LEFM 3xxCi User Manual
IB1406 Rev 12
Section 1
Page 5
August 2017
LEFM 3xxCi Meter Body
The meter body contains up to eight pairs of acoustic transducers and a temperature sensor (RTD).
The meter body is a specially designed section of pipe that contains pairs of transducer housings that are
positioned to provide acoustic paths at a 65° angle to the flow direction. They are spaced in accordance
with the Gaussian Method of flow integration. The transducers are installed inside these housings.
Each transducer module contains a piezoelectric crystal which transmits and receives acoustic energy in
the form of ultrasonic pulses (typically 200 kHz). A distinguishing design feature is that the transducer
modules may be removed from their housings for maintenance while the meter body is in the pipeline
without affecting the pressure boundary (i.e. no special extraction tools required).
LEFM 3xxCi Transmitter
The transmitter houses the display, which shows the flow data, including flow rate, total flow volume, gas
properties, analog input data, alarm indication, fault detection, and acoustic diagnostic information.
The transmitter performs all control and timing for the generation and measurement of acoustic pulses.
Acoustic processing is performed by specialized proprietary boards that are designed to achieve high
sampling rates, provide stable ultrasonic signals, and eliminate zero drift. The circuit boards within the
transmitter are programmed to perform the following functions:
•
Step through the ultrasonic path cycles
•
Provide gain control for each ultrasonic path
•
Compute flow
•
Generate pulse outputs and analog outputs
The transmitter offers the following inputs/outputs:
•
Standard volume pulse output
•
The K-factors used to configure transmitters at the factory are listed in Table 1.1. The user may
configure the K-factor as needed.
•
Analog Inputs (up to 3)
o
Product temperature
o
Product pressure
•
Analog Outputs (up to 2)
o
Flow
o
Any Modbus Register (See Modbus manual)
•
Communications
o
RS-485 ports (half duplex; up to 3) – Modbus RTU
o
Ethernet port (via Copper or Fiber) with Modbus TCPIP
o
Optional HART channel (operates on second analog output)
•
Digital Outputs (4)
o
Status
o
Standard volume pulse outputs
•
The K-factors used for factory transmitter configuration are listed in Table 1.1 below.
