Siemens sitrans LU01 - Manual (Page 91)

7ML19985BE02 SITRANS LU01 – INSTRUCTION MANUAL Page 85
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Technical Reference
Transmit Pulse
The SITRANS LU01 transmit pulse consists of one or more electrical shot pulses, which
are supplied to the scanning relay. The scanning relay is activated as required, to supply
the transmit pulse to the Transducer(s) connected to the SITRANS LU01 terminals.
The transducer fires an acoustic shot for each electrical pulse supplied. After each shot
is fired, sufficient time is provided for
echo (shot reflection) reception, before the next (if
applicable) shot is fired. After all shots of the transmit pulse are fired, the resultant
echoes are processed.
The transmit pulse shot number, frequency, duration, delay, and associated measurement
range are defined by parameters P803 and P840 to P852.
Echo Processing
Echo processing consists of echo enhancement, true echo selection, and selected echo
verification.
Echo Enhancement is achieved by filtering (P821 and P822) and reforming (P823) the echo
profile (digitized signal representing the echo signal received).
True echo selection is achieved by establishing the criteria which a portion of the echo
profile must meet to be considered the true echo (echo reflected by the intended target).
Insignificant portions of the echo profile outside of the measurement range (Span P007 +
Range Extension P801), below the TVT Curve (P830 to P835), and less than the Confidence
Threshold (P804) and Short Shot Floor (P851) are automatically disregarded.
The remaining portions of the Echo Profile are evaluated using the Algorithm(s) (P820)
and Short Shot Bias (P850) programmed. When a combination of Algorithms are used,
the portion of the Echo Profile providing the best averaged Echo Confidence (P805), is
selected as the true echo.
True echo verification is automatic. the position (relation in time after transmit) of the new
echo is compared to that of the previously accepted echo. When the new echo is within
the Echo Lock Window (P713), it is accepted and displays, outputs, and relays are
updated as restricted by the Fuzz Filter (P710) and Rate Parameters (P700 to P703). If the
new echo is outside of the Echo Lock Window, the new echo is not accepted until Echo
Lock (P711) requirements are satisfied.