Field device adapter for wireless data transfer

Disclosed is a field device adapter for wireless data transfer for connection to a field-device-internal interface provided for a display, comprising: an interface for connection to the field-device-internal interface; a radio module configured to wirelessly transmit a data packet on a low-power wide-area network, wherein the radio module is further configured to only transmit the data packet and not to receive any data packets; adapter electronics configured to limit an energy provided via the field-device-internal interface to a predefined value and to charge a stored energy source with the limited energy. The adapter electronics are further configured to monitor a state of charge of the stored energy source and, based on the state of charge, to provide the radio module with an energy originating from the stored energy source for transmitting the data packet.