The question we hear most after a digital inclinometer goes on board is 'how should we read the numbers?'. Roll and pitch become far more useful when you separate the value the vessel settles at from the size of the swing. This note explains how to read an electronic inclinometer on ships during cargo work and in heavy weather. For choosing and installing one, see digital inclinometer for ships: how to choose one and where to install it.
1. Start with the two numbers on the display
- Roll: the side-to-side inclination. Devices differ on whether port or starboard is positive, so confirm the direction at installation and label it next to the display.
- Pitch: the fore-and-aft inclination. Define the sign for bow down and bow up in the same way.
- Zero point: check that the display reads close to zero with the vessel upright. If the zero is off, every judgement made from the readings is off too.
2. Separate the steady offset from the swing
- Centre value: the midpoint the readings move around. A roll centre away from zero can mean the vessel is listing because of how cargo, fuel or ballast is distributed; the pitch centre shows trim by the bow or stern.
- Swing: how far the readings move either side of the centre, showing rolling and pitching in waves and wind.
- Lopsided swing: if the vessel heels much further to one side, check whether a list or a beam wind is adding to the motion.
3. During cargo work, watch the centre value
- Record roll and pitch before work starts as a baseline.
- If the roll centre keeps moving in one direction as loading or discharge goes on, use it as a cue to review the sequence or ballast.
- When work ends, compare the final readings with the planned condition and keep a record. With a digital inclinometer for ships that logs readings with dates, before-and-after values can be compared directly.
- Inclinometer readings support on-site checks. They do not replace stability calculations or the loading plan.
4. In heavy weather, watch the size and period of the swing
- Trend: look at whether the swing grows or shrinks over a period of time rather than at one large reading.
- Period: if one roll takes longer than usual to complete, stability may have reduced, so check the loading and ballast condition as well.
- Course and speed changes: when the wave period and the vessel's roll period line up, rolling can build up suddenly. After changing course or speed, check on the inclinometer how the swing responds.
- Writing the master's caution levels next to the display helps every watchkeeper judge by the same standard.
5. Replay records for later review
- Keep the device's date and time in step with the ship's clock so records line up with the logbook and cargo records.
- Note the date and time of any unusual event, then replay that period to check how roll and pitch changed.
- Check how long the device keeps its records, and save the periods you need for reports separately.
6. What to check when readings look wrong
- If roll or pitch is off zero with the vessel upright, recheck the zero point.
- If readings jump or freeze, check how the sensor is fixed, and the power and cabling.
- Add the inclinometer to the routine checks for bridge equipment so it is not missed. For onboard equipment checks, see 7 preventive checks that reduce vessel IT failures.
Ocean Connect supplies the IM330 electronic inclinometer for ships with a partner and supports bridge installation and zero-point and function checks. See our vessel IT maintenance services for equipment and IT care on board, and if you need an inclinometer installed or checked, contact us via the online inquiry form or our emergency 24-hour helpdesk (+82-70-7588-0611~0612).