# Inductance of helmholtz coil

Besides creating magnetic fields, Helmholtz coils are also used in scientific apparatus to cancel external magnetic fields, such as the Earth's magnetic field. A Helmholtz pair consists of two identical circular magnetic coils solenoids that are placed symmetrically along a common axis, one on each side of the experimental area, and separated by a distance h equal to the radius R of the coil.

Each coil carries an equal electric current in the same direction. Magnetic field has significant impact on plants and seeds both at the physical and molecular level. The Helmholtz coil that can generate a uniform magnetic field in a large area can be ideal for Biomagnetic experiments, and this was the main motive of the Helmholtz coil design, it had bioelectric perspective.

Bioelectric experiments with plants and seeds require large volume of uniform magnetic field for exposure. The ordinary Helmholtz coil, 30 cm diameter, has insignificant volume of uniform magnetic field for biomagnetic experiments which requires large number of samples. The Helmholtz coil was designed for treating seeds at a time.

It was designed such that it is driven by both AC and DC current source. The Rodin maths coil was also designed such that it would withstand temperature rise even when driven for long periods of time.

This is necessary because bioelectric experiments involve long period of exposure in the magnetic field, sometimes requiring several days of exposure. Figure 1 — model of Helmholtz coil. Table 1 contains the Helmholtz coil parameters and dimension. Table 1 — Parameters and dimensions of Helmholtz coil. Due to the symmetry conditions only quarter of the whole model was simulated. This approach reduces the time taken to solve internal branding. strategie di marca per la cultura d compromising the solution accuracy. The AC Magnetic or the so-called time harmonic magnetic analysis belongs to the low-frequency electromagnetic domain or regime; i.

In addition, the fields are time harmonic. These effects include: Eddy currents, skin effects, power loss due to eddy currents. The AC Magnetic solver computes the electric fields excited by a Sinusoidal or alternating varying voltage or a Sinusoidal or alternating varying current.

A tangential flux must be applied on faces of model where we want to use symmetry conditions. Figure 6- faces where applied tangential flux. Figure 7 shows the mesh on Helmholtz coil. Meshing is a crucial step in any FEA simulation. EMS estimates a global element size for the model taking into consideration its volume, surface area, and other geometric details. The size of the generated mesh number of nodes and elements depends on the geometry and dimensions of the model, element size, mesh tolerance, and mesh control.

In the early stages of design analysis where approximate results may suffice, you can specify a larger element size for a faster solution. For a more accurate solution, a smaller element size may be required. We can control the mesh size from one body to another depending on its dimensions and its importance in the result by applying a mesh control.High frequency Helmholtz coils are often used to generate uniform but time varying high frequency magnetic field for a number of applications such magnetic field susceptibility, calibration, and scientific experiment.

A high frequency Helmholtz coil driver is needed to generate the required magnetic field. Because the magnetic field density is proportional to electrical current, to generate high magnetic field, high current is needed.

However, at high frequency the coils impedance is also became high impedance. For a given driver voltage amplitude, the coil current is inversely proportional to the coil impedance. Therefore the two opposing factors that affect magnetic field are current and frequency.

Achieving high frequency magnetic field is very difficult. This article discussed three techniques to produce high magnetic field for high frequency Helmholtz coils. Helmholtz coils, named after the German physicist Hermann von Helmholtz, is consisted of two identical electromagnetic coils place in parallel and aligned their centers in the same axis like a mirror image as shown in Figure 1.

Chapter 8.5.1: Field and inductance of a spherical coil

When electrical current pass through the high frequency Helmholtz coils in the same direction, it creates a highly uniform magnetic field in a 3-dimension volume of space inside the coils. Figure 1: One-axis high frequency Helmholtz coils is consisted a pair of coils with radius R and separated by a distance equal to R. High frequency Helmholtz coils are constructed by two coils. Because the two magnetic coils are designed to be identical, uniform magnetic field is achieved when the coil radius is equal to the separation distance.

The two coils are connected in series such that identical current feeding both of them creates two identical magnetic fields. The two added fields achieved uniform magnetic field in a cylindrical volume of space in the center between the two parallel coils. High frequency Helmholtz coils are available in 1, 2, or 3 axes. Multiple axis magnetic coils generate magnetic fields in any direction in the three dimensions space inside the Helmholtz pair.

The most common high frequency Helmholtz coils are circular. Square Helmholtz coils are also commonly available. Each Helmholtz coil is constructed by loops of electrical copper wires. When electrical current is passing through it, magnetic field is generated. The magnetic field density is proportional to current. The Helmholtz coils magnetic field equation is given below.

From Equation 1, smaller radius coil generates higher magnetic field density. Also the more number of turns in each coil the stronger the magnetic field. Helmholtz magnetic field is generated either using AC or DC current. Most Helmholtz coils applications are static constant magnetic field using DC current.This website uses cookies to function and to improve your experience.

