3B Scientific Teltron Critical Potentials Tube S with He-Filling - Manual (Page 2)

UE502050 3B SCIENTIFIC® PHYSICS EXPERIMENT
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LIST OF APPARATUS
1 Critical Potential Tube S with He-Filling U18560
1 Tube Holder S U185001
1 Control Unit for Critical Potential Tubes U18650
1 DC Power Supply, 0–5 V, 2 A, e.g. U33020
1 3B NETlog™ U11300
1 3B NETlab™ U11310
1 Set of 15 Experiment Leads, 75 cm 1 mm² U13800
1 PC with Windows 98/2000/XP, Internet Explorer 6 or
later and USB connection
SAFETY INSTRUCTIONS
Hot cathode tubes are thin-walled, highly evacuated glass tubes.
Treat them carefully as there is a risk of implosion!
•
Do not subject the tube to mechanical stresses.
•
Ensure that the connecting lead to the collector ring is not
under any tension and there is no risk of it being accidentally
pulled out.
SET-UP
•
Fit the critical potential tube into the tube holder, ensuring
that the contact pins of the tube are correctly and fully
engaged in the tube socket of the holder. The central guide pin
of the tube should project slightly at the back of the holder.
•
Connect the sockets F3 and F4 of the tube holder to the output
terminals of the DC power supply.
•
Connect socket C5 of the tube holder to the negative terminal
of the output V
A
on the control unit (C5 and F4 are connected
together internally inside the tube).
•
Connect socket A1 to the positive terminal of the output V
A
on
the control unit and to the negative terminal of a 1.5 V battery.
•
Connect the positive terminal of a 1.5 V battery to an earth
socket on the control unit.
•
Fit the screening frame over the tube, push its folded edge into
the opening in the tube holder and connect it to an earth
socket on the control unit.
•
Connect the lead from the collector ring to the BNC input
socket of the control unit.
EXPERIMENT PROCEDURE
Preparation:
•
At the output V
A
of the control unit, set the minimum voltage to
about 15 V and the maximum voltage to about 28 V, by using
the 3B NETlog™ unit to measure the smaller (by a factor of
1000) voltage between socket 3 and earth and that between
socket 4 and earth.
•
Connect the 3B NETlog™ unit to the computer.
•
Connect the output “Fast 1” from the control unit to input A of
the 3B NETlog™ unit and the output “Fast 2” to input B.
•
Switch on the 3B NETlog™ unit and start the 3B NETlab™
program on the computer.
•
Select the “Measurement lab” function and open a new data
record.
•
Select analog inputs A and B and DC voltage mode (VDC),
setting the measurement ranges to 200 mV for A and 2 V for B.
•
Enter the formula I = -667 * “Input_B“ (unit: pA).
•
Set the following parameters: Measurement interval = 50 µs,
Measurement duration = .05 s
Mode = Standard.
•
Set triggering to occur on the input signal’s rising edge (20%).
•
On the DC power supply, set the heater voltage to 2.7 V.
Fig. 3: Experiment set-up for measuring the critical potentials of helium