RTC
®
5 PC Interface Board
Rev. 1.9 e
8 Advanced Functions for Scan Head and Laser Control
202
innovators for industry
Supplemental Information about Calibration
• The accuracy of fit of the set drift compensation
can decrease with increasing time. Therefore,
calibration should be repeated after appropriate
time intervals. The shorter the time interval
between individual calibrations, the higher the
attained long-term repeatability. Time intervals
are typically in the range of minutes. Events such
as workpiece changes or line feeds are ideal
opportunities for conducting a new calibration.
• The accuracy of fit of the calibration, and the
thereby attained long-term repeatability, are
further enhanced by steady environmental and
load conditions.
• If an error occurs (e.g. due to excessive spread
during a measurement cycle, see below) during
the measurement routine for determining the
Home-In positions after
Command
= 0, 1
or 3), then no reference values will be stored for
the affected axis (
Command
= 0) and the gain and
offset factors will remain unchanged (
Command
=
1; in contrast,
Command
= 0 always initializes gain
returns 0 instead of
faulty values.
• The measurement routine determines the Home-
In positions during a cycle of several measure-
ments. If deviations between the individual
measurements are too large (maximum –
minimum > 96 bits), the measurement routine
aborts and an error (return value 2) is returned.
An error within an individual measurement cycle
might indicate that stable temperature condi-
tions have yet to be attained or that a brief
mechanical or electrical disturbance has occurred.
If significant spreading occurs within an indi-
vidual measurement cycle, we recommend the
following:
– either a further measurement cycle is immedi-
ately conducted or
– the error is initially ignored while using the cur-
rent gain and offset values until new correction
values are determined via the next (successful)
measurement cycle.
If significant spreading occurs across several
measurement cycles, then it might be appropriate
to halt the application until one of the subse-
quent measurement cycles is successful.
Significant spreading across several measurement
cycles and over a long time period might indicate
a defect in the internal sensor system or another
part of the scan system. But because continuous
(mechanical or electrical) external disturbances or
contamination can also impair automatic self-
calibration, the scan system and its environment
should in such cases be appropriately inspected
to assess overall functionality.
• Certain hardware error states (e.g. signal faulty or
not found) get permanently stored in the
EEPROM. After correcting the error, you must call
with
Command
= 0 or 4 to clear the error
state. Until this time, correction with
Command
= 1
or 3 isn’t possible.
