A field device adapter for wireless data transfer for connection to a field-device-internal interface provided for a display of a field device, the adapter comprising: - an interface for connection to the field-device-internal interface provided for the display of the field device; - a radio module, which is configured to wirelessly transmit a data packet in accordance with a standard of a low-power wide-area network, wherein the radio module is further configured to only transmit the data packet and not to receive data packets; - adapter electronics (10, 16, 17, 18), which are configured to convert the data originating from the field device into data packets via the field-device-internal interface, preferably into data packets of a constant or of different sizes, and also to limit an energy provided via the field-device-internal interface to a predetermined value and to charge an energy storage unit with the limited energy, preferably continuously, wherein the predetermined value is set such that the value corresponds at most to a maximum energy requirement of the provided display, and the adapter electronics (10, 16, 17, 18) are further configured to monitor a state of charge of the energy storage unit and, based on the state of charge, to provide the radio module with an energy originating from the energy storage unit for transmitting the data packet so that the radio module transmits the data packet, wherein the adapter electronics (10, 16, 17, 18) are also configured to compare a currently determined state of charge with a predetermined state of charge and, when the predetermined state of charge is reached, to provide the radio module with an energy originating from the energy storage unit for transmitting the data packet so that the radio module transmits the data packet. - an interface for connection to the field-device-internal interface provided for the display of the field device; - a radio module, which is configured to wirelessly transmit a data packet in accordance with a standard of a low-power wide-area network, wherein the radio module is further configured to only transmit the data packet and not to receive data packets; - adapter electronics (10, 16, 17, 18), which are configured to convert the data originating from the field device into data packets via the field-device-internal interface, preferably into data packets of a constant or of different sizes, and also to limit an energy provided via the field-device-internal interface to a predetermined value and to charge an energy storage unit with the limited energy, preferably continuously, wherein the predetermined value is set such that the value corresponds at most to a maximum energy requirement of the provided display, and the adapter electronics (10, 16, 17, 18) are further configured to monitor a state of charge of the energy storage unit and, based on the state of charge, to provide the radio module with an energy originating from the energy storage unit for transmitting the data packet so that the radio module transmits the data packet, wherein the adapter electronics (10, 16, 17, 18) are also configured to compare a currently determined state of charge with a predetermined state of charge and, when the predetermined state of charge is reached, to provide the radio module with an energy originating from the energy storage unit for transmitting the data packet so that the radio module transmits the data packet.