Cleaning apparatus including a rotating spray head assembly rotation sensor

A containment tank assembly comprising:

• a tank including an inner surface;
• and
• a cleaning apparatus mounted to the tank, wherein the cleaning apparatus comprises:
• an elongate arm;
• a rotary spray head assembly rotationally coupled to an end of the elongate arm;
• a rotating nozzle assembly rotationally coupled to the rotary spray head assembly;
• a magnetic field source coupled to the rotary spray head so as to generate a spatially changing magnetic field in accordance with a rotation of the rotary spray head assembly in relation to the end of the elongate arm;
• and
• a magnet field sensor carried at the end of the elongate arm to which the rotary spray head assembly is rotationally coupled,
• wherein the magnetic field sensor, in operation, generates a sensor signal that varies in accordance with the spatially changing magnetic field in accordance with rotation of the rotary spray head assembly, and
• wherein the rotary spray head assembly provides an interconnecting structure between the elongate arm and the rotating nozzle assembly.