With the continuous development of ship industry, marine instruments such as voyage data recorder, security alarm device, etc. are also growing rapidly. Different from other instruments, marine instruments have their own particularity, including narrow use space, working time, variety, complex signal, high safety and reliability requirements. In order to ensure the safety, the interference between the instruments and equipment or between the wires must be considered, so the electromagnetic compatibility (EMC) of marine instruments has become an important mandatory test.
There are many EMC test items of marine instruments, including conducted disturbance, radiated disturbance of shell port, immunity of electrical fast transient pulse group, immunity of electrostatic discharge, etc. Test the energy fluctuation of anti-interference ability, immunity of electrical fast transient pulse group, immunity of conduction induced by RF field, etc. Generally, there are great differences between domestic and foreign marine instruments in this respect. The anti-interference ability of domestic samples is very strong, while that of foreign samples is good.
The safe distance of compass is also one of the electromagnetic compatibility test items of marine instruments. Because compass determines the direction, speed, time, etc. of ship navigation, it has a special position. Therefore, it is necessary to eliminate the interference of other ships to ensure safety. The minimum safe distance test of compass can use the relationship between the intensity of the earth's magnetic field and the angle to convert the measurement of the angle into the intensity of the magnetic field. The smaller the compass safety distance is, the stronger the anti-interference ability of the sample is.
The EMC of marine instrument can consider all aspects comprehensively, such as the separation of primary and secondary circuits by power supply, the separation of digital circuit and analog circuit of printed circuit board, the formation of closed loop by ground wire to reduce potential difference, the consideration of magnetic shield and electric shield in case, the ground wire as thick as possible, and the selection of appropriate cables, etc..
Marine instrumentation generally requires CCS validation, following EMC standards as it should conform to IEC 60945.