## 3 A Short Overview of Selected Examples of Measuring and Monitoring Systems on Sea Ships
### Measurement of the Operational Parameters of Main Engine  
Main engine can be monitored based on general output or detailed signals describing engine operation performance such as cylinder combustion pressure. The latter requires special equipment since very high resolution of signal recording is required. In order to reproduce dynamics of combustion process, angular resolution of 0.1 degree of crankshaft position must be provided. For this purpose, FPGA processing unit in real time is employed. Data acquisition of following analog signals of engine operation are executed:  
* Crankshaft angular position;
* Combustion pressure;
* Exhaust valve position (EVP);
* Injection quantity sensor position (for selected engines);
* Gas admission valves (GAV) positions (for selected engines). The above data are post-processed and usually depicted in reference to cylinder top dead position as shown on Figure 4, in exemplary combustion pressure process monitoring. Main engine general output may be monitored with use of shaft torque meter [14]. A good illustration of such a kind of measurement is propulsion control assistance system ETNP-10 for optimization of ship operation according to operation area of the main engine, being a part of information provided by SeaPerformer system, is depicted in Figure 5[14]. Both cases actual engine load and rotational speed (dots) are presented in reference to so called engine layout or engine operational envelope. Engine layout presents standard operation area (green) over-speed area (yellow) and over-load area (red). Clear color indication allows ship crew to monitor engine operation and prevent conditions which may results in fault. As an extension to ETNP-10 user interface visualization which is devoted to actual engine conditions, SeaPerformer system may be used for engine monitoring in longer time range. The SeaPerformer system measures the torque on shaft and revolution (RPM-Revolution Per Minute) of the main engine. Other parameters like power, fuel consumption, energy and ship's speed are calculated. Figure 4: Combustion pressure monitoring of main engine [14]. (Courtesy of Enamor Ltd.). Based on the state-of-the-art [5; 17; 18], measurement of torque can be done with use of measurement of the torsion angle \(\varphi\) of propeller shaft during running of engine. Different torque measurement methods can be applied. In many methods, strain gauges as the sensors are used [5]. This solution requires the strain gauges to be placed directly on the rotating shaft and additional measurement of RPM should be performed. The strain gauges are configured in bridge system equipped with slip rings and brush contact devices. The strain gauges bridge is fed through the two slip rings and output signal taken from the bridge diagonal is also provided with two slip rings. The all slip rings are fitted on the rotating shaft and they provide a continuous electrical connection through brushes on stationary contacts. At the same time, slip ring and brush contact solution are important disadvantages of this method. The other solution, free of aforementioned weaknesses, is based on the photo-optical method [17; 18; 19] (Figure 6), which uses two specially designed teethed rings. Each ring is fixed separately in same distance \"1\" on the shaft, but the teeth are placed in the same plane which is presented in Figure 6a. Such a solution gives possibility for use of only one photo-optical detector. The relation between teethed rings is proportional to the torsion angle of the shaft. In this method measurement of RPM by additional sensor is not required. In the case when the shaft is without load, the torsion angle \(\varphi=0\). This situation is presented in Figure 6b. Electric signal received from photo-optical detector shows that pulse period T\({}_{1}\) and T\({}_{2}\) are equal. When the load of the shaft occurs, the torsion angle is higher than 0.