3B Scientific Test Vessel - Handbuch (Seite 7)

7
1. Introduction
In 1932 Debye and Sears demonstrated for the first time
how light is refracted when passing through a fluid ex-
cited to high-frequency oscillation. The maxima and
minima in density act here like the grid elements of
an optical diffraction grating. The grating constant
corresponds to the ultrasonic wavelength and is thus
dependent on the frequency of the ultrasound and the
speed of sound in the medium through which the
sound is travelling.
The CW (continuous wave) generator with its accompa-
nying broad-band ultrasound transducer, along with
an adjustable test vesseland its integrated laser holder,
mean that it is possible for the first time to demon-
strate this phenomenon to schoolchildren and college
students alike using simple and compact equipment.
The equipment can demonstrate both frequency de-
pendence (with four different frequencies) and the ul-
trasonic wavelength in various fluids, allowing the
speed of sound in the medium to be calculated.
It is also possible to project standing ultrasonic waves
by inserting an optical lens between the laser source
and the ultrasonic waves. The waves are then projected
by the diverging laser beam.
2. Components
2.1 Ultrasound generator - operating elements
1 Mains switch
2 On/off switch for laser
3 Connector socket for laser
4 Control light for laser
5 Connector socket for ultrasonic transducer
6 Control light for ultrasonic transducer
7 Monitor output
8 On/off switch for ultrasound
9 Frequency selection switch
bl Voltage display
bm Voltage setting
The ultrasound generator generates continuous high-
power ultrasonic waves (CW = continuous wave). The
voltage
bm can be adjusted between 5 and 65 V. There
is an LCD display for the voltage output bl . The trans-
mitted voltage can be switched off separately 8 . The
frequency can be set to one of four frequencies (1, 2, 4
or 8 MHz)
9 . An additional monitor output 7 allows
the output frequency to be determined precisely with
the aid of an oscilloscope or a frequency counter. A
suitable output
3 is provided to supply power to a
laser diode. This can also be switched off separately
2 .
Adjustment of mains voltage
The ultrasound generator can operate with 230 V or
115 V mains voltage. A voltage selector switch is situ-
ated on the rear of the casing and is hidden beneath
the covering to the right of the rear panel. A screw-
driver is used to alter the switch setting (see illustra-
tion). If the mains voltage is altered, the fuse needs to
be changed to suit the mains voltage. A T630 mA fuse
should be used with 115 V mains voltage and a T315
mA fuse for 230 V mains.
Warning:
Unplug from the mains before altering the mains set-
ting.
No voltage may be applied to the device while making
the adjustment,
115
230
1
2
3
1 2 3 4 5 6 7
bm
bl
9
8
1 Remove the two screws from the rear panelling and take off
the panel. The voltage selector switch is revealed.
2 Fuse
115 V 630 mA
230 V 315 mA
3 An arrow indicates the voltage that is currently set. Adjust using
a screwdriver inserted into the slit.