HEIDENHAIN PWM 20 - Manual (Page 182)

November 2014 Checking incremental encoders 185
Examples:
All parameters are within the green range.
This PWT display indicates that the encoder must be considered defective - the reference
signal function is faulty!
The signal amplitude is noticeable, but still within the yellow range.
Recommendation: Use the Analog function to analyze the output signals in detail.