RealNetworks Interview Question: How many sensors do you need ... | Glassdoor

Interview Question

Senior Technical Program Manager Interview Seattle, WA

How many sensors do you need and where should they be

  placed to detect rotation/direction of a spinning disk?

Interview Answer

2 Answers


2 at 90 degrees

Interview Candidate on Jun 19, 2010

A single sensor will detect rotation speed, it will not show direction. Two sensors would detect rotation and could be used to detect direction if the sensors are also able to calculate speed; however they will not show direction unless the speed is known. The third sensor is needed to show direction by the sequence of the sensors being tripped if the speed cannot be determined. The placement of the sensors is only significant if you need to calculate uniformity of speed in the rotation. If uniformity of speed is not a concern then the sensors should be placed in the most economical position for installation, just not 180 degrees for the two sensor placement as you need a time differential in the speed/rotation calculation.

Jim on Aug 27, 2012

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