For a modern electronically controlled engine, simply knowing the RPM is not enough. The control system must constantly understand the exact angular position of the crankshaft — Crank Angle.
The operation of the main engine processes is linked to it:
Fuel Injection, Gas Admission, Pilot Injection, Exhaust Valve and Cylinder Lubrication.
Proximity Sensors installed near the Intermediate Gear Wheel are used to determine the position. The sensors detect the passing gear teeth and generate a sequence of pulses.
But why are the sensors installed in pairs?
Due to the slight offset between them, the system receives different signal sequences:
00 → 10 → 11 → 01
or
00 → 01 → 11 → 10
Based on the order in which these signals change, UNIC determines the engine rotation direction — Ahead or Astern.
In other words, the system is concerned not only with the presence of a signal, but also with the sequence of its changes.
This is one of the key features of modern electronically controlled engines: the system constantly compares, checks and confirms the data it receives.
Understanding this logic is especially important when troubleshooting. When an engineer understands which signal UNIC expects and why, an Alarm is no longer just a message on the screen — it becomes clear where to look for the cause of the failure.
In the AtSea WinGD course, we examine in detail not only individual sensors and actuators, but also the operating logic of the engine control system itself.
In the next course updates, we will separately examine the operation of the Gear Wheel and Flywheel sensors, signal redundancy, engine reversing and system recovery after a Blackout.
AtSea — making complex things simple.
