6). Permanent controls are performed to check the quality and the accuracy of all the internal transfers and also to save the data in case of a power supply problem. The data saved in the memory may be read by external request.