## 1 Introduction  
The core information of this paper is based on a recently published paper [1], describing the problem of the vital role of measurement and monitoring of the operational parameters of main engine (power system) and temperature measurement in the ship's hazardous areas (cargo system) for safe and effective ship operation as a whole. Ships are very sophisticated maritime, industry objects. On the one hand, each ship or other floating object differs from the other, but on the other hand, all of them have a lot of common properties. A modern automated cargo ship as an object of measurement and control presents a complex structure of four main systems: navigation, power, cargo and crew living conditions. In each system there can be distinguished some subsystems, which are illustrated in Figure 1 (for each system there are only two corresponding subsystems, but there can be more). Among all those mentioned above, the electric power subsystem is very important and it has a significant influence on the other systems and subsystems. It is worth underlining that there is a close relation between electric power and propulsion systems. More and more often we can meet not only with traditional sources of electrical energy as a set of diesel-generator units for electric power, but other configurations are also used, e.g., additional shaft generators or generators supplied by system utilizing heat from exhaust gases of the main engine. The electrical generators can also be driven by classical engines powered by gas or gas turbines. In recent years, electric ships have been explored more intensively and high voltage electrical systems are often used to additionally raise efficiency of such solutions. Taking into consideration different aspects like efficiency, reliability, environmental protection and economical effectiveness, AC (Alternating Current) electrical systems are already partially supported by DC (Direct Current) creating hybrid electric power system, and in the near future they can even be replaced by these new solutions, especially on small ships using renewable energy sources. It is worth mentioning that at the ships available, electrical power is comparable to the loads, which is automatically adjusted. Among all mentioned above, the electric power subsystem is very important and it has a significant influence on the other systems and subsystems. All of the very sophisticated systems of a ship require supervision by monitoring and control systems. Additional systems with safety functions are installed. Safety functions have higher priority than normal operation functions. At present, usually the distributed microprocessor systems are used for implementation of the measurement, monitoring, control and safety functions. Microprocessor systems are more susceptible to electromagnetic interference and disturbances of power supply than traditional analog systems. In this paper two typical case studies related to ship practice are presented. These studies are addressed to critical operational parameters, like main engine parameters in ships' power plants or temperature in ship tanks. A novelty of this paper concerns the carrying out and analysis of the main engine signals as well as the experimental research of newly implemented SeaPerformer System--in the case of main engine research. In the second case, a new approach concerns in-depth theoretical analysis of the temperature measurement line of liquefied gas in tanks together with consequences resulting from it. This in-depth analysis is resulting in identifying and explaining the reasons of new additional error, which may appear during the temperature measurement in the ship's hazardous areas.