GEODEVICE MiniMag Manuel utilisateur

OPERATION MANUAL

Overhauser magnetometer

MiniMag

 
2
Overhauser magnetometer MiniMag 
 
Contents 
INTRODUCTION.............................................................................................................................................................4 
DESCRIPTION AND PRINCIPLES OF OPERATION ........................................................................................................6 
1 Description of the product..................................................................................................................................6 
1.1 Designation ..................................................................................................................................................6 
1.2 Technical characteristics, parameters and dimensions................................................................................6 
1.3 Package contents .........................................................................................................................................7 
1.4 Structure and Functioning............................................................................................................................8 
1.4.1 Principle of operation................................................................................................................................8 
1.4.2 Measurement cycle...................................................................................................................................8 
1.5 Storage & shipping case...............................................................................................................................8 
2 Magnetometer description and principles of operation.....................................................................................9 
3 Operating controls and operator control chart.................................................................................................11 
3.1 Operating controls .....................................................................................................................................11 
3.2 Operator control chart...............................................................................................................................12 
INTENDED USE .........................................................................................................................................................14 
1 Operating limitations ........................................................................................................................................14 
2 Preparation for use ...........................................................................................................................................15 
2.1 General safety instructions for use ............................................................................................................15 
2.2 The procedure and workflow to prepare the device for use......................................................................15 
3 USAGE ...............................................................................................................................................................18 
3.1 Initial setup window, viewing GNSS data and entering the main menu.....................................................20 
3.1.1 Initial setup window............................................................................................................................20 
3.1.2 Viewing GNSS data..............................................................................................................................20 
3.1.3 Exit to the main menu.........................................................................................................................21 
3.2 Operating modes .......................................................................................................................................21 
3.2.1 Test mode ...........................................................................................................................................21 
3.2.2 Manual mode......................................................................................................................................22 
3.2.3 Automatic mode .................................................................................................................................25 
3.3 Viewing information...................................................................................................................................26 
3.4 Erasing information from the magnetometer memory (clearing memory) ...............................................28 
3.5 Magnetometer settings control .................................................................................................................28 
3.5.1 Signal search .......................................................................................................................................29 
3.5.2 Language choice..................................................................................................................................30 
3.5.3 Time zone............................................................................................................................................30 
3.5.4 Information about device....................................................................................................................30 
3.5.5 Corrections..........................................................................................................................................31 

 
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Overhauser magnetometer MiniMag 
3.6 Safety measures during device using .........................................................................................................31 
3.7 Procedure for completing operation with the device ................................................................................32 
3.8 Data export from the magnetometer memory to a PC..............................................................................33 
3.9 Real-time data output to PC.......................................................................................................................36 
4 Actions during extreme conditions ...................................................................................................................41 
5 List of possible malfunctions.............................................................................................................................42 
REPAIR......................................................................................................................................................................44 
STORAGE..................................................................................................................................................................45 
TRANSPORTATION....................................................................................................................................................46 
RECYCLING ...............................................................................................................................................................47 
APPENDIX.................................................................................................................................................................48 
1 General recommendations for magnetic survey fulfillment with Overhauser Magnetometers MiniMag........48 
1.1 Installation of a Base station ......................................................................................................................48 
1.2 Magnetic survey with Rover.......................................................................................................................48 
2 Earth’s magnetic field inclination and total intensity maps ..............................................................................50 
2.1 Main field inclination map..........................................................................................................................50 
2.2 Main field total intensity ............................................................................................................................51 
3 Li-ion battery.....................................................................................................................................................52 
3.1 Battery specifications.................................................................................................................................52 
3.2 Charge........................................................................................................................................................52 
3.3 Precautions ................................................................................................................................................52 
4 Li-ion battery charger........................................................................................................................................54 
4.1 Charger specifications................................................................................................................................54 
4.2 Charge........................................................................................................................................................54 
4.3 Precautions ................................................................................................................................................55 
5 Pinout scheme of the magnetometer cables ....................................................................................................56 
5.1 Cable “Control Unit to Magnetometer Unit” .............................................................................................56 
5.2 USB cable ...................................................................................................................................................56 
5.3 Remote start cable.....................................................................................................................................57 
5.4 Li-ion battery cable ....................................................................................................................................57 
6 Material Safety Data Sheet for Li-ion battery....................................................................................................58 
 
 

Overhauser magnetometer MiniMag

INTRODUCTION

This operation manual (hereinafter referred to as OM) is designed for studying the device, its

principle of operation and proper use of the Overhauser magnetometer MiniMag (hereinafter —

magnetometer / device / product) by the operating personnel.

