Bartington Mag690 Manuale utente
Operation Manual for
Mag690 Three-Axis Fluxgate Magnetometer
BARTINGTON INSTRUMENTS
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Table of Contents
1. About this Manual 4
1.1. Symbols Glossary 4
2. Safe Use 4
3. Introduction to the Mag690 4
3.1. Vector Measurements and Conventions 5
4. Installing the Mag690 6
4.1. Siting the Magnetometer (Environment Recommendations) 6
4.2. Connection Recommendations 6
4.2.1. Connector Pin Allocation 6
4.2.2. Interface 6
4.2.3. Power Supplies 6
4.3. Pre-Installation Tests 7
4.4. Mounting Recommendations 7
4.5. Post Installation Testing 8
5. Using the Mag690 8
5.1. Cabling 8
5.2. Connecting Power 8
5.3. Response 9
5.4. Electromagnetic Compatibility 9
5.5. Performance 9
5.5.1. Signal Processing 9
5.6. Magnetic Hysteresis 10
5.7. Environmental Precautions 10
6. Troubleshooting 11
7. Care and Maintenance 11
7.1. Cleaning the Mag690 11
7.2. Calibration 12
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8. Storage and Transport 12
9. End of Life Disposal 12
9.1. Waste Electrical and Electronic Equipment (WEEE) Regulations 12
Appendix 1: Use of Alternative Power Supplies 13
A1.1. Signal/Power Ground 13
A1.2. Recommended Connection Method 14
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1. About this Manual
This manual describes the installation, operation and maintenance of the Mag690 Magnetic Field
Sensor. It should be read in conjunction with product brochure DS2604 and outline drawings
which can be found on the product page on the Bartington Instruments website at www.
bartington.com.
Note that failure to follow the instructions in this manual may invalidate your product’s warranty.
If in doubt, do not hesitate to contact Bartington Instruments.
1.1. Symbols Glossary
The following symbols used within this manual call your attention to specific types of
information:
WARNING: Indicates a situation in which serious bodily injury or death could result if the
warning is ignored.
Caution: Indicates a situation in which bodily injury or damage to your instrument, or both,
could result if the caution is ignored.
This symbol identifies items that must be disposed of safely to prevent unnecessary
damage to the environment.
Note: A note provides useful supporting information and sometimes suggests how to make
better use of your purchase.
2. Safe Use
WARNING: These products are not qualified for use in explosive atmospheres or life
support systems. Consult Bartington Instruments for advice.
Caution: To prevent irreparable damage, electrostatic discharge (ESD) protection and
precautions must be used when handling the unpackaged sensor electronics board.
3. Introduction to the Mag690
The Mag690 is a magnetometer consisting of a cluster of three feedback stabilised fluxgate
sensors arranged along X, Y and Z axes. Each axis provides a highly linear magnetic response
with low hysteresis and low cross talk between axes.
It is a cost effective sensor suitable for many general purpose applications. Fully encapsulated
construction ensures that the Mag690 can be used in the field as well as in a laboratory
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environment. High stability circuitry ensures that a minimum of ten years’ service should be
expected.
The sensor has no power supply or data processing abilities of its own and must always be
connected to a power supply to be able to function.
The flying lead cable supplied as standard with the Mag690FL enables the user to choose their
preferred connector.
The Mag690MX and Mag690U include low-cost connectors for users working in laboratories or
intending to fit the sensor inside their own enclosures.
The standard Mag690 has a pre-fitted circular connector rated IP67 for use in locations where
the sensor will be exposed to the elements.
3.1. Vector Measurements and Conventions
The magnetometer produces three independent analogue output voltages in response to the
magnitude and direction of the orthogonal components of a magnetic field. A ‘right-hand’ co-
ordinate system is adopted (Figure 1). In this system, the X, Y and Z axis correspond to the
thumb, first and second finger respectively of the right hand. By convention, the magnetometer
should be installed so that the X axis is arranged to point north, the Y axis to point east and the Z
axis to point down.
