System for determining or monitoring a process variable in an automation technology installation with at least a higher-level unit and a multitude of field devices (F1, F2, F3, F4), which each have a sensor, and/or an actuator and an electronics unit, wherein the field devices (F1, F2, F3, F4) generate data, specifically measurement data, control data, calibration/parameterization data, diagnostic data, history data and/or status data, wherein the field devices (F1, F2, F3, F4) have a communication connection with one another via a wired or wireless communication network, and wherein the higher-level unit and the field devices (F1, F2, F3, F4) constitute user nodes, characterized in that the user nodes function and interact according to a Distributed Ledger or Blockchain technology, said system comprising: - A multitude of transaction creation units, wherein the transaction creation units are integrated into the electronic units of the field devices (F1, F2, F3, F4) or the field devices (F1, F2, F3, F4) have modular additional electronic units, particularly plug-in modules, in which the transaction creation units are implemented, wherein one of the transaction creation units is assigned to each of the field devices (F1, F2, F3, F4), wherein the transaction creation units create transactions and wherein a created transaction contains data from the field devices (F1, F2, F3, F4) respectively assigned to the transaction creation units; - At least one block creation unit, which is implemented in the higher-level unit and which processes at least one created transaction for a data block (BL1, BL2, BL3) at regular intervals; - A multitude of validation units, which check the validity of the data block and/or the transactions, wherein the data block (BL1, BL2, BL3) is valid if at least a predefined number of validation units successfully validate the data block (BL1, BL2, BL3), and wherein one of the validation units is assigned, respectively, to each of the user nodes, and - A multitude of decentralized databases designed to save data blocks (BL1, BL2, BL3), wherein the valid data block (BL1, BL2, BL3) is saved in each of the databases. - A multitude of transaction creation units, wherein the transaction creation units are integrated into the electronic units of the field devices (F1, F2, F3, F4) or the field devices (F1, F2, F3, F4) have modular additional electronic units, particularly plug-in modules, in which the transaction creation units are implemented, wherein one of the transaction creation units is assigned to each of the field devices (F1, F2, F3, F4), wherein the transaction creation units create transactions and wherein a created transaction contains data from the field devices (F1, F2, F3, F4) respectively assigned to the transaction creation units; - At least one block creation unit, which is implemented in the higher-level unit and which processes at least one created transaction for a data block (BL1, BL2, BL3) at regular intervals; - A multitude of validation units, which check the validity of the data block and/or the transactions, wherein the data block (BL1, BL2, BL3) is valid if at least a predefined number of validation units successfully validate the data block (BL1, BL2, BL3), and wherein one of the validation units is assigned, respectively, to each of the user nodes, and - A multitude of decentralized databases designed to save data blocks (BL1, BL2, BL3), wherein the valid data block (BL1, BL2, BL3) is saved in each of the databases.