Siemens LMV51 Series Basic Documentation page 274

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19.6 Self-test
During the startup phase and during operation, the system performs a number of self-
tests to ensure that the O
19.6.1 Sensor test
To detect aging O
2 sensors, a sensor test is made
fied by its increased internal resistance. The cell is considered too old when the internal
resistance measured is Ri < 5 Ω or Ri > 150 Ω.
The test is made at 23-hour intervals. To perform the test, a constant O2 value is es-
sential. This requirement is satisfied after prepurging or when a stationary load point is
reached. The system performs the test after 23 hours as soon as such stationary val-
ues are available. If this is not the case after 24 hours, the load will be "frozen" in op-
eration so that the test can be made. If the system is in standby mode, the test will be
performed during the next startup phase (maximum 3 repetitions).
If the test is negative, the system's response will be one of the following, depending on
the parameter setting of «O2Ctrl/Guard»:
Parameter:
O Ctrl/Guard (auto deact / man deact / O
2
conAutoDeact)
man deact O2 trim controller and O2 monitor are deactivated. No sensor test will
(auto deact): be made.
O2-guard / O2- O2 trim controller / O2 monitor is / are activated. If the test is nega-
control: tive, safety shutdown will take place, followed by a repetition if possi-
ble, otherwise lockout.
conAutoDeact: Both the O2 trim controller and the O2 monitor are activated. If the
test is negative, O2 trim control will be deactivated and the burner will
be started up without O2 trim control.
Basic Documentation LMV5...
19 Addendum 4: LMV52... with O2 trim control and O2 module
sensor is working correctly.
2
. An aged measuring cell can be identi-
-guard/ O -control /
2 2
CC1P7550en
13.08.2004