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5
4,5
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0
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Graph 2: Plot of output voltage Ua against reciprocal of effective plate separation D
6.3 Measurement of potential using flame
sensor 102199
The flame of the sensor produces ions, which
means that charges migrate towards the flame
sensor tube out of the region of the electric field
and therefore towards the measuring equipment.
The equalisation of charge by this process con-
tinues until the electric field is again formed with-
out any disturbance and the probe has arrived at
the same electric potential present at the point
where the measurement is being made.
Due to the slight compensation currents and the
unavoidable capacitances which result in the
connecting leads and the voltage measurement
plate, longer time constants (measurement
times) may arise depending on the location of
the measurement.
6.3.1 Measurement of potential in uniform
field
Additionally required:
1 Flame sensor
1 High-voltage power supply
10 kV @115 V
or
1 High-voltage power supply
10 kV @230 V
2 Resistors, 10 MΩ
1 Digital multimeter, e.g.
3B Scientific GmbH ▪ Rudorffweg 8 ▪ 21031 Hamburg ▪ Germany ▪
Fig. 4: Flame sensor in uniform field of plate capacitor
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The flame tube of the flame sensor is to be set
up on a rail such that it can be moved inside the
uniform field between two capacitor plates (sepa-
ration d = 10 cm) (cf. Fig. 4).
The electric field and a multimeter connected
downstream from it act as a static voltmeter.
After a certain delay, the flame tube of the sen-
sor assumes the potential φ corresponding to the
equipotential lines of the electric field.
φ = d/s * U = 0.5 * U
Alternatively, the experiment can be done with
both positive and negative high voltages (bipo-
lar). In that case, the left-hand capacitor plate
should not be connected to "0" but to the nega-
tive voltage output of the high-voltage supply via
a second large resistor (1022192).
At position s/2, the voltage at the electrometer
output will then read "0".
1021799
1019238
1019234
1022192
1002784
Subject to technical amendments
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7. Storage, cleaning and disposal
Store the equipment in a clean, dry and dust-
free location.
Disconnect the equipment from its power
supply before cleaning.
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