## 4 Conclusions  
In many cases, ship measurement methods require individual and specific approach, because of the marine environment influence. Such affecting factors like vibration, ship rolling and pitching, temperature, humidity, salinity or changeable weather conditions must be taken into account. In this context, well known currently existing and applied measurement methods and devices should be completed and developed. Two case studies, addressed to operational parameters of main engine and temperature measurement of liquefied gas in ship tanks, are shortly described from the perspective of a new approach to analysis of their operation in specific conditions, which are vibrating environment and hazardous area, respectively. This new approach is presented with stressing proposed novelties against the state-of-the-art and in relation to the operational parameters of main engine in ship power plant consists in, that:  
* not only traditionally measured quantities on the main engine shaft like torque and RPM are measured but also some other main engine characteristic quantities, related to crankshaft angular position, combustion pressure, exhaust valve position, injection quantity sensor position and gas admission valve position are taken into account,
* in the presented photo-optical method based on the measurement of the torsion angle of the shaft, a measurement of RPM by additional sensor is not required, contrary to the method based on strain  
Figure 14: Graphical illustration of influence of unexpected alternating current on a measurement error. gauges. Moreover, presented photo-optical method is free of slip rings and brush contact devices, which are a serious maintenance problem in previously applied torque measurement method,
* described photo-optical method, aided by new solution of torque meter related transmitter gives possibility for use of only one photo-optical detector and at the same time the influence of changeable conditions and work parameters of transmitter and electronic sets of photo-optical detector circuit on measurement accuracy is significantly reduced comparing with other previously used solutions equipped with two photo-optical detectors,
* extended application of the aforementioned photo-optical method in SeaPerformer system enables not only measurement the torque on shaft and revolution (RPM) of the main engine, but also a calculation of other parameters like power, fuel consumption, energy and propeller slip. In consequence, also monitoring of main engine specific oil consumption (SFOC) trend is executed. Aforementioned monitoring is supported by data acquisition of engine operation signals related to crankshaft angus or position, combustion pressure, exhaust valve position (EVP), injection quantity sensor position and gas admission valve (GAV) position respectively,
* Next, in wider perspective, engine performance evaluation based on momentary fuel consumption analysis and main engine load is carried out. Monitoring of the above listed operational parameters of main engine aided by a new class of systems like SeaPerformer gives possibility for operational optimization of main engine exploitation and constitutes a new perspective comparing with hitherto used solutions in considered field of research. On the other hand, the new approach of analysis in relation to the temperature measurement in ship tanks, with placing emphasis on presented novelties consists in, that:  
* Temperature measurement in ship's hazardous areas covers not only use of intrinsically safe solutions for design of temperature measurement line, but also takes into account the additional measurement errors caused in the real measurement circuits by own capacities of long distances of sensors (predominant solutions are based on the Pt-100 sensors), screened cables, grounding and dynamic properties of a transmitter.