GMW BARTINGTON MAG-03-OCTO-PSU Manual

GMW
_________________________________________________________________________________
GMW
955 Industrial Road, San Carlos, CA 94070 Tel: [phone] Fax: [phone]
Email: [email protected] Web site: http://www.gmw.com
BARTINGTON
MAG-03-OCTO-PSU
POWER SUPPLY UNIT
OPERATION/MAINTENANCE MANUAL
Distributed by:
GMW Associates
955 Industrial Road, San Carlos, CA 94070 USA
Tel: [phone] Fax: [phone]
Email: [email protected]
website: http://www.gmw.com
Manufactured by:
Bartington Instruments Ltd.
10 Thorney Leys Business Park
Witney, Oxford OX8 7GE
England
Tel: [phone] Fax: [phone]
Email: [email protected]
website: http://www.bartington.com Issue 3Jan 01

OM1561 ISSUE 3 PAGE 1of 11
OM1561
OPERATION/MAINTENANCE MANUAL
FOR Mag-03-OCTO-PSU POWER SUPPLY UNIT
January 2001
Bartington Instruments Ltd
10 Thorney Leys Business Park
Oxford OX28 4GG England
Tel: [phone]
Fax: [phone]
In the interest of product improvement, Bartington Instruments Ltd. reserves the right to change any part
of the design of this product without prior notice.
This product is not qualified for use in explosive atmospheres or life support systems. Consult
Bartington Instruments for advice.
The copyright of this document is the property of Bartington Instruments Ltd. The document is supplied
on the condition that it is to be treated commercially confidential and it may not therefore be disclosed to
any third party without the written authorisation of the Managing Directors of Bartington Instruments.

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LIST OF CONTENTS
1 INTRODUCTION
2 POWER
3 FILTERS
4 BUFFERS
5 CONNECTORS
6 CABLES
7 ANALOG VOLTAGE MEASUREMENTS
8 Mag-03-OCTO-PSU WITH Mag-03 SERIES SENSORS
9 BATTERY CHARGING
10 BATTERY CARE
11 ANALOG OUTPUT
12 TAKING MEASUREMENTS
12.1 CONNECTING UP
12.2 FILTER SECTION
12.3 ADDITIONAL FILTERS
12.4 OVERLOAD
12.5 AC MEASUREMENT PRECAUTIONS
12.6 ELECTROMAGNETIC COMPATIBILITY
13 REPLACING THE INTERNAL BATTERY PACK
14 OPERATION WITH AN EXTERNAL BATTERY PACK
15 SPECIFICATIONS
LIST OF FIGURES
FIGURE 1 Mag-03-OCTO-PSU OUTLINE DRAWING
FIGURE 2 Mag-03-OCTO-PSU SIMPLIFIED SCHEMATIC

