A measurement system with improved data transmission capabilities to enable efficient data transfers in a radio frequency difficult environment. According to the invention two different data transmission protocols are used, each transmitting within its own radio frequency band. The first data transmission protocol is an unsynchronized network where nodes can actively poke a concentrator to get attention. When a node has the concentrator's attention, the concentrator will then switch the node over to a second data transmission protocol which is a time division multiplexing network at a different frequency band. The TDM network is able to selectively and efficiently transfer both small and larger data packets. The concentrator is able to have both networks active at the same time.