Written by Carsten Frederiksen

The Dewesoft EtherCAT data acquisition devices have already become standard in distributed, industrial monitoring applications. But when we are talking about monitoring the HongKong - Zhuhai - Macao bridge, “distributed” word enters a new dimension.


With a total length of 50 km, the Hong Kong-Zhuhai-Macao Bridge (HZMB) is regarded as the longest sea bridge in the world.

One part of this monument’s structural health monitoring system is the measurement of tri-axial accelerometers at the navigation spans. The purpose is to detect the occurrence of the ship impacting as well as to determine the global dynamic characteristics of the structure’s viaduct bridges.

modern bridge in water and small boat underneath it


For the Hong Kong part of the HZMB bridge, the 200 highest precision acceleration channels are needed, distributed over the distance of several kilometers. These channels are clustered into six independent subsystems (DAU 1, DAU2, .. DAU 6) as shown on the schematic below.

The data of each DAU subsystem are stored locally and in parallel to a database engine running on a central server.

Main requirements:

  • Fully remote controlled system operation
  • Synchronization accuracy between each DAU: better than 1 msec (10 µs within each DAU)
  • Aliasing-free acquisition over complete sampling range (up to 10kS/sec)
  • ADC resolution ≥ 24Bit with 0.1 % basic accuracy
  • Sensors power must be supplied out of the DAQ system (±15 Volt)


The performance of the SIRIUS EtherCAT data acquisition system - SIRIUSie-8xLV fits perfectly to the used sensor.

For the long distances between the slices to each DAU and the mixed network topology (daisy chain and star) the connection possibilities of our EtherCAT devices were expanded using fiber optics connections:

  • The low latency EtherCAT® to Fiber optic converter (ADAPTER-OPTIC-ECAT) allows expansion of the distance over several kilometers.
  • Up to 8 EtherCAT® lines can be connected with a dedicated EtherCAT® hub (ECAT-HUB-8).
  • NTP-Sync is used for synchronization between the DAU’s.


Feel safe when driving from Hong Kong to Macao or vice versa. This bridge is monitored with the world’s most accurate distributed data acquisition system - SIRIUS EtherCAT.

Learn more:

modern bridge in the water from above