1. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM LOW COST FLUXGATE MAGNETOMETER DEVELOPMENT USING PROGRAMABLE LOGIC CONTROLLER FOR SAMA MONITORING IN SOUTH OF BRAZIL ANTUNES, CASSIO ESPINDOLA 1; Campos, Alexandre 2; Schuch, Nelson Jorge 1; Trivedi, Nalin Babulal 3; Savian, Fernando de Souza 1; Siqueira, Josemar 1. 1 – Southern Regional Space Research Center – CRS/INPE-MCT in collaboration with the Space Science Laboratory of Santa Maria – LACESM/CT-UFSM, Santa Maria, RS, Brazil. 2 – Federal University of Santa Maria – NUPEDEE/UFSM, Santa Maria, RS, Brazil. 3 – National Institute for Space Research – INPE-MCT, São José dos Campos, SP, Brazil. IAGA 2009 Scientific Assembly August 23 – 28, 2009 – Sopron, Hungary

2. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM Objectives:  To create Capacity Building in geophysics instrumentation for development of equipments in Brazil;  To create basic conditions for development of low cost magnetometers in the South of Brazil;  To propose a circuit topology for fluxgate magnetometers using microcontrollers;

3. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM SOUTHERN REGIONAL SPACE RESEARCH CENTER CRS/INPE Panoramic view of the main building at Santa Maria, RS, Brazil AN ACTIVE AND PASSIVE SITE FOR INSTRUMENTATION SYSTEMS Geographic Coordination: Latitude: 29º 26´ 24”,06 S Longitude: 53º 48´ 38”,98 W Ellipsoidal Altitude : 488 m SOUTHERN SPACE OBSERVATORY SSO/CRS – INPE Main gate and buildings 1, 2, 3, 5 and 6 at São Martinho da Serra, RS, Brazil Geomagnetic Coordination: Latitude: 19º 13´ 48” S Longitude: 16º 30´ E Inclination or “dip”: 33º S Total Geomagnetic Field: 22,800 nT. A PASSIVE SITE FOR INSTRUMENTATION SYSTEMS WHERE THE MAGNETOMETERS PROTOTYPES WERE TESTED

4. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM The South Space Observatory, in the south of Brazil, is located near the center of the South Atlantic Magnetic Anomaly – SAMA, which has the smallest Total Intensity Field (about 23000 nT). South Atlantic Magnetic Anomaly region. In purple the isodynamic lines representing the Total Intensity (nanoteslas). In blue the annual variation (nanoteslas). Source: National Observatory – ON/MCT, Rio de Janeiro, Brazil. Source: PDF world map at CIA World Fact Book South Space Observatory

5. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM The ring core fluxgate magnetometer has only two windings: the drive (or the primary) winding and the sense (or the secondary) winding. The second harmonic signal intensity detected is linearly related with the external field variation. Block diagram of the ring-core fluxgate magnetometer.

6. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM THE SENSOR MAGNETIZATION x FREQUENCY RESPONSE METHOD  To determinate the best frequency range response of the magnetic sensors tests were performed to define the best symmetric BxH curve of the material core. The Figure shows the circuit assembly used to perform the magnetization tests at the CRS’s Lab. facilities in Santa Maria.  Histerese of the magnetic material curves were obtained by the modified Rowlandof’s ring method proposed by RODRIGUES, 1995.

7. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM The sensor’s 2 kHz histerese curve The sensor’s 4 kHz histerese curve RESULTS OF THE SENSOR MAGNETIZATION – I

8. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM The sensor’s 8 kHz histerese curve The sensor’s 12 kHz histerese curve RESULTS OF THE SENSOR MAGNETIZATION – II

9. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM The detected second harmonics for 4 kHz

10. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM The detected second harmonics for 8 kHz

11. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM THE BAND PASS FILTER SPECIFICATION The Butterworth method was used since it provides the best flat pass band. Lower frequency band cut off Upper frequency band cut off 2

12. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM THE 6TH ORDER BAND PASS TRANSFER FUNCTION

13. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM THE 8TH ORDER BAND PASS TRANSFER FUNCTION

14. SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/INPE-MCT SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM/CT-UFSM  The best excitation frequency was f0 = 4 kHz for the sensor of the prototype magnetometer developed at the CRS/INPE, in Santa Maria.  Two pass band filter specification were selected in order to be used in the magnetometer circuitry development.  Capacity Building is been implemented for the development of geophysics instrumentation in South Brazil (UFSM x INPE). FUTURE: Microcontroller devices will be tested for the development of low cost magnetometers to upgrade the equipment efficiency on data acquisition and storage. CONCLUSIONS THANK YOU – MUITO OBRIGADO cassio@lacesm.ufsm.br