3B Scientific Premium Franck-Hertz Experiment Heater User Manual
3B SCIENTIFIC
®
PHYSICS
Franck-Hertz Tube with Hg Filling and Heating Chamber (230 V, 50/60 Hz)
Franck-Hertz Tube with Hg Filling and Heating Chamber (115 V, 50/60 Hz)
1006795 (230 V, 50/60 Hz)
1006794 (115 V, 50/60 Hz)
Instruction sheet
06/12 ALF
1. Safety instructions
The apparatus conforms to the safety regulations for
electrical test, control and laboratory equipment as
specified in DIN EN 61010 Part 1. Its protection classification is deemed to be class I. It is intended for use in dry
rooms suitable for electrical equipment or installations.
Safe operation of the equipment is guaranteed, provided it is used correctly. However, there is no guarantee of safety if the equipment is used in an improper or careless manner. If it is deemed that the
equipment can no longer be operated without risk
(e.g. visible damage has occurred), the equipment
should be switched off immediately and secured
against any inadvertent use.
In schools and training institutions, operation of the
apparatus is to be responsibly supervised by trained
personnel.
• Before putting the equipment into operation, con-
firm it is compatible with the local mains voltage.
• Before setting up or starting any experiments,
check the apparatus for any damage.
• In the event of any malfunction/defect or visible
damage, switch off the equipment immediately
and secure it against any inadvertent use.
• The instrument may only be connected to the
mains via a socket that has an earth connection.
• Only trained electricians are permitted to open
up the apparatus’ housing.
Beware: Risk of burns! The viewing windows and the
walls of the heating chamber can reach temperatures of up to 300° C during operation.
• Set up the heating chamber on a heat-resistant
surface.
• When the heating chamber is in operation, do
not attempt to touch or move the apparatus.
Only move or transport the equipment by using
the insulated handle.
• Allow the apparatus to cool before dismantling
the experiment.
Beware: There is always a risk that glass can break
and cause injury.
• Use all six knurled screws to affix the front plate
to the heating chamber.
• Do not subject the tube to any mechanical
stress. Do not put kinks in any connecting leads.
The Franck-Hertz tube contains mercury.
• If the glass breaks and mercury escapes, make
sure to observe safety regulations relating to the
handling of mercury.
1
2. Description
The Franck-Hertz tube with its mercury filling is used
to demonstrate the quantised release of energy by
free electrons colliding with mercury atoms and to
determine that the excitation energy for the mercury
resonance line (6
1
S0 – 63P1) is 4.9 eV.
Franck-Hertz tube attached to front plate
The Franck-Hertz tube is a highly evacuated electron
tube containing mercury with its electrodes set up in
parallel planes. The electrodes consist of an indirectly
heated oxide cathode, an anode grid and a collector
electrode. In order to increase the likelihood of collisions, the distance between the anode and cathode
has been made large (8 mm) in comparison to the
mean free path in a mercury atmosphere (for a temperature of approx. 180°C). By contrast, the distance
between anode and collector is small. An earth ring is
located level with the anode grille to prevent disturbance due to background radiation. The tube is
mounted on the front plate of the heating chamber
and can be removed or exchanged. The front plate
also has ceramic-insulated sockets and a schematic
diagram of the tube. The Franck-Hertz tube is
mounted in such a way that the whole tube and its
connecting wires can all be maintained at constant
temperature. This is necessary because the density of
the mercury vapour is always determined at the coldest point of the tube. Leakage currents resulting from
radiation due to ion conduction in the hot glass walls
are prevented by a protective sintered alumina ring. A
fixed attenuating resistor (10 kΩ) is inserted between
the sockets for the accelerating voltage and for the
anode of the tube. This protects the tube in the event
of excessive voltage occurring due to arcing. The voltage drop across this resistor can be neglected when
measurements are being made.
Heating chamber
The heating chamber serves to establish the vapour
pressure inside the Franck-Hertz tube with its mercury
filling and helps you carry out experiments with a sodium fluorescence tube (1000913).
It consists of a powder-coated sheet steel casing with
two viewing windows. The front plate is attached via
six knurled screws. The chamber is heated via a tubular heating element in the chamber floor. Temperature measurement and regulation is carried via an
integrated micro-controller and a PT 100 thermocouple. A digital temperature display allows you to
read off the temperature set-point and the actual
temperature value. The “SET” button can be used to
toggle the display between ° Celsius and ° Fahrenheit. The “+/-” keys allow you to set the set-point for
the temperature in steps of 1 K. There is an opening
at the top with a spring clip for holding a thermometer and a thermally insulated carrying handle.
The apparatus 1006794 is for operation with a mains
voltage of 115 V (±10%), and the unit 1006795 is for
operation with a mains voltage of 230 V (±10%).
2.1 Scope of delivery
1 Franck-Hertz tube with mercury filling mounted
on front-plate
1 Heating chamber without front plate
1 Instruction sheet
1 Power switch 2 Operating display
3 “SET” button 4 Display
5 “+/-” buttons 6 Thermal insulation
7 Knurled screws 8 Front plate with Franck-
8 Hertz tube attached (not
8 shown)
9 Cathode socket 10 Tube filament socket
11 Anode socket 12 BNC socket for signal
12 output
13 Heating chamber 14 Spring clip for thermometer
15 Handle
3. Technical data
Franck-Hertz tube
Filament: 4 to 12 V AC/DC
Grid voltage: 0 to 70 V
Bias voltage: 1.5 V approx.
Operating temperature: 200° C approx.
Tube dimensions: 130 mm x 26 mm diam.
Weight: 380 g approx.
Heating chamber
Mains voltage: See back of case
Dimensions of front
opening: 230 x 160 mm² approx.
Heating power: 800 W (230 V, 50/60 Hz)
400 W (115 V, 50/60 Hz)
Maximum temperature: 300°C (230 V, 50/60 Hz)
250°C (115 V, 50/60 Hz)
Temperature constancy: ±1°C approx.
Dimensions: 335x180x165 mm³ approx.
Weight: 5.6 kg approx.
2
Loading...