Sensors and instrumentation play a critical role in the operation of a sea going vessel, which means you need to be able to trust the readings they provide. Buying the best sensor is not  enough, you will need to maintain it as the readings will drift over time. To ensure sensors in operation are trustworthy, they will need adjustment from time to time, as readings can drift. Enabling the crew to perform on-site calibration it is often possible to maintain valid certificates which ensures the accuracy of equipment such as manometers, temperature sensors and pressure switches is kept.