FeedbackNoiseFault

Applies to: Servo axes.
FeedbackNoiseFault is a Boolean attribute. It is set when the servo module detects simultaneous transitions of the feedback A and B channels, known as "feedback noise" (see following illustration). Feedback noise is most often caused by loss of quadrature in the feedback device itself, or by radiated common-mode noise signals being picked up by the feedback device wiring, both of which may be seen on an oscilloscope.
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For example, loss of channel quadrature for an encoder can be caused by physical misalignment of the feedback transducer components, or excessive capacitance (or other delays) on the encoder signals. Proper grounding and shielding techniques can usually cure radiated noise problems. See the 1756-M02AE Installation and Setup manual for information on grounding and shielding.
FeedbackNoiseFault is a recoverable fault.
To clear a FeedbackNoiseFault:
  1. Fix the faulty feedback connection or device.
  2. Be sure your program or fault handling routine contains either a
    • Fault Reset (MAFR) instruction, to clear all motion faults for an axis, or
    • Shutdown Reset (MASR or MGSR) instruction to return to the axis ready operating state.
The occurrence of a FeedbackNoiseFault on a Servo axis sets bit #5 of the ServoFault attribute, the PhysicalAxisFault attribute and bit #0 of the AxisFault attribute.
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