012-03498C
Shielded cable with
,BNCconnectors
Voltmeter: 0-1 VDC
I,,
the anode current)
(Voltage proportional
t
Important:
If
an oscilloscope is
used in this setup, the
Voltmeters are not
needed.
If
the voltme-
ters are used, the
oscilloscope is not
needed.
I
I
'
oscilloscope:
y-input
Voltmeter:
0-30
VDC
rat ing Vo
e)
Sample of oscilloscope display
I
Figure 4 Franck-Hertz Experiment Using the Control Unit
B.
Using the Control Unit and Voltmeters
1.
Remove the
six thumbscrews that secure the front panel
of the Franck-Hertz Oven. Replace the front panel with
the Franck-Hertz
Tube
as
shown in Figure
4.
2.
Insert a centigrade thermometer
(0-200 degrees) into the
hole in the top
of the oven. Insert it
so
the tip of the
thermometer
is near the center of the
tube.
3. Check the label and plug the oven into
an
appropriate
AC power outlet, then
turn
the thermostat dial
to
180
Let the oven heat up for 10-15 minutes. Keep
an
eye
on the thermometer.
Do
not let the oven temperature
exceed 205
4.
Connect the
tube,
control
unit,
and voltmeters as shown
in Figure
4
(the oscilloscope connections that are shown
in the figure
are
not necessary when using voltmeters).
5.
Switch on
the
control unit, but only AFTER the
tube
has
been allowed to warmp up for 10-15 minutes. Initially,
set the controls
as
follows:
6.
7.
8.
9.
Heater:
midrange (about 5.5
V)
Amplifier:
Gain
-
maximum
gain (fully clockwise)
Va:
Switch-Man.
(-
)
Zero
-
midrange
Adjust
-
zero (fully counterclockwise)
Allow at least
90 seconds for the cathode
to
heat up.
Adjust the Amplifier
Zero
so
that the amplifier output is
zero volts (if it won't go to zero, just adjust it
as
close
to
zero
as
possible).
Increase the accelerating voltage in increments
of
about
0.5 volts, by turning the
Va
Adjust knob clockwise.
At
each value of
Va,
record
Va
and the corresponding value
for the amplifier output.
Note: The amplifier output is not equal
to
Ic.
It is
a
voltage that is proportional
to
Ic.
See
Analyzing
the
Experiment
at the end of the manual
for details about manipulating and analyzing your
data.