Helmholtz Coil Systems

Innovation in Magnetic Field Measuring Instruments
Helmholtz Coil Systems

Helmholtz Coil Systems
Helmholtz Coil Systems
Bartington Instruments’ HC1 and HC2 Helmholtz Coils are for calibrating magnetic field
sensors, or conducting any test or experiment requiring a known magnetic environment.
The full system consists of: an assembly of up to three pairs of coils, with a choice
of sizes (HC1 or HC2); a Power Amplifier (PA1); a Control Unit (CU1); and a National
Instruments PXI control system that provides software control and additional functions.
Features
• Choice of coil assembly minimum diameter: 500mm or 1m
• Field generated in up to three axes
• HC1 or HC2 coil assembly can be provided on its own
• Mounting table provided to hold the test item inside the homogeneous volume
• HC2 only: coils provided in flat-pack assembly to facilitate freight and installation
Applications
• Calibration of three-axis magnetic field sensors
• Creation of a known magnetic environment

HC1 and HC2 Helmholtz Coils
Each pair of coils generates a homogeneous magnetic field in one specific axis: X, Y or Z. The coils can be calibrated to add to or
subtract from distortions in the Earth’s magnetic field.
Customers may specify the number of axes, and hence pairs of coils, required. The two-axis version is available in any combination (X+Y,
X+Z or Y+Z) which must be specified at order. The HC2 coils are provided in flat-pack form for assembly at the customer’s convenience.
Specifications
Performance: HC1 HC2
Number of axes 1, 2 or 3
Parallelism ±1°
Mounting to datum ±1° (electronic adjustment possible to

Helmholtz Coil Systems
PA1 Power Amplifier
The PA1 Power Amplifier determines the input current to the HC1 and HC2 coil
assemblies. This 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. The supply from a standard
wall outlet should be suitable in most countries. The amplifier is fan-cooled with a selfresetting
thermal shut-down mechanism to prevent damage through overheating.
Specifications
Environmental
Operating temperature range
Storage temperature
Operating humidity
+15°C to +30°C
+10°C to +40°C
Up to 90% RH non-condensing
Mechanical
Enclosure dimensions
6U 19in rack mount box
Height: 27cm
Width: 51cm
Depth: 60cm
Enclosure gross weight 1
1-axis: 40kg
2-axis: 45kg
3-axis: 50kg
1 Weight varies as the PA1 contains one fan and amplifier channel per pair of coils in use.
Electrical
Input connector
Coils output connector
Current monitor output connector
Power requirement
Maximum power consumed
Hirose RM15TRD-10S
Neutrik Speakon 8 poles
Hirose RM15TRD-10P
100V–230V AC, 50/60Hz permanent installation
1.5kW
Control input (maximum voltage) ±10V
Current monitor output (maximum voltage) ±15V
Coil drive output (minimum voltage)
Maximum total output current to
Helmholtz coils
±25V (no load)
29A (maximum 20A per axis)
Output impedence per individual axis 1.35Ω

CU1 Control Unit
The CU1 Control Unit is the interface between the PA1 and the PXI control system that
governs the operation of the Helmholtz Coil Systems, 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. a PXI system).
Specifications
Functionality
Magnetometer / auxiliary sensing Description Two separate inputs compatible with
most Bartington magnetometers with
up to 3 axes, differential or single-ended
output, dual or single rail
Analogue input
Input filter
Supply output:
Magnetometer
Auxiliary
Connector
Mating connector
Up to ±10V differential or single-ended
Type Butterworth 2-pole 12dB per octave
low pass
Frequencies (software selectable):
10kHz, 1kHz, 100Hz & 10Hz
0 to ±20V programmable, limited to
100mA (compatible with single or dual
supply devices)
±15V limited to 50mA per sensor
channel. Power output protected by selfresetting
semiconductor fuses
Hirose RM15TRD-10P (front panel)
Hirose RM15TRD-10S (supplied on
request)
Maximum cable length 10m 1
Current sense Description Up to three axes connected to current
sense output on Helmholtz drive
amplifier
Analogue input
Input filter
Connector
Mating connector
Up to ±10V differential
Type Butterworth 2-pole 12dB per octave
low pass
Frequencies (software selectable):
10kHz, 1kHz, 100Hz & 10Hz
Hirose RM15TRD-10P (front panel)
Hirose RM15TRD-10S (supplied on
request)
Maximum cable length 3m 1
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Helmholtz Coil Systems
Output to PA1 Power Amplifier Description Up to three axes connected to Helmholtz
drive amplifier
Analogue output
Connector
Mating connector
±10V differential
Hirose RM15TRD-10S (front panel)
Hirose RM15TRD-10P (supplied on
request)
Maximum cable length 3m 1
NI DAQ interface Description Two separate interfaces for NI DAQ card
Connector 2 x 68-way Harting 6001 068 5232
Mating cable
NI cable SHC68-68EPM
1
This is to ensure compliance with FCC and CE regulatory approvals.
Maximum cable length 3m 1
Environmental
Operating temperature range
Operating humidity
Storage temperature
+10ºC to +50ºC
0 to 50% RH non-condensing
-40ºC to +85ºC
Mechanical
Dimensions
Weight
The CU1 conforms to the standard 19-inch rack mount specification and is 1U high
2.4kg
Electrical
Power supply voltage
100–250V AC 50/60Hz
Power supply current 1100mA (115V) / 640mA (230V) type 2
Power input (rear panel)
3-way IEC 320 with integral filter (mains cable provided)
Working common mode input voltage ±10V
Absolute maximum input voltage
±15V on any input pin
ESD Protection
2 A 1A slow blow fuse is fitted internally to limit mains supply current to the power supply module
±15V on any input pin
Comprehensive ESD surge protection on input and output channels for ESD and
lightning protection

Control System Components
A test, measurement and control system is required to drive and monitor the CU1
Control Unit. The control system provides additional functions, including analogue to
digital conversion of signals from the device under test.
For this purpose, 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.
Recommended National Instruments components
Cardframe
Processor
PXI-1042*
PXI-8106*
DAQ module
* See the National Instruments website at www.ni.com for specifications of these products.
PXI-6289*
Compatibility
Combination PA1 with HC1 PA1 with HC2
Maximum field DC single axis 1 >±500µT >±250µT
Corner frequency 100Hz 20Hz
Maximum field at AC (single axis) >±100µT at 3kHz >±100µT at 300Hz
DC field compensation >±80µT >±45µT
1
Axis dependent, stated for larger coil. Smaller coils can achieve approximately 20% higher fields.
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DS2613/7
Bartington Instruments Limited,
5, 10 & 11 Thorney Leys Business Park,
Witney, Oxford, OX28 4GE, England.
T: +44 (0)1993 706565
F: +44 (0)1993 774813
E: sales@bartington.com
The specifications of the products described in this brochure are subject
to change without prior notice.
Bartington® is a registered trademark of Bartington Instruments Ltd.
www.bartington.com