Rotary Encoders are another use case for inductive sensing. This section discusses the design of inductive rotary encoder. The construction of rotary encoder involves two sensor coils and N number of targets placed on the rotating platform as shown in the figure below.
Construction of Inductive Rotary Encoder
The number of targets (N) decides the angular resolution as shown in:
Angular resolution = 360/(N*4)
The sensor coils need to be separated at an angle twice the angular resolution. For example, if the number of targets N = 8, then the achievable angular resolution is 11.25° and the required spacing between sensor coils is 22.5°. The direction of rotation can be determined using the previous value of coil ‘A’ and the current value of coil ‘B’ as shown in Table 2. If the current value of coil ‘B’ and previous value of coil ‘A’ are same, it means the direction of rotation is anti-clockwise direction; if the values are different, then is the direction of rotation is clockwise.
Direction of Rotation
To find out more on MoT designs, please see the Inductive Sensing Design Guide.