SW Ultrasonics Set
3B SCIENTIFIC
SW Set - Ultrasonics (230 V, 50/60 Hz) 1012845
SW Set - Ultrasonics (115 V, 50/60 Hz) 1012846
Instruction manual
08/12 TL
®
PHYSICS
1. Description
The SW set for ultrasonics is designed to demonstrate the fundamental properties of waves in
the form of a space-saving table-top set-up,
using 40-kHz ultrasonic waves as an example.
The sound is propagated along the surface of
the table, to a good approximation. Diffraction
objects, plane and convex mirrors etc. are therefore designed to be set up in the plane above
the table top. This facilitates setting up easily
understood experiments using work templates
and overlays.
Suitable probes make it possible to record oscillations at any point of the wave and to measure
the field of sound after reflection, wave diffraction and interference. One of these probes, the
ultrasonic pen, also features a phase indicator in
the form of an LED, the brightness of which is
reduced to a minimum when the phase difference between the point where the measurement
is being made and a selected reference point is
a multiple of 360°. The ultrasonic pen can thus
be used to record wave fronts as lines of similar
phase, for example (isophases).
For some advanced experiments it is recommended that a multimeter with a suitable frequency response be used to measure the amplitude of ultrasonic waves. Connecting a dualchannel oscilloscope allows the ultrasonic oscillations at the location of the probe to be displayed.
The equipment set with the order no. 1012845 is
designed for mains voltage of 230 V (±10%),
while set no. 1012846 is for 115 V (±10%).
1
2. Equipment supplied
1 Holder for ultrasonic pen
2 Ultrasonic pen
3 BNC cable, 1 m (2x)
4 Microphone probes (2x)
5 BNC/4-mm cable
6 Set for double slit
including 2 mirrors/reflectors
7 Electronics board
8 Fresnel zone plate
9 Semi-transparent mirror, 50%
10 Semi-transparent mirror, 25%
11 Ultrasonic absorber
12 Convex mirror
13 Ultrasonic transmitter, 40 kHz (2x)
14 Plug-in power supply (230 V, 50/60 Hz)
or
1 Plug-in power supply (115 V, 50/60 Hz)
not shown
1 Set of templates not shown
3. Electrical safety
The SW ultrasonics set conforms to safety regulations for electrical measurement, control and
laboratory equipment as specified in DIN EN
61010 part 1. It is designed for operation in dry
rooms suitable for electrical equipment.
Safe operation of the system is guaranteed if used
as stipulated. Safety cannot, however, be assured if
the equipment is treated incorrectly or carelessly.
4. CE compliance
The SW ultrasonics set (electronics board, ultrasonic pen and microphone probe) conform to
European guidelines for electromagnetic compatibility (EC 108/2004) and are therefore CE
compliant.
2
5.1 Electronics board
Δϕ
AB
A
5. Components
12 91013
11
12V AC
G
2
f
B
1 3 5 86 72 4
Fig. 1 Electronics board
1 Switch S1
2 Input for channel B
3 Switch S2
4 Output for channel B
5 Frequency trimmer for generator G2
6 Amplitude trimmer for generator G2
7 Switch S3
8 Outputs for generator G2
9 Outputs for generator G1
10 Amplitude trimmer for generator G1
11 Co-axial connector for plug-in power supply
12 Output for channel A
13 Input for channel A
40 kHz25 kHz
The electronics board for operating the equipment provides the power feed for the ultrasonic
transmitter and amplification for signals from the
microphone probes or ultrasonic pen, as well as
handling control of the phase indicator in the
ultrasonic pen.
The electronics board consists of a generator
block in two parts and a two-channel amplifier
block, which also includes a functional unit for
comparing phase between the two channels.
The AC voltages for the ultrasonic transmitter
are produced in the generator block. Generator
G1 is stabilised to 40.000 kHz by a quartz oscillator, while G2 can be switched between frequencies of 25 and 40 kHz, which can also be
varied by about ±0.5%. Both generators are
equipped with an amplitude trimmer and two
output sockets connected in parallel.
In the amplifier block, the voltages from the ultrasonic probes are amplified and output to the
BNC sockets. It is possible to connect a highpass filter into the circuit for both channels, in
order to filter out low-frequency components of
the sound.
After the input amplifiers there is a functional
block which compares the signals from channels
3
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