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1 INTRODUCTION –SEE FIG 1
This manual describes the operation of the Mag-03-OCTO-PSU power supply unit. The unit provides
a battery backed power supply of ±12V for up to eight Mag-03 series three-axis fluxgate magnetic field
sensors. Signal inputs from the Mag-03 sensors are fully differential and the buffered outputs can be
selected to be all a.c. or all d.c. coupled. The connector pin allocation details are given in the
SPECIFICATIONS section.
2 POWER
The Mag-03-OCTO-PSU contains a 12V, 4Ah rechargeable Nickel Metal Hydride battery pack. The
battery is charged from the 240Vac or 120Vac mains adaptor supplied, which provides a regulated
supply of 12Vdc at 1.25A. When in good condition the battery will power eight Mag-03 sensors for up
to 10 hours.
A switch controls the power to the sensors. A 2.1mm input socket is provided for connecting the 12V
mains adaptor for charging the battery. The centre pin is positive and the battery pack input is protected
against reversed polarity. The sensors may be operated during battery charging provided the ambient
temperature is below 30°C. This is a precaution to avoid excessive internal temperatures.
A red indicator is constantly illuminated when the battery is being charged. The battery should always
be charged after use.
The +12V supply for the Mag-03 series of magnetic field sensors is provided by the battery pack and
the -12V supply by a dc to dc converter. Each Mag-03 sensor is connected by a 6-conductor cable,
the screen of which is used for the 0V power supply return (common) line. (See Figure 2)
3 FILTERS
A low pass and a high pass filter are included in the signal path of the outputs from the X, Y and Z axes
of each of the sensors. The low pass filters provide a frequency response from dc to 4.5kHz. These
filters remove the high frequency noise components of the signal from the sensor.
The high pass filters have a fixed low frequency cut off at 0.1Hz and are intended to isolate the dc or
static field component so that the alternating components above this frequency can be measured or
analysed. A switch allows the high pass filters to be de-selected or selected to provide a sensor
response from dc to 3kHz or an ac response from0.1Hz to 3kHz.
4 BUFFERS
The three XYZ signal outputs from each individual magnetometer share a common signal return line
which is separate from the power return line. In this way dc errors which could arise due to power
supply return currents are completely eliminated. The common mode rejection ratio is 50dB minimum.
The three signal lines from each magnetometer are buffered by an amplifier with a fully differential input
stage, filtered and fed via a buffer to the appropriate pin of one of the two output connectors. The signal

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common is also buffered. The buffers allow long cables and low input impedance data acquisition
systems to be used. The load should not be less than 10kohm resistance or greater than 2000pF.
The output common is referenced to the internal chassis ground.
5CONNECTORS
Each Mag-03 sensor is connected to one of the eight Hirose 10-pin connectors on the front panel. The
filtered and buffered sensor outputs are available through two 37-way Cannon D type connectors with
four sensors being allocated to each connector. A nine-pin Cannon D type connector is available for
connecting external temperature sensors and the output signals from these are linked internally to the 37-
way connectors.
6CABLES
Cables can be supplied to connect any of the Mag-03 series of sensors to the Mag-03-OCTO-PSU.
Details are given in the operation manual for the sensor. The cables carry the supply voltage to the
magnetic field sensor with the 0V connected through the screen. Analog signals are returned via three
conductors and the analog return is via a separate conductor.
The maximum cable length of 600 metres is derived from the following considerations:
(a) Above this length the positive supply current of up to 30mA will produce a 1.5 V voltage
drop which may restrict the analog output swing especially where a low voltage supply is
used.
(b)
Above this length the maximum capability for capacitance loading of the magnetic field
sensor output will be exceeded.
Cables other than those provided by Bartington Instruments should generally conform to the
specifications given and a screened type is essential if low noise performance is to be achieved. An
example of an alternative cable is Belden Type 9536 for use in protected conditions, e.g. ducts etc.
7 ANALOG VOLTAGE MEASUREMENTS
To obtain the full precision of the magnetic field sensor the analog outputs should be connected only to
analog inputs which have an impedance greater than 10 kΩ.
8 Mag-03-OCTO-PSU WITH Mag-03 SERIES SENSORS
Use of the Mag-03-OCTO-PSU power supply eliminates any problems which may be encountered in
providing a suitable isolated power source for an array of sensors. The unit also provides additional
filtering of the analog signals to improve the signal to noise ratio. The high pass filter sections can be
selected to provide either a dc or ac response.

