HEIDENHAIN PWM 20 - Manual (Page 93)

94 HEIDENHAIN ATS Software User's Manual
5.5 Diagnostics
5.5.1 Absolute/incremental deviation
With the function "Comparison of absolute and incremental values" absolute encoders can be
checked for the following defects:
 Code transition errors between absolute and incremental values
 Scale contamination and resulting signal and position errors
 Signal interferences (interference problems with resulting positioning errors)
Internal propagation and calculation times, etc., may cause a difference between the absolute
and the incremental position values.
Deviation span and accuracy (displayed in LSB*) are defined for different velocity ranges.
*) LSB = Least Significant Bit
Example: On an LC with 10 nm resolution, 1 LSB is a traverse distance of 10 nm.
Note
Display and functions may vary depending on the product key and the connected encoder!
Note
The absolute value is calculated at the scanning point (scanning unit or electronics of rotary
encoder) and is serially transferred to the PWM 20 or IK 215 as an absolute data word.
The incremental signals are transferred to the subsequent electronics via the analog
interface and are processed there (interpolated, digitized).
In the test unit, the absolute and the incremental position values are compared to each
other, and the difference is displayed as deviation span.
The different signal paths (propagation times caused by different cable lengths) result in a
deviation between the absolute and the incremental position display; the deviations must
not exceed the specified accuracy ranges.
Attention
The absolute value of the deviation span must not exceed the specified accuracy of the
velocity range.
If the tolerance is exceeded, the deviation span is displayed in red color.