By continuing to use our site, you agree to our use of cookies. Have you ever wanted to query the results of your model within an arbitrary geometric subregion?

## Coil Inductance Calculator

You might think that this requires adding geometries to a model and recomputing the solution. We will demonstrate this in the context of computing mutual inductance between coils and discuss simpler techniques that can be used for a reduced set of cases.

The magnetic flux density, the B -field, is plotted in the space around these primary coils. Suppose that we want to introduce a smaller pickup coil in the space between the larger primary coils. This pickup coil intercepts part of the magnetic flux and is defined by its outside perimeter curve C and enclosed area A.

The magnetic flux density around a Helmholtz coil with a pickup coil inside. The enclosed area of the coil is shaded in gray. We want to recompute the mutual inductance as the pickup coil changes orientation.

We can place the pickup coil at any location and orientation around the primary coils, solve the model, and evaluate either of the above integrals. We can even add the pickup coil geometry features after solving the model by using the Update Solution functionality. This functionality remeshes the entire model geometry and maps the previously computed solution from the old mesh onto the new mesh.

This is appropriate and easy to do if the changes to the geometry do not affect the solution and if we only want to try out a few different pickup coil locations. Suppose that we want to try out many different locations and orientations for the pickup coil. We can achieve this by using a combination of multiple geometry components, the General Extrusion component coupling, and Integration component couplings.

We begin with the existing Helmholtz coil example and introduce another 3D component into our model. The Rotate and Move geometry features enable us to reorient the coil into any position that we would like. For visualization purposes, we can also include the edges that define the primary coils, as shown in the screenshot below. The setup of a second component and geometry. The spatial coordinates of Component 2 overlap exactly with Component 1but otherwise there is no connection between the two.

A mapping is introduced via the General Extrusion component coupling that is defined in Component 1. This coupling uses a Source Selection for all of the domains in Component 1.

Whenever this coupling is evaluated at a point in space in Component 2it takes the fields at the same point in space in Component 1. The approach of using two components and mapping the solution between them is also introduced in the Submodeling Analysis of a Shaft tutorial model. Within Component 2we define two Integration component couplings, one defined over the edges of the pickup coil, named intCand the other over the cross-sectional boundary, named intA.

This allows us to compute the mutual inductance with either of the above approaches by defining two variables. Since there are multiple components in the model, we must use the full name of the component couplings and fields that reside within Component 1. Also, note that the normal vector and perimeter tangent vector can be oriented in one of two opposite directions, which results in a sign change that we need to be aware of. Integration component coupling defined over the pickup coil perimeter in the second component.

We can also sweep over different positions and orientations of the pickup coil. We already have the solution for the magnetic fields computed in Study 1. We add a second study that includes a parametric sweep, but does not solve for any physics. Within the study step settings, we can specify that we want to use the existing solution for the magnetic field, as shown in the screenshot below.

Study step settings showing how the solution from Study 1 is used in Study 2. This second study takes relatively little computational resources when compared to remeshing the entire model and re-solving for the magnetic fields. For each different position of the pickup coil, the software only needs to remesh the pickup coil surface.Visit TS Page. Ask Us Questions. Request a Quote. Helmholtz coil is named after the German physicist Hermann von Helmholtz.

It is comprised of two identical magnetic coils positioned in parallel to each other, and their centers are aligned in the same x- axis. The two coils are separated by a distance equal to the radius like a mirror image as shown in Figure 1. When current is passing through the two coils in the same direction, it generates a uniform magnetic field in a three- dimension region of space within the coils.

Figure 3. High- frequency Helmholtz coils are represented by two series connected LCR circuits. Since the two electromagnetic coils are identical, uniform magnetic field is obtained when the separation distance is equal to the coil radius.

Usually the two coils are connected in series so that equal current is feeding the two coils will create two identical magnetic fields.

The two added Helmholtz fields achieve highly uniform magnetic field in a cylindrical volume of space in the center between the two coils. Helmholtz coil are available in 1- axis, 2- axis, or 3- axis.

Most Helmholtz coils are circular, but some are square. Square Helmholtz coil offers large working space than circular. Majority of Helmholtz coils used for scientific experiments generate static constant magnetic fields. Static magnetic field uses Direct Current. In some test and measurement applications require non- static electromagnetic fields at high frequencies kilohertz to Megahertz. The magnetic field inside the coils in the center is given below. Helmholtz Coils for Sale.

Helmholtz Coil Design Resources.The coil is the most recognizable form of an inductor. This tool is designed to calculate the inductance of a coil of wire given the number of turns, the loop diameter, wire diameter, and the permeability of the medium.

