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Chapter 2 Measurement Principle
■
2.1 Basic measurement principle
The basic measurement principle used by this product to obtain a magnetic field
strength H and a magnetic flux density B generating in a sample to be measured is
explained using the 2-coil method.
Fig.2-1 shows a measured sample to which the primary turns are applied for
excitation (No. of turns: N
detecting the magnetic flux density (No. of turns: N
the diagram outlining a measured sample connected to this product
using the optional power amplifier.
The signal generator built in this product generates an excitation signal and
the power amplifier amplifies the signal, allowing the exciting current i
through the primary turns.
The exciting signal i
(t) is converted into a voltage Vs (t) by the shunt resistor
1
with a resistance value of Rs built in this product.
Power amplifier
パワ－アンプ
信号発生器
Signal generator
Fig.2-2 Diagram outlining a measured sample connecting to this product
Therefore, the magnetic field strength H (t) generating in the measured sample can be obtained using:
N
H
t
An induced voltage V
(t) is also generated between both sides of the secondary turns. Therefore, the magnetic flux density B (t) in the
2
measured sample can be obtained using:
B
) (
t
) and the secondary turns are applied for
1
). Fig.2-2 shows
2
i
(t)
1
R
S
i
t
N
V
t
1
1
1
s
L
L
R
e
e
s
1
t
V
d
2
N
A
0
2
e
(t) to flow
1
A measured sample
被測定試料
(2.1)
(2.2)
7
B-H ANALYZER SY-8218 / SY-8219
N
No. of primary turns
1:
N
: No. of secondary turns
2
Ae: Effective net core area
Le: Effective length of magnetic path
Ve: Effective volume
Secondary turns
2次巻線
N
1
Primary turns
1次巻線
A
V
e
Fig.2-1 Shape of sample
+
V
-
+
V
-
N
2
e
(t)
2
(t)
S
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