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Idiomas disponibles
5. Pin assignment
Fig. 1 A Heating element, B Sample current through
germanium crystal, C PT100 thermocouple
6. Operation
Installation of the circuit board in the Hall effect
console and the circuit diagram for the experiment are
included in the instruction manual for the Hall effect
equipment itself.
7. Care and maintenance
•
Use a soft brush to clean the board. Do not touch
the crystal with your fingers if possible.
•
Keep in the original box after the equipment has
been used and has cooled down.
8. Disposal
•
If you need to dispose of the circuit board, never
throw it away in normal domestic waste. Local
regulations
for
equipment will apply.
The packaging is made of environmentally-friendly
materials and can be recycled.
•
You can dispose of it at local recycling points.
Elwe Didactic GmbH • Steinfelsstr. 5 • 08248 Klingenthal • Germany •
3B Scientific GmbH • Rudorffweg 8 • 21031 Hamburg • Germany •
the
disposal
of
electrical
Subject to technical amendments
© Copyright 2012 3B Scientific GmbH
9. Experiments
Measurement of conductivity as a function of
temperature
U / mV
3000
2500
2000
1500
1000
500
0
300
350
Fig. 2 Sample voltage U as a function of temperature T
(Voltage drop across germanium crystal for sample currents
of 2 and 3 mA)
Measurements:
U
: Sample voltage (basic apparatus)
P
T
: Sample temperature (basic apparatus)
P
Derived values:
I
σ
=
⋅
Conductivity:
U
10
Absolute temperature in Kelvin:
⎛
⎞
1
σ
=
⎜
⎟
Form:
ln
f
⎝
⎠
T
This is because at high temperatures (intrinsic
conductivity) the following applies:
Eg 1
σ
=
σ
⋅
ln
ln
-
2
K
T
Eg ≈ 0.7 eV
eV
5 −
= .
⋅
k
8
625
10
K
σ
ln ( / S/m)
6
5
4
3
2
1
0
0.0022
0.0024
0.0026
0.0028
Fig. 3 Conductivity σ as a function of absolute temperature T
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www.3bscientific.com
I = 2 mA
I = 3 mA
400
450
T / K
20
mm
⋅
mm
1
mm
=
+
T
T
273,15
K
P
band gap for germanium
Boltzmann's constant
I = 2 mA
I = 3 mA
0.0030
0.0032
0.0034
1/ / 1/K
T
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