Teledyne ADFM Analog Output Module, Техническое руководство, Страница: 18 / 156

Chapter 1
To allow measurements close to the bottom of the pipe or channel and to
minimize debris collection on the transducer, the ADFM transducer is de-
signed to have a low profile. It therefore contains a minimum of required
electronics. The Electronics Unit and transducer contain all circuitry and
systems needed to measure directional flow, the level within the sewer pipe,
to record results, and to transfer data from and to local or remote locations.
Use of a laptop computer running Windows 95 and the WinADFM software
is recommended for initial setup of the ADFM on-site. Subsequent data
collection and re-programming may be performed locally or remotely via
modem if a telephone telemetry connection is available.
1-4.1 What is an ADFM?
The ADFM Velocity Profiler
™
(ADFM) is a flow meter based on the Dop-
pler principle. The ADFM consists of a transducer assembly mounted in the
flow, a signal processing unit and an interface cable
1-4.2 Principles of Operation
Figure 1-24 shows a typical ADFM installation for measuring open channel
flow in a pipe. A transducer assembly is mounted on the invert of a pipe or
channel. Piezoelectric ceramics emit short pulses along narrow acoustic
beams pointing in different directions. Echoes of these pulses are backscat-
tered from material suspended in the flow. As this material has motion rela-
tive to the transducer, the echoes are Doppler shifted in frequency. Meas-
urement of this frequency enables the calculation of the flow speed. A fifth
ceramic mounted in the center of the transducer assembly, and aimed verti-
cally, is used to measure the depth.
Depth cells
Flow pattern
transducer
Velocity Profile #1
Velocity Profile #2
Figure 1-2. Typical ADFM installation
page 1-4 MGD Technologies, Inc.