This OM contains information about the configuration, design, principle of operation, technical

characteristics of the magnetometer, operational limitations; instructions for preparing for

operation, usage, transportation and storage; safety precautions; disposal instructions and other

information regarding the magnetometer necessary for its correct usage in order to maintain the

operational reliability and safety of the device.

ATTENTION: REPAIR OF THE MAGNETOMETER IS CARRIED OUT EXCLUSIVELY BY THE

MANUFACTURER (GEODEVICE) or by specialized services and professionals who have been trained

and have a certificate for the right to carry out repairs, issued by GEODEVICE.

The requirements of this OM are mandatory for all persons involved in the operation, storage,

transportation, further disposal and other manipulations with the magnetometer.

This OM should always be in close proximity to the place of operation of the device and be

accessible to operating personnel.

The operational reliability and safety of the magnetometer is guaranteed only if all of the following

conditions are met at the same time:

- usage of the device for its intended purpose;

- operation of the magnetometer in acceptable environments and conditions in accordance with

the OM;

- compliance with the instructions for use, safety measures and all other recommendations and

requirements of this OM.

IT IS PROHIBITED TO OPEN / DISASSEMBLE THE MAGNETOMETER, AS WELL AS TO MAKE

MODIFICATIONS IN THE DESIGN OF THE DEVICE, DEVELOP IT WITHOUT DUE APPROVAL OBTAINED

FROM THE MANUFACTURER.

In case of violation (non-compliance) of the requirements given in this OM, the manufacturer is

not responsible for the consequences arising in connection with this (accident, damage to

property, injury, etc.)

Manufacturer is constantly improving its equipment and reserves the right to make changes to the

design of the magnetometer, change its technical characteristics and completeness. In this regard,

there may be insignificant differences between what is described in this OM and the supplied

magnetometer, which do not fundamentally affect the conditions of its operation.

Overhauser magnetometer MiniMag

The following abbreviations and notations are used in this OM:

SEU —signal excitation unit,

HFG —high-frequency generator,

GPS —Global Positioning System,

DNP —dynamic nuclear polarization,

MU —magnetometer unit,

ETF —Earth’s total field,

CU —control unit,

OS —operating system,

PC —personal computer,

SE —sensitive element,

SC —signal conditioner.

Overhauser magnetometer MiniMag

1. DESCRIPTION AND PRINCIPLES OF OPERATION

1.1 Description of the product

1.1.1 Designation

Overhauser magnetometer MiniMag is designed for high-precision measurements of the module

of the full vector of the geomagnetic field. The sensor used in the design of the magnetometer (the

principle of which is based on the Overhauser effect application), does not require maintenance

and operates steadily for at least 10 years without deterioration of technical characteristics.

MiniMag can be used as a rover hand-held magnetometer, autonomous or remote base station.

Increased absolute accuracy and real-time data transfer allow MiniMag to be used in magnetic

observatories. Integrated GPS/GLONASS receiver enables automatic coordinate gridding of

measurement stations and time synchronization with the base station making convenient the

survey implementation as well as data processing.

1.1.2 Technical characteristics, parameters and dimensions

Table 1. Technical characteristics, parameters and dimensions

Parameter

Value

Principle of operation

based on the Overhauser effect application

Range

20 000 ÷ 110 000 nT

Absolute accuracy

0.2 nT

Sensitivity

0.015 nT in cycle 3 s / 0.026 nT/√Hz

Resolution

0.001 nT

Optimal angle between the axis of the sensor and

the field vector

90°

The working range of inclination relative to the

optimal angle

±45°

Orientation error

0.5 nT (±45°)

Gradient tolerance

10 000 nT/m

Minimum measurement cycle

0.5 s

Radical stability

10 years at standard conditions

Communication interface with PC

USB

Memory capacity

1 000 000 (in base magnetic station mode),

250 000 (with coordinate referencing)

Power

10 ÷16.8 V, Li-ion or Pb battery

Power consumption

3.7 W in 2 s cycle

3.2 W in 3 s cycle

1.4 W in 10 s cycle

Operating temperature range

−40 ÷ +60 °C, readability of the display is provided

at temperatures above −20 °C

Weight

3.1 kg (with battery)

