3B Scientific Electric Field Meter (115 V, 50__60 Hz) - Manual (Page 7)

3
• After plugging into the mains, wait a few minutes
for the instrument to reach normal working
temperature.
• To avoid damage to the electric field meter, do
not touch the rotating vaned wheel.
• The insulating parts of the instrument and the
measurement plates must be kept clean and dry
(avoid touching them). When the air is very
humid, it may be necessary to dry them in a
current of warm air (use a hair-dryer).
For measurements of electric field strength, the
induction plate should be positioned below the
screening plate. The difference
Δd is approximately 1
mm, and for precise measurements it must be
determined experimentally and taken into account in
the measurements. The field strength E is calculated
from the voltage U and the distance d between the
plates according to the formula
d d
U
E
Δ +
=
.
6.2 Zero-point calibration
• First calibrate the zero-point for the indicating
instrument (e.g., a voltmeter – see relevant
instruction sheet).
• Connect the indicating instrument to the voltage
output of the electric field meter.
• Place the voltage measurement plate in position
at the shorter distance and secure it with the
knurled screw.
• Turn the measurement range switch to the “U”
position and set to the highest range.
• Connect the measurement plate to the earth
socket of the screening cylinder.
• Switch on the electric field meter and set the zero
point using offset adjustment.
• Calibrate the zero-point for the two lower
measurement ranges by the same procedure.
6.3 Measurement of the field strength in a plate
capacitor
This experiment requires a DC power supply with a
smoothed voltage outout, for example:
1 DC power supply, 500 V U33000- 230
or
1 DC power supply, 500 V
U33000- 115
1 Resistor 300 k
Ω
U51013
1 Contact rod U8497730
• Set up the experiment as shown in Fig. 2.
• Connect the indicating instrument to the voltage
output of the electric field meter.
• Place the capacitor plate for voltage
measurements on the screening cylinder and
secure it with the knurled screw.
• Place the required spacer discs on the capacitor
plate for voltage measurements and place the
other capacitor plate on top.
• Connect the positive output terminal of the DC
power supply to the upper capacitor plate and the
negative output terminal to the earth socket of
the screening cylinder.
• Turn the measurement range switch to the “E”
position and select the required range.
• Switch on the electric field meter and the DC
power supply.
• Make a connection between the person
conducting the experiment and the earth socket
of the screening cylinder.
• Carry out the measurement.
• Compare the measured field strength with the
theoretical value.
• Make a series of similar measurements with
different distances between the plates using the
spacer discs, to demonstrate the dependence of
the field strength on the plate separation.
• After the experiment, discharge the capacitor
plate by connecting it to the screening cylinder.
6.4 Measurement of voltages using the instrument
as an induction electrometer
Additional equipment required:
1 High voltage power supply, 5 kV U33010-230
or
1 High voltage power supply, 5 kV
U33010-115
1 Resistor 300 k
Ω
U51013
1 Contact rod U8497730
• Set up the experiment as shown in Fig. 3.
• Connect the indicating instrument to the voltage
output of the electric field meter.
• Depending on the voltage to be measured, place
the appropriate voltage measurement plate on
the screening cylinder and secure it with the
knurled screw.
• Connect the positive output terminal of the high
voltage power supply to the voltage measurement
plate and the negative output terminal to the
earth socket of the screening cylinder.
• Turn the measurement range switch to the “U”
position and select the required range.
• Switch on the electric field meter and the high
voltage power supply.
• Make a connection between the experimenter and
the earth socket of the screening cylinder.
• Carry out the measurement.
• After the experiment, discharge the voltage
measurement plate by connecting it to the
screening cylinder.