The present finding refers to a monitoring device configured to monitor information associated with the functioning of a solar panel (12-1, 12-2, 12-3, 12-n). The monitoring device (28-1, 28-2, 28-3, 28-n) comprises connection poles (23a, 24a) that can be connected to electrical connections (21) of the panel and reading means adapted to read the information associated with the functioning of the panel (12-1, 12-2, 12-3, 12-n), such information being selected at least from a group comprising: voltage of the panel, current of the panel, temperature of the panel, pressure and illuminance. The device also comprises a transmitter circuit configured to transmit the information by using the connection poles (23a, 24a), a micro-processor circuit connected to the transmitter circuit and configured to activate the transmitter circuit to transmit the information. The device also comprises an identification circuit connected with the micro-processor circuit (32) and configured to represent a certain identification number of the monitoring device (28-1, 28-2, 28-3, 28-n) associated with the panel (12-1, 12-2, 12- 3, 12-n) such that the micro-processor circuit (32) is adapted to recognize, by means of the identification circuit, a synchronization signal that can be received through the connection poles (23a, 24a) and to activate the transmitter circuit (37), in reply to the acknowledgement of the synchronization signal. The finding also refers to a monitoring system which comprises the device and to a functioning method of the same.