Bartington Instruments’ Helmholtz Coil Systems are for calibrating magnetic field sensors, or performing any operation that requires a known magnetic environment. The coils can be calibrated to add to or subtract from distortions in the Earth’s magnetic field.
The coil assemblies are available with diameters of 500mm (HC1) or 1 meter (HC2). Each generates a homogeneous magnetic field, up to 500µT at DC and up to 5kHz at 100µT, in one, two or three axes (HC1) or three axes only (HC2). The two-axis version is available in any combination: X+Y, Y+Z, X+Z. The HC1 produces a 0.1% homogeneous magnetic field of 260cm3; the HC2, for testing larger items, provides a homogeneous field of 14000cm3 with <1% error, or 2500cm3 with <0.1% error. For both assemblies a mounting table is provided to hold the test item inside the homogeneity volume.
To facilitate freight and installation, the HC2 comes in a flat pack form that can be assembled and disassembled at the customer’s convenience.
As well as the coils, the Helmholtz Coil Systems include a Power Amplifier (PA1) and a Control Unit (CU1), and a computer-controlled PXI test, measurement and control system that provides additional functions, including analogue to digital conversion of signals from the device under test. The coil assemblies can be purchased separately from the rest of the system.
The PA1 Power Amplifier determines the input current to the HC1 and HC2 coil assemblies, which in turn allows the field generated by each pair of coils to be determined. Variations in the static and generated fields in each axis can be compensated for by adjusting controls on the front panel. Electronic orthogonality adjustment is available, together with calibration features to improve the accuracy of current measurement.
The PA1 runs from a standard single phase AC line supply as provided by a standard wall outlet. The amplifier is fan-cooled, with a self-resetting thermal shut-down mechanism to prevent damage through overheating.
The CU1 Control Unit allows the user to set the field, set any DC compensation as required, and receive feedback from the Helmholtz Coil. It is also the interface between the PA1 and the PXI system, buffering and filtering signals between these two items. The device under test is also connected to the CU1, and a reference magnetometer can be connected to its auxiliary socket. The CU1 powers these devices, as well as filtering their signals and passing them to the analogue-to-digital converter (e.g. the PXI system).
For the test, measurement and control system, Bartington Instruments can supply a National Instruments PXI control system with an inbuilt PC and A/D acquisition card, with control software based on National Instruments’ LabVIEW™ pre-installed and configured. Alternatively a PC running Windows and fitted with a PCI Express card PCIe-6353 may be used.
Bartington Instruments Helmholtz Coil Systems: www.bartington.com/helmholtz-coil-three-axis-system
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