3B Scientific Plate Capacitor D User Manual
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racy of 1/10 mm. A switch (5) can turn the display
of the measuring unit on or off, while the actual
measurement acquisition continues. Another
switch (4) switches the units for the display be-
tween mm and inches.
3. Technical data
Plate surface area:
500 cm
2
Plate thickness:
3 mm
Plate spacing:
0 – 160 mm
Accuracy: 1/10
mm
Measuring unit:
Electronic
0….160
mm
Battery for measuring unit: LR44
Dimensions:
400 x 260 x 340 mm³
Weight:
4 kg approx.
4. Operation
4.1 General notes
Never hold the plate capacitor apparatus other
than by the guide rail (2) and the stator (14).
Conducting deposits on insulating plastic parts
of the capacitor plates could lead to errors in
measurements.
•
Before use, clean the apparatus with a dry,
microfibre cloth.
•
Protect the guide rail (2) from dirt and dust.
If necessary, you should clean it using a thin
brush or cloth.
•
After use, close the plates together and se-
cure them with the fastening screw (9) for
storage.
•
Store the apparatus in a dry, dust –free loca-
tion.
If the plate capacitor apparatus has not been
used for a long period, it is possible to remove
the watch battery from the measuring unit.
•
Do not dispose of the
battery in the regular
household garbage.
Follow the local
regulations (In Ger-
many: BattG; EU:
2006/66/EG).
4.2 Preparation
•
Perform the experiment on a level surface
where the apparatus cannot tip over.
•
Make sure the wires to the plates are as
short as possible.
•
Before using the measuring unit, configure
the display to zero with the two plates closed
together. Push the movable plate gently
against the fixed stator plate and then press
the zero configuration button (6).
The fine adjustment screw is to aid with precise
adjustment of the distance when the separation
between the plates is small. The guide block
(10) should also be gently pressed against the
adjustment screw.
5. Sample experiment
Measurement of electric field constant ε
0
The following equipment is also required to com-
plete the experiment:
1 Function generator, FG 100 (230 V, 50/60 Hz)
1009957
or
1 Function generator, FG 100 (115 V, 50/60 Hz)
1009956
1 Precision resistor, 10 k
Ω 1000685
1 Analogue oscilloscope 2x 30 MHz 1002777
1 HF patch cord, BNC/4 mm plug
1002748
Leads for experiments
•
Set up the experiment as shown in Fig. 2.
•
Charge up the plate capacitor via the resistor
at regular intervals using the function genera-
tor (square wave voltage). The frequency
should be between 10 and 50 kHz.
Due to the capacitance C of the plate capacitor,
the current (measured via the voltage across the
resistor U
R
) during charging and discharging
exhibits a periodic exponential curve over time
and is characterised by the time constant
τ.
C
R
⋅
=
τ
(1)
τ
−
⋅
=
/
0
)
(
t
R
e
U
t
U
(2)
•
From the voltage traces on the oscilloscope,
determine the time t
0
taken for the voltage to
drop to half of the applied voltage.
Fig. 1 Voltage curve as traced using an oscilloscope
2
ln
0
⋅
=
R
t
C
(3)