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1. Safety instructions
The ultra-high-resistance input circuit of the
electrometer can be damaged by applying an excessive
voltage:
•
Do not exceed the maximum input voltage of ± 8 V!
A higher voltage is only permissible with the condition
that if a person touches conducting parts it is instantly
reduced to the above or a lower value. The voltage
sources mentioned in this instruction sheet fulfil that
condition.
•
Do not connect any external voltage source to the
output socket (10)!
•
If a capacitative voltage-divider circuit is used to
measure voltages above 10 V, it must be provided
with an SEG capacitor that can withstand the full
applied voltage!
2. Description
Impedance-changer with an extremely high input
resistance for measuring very small charges and very
small currents.
It is suitable for quasi-static measurement of voltages up
to ± 8 V, for high-resistance measurement of voltages
8 V
above ±
using a resistive voltage divider, for quasi-
static measurement of voltages above ±
capacitative voltage divider, for measurement of very
small currents using a high-resistance shunt, and for
measurement of charges.
3. Technical data
Amplification factor:
Input resistance:
Output resistance:
Input current:
Input capacitance:
Supply voltage:
Overvoltage tolerated for
voltage sources safe against
accidental contact:
Connections:
8 V
using a
1.00
Ω
12
> 10
< 1 kΩ
< 10 pA
< 50 pF
12 V AC / 50-69 Hz /
100 mA
1 kV (sources with low
output resistance)
10 kV (sources with
high output resistance)
4 mm safety sockets
•
Plug the 12 V AC adaptor into the electrometer and
switch the instrument on.
•
Connect a suitable voltage meter with a mid-scale
zero-setting
adjustment,
multimeter AM50 (U17450), multimeter ESCOLA2
(U8531170), or multimeter ESCOLA10 (U8531160), to
the output sockets of the multimeter.
•
Select the 10 V DC range and set the zero point at
the middle of the scale.
•
Short-circuit the "IN" (3) input socket to the earth
socket (4) with a 19 mm bridging plug, or:
•
Discharge (short-circuit) the Faraday cup (U8496460)
that is plugged into the input socket (2) by using the
handling rod with 4 mm hole (U8430245) that is
connected to the earth socket (5).
•
While maintaining the short-circuit, adjust the offset
of the output voltage at socket (10) to a minimum.
•
Quickly carry out the measurement for the chosen
experiment, before there is time for stray charges to
build up at the input being measured.
•
Before starting a new experiment, short-circuit the
input to earth again, and if necessary readjust the
offset.
5. Sample experiment
Measuring charges in electrostatics
Apparatus needed:
1 Electrometer
1 Analogue multimeter AM50
1 Faraday cup
1 Capacitor, 10 nF, 160 V
2 Friction rods
1 Experiment lead, 75 cm
1 Handling rod with 4 mm hole
1 Cloth for rubbing friction rods
•
Set up the experiment as shown in Figure 1.
•
Plug the Faraday cup and the 10 nF capacitor into
the appropriate 4 mm sockets.
•
Connect the multimeter to the output socket "OUT"
(10) and the corresponding earth socket (9).
•
Select the 10 V DC range on the multimeter.
•
Plug the experiment lead into the socket for the
handling rod (5) and into the 4 mm hole in the rod.
•
Take the handling rod in one hand and, without
releasing it, discharge the Faraday cup.
•
With the other hand, immerse the test object (e.g.
the friction rod after rubbing) into the field-free
interior of the Faraday cup so that the whole of its
2
4. Operation
such
as
U8531408
U17450
U8496460
U8403501
U11053
U13800
U8430245
analogue
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