24-Bit Geophysical EM Measurement System As in seismics, technological advances in electromagnetic recording systems have emphasised the require­ment for simultaneous multi-channel data acquisition.

The Multi-Method Network Geophysical Measurement System GMS‑07 is the result of over 30 years of metronix´s experience in the design and manufacture of electromagnetic geophysical instruments.

The electric and/or magnetic field sensors are connected directly to the ADU‑07e (Analog/Digital Signal Conditioning Unit), which is the core unit of this system. Multiple ADU‑07e units can be connected to a network using simple, light-weight and inexpensive network cable or Wireless LAN. Each ADU‑07e can be operated as a stand alone system, in a network or as part of an array in which each unit is synchronized by its in-built GPS clock.

  • High data quality due to 24 Bit Analog/Digital conversion technology
  • Can be operated as a stand alone or as a multi-channel network system when connecting multiple ADU‑07e in a Local Area Network (LAN, WLAN)
  • Multiple stand alone systems are synchronized with GPS clock accuracy
  • Compatible with all metronix sensors
  • Automatic unattended recording mode
  • Automated system self check of ADU‑07e and sensors during set up
  • Automatic input offset compensation eliminates self potential of electrodes
  • Realtime display of time series and many MT-parameters in online mode
  • 12 V battery powered. Only a single battery is required for each ADU incl. sensors
  • Compact, light-weight, ruggedized and water-proof instrument design
  • Wide operating temperature range from -40°C to +60°C

Metronix builds data logger and induction coils for more than 30 years.

Hardware The ADU‑07e electronics are housed in a small waterproof box only 7kg in weight. It comprises the complete circuitry for analog signal conditioning, 24 Bit A/D conversion and data storage. A very precise GPS-controlled time base guarantees synchronous recordings even under difficult GPS reception conditions.

The ADU‑07e can be tailored according to the user´s requirements. So the ADU contains 10 slots which can be equipped with 2 different types of A/D converter boards. A/D converter Type L is optimized for lower frequency recordings in a range from DC up to 500Hz whilst the second type H is optimized for high frequency recordings in a signal range from 1Hz up to 250kHz. For instance a broadband standard ADU‑07e is equipped with 5 low-frequency and 5 high-frequency A/D converter modules. It is possible to obtain high-frequency soundings during running low-frequency recording. Different types of sensors can be connected to the ADU and can even be operated in parallel. Example: A fluxgate sensor is connected for low-frequency sounding and induction coils cover the higher frequency range simultaneously.

Software The ADU‑07e has a built-in web server. All necessary setups to run a measurement are controlled by the web interface and can be accessed by any web browser; no software needs to be installed on your laptop or PDA. The software MAPROS (free) performs standard and remote reference processing of the time series data using robust algorithms. Online processing inside the ADU‑07e with unattended data publishing on the ADU's web server is under construction. Using an external GPS controlled transmitter the ADU‑07e provides CSAMT/CSEMM recordings with real-time stacking.

Configuration Examples

Single Site Configuration In this configuration a single ADU‑07e runs either in a stand alone mode and records the data according to a time schedule pre-programmed on its internal flashdisk. For highest performance an external computer can control the ADU via the USB 2.0 interface; in the latter case incoming data is processed and displayed in real time.

Multiple Site Configuration In this configuration several ADU‑07e systems are synchronized by their built-in GPS clocks, and they record the data synchronously. A typical application for this configuration is the Remote Reference method or Array Mapping. This arrangement is used for a grid with wide-spaced recording sites where cabling is impractical or cannot be handled economically.

Network Configuration

Multiple ADUs are connected to a network by cable or WLAN. A typical example for this configuration is E‑MAP or field setups, where a close-spaced station grid is required.