Jeulin 223 008 Mode D'emploi page 50

Ultrasounds
Moduson table
Ref :
223 008
3.1 Step 2: Protocol
 Preliminary setting of the transmitters
The main transmitter is assumed to be set at its maximum transmission level. It is connected
to the MODUSON transmitter 2.
The two transmitters connected to the same signal generator are synchronous sources.
However, the following adjustments are required to give them an identical amplitude:
1. Install the two transmitters in the magnetic recess on the moulded PVC table. Place them
2. Disconnect the transmitter 2 and observe the signal transmitted by the main transmitter
3. Switch the main transmitter ON: then the two transmitters operate simultaneously and
 Measurements:
The oscilloscope settings are 0.1 V/div for vertical amplification and on 0.1 msec/div for
horizontal sweep.
Note : The minima are more easily identified that the peaks. However, the minima are not zero and
they are less and less marked. The amplitudes of the interfering signals are not equal and the
difference between them increases as the distances d
ENGLISH
at a distance of e.g. 2 cm from each other (smallest distance). Place a receiver in one of
the arc-shaped recesses opposite the zero-degree angle value (then the receiver is
located on the median of the segment joining the two receivers and it is equidistant
between them) and connect it to the vertical input of an oscilloscope.
and sensed by the receiver. Record the amplitude value. Connect the transmitter 2 and
switch the main transmitter OFF (in this position, the transmitter member is off but the
generator is not and continues delivering the same signal on the BNC connector, hence
to the transmitter 2), then only the transmitter 2 is active. Using the transmitter
potentiometer, trim the amplitude of the received signal so that the amplitude value is
identical to the previous reading.
they have the same amplitude. This produces a peak that is sensed by the receiver (a
slight position adjustment by 1–2 degrees may be necessary to obtain this peak).
• Select the distance a between the 2 transmitters (3 values are marked: a=2 cm, a=4
cm and a=8 cm, but any other value from 2 to 4 cm can be measured by means of a
20-cm rule) and the radius D of the receiver displacement arc (2 radii can be used:
D=15 cm and D=30 cm).
• Let for example the values a=4 cm and D=15 cm.
• Once the receiver has been installed, its displacement inside the arc-shaped recess
will produce a succession of peaks and minima having the amplitude of the signal
sensed by the receiver and observed on the oscilloscope screen.
• This is the series of the antinodes and nodes corresponding to the constructive and
destructive interferences that appear in the vicinity of the two synchronous sources
used.
• To obtain good measurements, proceed as follows:
o position the transmitter opposite the zero-degree graduation
o this corresponds to an amplitude peak (trim as required)
o slowly move the receiver towards the increasing values of the angle θ (e.g. to the
right)
o stop when the first amplitude peak of the received signal is obtained, trim, read and
record the corresponding value
o continue until the extreme receiver position is reached
o repeat these steps for the values of the angle θ to the left.
• Repeat the above steps for the angles corresponding to the amplitude minima.
and d become different.
1 2
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