Instruction Manual

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2.2. Microphone probe
The microphone probe is used to measure changes in
sound pressure inside Kundt’s tube.
A miniature microphone is attached to the end of a long
rod made of stainless steel. It is connected by means of
a 5-pole DIN plug to the battery box (U20602). This battery
box also has a terminal for connecting an oscilloscope or
voltmeter. The microphone probe can be connected
directly to the digital counter (U21000) via the adapter
U20603.
Microphone’s frequency range: 20 Hz to 20000 Hz
Probe’s dimensions: 740 mm x 8 mm Ø
Connection cable’s length: 2 m
2.3. Battery box
The battery box supplies the microphones (for instance,
U20601 or U18030) and other analog sensors with a po-
wer of 5 V DC so that they can be connected directly with
a measuring device or an oscilloscope.
The box consists of a compartment for a 9-V alkaline
battery which supplies the required 5 V DC via a regulator.
Two 6-pole DIN jacks (180°) and one 8-pole DIN jack (270°)
are available as input channels. Two 5-pole DIN jacks and
two 4-mm safety jacks serve for connecting measuring
devices.
Dimensions: 143 mm x 84 mm x 37 mm
1 DIN jacks for connecting measuring devices
2 4-mm safety jacks for connecting an oscilloscope,
voltmeter or interface
3 DIN jack for connecting various sensors or a LabPro
interface via an output adapter
4 DIN jacks for connecting microphones
Note:In order to make simultaneous use of the micro-
phone probe U20601 and an oscilloscope, connect the
microphone probe to the sensor input (3) and the oscil-
loscope to the output (2).
3. Sample experiments
3.1 Stationary waves in a closed tube
3.2 Stationary waves in carbon dioxide
3.3 Stationary waves in a tube with one closed end
3. Stationary waves in an open tube
3.5 Changes in the air column
Sound source: Tuning fork or loudspeaker
To perform these experiments, additional use is re-
quired of a function generator (for example, U21015)
to excite the loudspeaker, and an oscilloscope (for
instance, U11175) to display the oscillation nodes
and antinodes.
3.6 Determination of the speed of sound in air
• Install Kundt’s tube with closed ends and the mi-
crophone probe on a tripod; connect a function
generator (for instance, U21015) and an oscilloscope
(for instance, U11175).
• Apply a frequency f = 2700 Hz to the loudspeaker.
• Move the microphone probe past the nodes and
measure the intervals between them using the scale.
• The average interval between two neighbouring
nodes turns out to be 6.3 cm.
• This results in a wavelength λ = 12.6 cm.
• The speed of sound c is calculated with the for-
mula c = f · λ
c = 2,7 · 10
3
· 12,6 · 10
–2
m/s = 340 m/s
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3B Scientific GmbH • Rudorffweg 8 • 21031 Hamburg • Germany • www.3bscientific.com • Technical amendments are possible