Siemens SITRANS LUT400, Operating Instructions Manual

Page: 570 / 601

A5E33329501 SITRANS LUT400 (HART) – OPERATING INSTRUCTIONS Page 257
mmm
mm
App. A -
Te
c
hni
cal Ref
.
Appendix A - Technical Reference
Principles of Operation
The SITRANS LUT400 is a high quality ultrasonic controller, configured to meet the needs
of different applications, from medium range solids applications to liquids management
with open channel measurement capability. The LUT400 features our next generation of
Sonic Intelligence
®
advanced echo-processing software for increased reading reliability.
Process Variables
The Primary Variable (PV) is one of six process variables, and is set in
2.5.1.Current Output
Function
:
• Level (difference between material level and Low Calibration Point),
• Space (difference between material level and High Calibration Point),
• Distance (difference between material level and sensor reference point),
• Head (difference between liquid level and Zero Head),
• Volume (volume of material based on level),
• Flow (flowrate in an open channel, based on head).
Transmit Pulse
The transmit pulse consists of one or more electrical “shot” pulses, which are supplied to
the transducer connected to the SITRANS LUT400 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 frequency, duration, delay, and associated measurement range are
defined by parameters in the Setup menu (see
Setup
on page 138.)
Echo Processing
SITRANS LUT400 uses next generation Sonic Intelligence® for echo processing.
Next generation Sonic Intelligence provides adaptive digital filtering of the transducer
signal. For example, when noise levels are high, filters are adjusted to maximize the
signal to noise ratio. This advanced Sonic Intelligence not only allows for better filtering,
but provides improved tracking of echos, and more sophisticated echo positioning
algorithms.
Echo processing consists of echo enhancement, true echo selection, and selected echo
verification.
Echo enhancement is achieved by filtering (
2.12.2.4. Narrow Echo Filter
) and reforming
(
2.12.2.3. Reform Echo
) the echo profile.
Note: Where a number precedes a parameter name (for example,
2.12.2.4. Narrow Echo
Filter
) this is the parameter access number via the local display. See
Parameter
reference (LUI)
on page 137 for a complete list of parameters.