

Description 
The SpinCoil series of Helmholtz coils are used to generate uniform magnetic field over certain volume in space. Each set of Helmholtz coils consists of two coils in a special arrangement to maximize the spatial volume of uniform magnetic field. The magnetic field generated is propositional to a DC or AC current into the coil. We provide a calibration curve between the field and the strength of DC current, called fieldcurrent calibration. We offer standard Helmholtz coils with different dimensions for generating single axis, twoaxis, or threeaxis magnetic field.
The SpinCoil7X is a set of 7" diameter Helmholtz Coils that can generate single axis magnetic field.


Features 
Quality Construction: SpinCoil series of Helmholtz coils use high quality insulating materials for the physical frame. The conducting wires are encapsulated in epoxy for mechanical stability. The physical package and the windings of the wires are manufactured for maximum field uniformity and stability.
Accurate Calibration: We design the Helmholtz coils’ physical and electrical parameters based on the theory of electromagnetism. On top of this, we provide an accurate experimental calibration data for each set of Helmholtz coils. Calibration accuracy is 0.4%
Adaptive Platform Design: We provide a set of mounting holes for the sample holder platform in the uniform field region. Customer can also purchase sample holder platform which guarantees central alignment for measuring sample.
Easy Operation: Colored banana connectors on the stand of the Helmholtz coils are used to connect to the external power supply, with each color indicating the polarity of current direction, and hence, the field direction.
Multiaxis Magnetic Field Generation: The SpinCoil series are designed such that single, double, or triple sets of Helmholtz coils can be easily assembled together. As a result, you can generate magnetic field vectors in X, XY, or XYZ coordinates.
Customer centered services: We guarantee our products against defective parts and poor workmanship. In case your SpinCoil is under repair, we will provide you with a loaner, so that the disruption to your measurement is minimized. 
Applications 
The SpinCoil series of Helmholtz coils can be used for multiple purposes.

Calibration of magnetic sensors

Measurement of magnetoresistance of magnetic or spintronic devices

Measurement of Hall effect of magnetic or spintronic devices

Measurement of magnetic properties of materials (e.g., magnetic susceptibility)

Generation of magnetic field in a moderate to large spatial volume

Generation of static or dynamic (e.g., rotating) magnetic field vectors

Educational demonstration of magnetic field generation

Observation of interaction between magnetic field and magnets

Generation of zero field environment by canceling the earth's magnetic field

Confinement of plasma inside an evacuated container (e.g., a glass bulb)

Use for nuclear magnetic resonance experiment

Technical Specification 
Model 
SpinCoil7X 
SpinCoil9X 
SpinCoil11X 
Price 
$1,695 
$1,895 
$2,095 
Axis 
Oneaxis 
Oneaxis 
Oneaxis 
Magnetic Field 
20 Gauss/A 
18 Gauss/A 
15 Gauss/A 
Max. Continuous Field 
40 Gauss 
36 Gauss 
30 Gauss 
Field Uniformity 
0.4% within a cylinder 1.75" D and length 
0.4% within a cylinder 2.25" D and length 
0.4% within a cylinder 2.75" D and length 
Total Resistance 
18 Ohms 
16 Ohms 
14 Ohms 
Total Inductance 
90 mH 
100 mH 
110 mH 
Coil Inner Diameter 
7.0 in 
9.0 in 
11.0 in 
Electrical Connector 
Banana Jacks 
Banana Jacks 
Banana Jacks 
Theory of Operation of Helmholtz Coils
The Helmholtz Coils use two identical coils of conductive wire to produce a three dimensional region containing a uniform magnetic field. It achieves such a goal by positioning the coils so that certain field components cancel each other out while other components reinforce each other.
The main parts of the Helmholtz Coils are the two coils of wire. Since the coils are identical in every way, (wire material, wire gauge, resistance, radius R), feeding the same current to both coils will create two identical magnetic fields. The key characteristic of the Helmholtz Coils is how the two coils are placed. Each coil lies along the same axis, and the separation between the coils is equal to each coil’s radius.
When current passes through the coils, the ensuing magnetic fields then interact in important ways in the space between the two coils. Applying the Right Hand Rule, one sees that the fields perpendicular to the common axis run into each other and cancel each other out. The same rule also shows that the fields parallel to the common axis run in the same direction, reinforcing each other. All the canceling and reinforcing leaves a uniform field in a cylindrical volume between the two coils. Specifically, the volume has a radius (r) equal to 25% of coil radius (R) and a length equal to 50% of the distance between the two coils.
Applying the BiotSavart Law and simplifying the relation between input current and magnetic field strength in the uniform region becomes:
B = (0.8991×10^{6} nI)/R
B = field in Tesla
n = number of turns in a coil
I = current in amperes
R = coil radius in meters 
 