Figure 1. Illustration of the Right Hand Rule
North
+X
Thumb
Down
+Z
2nd Finger
East
+Y
1st Finger
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The centres of the three vector sensors are superimposed. Each orientation is denoted on the
magnetometer’s label. The point of each vector arrow indicates the positive direction of each
axis.
4. Installing the Mag690
4.1. Siting the Magnetometer (Environment Recommendations)
Note: Site the magnetometer several metres from any magnetic base rock to avoid
compromising measurements.
Note: Site the magnetometer several tens of metres from very large ferromagnetic objects
that could create fields exceeding the measuring range of the sensor.
Note: Avoid siting the sensor near any ferromagnetic objects that may be subjected to the
effects of magnetic hysteresis, which would affect the sensor in an unpredictable manner.
Note: Conduct a magnetic evaluation of any proposed installation site to establish that
it is free from magnetic contaminants. Carry out such an evaluation using total field or
resonance magnetometers.
4.2. Connection Recommendations
4.2.1. Connector Pin Allocation
The connector pin or cable colour allocation for the connection to each package type is shown on
the appropriate outline drawing on the product page.
Caution: When fitting your choice of connector to the Mag690FL, carefully follow any
instructions and recommendations issued by the connector manufacturer(s).
4.2.2. Interface
Diodes protect against reverse connection of power voltages of up to 40V. X, Y and Z outputs are
protected against short circuit to 0V.
Caution: Short circuits from output to either power rail may result in permanent damage to
the sensor. Limit the power supply current to 100mA to minimise risk of damage caused by
incorrect connection.
The analogue outputs for the X, Y and Z axes are buffered to give a low output impedance,
enabling the unit to be operated over long cables and interfaced to low impedance data
acquisition systems.
4.2.3. Power Supplies
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The Bartington PSU1, Magmeter, SCU1 and Spectramag-6 are ideal power supply units.
Alternatively, users may wish to provide their own power supply. Refer to Appendix 1 for further
information.
4.3. Pre-Installation Tests
The Mag690FL allows users to select their preferred connector.
Caution: Ensure any crimp terminals are the correct size for 7 x 0.2mm / 24AWG wire.
Prior to the installation of the system, the magnetometer, cable and power supply must be fully
tested to ensure correct function as follows:
1. Test the cables for continuity (using an electrical continuity tester or ohmmeter).
a. Test the cables end to end at the connectors to ensure that the correct pins have been
allocated to the conductors and that there are no open or high resistance circuits.
b. Test the cables at the connectors to ensure that there are no short circuits between the
conductors.
Caution: Take care to avoid bending or otherwise damaging the contacts whilst conducting
the tests.
Caution: Carefully check for correct connection before applying power. Applying incorrect
polarity or power to output connections may cause irreparable damage to the sensor.
2. Check the power supply output voltage using a voltmeter. Refer to the product brochure for
the required values.
Caution: Switch off the power supply before connecting to the Mag690.
3. Connect the magnetometer to the cable connector.
4. Connect the power supply to the other cable connector.
5. Switch on the power supply and wait until the magnetometer has stabilised. Refer to the
product brochure for warm-up times.
4.4. Mounting Recommendations
Each magnetometer has a set of mounting holes to allow attachment to a stable base or fixture.
Refer to the mechanical drawings on the product page for details.
The sensor can also mounted on the Bartington Instruments Mag-TA Universal Tripod Adaptor.
See product brochure datasheet DS3140, available from Bartington Instruments, for instructions
on how to do this.
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4.5. Post Installation Testing
1. Site the magnetometer and install the power supply and cabling.
2. Switch on the power supply and wait until the magnetometer has stabilised. Refer to the
product brochure for warm-up times.
3. Confirm no magnetic objects are moving in the vicinity.
4. Monitor the sensor outputs.
5. Confirm that the sum of the measured magnetic field vectors is similar to the expected local
earth field.
5. Using the Mag690
5.1. Cabling
Note: The connecting cable to the sensor should be an eight-core screened cable. Two
cores will be used for positive and negative power supply lines, three cores for output
signals, one core for signal common and one for power supply ground. The screen should
be connected to supply ground at the supply end only. The capacitance between cores
should be less than 200pF per metre. A cable with individually shielded cores should be
considered for long cable applications.