Note that you can choose the unit of measurements for the loop diameter and wire diameter. The number of turns is always assumed as a whole number it's hard to do a 3. The capacitor in parallel with the trigger coil charged up to V using the low-resistance path provided by the SCR. However, once the capacitor was fully charged, the short-circuit path to ground provided by the SCR was removed, and the capacitor immediately started to discharge through the trigger coil.

Since the only resistance in the time constant for the inductive network is the relatively low resistance of the coil itself, the current through the coil grew at a very rapid rate. A significant voltage was then developed across the coil.

This voltage was in turn increased by transformer action to the secondary coil of the autotransformer, and the flash lamp was ignited. That high voltage generated across the trigger coil will also appear directly across the capacitor of the trigger network. The result is that it will begin to charge up again until the generated voltage across the coil drops to zero volts. However, when it does drop, the capacitor will again discharge through the coil, establish another charging current through the coil, and again develop a voltage across the coil.

Inductors can be found in a wide variety of common electronic circuits in the home. This feature is particularly important for dimmers, since they are most commonly used to control the light intensity of an incandescent lamp. The inductor is also effective in blocking high-frequency noise RFI generated by the switching action of the triac in the dimmer. A capacitor is also normally included from line to neutral to prevent any voltage spikes from affecting the operation of the dimmer and the applied load lamp, etc.

Hello sir, do you think a Henries inductor coil normal? The inductor is a common school use transformer turn coil, with wire diameter about 0. Could this be possible? So it suggests the permeability of the iron core is about The calculator is very good.

This is in agreement with your formula but it does not apper to be correct. By using equations from electronics texts or manuals like Bleaney,Electricity and Magnetism I obtain a value around uH. I have actually built such a coil, and measured a value around uH. Am I using your calculator in the wrong way? Or is there some error in it? This is way out, to the point of not even being useful. It is actually worse than when I used to calculate turns using area and AL values back in about That got you within a few turns but this is out by a factor of at least 3.

### Numerical simulation of Helmholtz coil

I have in front of me an air core coil of 0. It has 6 and a bit layers. You say that it should be 1. If only life were so cheap.

I measured to approximately layer 3. You might be helpful to the people selling copper wire, but how does it help me trying to make a 0.Since we have designed, built and tested custom magnetic coils for a variety of applications, for use in air, in vacuum and in other demanding environments. Look through our spec sheets below for examples of our custom coils.

Try our Helmholtz Coil Calculator to find the maximum field strength of a coil set. What is a Helmholtz Coil?

Coil Radius[m]. Pulse Time [s]. Current in Coil [A]. Number of Turns. Electromagnetic coils produce a magnetic field when a current runs through them. This is due to Ampere's Law. The strength of the field varies with the amount of electric current. These fields have many applications both for scientific research and for industrial uses. Here are some common uses of electromagnets:. Overview Team. Magnets Overview. Helmholtz Coils. Microscope Magnets. We can design, build, and wind custom coil assemblies for your application in the lab or in the factory. If you have a design in mind or need assistance shaping your magnetic field, let our engineers know: Email us for more information or call us at Check out what we're doing at WSI! Subscribe to our monthly newsletter:.A Helmholtz coil is a device for producing a region of nearly uniform magnetic fieldnamed after the German physicist Hermann von Helmholtz.

It consists of two electromagnets on the same axis. Besides creating magnetic fields, Helmholtz coils are also used in scientific apparatus to cancel external magnetic fields, such as the Earth's magnetic field.

Each coil carries an equal electric current in the same direction. In some applications, a Helmholtz coil is used to cancel out the Earth's magnetic fieldproducing a region with a magnetic field intensity much closer to zero.

The calculation of the exact magnetic field at any point in space is mathematically complex and involves the study of Bessel functions. By symmetry, the odd-order terms in the expansion are zero. The calculation detailed below gives the exact value of the magnetic field at the center point. If the radius is Rthe number of turns in each coil is n and the current through the coils is Ithen the magnetic field B at the midpoint between the coils will be given by. Start with the formula for the on-axis field due to a single wire loop which is itself derived from the Biot—Savart law : .

The Helmholtz coils consists of n turns of wire, so the equivalent current in a one-turn coil is n times the current I in the n -turn coil. Substituting nI for I in the above formula gives the field for an n -turn coil:. From symmetry, the field strength at the midpoint will be twice the single coil value:. Most Helmholtz coils use DC direct current to produce a static magnetic field. Many applications and experiments require a time-varying magnetic field. These applications include magnetic field susceptibility tests, scientific experiments, and biomedical studies the interaction between magnetic field and living tissue.

The required magnetic fields are usually either pulse or continuous sinewave. An AC Helmholtz coil driver is needed to generate the required time-varying magnetic field. The waveform amplifier driver must be able to output high AC current to produce the magnetic field.

Use the above equation in the mathematics section to calculate the coil current for a desired magnetic field, B.