Digital Measuring System for Monitoring Motor Shaft Parameters on Ships

The robust measuring system for continuous monitoring of the ship motor shaft average torque, power and rotational speed was developed and tested. The system was designed for permanent installation in ships under realistic working conditions. The strain gage sensor is employed to measure the torque, while the shaft rotational speed is measured by the inductive proximity switch. Contactless power transmission subsystem was developed, based on the specifically designed rotary transformer, operating at the low frequency. Strain measurement results are transmitted over the near-field low frequency capacitive link using specifically designed communication protocol, based on the digital modulation principle. Receiver microprocessor-based unit processes measured data and transmits the results to the monitoring human-machine interface over some common industrial analog and digital communication protocols. The principal advantages of the novel measuring system design over some existing commercial solutions are higher accuracy, increased stability and reliability, simplified calibration procedure and wireless signal transmission and processing completely in a digital form, hence reducing the most common shortcomings of standard analog systems.