Parameterization and programming
ELX3351
43
Version: 1.3.1
Note
Calibration
The calibration is of great importance for the accuracy of the system. In order to increase
this, the filter should be set as strong as possible over the entire calibration phase. It may
take several seconds before a static value is obtained.
Note
Local storage
The values modified during the theoretical and practical calibration are stored in a local
EEPROM. This can be written to up to 1 million time. In order to prolong the life of the EEP-
ROM, therefore, the commands should not be executed cyclically.
5.3.2
Self-calibration
Self-calibration of the measuring amplifiers
The measuring amplifiers are periodically subjected to examination and self-calibration. Several analog
switches are provided for this purpose, so that the various calibration signals can be connected. It is
important for this process that the entire signal path, including all passive components, is examined at every
phase of the calibration. Only the interference suppression elements (L/C combination) and the analog
switches themselves cannot be examined. In addition, a self-test is carried out at longer intervals.
The self-calibration is carried out every 3 minutes in the default setting.
•
Self-calibration
The time interval is set in 100 ms steps with object
Duration approx. 150 ms
By means of the self-calibration of the input stages at the two operating points (zero point and final value),
the two measuring channels are calibrated to each other.
Interface for controller
The self-calibration takes place automatically at the defined intervals. In order to prevent calibration during a
time-critical measurement, the automatic calibration can be disabled permanently via the
Disable calibration
bit in
ControlWord
. If it should be additional necessary to carry out a manual test, this is started by a rising
edge of the
Start manual calibration
bit in the process image.
While the terminal is performing a self-calibration, the
Calibration in progress
bit is set in the process image.
Once started, a self-calibration cannot be aborted.
If the self-calibration has been disabled by
Disable calibration
, it can nevertheless be started by the
Start
calibration
process data bit.
Note
Self-calibration
The self-calibration takes place for the first time directly after starting up the terminal. At this
point the supply voltage must already be applied. If the supply voltage is only applied later,
the self-calibration must be manually initiated (process data bit:
Start calibration
).
The self-calibration must be executed at least once after each start-up.
A lower measuring accuracy is expected if the self-calibration is disabled for a longer period
or permanently.
After a change in the CoE settings (section x80nn), a self-calibration is always performed (even if
DisabledCalibration
= TRUE), since the settings affect the measurement. Changing the CoE settings during
an ongoing measurement should therefore be avoided, if possible.
