Instrumentation & Measurement Magazine 26-1 - 53

Real-time Imaging Monitoring Test of
Pollutants
Fig. 2. Ultrasonic images of particulate contaminants in streams using model
sediment particles.
Different surfaces and obstacles will produce different echoes.
Therefore, the basic principle of PUDI is to send an orderly series
of ultrasonic waves into the interior of an object, and scan
in a certain order, and then continuously detect the delay time
and intensity of the ultrasonic echoes. The ultrasonic image
can be obtained after a series of internal signal processing of
electronic circuits and computers [9]. The ultrasonic image records
the echoes' information and can judge the structure and
changing characteristics of the object's inner structures.
The obtained ultrasonic image of water flow and granular
pollutants from the PUDI is a profile in the model test, as
shown in Fig. 2 and Fig. 3. Imaging spots are formed by the
suspension movement of particulate pollutants (instead of
sediment-laden particles), and sand wave terrain imaging
bright bands formed by the strong reflection of the bottom bed
surface. At the same time, because of the movement of suspended
particulate pollutants and the characteristics of the
soil and rock terrain itself, there may be some reflection image
of the bed surface terrain. Therefore, as illustrated in Fig. 2 and
Fig. 3, the background texture features and the imaging spot
noise near the bed surface will be strong or weak according to
water flow conditions.
Ultrasonic Imaging Test System
The main equipment and instruments needed in this paper
have two kinds of PUDI, which are available for use during
our imaging monitoring test of pollutants. They are a portable
B-mode ultrasonic convex array instrument (TY-6858-I)
and an Apogee 1100 digital color Doppler ultrasound diagnostic
system. We built an ultrasonic imaging test system
for the real-time detection of pollutants in indoor water. The
system is mainly composed of a flume control system, the ultrasound
imaging acquisition system and a signal processing
system, as shown in Fig. 4. The flume control system is mainly
composed of glass water tank, water pump and frequency converter,
which is used to control the water flow speed and other
main equipment. The ultrasound imaging acquisition system
is mainly composed of the PUDI, video image acquisition
card, computer, and other parts. The signal processing system
is mainly a computer and its supporting signal processing software,
which contains its own independently developed image
signal processing software. The TY-6858-I ultrasound instrument
is a traditional analogue PUDI, and the output signal is
standard analogue video signal. Therefore, it is necessary to
configure a video image acquisition card to realize the realtime
transmission of image signals collected by the PUDI. The
PUDI provides a video output port, and the video image acquisition
card is installed on the computer through the PCI
port. The video output port of PUDI is connected through a
data line to realize the connection between the ultrasonic video
image and the computer. The ultrasound imaging test system
for indoor experiments is shown in Fig. 4.
In order to obtain a better pattern ultrasonic image, the
ultrasonic probe should be placed in a place where the flow
or area is relatively stable. In the test, by adjusting the relevant
buttons in the control panel of the PUDI, the appropriate
parameters are selected to obtain a better ultrasonic image.
During the test process, the parameters related to the PUDI are
generally set as follows: the frequency of the ultrasonic wave
is set as 5 MHz, the type of focus is set as 2 and 3, the near-field
gain can be set as 0, and the long-range gain can be set as 12. All
of the parameters can be changed according to the actual testing
conditions.
Monitoring Experiment by Using the System
In view of the underwater pollutants and the granular pollutants
at the interface of soil and rock, the probe of the PUDI was
directly placed under the surface of the field water for observation
and analysis. After that, the ultrasound video images
of the imaging pollutants can be obtained directly from the
groundwater and the shallow surface of the underwater soft
rock mass. The PUDI system is composed by an improved
Apogee 1100 digital color Doppler ultrasound diagnostic system
this time, as shown in Fig. 5.
Fig. 3. Ultrasonic images of particulate contaminant parasitic boundaries
using model sediment particles.
February 2023
The morphological characteristics of imaging pollutants
in the water from video images are analyzed and identified,
IEEE Instrumentation & Measurement Magazine
53
Instrumentation & Measurement Magazine 26-1

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