Siemens SITRANS P300 Operating Instructions Manual page 85

the linearization values in the EEPROM are faulty. The same applies if the two end points of
the customized characteristic curve are exceeded for the status of the device variables of the
following function. If the analog-to-digital converter is put into overrange or underrange, the
identifiers HIGH LIMIT and LOW LIMIT are applied.
If the analog-to-digital converter is in overrange or underrange during pressure control, this
causes the status UNCERTAIN.
If the status of a device variable changes and it was right at the front of the sequence of
operations for a block, e.g. pressure, then all variables that are derived from it will take on
the same status. In the following example, the device variable "Pressure" has the status
BAD. Since the measurement type selector is set to "USER", the device variable "User" is
also given the status BAD.
The reasons for changes to the status of a device variable are summarized in the table. If
there were several reasons for a change in status, MANUAL always has the highest priority.
BAD follows as next highest and UNCERTAIN as the third highest priority.
Figure 7-6 Device status dependency
DV Device Variable
PV Primary Variable
SV Secondary Variable
TV Tertiary Variable
QV Quarternary Variable
SITRANS P300 with HART communication
Operating Instructions, 06/2005, A5E00359579-02
7.4 Selecting the measurement type
MA Zero value
ME Limit value
Operating functions via HART
7-11