Nominal voltage of Li-ion battery

14.6 V

Nominal capacity of the battery

4 A·h

Continuous operation time with a fully charged

battery and a 20 °C temperature

15.9 h in 2 s cycle

18.7 h in 3 s cycle

42 h in 10 s cycle

Overhauser magnetometer MiniMag

1.1.3 Package contents

The following components are included in the delivery:

•MiniMag magnetometer

•Console

•Set of cables

•Remote start module

•Li-ion battery with power cable

•Charger

•External power supply (for lead battery);

•Backpack harness;

•Rugged shipping / storage container;

•Data storage software

•Calibration certificate issued by authorized organization

•Operation manual

Figure 1 –Overhauser magnetometer MiniMag

Transportation of the Overhauser magnetometer MiniMag is carried out in a sealed, shockproof

casing made of bakelite plywood.

Overhauser magnetometer MiniMag

1.1.4 Structure and Functioning

1.1.4.1 Principle of operation

For measuring the geomagnetic field in a magnetometer, the phenomenon of protons’ free

precession of a prepolarized working agent in the ETF is used. In this case, the polarization of nuclei

is enhanced by the Overhauser effect (dynamic polarization of nuclei).

The Overhauser effect is a phenomenon that deploys the electron-proton interaction in order to

achieve the polarization of protons. To realize this effect, a specially developed compound is used

in the magnetometer, which contains a free radical atom (an atom with an unbound electron),

which is added to a proton-rich liquid. Unbound electrons in a solution can be easily excited by

high-frequency radio frequency radiation, which corresponds to a transition between energy

levels. Instead of re-releasing this energy in the form of emitted radiation, unbound electrons

transfer it to neighboring protons, which allows to polarize these protons without the need to

create a large artificial magnetic field. Therefore, such sensors can generate large-amplitude signals

with a high signal-to-noise ratio, with a power consumption of just a few watts. Standard proton

sensors cannot generate signals of this magnitude and quality, even when consuming several

hundred watts.

1.1.4.2 Measurement cycle

Each measurement cycle essentially consists of two steps:

1. Polarization —proton fluid of the sensitive element (SE) is excited by both constant and high-

frequency magnetic fields, thus, orienting the proton spins normally to the magnetic field of the

earth (ETF).

2. Measurement —after the exciting field is turned off, it begins free precession of protons in the

ETF. Attenuating sine-shape EMF proportional to ETF value is induced in the low-frequency coils of

SE:

  



where —precession frequency,

—total field,

  

 —proton gyromagnetic ratio.

1.1.5 Storage & shipping case

Magnetometer is delivered in the special case which protects the device from precipitation and

dust.

Overhauser magnetometer MiniMag

1.2 Magnetometer description and principles of operation.

Figure 2 –Overhauser magnetometer MiniMag: package contents

1 –magnetometer unit (MU);

2 –control unit (CU);

3 –sensitive element (SE);

4 –signal excitation unit (SEU);

5 –battery with cable;

6 –CU-to-MU connection cable;

7 –remote start module;

8 –charger;

9 –USB-cable;

10 –backpack harness.

Overhauser magnetometer MiniMag

Magnetometer unit

MU is intended for ETF measurement and consist of SE and SEU joined together using the non-

magnetic rode.

SE is intended for generating a signal from free precession of protons of working agent placed in

the magnetic field measured. SE contains a glass ampoule with a working agent placed in a high-

frequency circuit (HF circuit), on top of which low-frequency coils are wound that are designed for

recording the precession signal.

SEU is designed to provide a proton precession signal. In terms of construction, SEU is made in the

form of a separate unit, which includes HFG and SC

Control unit (CU)

Used to control the magnetometer, perform basic and auxiliary operations, record the results of

field measurements in non-volatile memory, followed by the information output of to PC.

Battery with power cable

Intended to power the electronic components of the magnetometer. A Li-Ion rechargeable battery

with a voltage of 14.8 V and a capacity of 4 A·h is used as a power source. Also, a 12 V lead-type

battery Delta CT 12025 can be used as a source, to connect which a power cable for connecting a

lead battery is present in the configuration of the device.

CU-to-MU connection cable

Designed for data transfer between the control panel and MU.

Cable with remote start button

Designed for remote start of magnetometer measurements.

Charger

Designed for charging the battery from AC 220 V, 50 Hz.

USB cable

Designed for connecting CU to PC.

Backpack harness

Designed for carrying the magnetometer during survey.

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