3B SCIENTIFIC PHYSICS 1000620 Instrucciones De Manejo página 11

Fig. 1 Experiment set-up with the control unit for critical potential tubes
7.2.1 Procedure with 3B NETlog
• At the output V
A
minimum voltage to about 10 V and the
maximum voltage to about 35 V, by using
the 3B NETlog™ unit to measure the
voltages (smaller by a factor of 1000)
between socket 3 and earth and that
between socket 4 and earth. Alternatively,
the voltages can be set up with the help of a
multimeter.
• Connect the 3B NETlog™
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. (See Fig. 2)
• 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 analogue inputs A and B and DC
•
voltage mode
measurement ranges to 200 mV for A and
2 V for B.
• Enter the formula I = -667 * "Input_B" (unit
pA).
TM
of the control unit, set the
unit to
(VDC), setting
C5
F4
F3
A1
+
1
2
• Set the following parameters: Measurement
interval = 50 µs, Measurement duration =
0.05 s, Mode = Recorder.
• Set triggering on the input A with rising edge
(20%).
• On the DC power supply, set the heater
voltage to 3.5 V.
• Start the graph-plotting of the experimental
data.
• Set up the graph with "relative time t in s" on
the
the x-axis and the quantity I on the y-axis.
• Repeat the measurements with slightly
higher heater
minimum
voltages U
• In the spectrum, identify the 2
19.8 eV and determine its position t
time axis.
• Identify the ionisation threshold at 24.6 eV
and determine its position t
the
axis.
• Enter a new formula for the quantity E
defined as 19.8 + 4.8 * (t - t
the unit eV; in this expression enter the
3
Battery Unit
-
OUT
3
60
200 mV
MAX
!
V
A
4
V
SET
HERTZ TUBE CONSOLE
MIN
0...±1 VOLT OUT 0...±1 VOLT OUT
SLOW
SLOW FAST
1 2 1 2
RUN
RING
voltages and
and maximum
to find the optimum graph.
A
2
)/( t
1
+
3
A
4
vary the
accelerating
3
S peak at
on the
1
on the time
- t ) with
2 1