PASCO WA-9611_13 SONOMETER - Manual (Page 15)

11
012-03489E Sonometer
Experiment 1: Resonance Modes of a Stretched String
EQUIPMENT NEEDED:
– WA-9611 Sonometer – Mass and mass hanger
– WA-9613 Driver/Detector Coils – Dual trace oscilloscope
– Function generator capable of delivering 0.5 amp
Procedure
➀ Set up the Sonometer as shown in Figure 1.1.
Start with the bridges 60 cm apart. Use any of the included strings and hang a mass of approxi-
mately 1 kg from the tensioning lever. Adjust the string adjustment knob so that the tensioning
lever is horizontal. Position the driver coil approximately 5 cm from one of the bridges and posi-
tion the detector near the center of the wire. Record the length, tension (mg), and linear density
of the string in Table 1.1.
➁ Set the signal generator to produce a sine wave and set the gain of the oscilloscope to approxi-
mately 5 mV/cm.
➂ Slowly increase the frequency of the signal to the driver coil, starting at approximately 25 Hz.
Listen for an increase in the volume of the sound from the sonometer and/or an increase in the size
of the detector signal on the oscilloscope screen. Frequencies that result in maximum string vibra-
tion are resonant frequencies. Determine the lowest frequency at which resonance occurs. This is
resonance in the first, or fundamental, mode. Measure this frequency and record it in Table 1.1.
➃ Start with the detector as close as you can get it to one of the bridges. Watch the oscilloscope as
you slide the detector slowly along the string. Locate and record the locations of each node and
antinode. Record your results in Table 1.1.
➄ Continue increasing the frequency to find successive resonant frequencies (at least five or six).
Record the resonance frequency for each mode, and the locations of nodes and antinodes in
Table 1.1.
Figure 1.1 Equipment Setup
Channel 2 (detector coil)
Channel 1 (driver coil)
Detector coil
1 kg
Driver coil String
adjustment
knob Tensioning
lever
WA-9611
SONOMETER
KEEP WEIGHTS AS NEAR TO FLOOR
AS POSSIBLE IN THE EVENT THE SONOMETER WIRE SHOULD BREAK
CAUTION!
1.75 kg MAXIMUM LOAD ON LEVER
BK PRECISION
200 Mhz OSCILLISCOPE MODEL
2 1 2 0
INTENSITY FOCUS
TRACE NOT ATION
TRIG LEVEL
COUPLE SOURCE
SLOPE - Y
TIME/DI V
X-POS
VAR VAR
VAR SWEEP
CAL CAL m V V
CH 1
VOLTZ/DIV CH 2
VOLTZ/DIV
CAL m V V
VERTICAL MODE
PULL XS PULL XS
CH 2
∞
CH 1
∞
AC
DC
AC
DC
AC CH1
CH2
ALT
EXT
POS POS NORM
EXT CH1
CH2 NORM EXT CH1 CH2
MANUAL AUT O T X-
YT X-
Y
LINE
CAL EXT CH4
POWER
200V
MAX 400V
MAX 400V
MAX
- +
+
-
T T L H I
Ω
G
N D
L O Ω M I
N
R A
N G E
A D J U S T
M A X
O U T P U T F R E Q U E N C Y
A M P L I T U
D E
P I - 9 5 8 7 B
D I G I T AL FUNCTION
G E N E R A TOR -
A M P L I F I E R
H E R T Z
WA V E F O R M
I N P U T G N D E X T E R N A L
DETECT OR
W A-9613
DRIVER
WA-9613
60 cm
Oscilloscope Frequency generator