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9 BATTERY CHARGING
A mains adaptor having a 12Vdc regulated output is supplied for battery charging. The unit supplied will
operate from either 110V or 220V/240Vac, 60Hz or 50Hz, and provides full electrical isolation from
the mains supply. As an alternative the battery may be charged from a vehicle dashboard 12V
connector.
Note: the -ve terminal of the front panel charging socket is connected, via the battery pack, to system
ground.
The power switch should normally be turned to off before charging. The internal battery will be
completely charged in around 16 hours when connected to the mains adaptor and the red indicator will
glow continuously while the battery is charging. The battery may be charged for 16 hours at any battery
charge state but the battery should not be left on charge continuously.
If the ambient temperature is below 30°C the sensors may be operated while the battery is being
charged. The battery charging period will not be increased.
10 BATTERY CARE
In order to maintain the battery in good condition it should be completely discharged and recharged
every three months. This applies whether the unit has been used regularly or not during this period. The
unit can be fully discharged by connecting one or more sensors and leaving the unit switched on. The
battery should then be recharged for 16 hours. The battery will fully self-discharge, when not in use, in
7-10 weeks.
11 ANALOG OUTPUT
The output impedance of the signal buffers is 50 ohms. If measurement errors of more than 0.5% are to
be avoided the analog outputs should not be loaded by an impedance of less than 10kΩor 2000pF.
Connection should be via a multiway screened cable of not more than 2 metres in length. If the analog
outputs are to be connected to a differential input then ensure that the common mode range of the input
is constrained to within a few volts of the system ground to which the magnetic field sensor is to be
connected. This may usually be done by establishing a connection between the sensor signal common
output and the system ground.
12 TAKING MEASUREMENTS
12.1 CONNECTING UP
Connection between the magnetic field sensor and the power supply should not be made or broken with
the power supply switched on as this could damage the magnetic field sensor.
12.2 FILTER SELECTION
The power supply contains a filter section for each channel. The low pass filters are always connected
to remove unwanted high frequency components from the signals and the high pass filters can be

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selected if required to block the static background field and provide only an ac response. The decision
to use either a dc or ac response will depend upon several factors.
(a) The need or otherwise to measure the static field.
(b) The dynamic range of any associated measuring instrument.
If a 16-bit A/D converter is used, it will have a resolution of ±1 in ±32768. This is just about sufficient
to digitise a terrestrial field strength of 47µT to 2 or 3 nT. Many 16-bit converters do not guarantee full
monotonicity over 16 bits.
If only the alternating component of the magnetic field is of interest, the static component can be rejected
by selecting AC on the AC/DC switch.
12.3 ADDITIONAL FILTERS
The output from the Mag-03 sensor will contain break-through from the operating frequency of the
sensors at 15.625kHz. The Mag-03-OCTO-PSU attenuates this component but care should be
exercised when connecting to a sampling A/D converter. Avoid sampling rates which are close to this
frequency and ideally choose an A/D converter with an anti-aliasing low pass filter with a cut-off
frequency as low as possible for the application.
12.4 OVERLOAD
Exposure of the magnetic field sensor to a flux between +120% and +200% or -120% and -400% of
the full-scale range will cause the analog output to saturate. Beyond this the output will become
unpredictable, usually slewing to the opposite polarity. The magnetic field sensor will not be harmed
permanently due to overload but this situation should be avoided.
12.5 AC MEASUREMENT PRECAUTIONS
The measurement and roll-off characteristics of the magnetic field sensor ensure great precision for
measurements obtained within the specified bandwidth and freedom from errors at frequencies above
the -3dB point. It must be noted, however, that all fluxgate magnetic field sensors employ some form of
synchronous phase detector operating at a particular frequency. This gives rise to modulation products
in the presence of an alternating flux close to the operating frequency. The magnitude of the products
will be equal to the magnitude of the detected flux (±3dB) for a difference frequency of ±1.5kHz. The
operating frequency of the Mag-03 series of magnetic sensors is 31.25kHz.
12.6 ELECTROMAGNETIC COMPATIBILITY
The Mag-03-OCTO-PSU contains no high frequency electronics likely to cause emissions which could
affect other apparatus and is heavily shielded. The constant voltage charger and battery combined with
tantalum capacitors provide good filtering to minimise any emissions. The unit is also unlikely to be
affected by interference from other equipment in the normal operating environment.
13 REPLACING THE INTERNAL BATTERY PACK

