Siemens SITRANS DA400 Operating Instructions Manual page 60

Signal processing
7.1 Evaluating acoustic channels
Step 1: Calculation of the measured value
In accordance with the "Block diagram for calculation of the measured value" figure, the
electrical signals from the sensors are amplified, filtered and converted into a digital signal by
an analog-to-digital converter. The sensors are simultaneously checked for cable failure. The
level is calculated from the signal and then filtered and further processed to a measured
value. The upper limit frequency of the filter is defined with parameters P.40 to P.44.
Depending on the parameters (P.1 to P.4), the sound level to be output as the measured
value is defined separately for each measurement channel:
● A simulated value in simulation mode.
● The maximum value in test mode.
● The low-filtered sound level in normal measurement mode.
Figure 7-1 Block diagram for calculation of the measured value
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SITRANS DA400 for material flow monitoring with protection against explosion
Operating Instructions, 09/2007, A5E00841152-01