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 Instrumentation
 HELMHOLTZ COILS
Helmholtz Coils
The Helmholtz coil system concept, developed by a German physicist over a century ago, is a system that is normally used to generate magnetic field levels of specified volume and uniformity, allowing scientists and engineers to perform numerous experiments and test functions that require a known ambient magnetic field. Helmholtz field generation can be static, time-varying DC or AC, depending on applications.
Applications range from cancelling the earth's magnetic field for certain experiments as well as generating magnetic fields for applications such as determining magnetic shielding effectiveness, determining the susceptibility of electronic equipment to magnetic fields, calibration of magnetometers and navigational equipment and for many bio-magnetic studies, just to name a few.
Helmholtz coils can also be used to sense magnetic fields when coupled with an integrating fluxmeter. This becomes a convenient way to determine the open circuit intrinsic characteristics of permanent magnet materials.
Accessory equipment such as Walker gaussmeters and magnetometers are available for magnetic field verification or incorporated as part of a closed loop system. Walker fluxmeters are also widely used in the Helmholtz/fluxmeter magnet measurement systems.
Applications
- Radiated Magnetic Field Immunity Testing
- Susceptibility measurements
- Calibration for navigational equipment
- Permanent magnet inspection
- Earth's field cancellation for bio-magnetic studies, etc.
- Magnetometer calibration
- Magnetoresistance measurement
- Hall probe calibration
- CRT adjustments
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ROUND, SINGLE AXIS HELMHOLTZ
For susceptibility testing
ROUND, SINGLE AXIS HELMHOLTZ
With stand included as part of the coil design. |
The basic, typical single axis Helmholtz coil system consists of two identically wound layered coils, wired in series, with a specific geometry wherein the mean radius is equal to the mean coil spacing. When either AC or DC power is applied to this coil geometry, a magnetic field volume is produced in which uniform conditions exist. The strength of the magnetic field generated is directly proportional to the number of conductor turns in the coils, the applied current, the physical size and the intercoil spacing between the coils.
Coil configurations of greater complexity are sometimes necessary in order to accommodate a particular application. Systems that consist of two (biaxial) or three (triaxial) coil pairs are often required. Each coil pair or axis is usually independently controlled through a dedicated power supply. As a result, the magnetic vector generated by each coil pair can be regulated to complement other coil pairs in providing a desired uniformity over a specified sample volume or coil center line. Triaxial systems, for example, can be used to negate the effects of the earth's field (between 400-750 milligauss). |
ROUND, TRIAXIAL
HELMHOLTZ SYSTEM
With controller to test
magnetic compasses. |
Radiated Magnetic Field Immunity Testing
Walker LDJ Scientific is your source for producing magnetic fields for Radiated Field Immunity Testing per SAE J1113/22.
A recommended testing technique which produces a frequency dependent magnetic field intensity for determining the immunity of electronic devices to magnetic fields generated by power transmission lines and generating stations. Let our technical staff work with you to determine the most economical system to meet your particular requirements. The actual size of the Device Under Test (DUT) will determine the size and configuration of your coil system.
160 dBpt (100 µT) @ 60 Hz, decreasing at a rate of 12 dB/Octave for odd harmonics of 60 Hz up to 30 kHz |
ROUND, TRIAXIAL HELMHOLTZ SYSTEM
With built-in platform and closed loop, feedback system. |
ROUND, SINGLE AXIS, MULTI-COIL HELMHOLTZ
For high field, high uniformity space restricted application. |
SINGLE AXIS
SPLIT BASE HELMHOLTZ
Equipment testing for the
transportation industry.
Compliance with SAE J1113/22 |
SQUARE, TRIAXIAL
HELMHOLTZ COIL SYSTEM
Earth's field cancellation
for bio-magnetic studies. |
Helmholtz Design Requests
The combined values of Walker LDJ Scientific experience, reliability, quality and performance has resulted in the production of many proven AC and DC Helmholtz coil system designs. Single, biaxial or triaxial Helmholtz coils with single or multi-pair coil sets, fixed or rotatable, are offered in round, square or rectangular configurations. Field levels from the gamma range (1 gamma = 1 nT = 10-5 G) to the kilogauss level can be generated with uniformity in parts per million (ppm) over a specified sample volume.
Information related to any Helmholtz design request should be provided by completing the Helmholtz questionnaire and returning a copy of the completed form for processing.
All unusual installation constraints should be noted on the application.
With our unique engineering and design approach and our unique manufacturing techniques, Walker LDJ Scientific is able to provide cost effective systems with features that meet your exact application requirements.
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SQUARE, BOX TYPE,
TRIAXIAL HELMHOLTZ
Designed specifically for
CRT adjustments in the
manufacturing environment.
SQUARE, SINGLE AXIS,
MULTI-COIL HELMHOLTZ
Another concept of a
space-restricted application. |
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