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The battery pack is supplied as a module with connectors, a power switch and indicator. To replace the
unit proceed as follows:
(a) Disconnect the mains adaptor and ensure the power switch is in the OFF (O) position.
(b) Undo the four screws on the underside of the unit and remove the top panel.
(c) Remove the 2.1mm connector from the battery unit which is connected to the printed circuit
board.
(d) Remove the 2.1mm connector from the battery unit which is connected to the rear panel
(e) Disconnect the black optical fibre from the indicator on the battery unit.
(f) Lift the battery pack from the unit noting the orientation.
(g) Insert a new battery pack in the same orientation.
(h) Connect the output of the pack to the printed circuit board socket, the input lead from the rear
panel to the input socket of the pack and the black optical fibre to the LED indicator on the
pack.
(i) Replace the top panel and secure with the four screws.
14 OPERATION WITH AN EXTERNAL BATTERY PACK
For applications where it is required to operate the power supply over long periods, it is possible to
remove the internal battery pack and connect it externally. The battery should be removed as described
above and the internal cable within the Mag-03-OCTO-PSU, which is normally connected to the
battery pack input, should be connected directly to the PCB connector. The enclosure lid can then be
replaced and the battery pack can be connected to the charging power input socket of the Mag-03-
OCTO-PSU. In this way several battery packs can be used in rotation with charging being carried out
remotely from the Mag-03-OCTO-PSU.

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15 SPECIFICATIONS
Electrical
Sensor power supply ±12V at 500mW per sensor. Power is on when power switch is on and battery is charged.
Sensor connector 8 off 10-pole Hirose plug type RM15TRD-10P
Output connectors 2 off 37 way D-type connector
1 off 9 way D-type connector
Battery Bartington rechargeable power pack 12V 4Ah
Battery status lamp On during charge
Battery charging supply 12V regulated dc from 240 or 120V mains adaptor, 1.25A minimum output
Battery charger socket 2.1mm dc socket
Charging time 16 hours
Fuse 4A internal
Mechanical
Enclosure Materials Polystyrene
Dimensions (mm) 237(L) X 222(W) X 70(H)
Weight 2.5kg with Battery Pack installed
Environmental
Operating temperature -32°C to +50°C (+30°C if simultaneously charging)
Storage temperature -33°C to +70°C
The specification of this product is liable to change without prior notice.

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Connector detail
CON1-CON8 Magnetic Sensor Connectors
Pin Function
1 X out
2 Y out
3 Z out
4 signal/power ground
5 signal/power ground
6 +12V supply
7 -12V supply
8,9,10 no connection
PL1 Signal Output Connector
Pin Function Pin Function Pin Function
1 13 25 3Y
2 14 26 3Z
3 15 27 4X
4 16 28 4Y
5 17 0V 29 4Z
6 18 1X 30 Pin1 PL2
7 19 1Y 31 Pin2 PL2
8 20 1Z 32 Pin3 PL2
9 21 2X 33 Pin4 PL2
10 22 2Y 34
11 23 2Z 35
12 24 3X 36,37
PL3 Signal Output Connector
Pin Function Pin Function Pin Function
1 13 25 7Y
2 14 26 7Z
3 15 27 8X
4 16 28 8Y
5 17 0V 29 8Z
6 18 5X 30 Pin5 PL3
7 19 5Y 31 Pin6 PL3
8 20 5Z 32 Pin7 PL3
9 21 6X 33 Pin8 PL3
10 22 6Y 34
11 23 6Z 35
12 24 7X 36,37
PL2 Temperature Sensor Connector
Pin Link to
1 Pin30 PL1
2 Pin31 PL1
3 Pin32 PL1
4 Pin33 PL1
5 Pin30 PL3
6 Pin31 PL3
7 Pin32 PL3
8 Pin33 PL3
9 0V

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OM1561 ISSUE 3 PAGE 11 of 11
Figure 1 -Mag-03-OCTO-PSU OUTLINE DRAWING

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Figure 2 -Mag-03-OCTO-PSU SIMPLFIED SCHEMATIC