Siemens SITRANS DA400 Operating Instructions Manual page 55

Process monitoring sitrans da400 for oscillating positive displacement pumps with protection against explosion

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Formation of the alarm messages

In accordance with the "Block diagram for the formation of alarm messages" figure, the

measured value is then monitored with a limit monitor with hysteresis for exceeding of a pre-

alarm "PrAL*" (parameters P.5, P.7, P.9, P.11) and a main alarm "AL*" (parameters P.6, P.8,

P.10, P.12).

The resulting signals "PrAL'*" and "AL'*" are used for evaluation by various trace timers. The

final alarms "PrAL*" and "AL*" are generated only when the signals "PrAL'*" and "AL'*" are

present for the configurable time "P.13/Time". The same response time also applies if the

value is below the alarm values. When the main alarm responds, the pre-alarm is also

activated.

Depending on parameter P.14/AcK, the alarms "PrAL*" and "AL*" are saved and can be

reset with the "ACK" button.

In the event of a sensor fault (cable failure), the alarm for the damaged channel will be

generated in addition to the fault summation message depending on configuration (P.1, P.2,

P.3, P.4).

Figure 7-2

Block diagram for formation of the alarm messages

SITRANS DA400 for oscillating positive displacement pumps with protection against explosion

Operating Instructions, 10/2007, A5E00841127-01

Signal processing

7.1 Evaluating acoustic channels

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