Note: Leads are susceptible to EM interference and should be screened wherever possible.
Note: The length of the cable is limited by the voltage drop in the power supply lines
and the capacitance between the cores. For this reason the cable should be limited to a
maximum length of 600 metres.
Bartington Instruments can supply cables for connecting the sensor to the PSU1, Magmeter,
SCU1 and Spectramag-6.
5.2. Connecting Power
Caution: Check that the polarity of the supply is correct. The power supply should
be connected to the sensor before the supply is energised as this prevents high
surge currents which could cause damage. Apply the positive and negative supplies
simultaneously, and avoid leaving the sensor connected to one polarity only.
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5.3. Response
The analogue output V, for any channel, is proportional to the axial component b of the total field
F. If qis the angle subtended between the direction of F and sensing axis of the fluxgate element,
then:
b = F cosq and V αF cosq
5.4. Electromagnetic Compatibility
Note: The Mag690 is not shielded for immunity from, or emission of, electromagnetic
fields. Any shield placed around the sensor will limit the bandwidth of the sensor response.
The emissions generated are at a low level with a primary frequency of 15kHz, being
the frequency of the energising field of the sensor. The sensor is required to respond to
magnetic fields within the specified frequency band.
Note: Ensure that the sensor is not operated in areas where a high electromagnetic field
exists, even if the frequency is above the bandwidth of the sensor, as false information may
appear due to aliasing. This effect is seen in data acquisition systems when the frequency
of sampling is lower than the frequency of the signal which is being sampled. It may
produce apparent signals at lower frequencies than the noise, which may be within the
frequency band of the sensor. Similarly, do not place the sensor near to any equipment
which may be affected by the fields produced by the sensor excitation.
5.5. Performance
5.5.1. Signal Processing
For different applications it may be necessary to process the signal from the sensor in different
ways.
a. In order to increase the sensitivity of the recording system it may be necessary to back-
off the earth’s field and amplify only the changes in the field from the current value. This
requires a high-pass filter, which could be a simple capacitively coupled arrangement or a
multi-pole filter to provide a steep roll off characteristic. These features are all present in the
SCU1 signal conditioning unit.
The output from all fluxgate sensors will contain noise from the driving electronics. For the
Mag690 this noise is at 15kHz, which is well above the bandwidth of the sensors. Where low
noise operation is required, a filter should always be provided to reject the noise which lies
outside the band of interest.
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b. When the sensor output is digitized, it may be necessary to include an analogue low-pass
anti-alias filter to prevent the creation of in-band noise by beating the 15kHz excitation with
the sampling clock of the digitizer.
The level of unwanted breakthrough at 15kHz has been minimized in the Mag690 but may
still cause an apparently raised noise level when sampled at low sampling frequencies
without further analogue filtering.
c. In applications such as surveillance and magnetic signature monitoring, it may be required
to remove both the DC standing field and all AC noise and pick-up above a set frequency. The
band of interest will be, say, 0.01 to 10Hz, and a band pass filter can be used to provide the
required signal.
The Magmeter and PSU1 power supply units, which can be used with all sensors, contain
three low pass filters with a -3dB point at 4.5kHz together with three high pass filters with a
-3dB point at 0.1Hz.
The SCU1 signal conditioning unit provides filters with independent control of the low and
high pass filter sections, together with offset and gain control for the output of each axis.
5.6. Magnetic Hysteresis
The Mag690 is designed to have an extremely low magnetic hysteresis. However, Bartington
Instruments recommends your magnetometer is not subjected to magnetic fields greater than
their stated measuring range for extended periods, as this could alter the DC offset. If this
occurs, the offset will exhibit drift as it returns to its original offset specification.
Caution: Subjecting the magnetometer to fields in excess of 2 x the nominal range may
cause inaccuracy in future measurements. Degaussing the magnetometer can reverse
such an effect.
5.7. Environmental Precautions
Refer to the product brochure for maximum environmental electrical and mechanical ratings.
Caution: Exceeding the maximum ratings may cause irreparable damage to your sensor.
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