3B Scientific Training Oscilloscope - Manual

3B SCIENTIFIC ® PHYSICS
1
Demonstration oscilloscope U8481350
Instruction sheet
01/08 CW/ALF
Inputs:
1 Anode
voltage
2 Cathode voltage
3 Wehnelt (focussing) voltage
4 Heater voltage (0)
5 Heater voltage (+)
6 Chassis
ground
7 Deflecting plate (left)
8 Deflecting plate (right)
Outputs:
9 Saw-tooth generator (-)
10 Saw-tooth generator (+)
11 Deflecting coils
12 Circular magnet (obscured by
deflection coil)
13 Cathode ray tube
14 Metal ring
15 Coarse adjustment for saw-
tooth frequency
16 Fine adjustment saw-tooth
frequency
1. Safety instructions
The demonstration oscilloscope is operated with volt-
ages, some of which are above 60 V.
• Always turn off power supply before making con-
nections.
• Use safety leads.
Since the glass tube is evacuated, there is an implo-
sion hazard.
• Do not subject the tube to sharp blows or me-
chanical stress.
In schools and training institutions, operation of the
device is to be responsibly supervised by trained per-
sonnel.
2. Description
The demonstration oscilloscope can be used to show
the deflection of an electron beam by electric and
magnetic fields, just as employed in TVs or conven-
tional oscilloscopes. Essentially, it consists of a cath-
ode ray tube that is supplied with voltage via 4-mm
plugs and is surrounded by a ring, to which deflecting
coils can be attached.
A cathode ray tube is an evacuated glass tube, the
neck of which contains a heated cathode and an an-
ode in the shape of a disc with a hole in the middle,
separated by a distance of approximately half a cen-
timetre. Electrons emitted from the heated cathode
are accelerated towards the anode. Some of them
pass through the hole to form a beam that strikes the
fluorescent screen (with zinc silicate coating) and thus
becomes visible as a green fluorescent dot. The beam
is focussed partly by a Wehnelt cylinder surrounding
the cathode, the potential of which is negative with