Final answer:
In discussing Karman vortex sensors, only Technician A is correct, as these sensors may have a burn-off circuit for cleaning, while Technician B is incorrect since these sensors do not contain a movable vane.
Step-by-step explanation:
The question pertains to Karman vortex sensors, which are used to measure fluid flow. Technician A claims these sensors have a burn-off circuit, which is used to keep the sensor clean by eliminating any debris or contaminants that could affect its accuracy. This is indeed a feature of some flow sensors, although it may not be specific to all Karman vortex sensors. Technician B mentions the sensor has a movable vane, which is not characteristic of Karman vortex sensors as these sensors work by detecting vortices shed by a bluff body in the flow path; they do not use a movable vane, instead relying on piezoelectric or ultrasound sensor elements to detect the vortices. Therefore, only Technician A is correct.