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Product Catalog:

Magnetic Field Coil

Product Detail:

Helmholtz Coil

helmholtz-coil

Helmholtz-coil

High evenness coil

Square helmholtz coil

Three axis equal diameter coil

AC magnetic field coil

Gradient magnetic field coil

 

Magnetic flux measuring coil

Power frequency magnetic field coil

Special type coil

 

Exploring coil

No magnetic sample unit

Introduction of Helmholtz Coil:

Hermann von Helmholtz (1821-1894)
German scientist and philosopher who made fundamental contributions to physiology, optics, electrodynamics, mathematics, and meterology.

Helmholtz Coils
A pair of conducting circular coils each having N turns, each carrying a current I, separated by a distance equivalent to the radius of the circular loops, produce a homogeneous magnetic field B in the mid-plane between the two circular coils.

Helmholtz Coil

a = radius of the coils
a = separation between the coils
a/2 = distance to the mid-plane
B = magnetic field at the mid-plane

Helmholtz Coil

What creates a magnetic field?
A magnetic field is created whenever charge is in motion--either moving in space or spinning around itself. A charge moving in space is called a "current" (denoted by the symbol I) and is measured in coulombs/sec or amperes.

The strength of magnetic field is measured at a point in space (often called the field point). In the case of the Helmholtz coils, the field points of interest are located in the mid-plane between the two coils. As shown in the equation above, the strength of the magnetic field is dependent upon three quantities:

the current I,
the number of turns N in each coil, and
the radius a of the coil.

The total current in each coil is NI.

Helmholtz Coil

 

How uniform is the magnetic field?
The "claim to fame" for the Helmholtz coil is its very uniform magnetic field. However, the question that naturally arises , "how uniform, and over what distance?" To determine the uniformity of the magnetic field requires more than the above equation and involves some complicated integral calculus. However, we can generate some figures that graphically show how the magnetic field varies on the mid-plane as a function of r (the distance from the axis of symmetry passing between the centers of the two coils) and d the separation between the two coils.

Helmholtz Coil
Coil spacing is "too close."
d = 0.8 a

In the figures to the right, we can see how uniform the magnetic field is on the mid-plane when the spacing d is too close, just right, and too far. The figures to the right are calculated for coils with a radius of 20 cm (i.e., a = 0.20 m).

The following integral was evaluated to produce the three curves at the right.

Helmholtz Coil
Coil spacing is "just right."
d = a


where the factor of "2" in the numerator takes into account the two coils, and b = d/2 is the distance from each coil to the mid-plane.

magnetic field
Coil spacing is "too far."
d = 1.2 a

How does the region of uniform magnetic filed vary with the radius of the Helmholtz coils?

The figures below show the range of uniform magnetic field as a function of the coil radius.


Here is a lab writeup describing the procedure for measuring the charge-to-mass ratio of an electron using the Helmholtz coils.

 

square helmholtz coil
Helmholtz Coil Measurement of magnetic field
square helmholtz coil
square helmholtz coil
square helmholtz coil

Using two same coils with equal radius and turns,arrange them to be coaxial and let their distance be equal to the radius of the coil,this called Helmholtz coil. It can be used to generate magnetic field from extremely weak magnetic to hundreds of Gauss.

Specifications:

Model
Shape
Averageradius (cm)
Center magnetic field
(Gs)
Power
(W)
Weight
(Kg)
(one axis)
DXHC150-2
Square
150
2
540~620
84
DXHC 100-10
Square
100
10
1200~1500
180
DXHC 100-5
Square
100
5
600~800
94
DXHC 100-2
Square
100
2
220~300
58
DXHC 75-10
Square
75
10
700~900
80
DXHC75-5
Square
75
5
360~430
53
DXHC75-2
Square
75
2
150~180
21
DXHC60-10
Square
60
10
500~600
68
DXHC60-2
Square
60
2
100~120
14
DXHC50-20
Square
50
20
600~700
61
DXHC50-10
Square
50
10
350~430
47
DXHC50-2
Square
50
2
70~90
15
DXHC40-50
Square
40
50
1000
98
DXHC40-10
Square
40
10
220~300
30
DXHC40-2
Square
40
2
45~60
15
DXMC30-100
Round
30
100
800
80
DXMC30-50
Round
30
50
500
40
DXMC30-10
Round
30
10
100~200
17
DXMC30-2
Round
30
2
24~48
8
DXMC25-1000
Round
25
1000
5000
500
DXMC25-500
Round
25
500
3000
250
DXMC25-300
Round
25
300
1800
150
DXMC25-200
Round
25
200
1200
100
DXMC25-100
Round
25
100
600
50
DXMC25-50
Round
25
50
300
25
DXMC25-10
Round
25
10
60~90
12
DXMC25-2
Round
25
2
12~18
8
DXMC20-500
Round
20
500
2000
160
DXMC20-300
Round
20
300
1200
96
DXMC20-200
Round
20
200
700
64
DXMC20-100
Round
20
100
350
32
DXMC20-50
Round
20
50
200
16
DXMC20-10
Round
20
10
40~65
8
DXMC20-5
Round
20
5
20~32
6
DXMC20-2
Round
20
2
8~15
5
DXMC15-300
Round
15
300
660
54
DXMC15-200
Round
15
200
430
36
DXMC15-100
Round
15
100
220
18
DXMC15-50
Round
15
50
110
9
DXMC15-10
Round
15
10
21~42
6
DXMC10-200
Round
10
200
200
20
DXMC10-100
Round
10
100
100
15
DXMC10-50
Round
10
50
50
8
DXMC10-10
Round
10
10
10~24
6
DXMC7-100
Round
7
100
50
7
DXMC7-50
Round
7
50
24
4
DXMC7-10
Round
7
5-12
10
2

Note: the models in red color can be made into three axis coils.

 

Feature: 

Open space, easy to use, magnetic field has a good linear relationship with current, magnetic field space has a very wide uniform area,which is suitable to generate one-dimensional, two-dimensional and three-dimensional space composite magnetic field.

Application:

 1.to generate standard magnetic field
 2.calibration for Hall probes and various magnetometers
 3.compensation for earth magnetic field
 4.judgement for magnetic shielding effect
5. measurement and removement for space radiation magnetic field
 6. for magnetic properties
 7.study for biomagnetism

Note:


 Magnetic field intensity: the value of the magnetic field in the magnetic field center,when power is maximum
Uniform area: the relatively homogeneous magnetic field space surrounding magnetic field centre, or the required magnetic field for users’experiments
Space uniformity: the magnetic deviation degree in uniform area
Stability: the degree of change when the magnetic field working over a period of time.
Working time:the longest using time
Work period: the interval time between continuous work for more than two times

Our company specializes in the design and production of the Helmholtz coil, could put forward design scheme and proceed multi-dimensional space design according to the magnetic field strength, magnetic field homogeneity and uniformity level. With precise design, precise calculation and elaborate manufacture, our products have been chosen for the tertiary institutions, research units and the vast majority of users,received high reputation.