Dishwashing machine comprising: a controller; a spray arm assembly comprising a spray arm having one or more spray holes for spraying a washing load with water, and a pipe for delivering water to the spray arm; a pump for pumping water through the pipe and to the spray arm; the pipe being constructed and arranged to at least partially restrict flow of water from the pump to at least a part of the spray arm dependent on spray arm orientation relative to the pipe, a power consumption of the pump thereby being dependent at least in part on the spray arm orientation relative to the pipe; and the controller being configured to monitor the power consumption of the pump in order to determine rotational information of the spray arm.