The Stratagem EH-5 is used to measure the electrical impedance at the earth’s surface using a series of simultaneous measurements of local electrical and magnetic field fluctuations.  These field measurements are made over a period of several minutes; Fourier transformed, and stored as power spectra.  The surface impedance calculated from these spectral values is a complex function of frequency where higher frequency data are influenced by shallow or nearby features, and lower frequency data are influenced by structures at greater depth and distance.  An MT sounding provides an estimate of vertical resistivity beneath the receiver site and also indicates the geoelectric complexity at the sounding site.   Stratagem EH5 measurements may be effectively applied in ground water investigations, subsurface characterization at environmental study sites, shallow mineral and geothermal exploration, and in civil engineering studies. The EH5 is also perfect for academics as it's easy to use, light weight, and portable and is a great introduction to students without prior knowledge of MT.   Because this battery-powered system is compact and portable, it is productive even on rough terrain and may be operated successfully in fairly hostile environments.  The speed and portability of the Stratagem EH-5 system allows for a flexible survey design.  Surface impedance results are immediately displayed as a resistivity sounding and may also be processed in groups of soundings and viewed in section while on site.  This flexibility enables the investigator to alter the survey design on site based on preliminary processing and examination of measurement results. For more information, read our brochure on the new Stratagem EH-5 Here!  

Features and benefits

  • Fully integrated, easy-to-use system - All hardware and software ready to go out-of-the-box. 

  • Rapid setup and data acquisition – Full sounding to 1000 meters

  • Real-time, in-field display – The Stratagem EH-5 is controlled using any Android or Windows device.

  • Resistivity mapping from 10 m to 1,000 m in a single setup – Perfect tool for high-resolution resistivity mapping for minerals and groundwater exploration, engineering and geotechnical site evaluation, and academic research. 

  • Simple to setup, rapid data acquisition, in-field display of MT parameters – The best tool for teaching MT and AMT concepts in an academic setting.

  •  Enhanced Signal Availability - Natural field MT signals and remote reference, provide the highest quality AMT data, even in the AMT dead zone 

  • Multiple Export Formats - Export data to suit your particular needs, including EDI format, AVG, Columnar ASCII DAT, and Geometrics Data Files 

  • Measure Both Scalar and Tensor Resistivity - Create representations of the subsurface geology more accurately 

  • Remote Reference - The optional EH5 remote reference station can be used to increase data quality throughout the frequency band and used as a second sounding expansion module to increase survey productivity


Technical Details

Stratagem EH-5 Specification List

Stratagem EH-5

Operating Principle: AMT, HSAMT. Audio magnetotellurics (AMT) and hybrid-source AMT (HSAMT) are electromagnetic exploration methods using naturally occurring currents flowing in the Earth's subsurface. In the AMT band, these are mostly generated by distant lightning strikes that can be up to several thousand kilometers away from the survey site. 
  • Frequency Range: 1 Hz to 100,000 Hz.
  • Number of Channels: five (Ex, Ey, Hx, Hy, Hz)
  • Electric Sensors:stainless steel stakes
  • Magnetic Sensors: G100k 1 Hz to 100,000 Hz induction coils with bandwidth of 10 Hz to 100,000 Hz
  • ADC:32-bit high-speed
  • Temperature Range:-20ºC to +85ºC
  • Controller-Data Logger:Ruggedized laptop PC or Android Tablet
  • GPS Synchronization Accuracy:<20 ns
  • Input Impedance:>20M Ohm
  • Dynamic Range:127 dB instantaneous
  • Noise Floor:<5nV/√Hz @ gain 20(10Hz-70kHz)
  • Receiver Storage Capacity:32GB
  • Acquisition Gain Settings:E: 1, 10, 20 and H: 1, 2, 5
  • Sample Rate:192 kHz, 6kHz, 75Hz
  • Receiver Dimensions:L36 cm x W36 cm x H32 cm
  • Receiver Weight:5.8kg
  • In-field QC:Time series, apparent resistivity, phase values, Bostic resistivity, and depth, AC-DC noise levels, spectral amplitudes
  • Power Consumption:8 Watts
  • Optional Remote Reference:Remote module available as option. May also be used as a second sounding station.
Geode EM3D Shipping Weights & DIMS

Shipping Weights & DIMS

Contents Dimensions (L x W x H) Weight
Case 1 - Stratagem EH-5 Instrument Only 10in x 7in x 8in 24cm x 16cm x 19cm 11.5lbs 5.2kg
Case 2 - Single Stratagem EH-5 w/ Laptop  4-5 boxes 143lbs 65kg


  • Geologic mapping from 10's to 1,000 meters and more for mining and minerals exploration
  • Mapping hydro-geologic features for groundwater exploration
  • Geothermal reservoir mapping 
  • Shallow oil and gas exploration 
  • Deep geotechnical and engineering application such as deep structure mapping for future dam sites, characterizing potential nuclear waste deposit integrity, viewing geological structures for deep mountain tunneling, etc
  • Excellent tool for academic research and teaching