3B Scientific Teltron Triode D, Vacuum - Manual (Page 2)

1
3. Technical data
Filament voltage: 7.5 V max.
Filament current: 3 A approx.
Anode voltage: 500 V max.
Anode current: U
A
400 V and U
F
6.3 V
U
G
0 V, I
A
0.4 mA approx.
U
G
+8 V, I
A
0.8 mA approx.
U
G
-8 V, I
A
0.04 mA approx.
Grid voltage: ± 10 V max.
Glass bulb: 130 mm diam. approx.
Total length: 300 mm approx.
4. Operation
To perform experiments using the triode, the
following equipment is also required:
1 Tube holder D
1008507
1 DC power supply 500 V (115 V, 50/60 Hz)
1003307
or
1 DC power supply 500 V (230 V, 50/60 Hz)
1003308
1 Analogue multimeter AM51 1003074
Additionally recommended:
Protective Adapter, 2-Pole 1009961
4.1 Setting up the tube in the tube holder
• The tube should not be mounted or removed
unless all power supplies are disconnected.
• Push the jaw clamp sliders on the stanchion of
the tube holder right back so that the jaws open.
• Push the bosses of the tube into the jaws.
• Push the jaw clamps forward on the stan-
chions to secure the tube within the jaws.
• If necessary plug the protective adapter onto
the connector sockets for the tube.
4.2 Removing the tube from the tube holder
• To remove the tube, push the jaw clamps right
back again and take the tube out of the jaws.
5. Example experiments
5.1 Generation of charge carriers by a hot
cathode (thermionic effect) and deter-
mining the polarity of the charge carriers
so emitted
• Set up the circuit as in Fig. 1. Connect the
minus pole of the anode voltage to the 4-mm
socket marked with a minus.
• Set the anode voltage U
A
to 400 V.
When the grid voltage U
G
is 0 V the anode cur-
rent is about 0.4 mA.
• Set the grid voltage to +10 V resp. -10 V.
If the voltage of the grid is positive with respect
to the anode, the anode current I
A
is considera-
bly increased. If the grid is negative with respect
to the cathode the anode current decreases.
A heater filament generates charge carriers.
Current flows between the cathode and the an-
ode. The charge carriers must be of negative
polarity because when the grid is negative with
respect to the cathode the flow of current de-
creases and when it is positive, the flow of cur-
rent increases.
5.2 Recording triode characteristics
• Set up the circuit as in Fig. 1. Connect the
minus pole of the anode voltage to the 4-mm
socket marked with a minus.
• I
A
– U
A
characteristics: for constant grid volt-
ages, determine the anode current as a
function of the anode voltage and plot the
values in a graph (refer to Fig. 2).
• I
A
– U
G
characteristics: for constant anode
voltages, determine the anode current as a
function of the grid voltage and plot the val-
ues in a graph (refer to Fig. 2).
5.3 Generating cathode rays
• Set up the circuit as in Fig. 3 so the grid and
cathode form a diode. Connect the minus
pole of the anode voltage U
A
to the 4-mm
socket marked with a minus.
• Raise the anode voltage U
A
from 10 V to 80 V
and measure the current flowing at the anode.
The current decreases at higher voltages since
the positive potential of the grid causes it to cap-
ture electrons causing an increase in the current
passing through the grid itself. Voltages greater
than 100 V can lead to the destruction of the grid.
Electrons accelerated by higher potentials be-
tween the grid and the cathode can be detected
beyond the grid (cathode rays). Increasing the
voltage leads to higher currents which indicates a
greater number of electrons being accelerated.
5.4 Triode amplifier
Also required:
1 AC/DC power supply 12 V (115 V, 50/60 Hz)
1001006
or
1 AC/DC power supply 12 V (230 V, 50/60 Hz)
1001007
1 Resistor 1 MΩ
1 Oscilloscope
• Set up the circuit as in Fig. 4. Connect the
minus pole of the anode voltage to the 4-mm
socket marked with a minus.
• Apply an anode voltage U
A
of about 300 V.
The oscilloscope is used to demonstrate the
amplification in the signal across the resistor.
• Repeat the experiment using a variety of
resistors.
Lower AC voltages at the grid lead to greater
changes in voltage across a resistor connected
in circuit with the anode. The amplification gain
increases with the size of the resistor.