GMR equipment in an snowy cold environment

Pioneered with an emphasis on multi-channel capability, GMR is recognized as the state-of-the-art in surface-NMR technology, delivering non-invasive imaging of groundwater with unparalleled power, speed, and precision.

Direct Imaging of Groundwater

The GMR system provides unambiguous detection of groundwater because the measured signal is generated by hydrogen in fluids. By probing the NMR properties of the subsurface, GMR provides quantitative images of water content as well as estimates of hydrogeologic parameters, including specific yield and permeability. Using GMR, it is possible to obtain detailed aquifer characterization before ever drilling a well.

Multi-Channel Hardware that Delivers

Built from the ground up to capture the advantage of a multi-channel processing, sophisticated GMR hardware provides unmatched performance and superior results. Features including the highest power output, the fastest switching, and the most flexible multi-channel architecture†, translate directly into enhanced imaging capabilities with detection of deeper, shorter, and smaller NMR signals. Cutting-edge electronics are packaged in a modular design with an emphasis on portability and safety.

Advanced Simple-to-Use Software

The GMR software package provides a user-friendly interface accessing patented algorithms to that exploit GMR’s multi-channel design for adaptive noise cancellation† and 2D imaging†. Acquisition and processing software enables real-time monitoring of data quality, while interpretation software includes tools to determine multi-exponential decay time distributions, and to estimate aquifer properties including bound/mobile water content and relative permeability.

GMR outside in Argentina


A Virtual Pump Test without the Well


Groundwater Resources

horses near GMR equipment testing groundwater

  • Take advantage of GMR’s non-invasive mapping of aquifers to select production well sites.
  • Obtain virtual pump test information without drilling.
  • Quantify aquifer flow and storage properties to parameterize hydrogeologic models.
  • Estimate hydraulic conductivity, transmissivity, and specific yield.


  • Increase the density and areal extent of your measurements with GMR’s portability, small footprint, and convenient deployment.
  • Image the subsurface in 1D, 2D, or even 3D to spatially resolve hydrogeologic parameters and identify zones of flow.


  • Locate water as a resource, plan for de-watering, or monitor impacts.
  • Detect groundwater non-invasively at depths of up to 150 meters.


  • Determine the water table unambiguously.
  • Measure partial water content in the unsaturated zone.
  • Quantify porosity and estimate bound and mobile water content.


  • Take advantage of Vista Clara’s flexible, highly capable, and customizable hardware and software platforms to work in new environments and open new areas of inquiry.


Boasting a rich array of sophisticated features and proprietary technology, GMR elevates surface NMR geophysics, delivering superior performance and data quality in an ever expanding range of environments and applications.

Groundbreaking Multi-Channel Design

The unique multi-channel architecture of the GMR system enables adaptive noise cancellation for vastly improved data quality as well as more efficient 2D or 3D groundwater imaging†. Four independent Tx/Rx channels (expandable to eight or more) allow for simultaneous measurements on multiple loops. GMR’s identical broadband frequency response on all channels is critical for effective noise cancellation.

Shortest Dead-Time

The ultra-short dead-time (<5 ms), of the GMR system means even the shortest NMR signals are captured. NMR signals are short for water in magnetic geology, in fine-grained sediments, or in the vadose zone. These important signals are invisible without a ultra-short dead-time capability.

Highest Power Output

With the highest power output available*, GMR enables detection of deeper and shorter groundwater signals. Proprietary efficient power conversion architecture enables output up to 800A and 6kV through larger loops using thinner, more portable cables.

Proprietary Pulse Sequences

Acquisition software includes sophisticated multiple-pulses measurements. These pulse sequences enable T1 recovery and T2 spin-echo or CPMG measurements, which yield more robust estimates of hydrogeologic properties. Advanced phase cycling suppresses artifacts for improved data quality.

High-resolution Inversion Software

Patented all-linear inversion software delivers superior spatial resolution of NMR signals, allowing the user to more precisely identify features of interest and derive aquifer properties. Advanced processing and interpretation algorithms are accessed through a straightforward GUI interface that is easy to learn and understand.

Priority on Safety

Safety is always the important consideration and is extensively integrated in the GMR design. Robust features protect the user from powerful electrical energy. As one example, all GMR wiring uses environmentally-rated no-touch connectors so that the operator never touches any conductive element of the high-voltage circuitry.

diagram of GMR measuring noise with detection loops




CPMG Measurements
CPMG Measurements



GMR 540V DC/DC Converter

Max. DC bus voltage: +/- 270V DC
Capacitance: 0.054 F
Charge current: +/- 1 A
Power supply: two 12V batteries

Auto shut-off
Analog voltmeters on panel

GMR 4800V Transmitter

Max. transmit voltage: 4800V AC
Max. transmit current: 600A, 25 A*s
Instrument dead time: <5ms
4 identical transmit/receive channels (expandable to 8 or 12)
Receiver input noise: 24-bit wideband simultaneous sampling
Pulse sequences for FID (single-pulse),T1 (90-90 pulse),and T2 (CPMG and spin echo) acquisition with phase-cycling.

Auto-shut down in overcurrent state.

GMR Tuning Unit

Max tuning capacitance 15.5μF (expandable to 31.5μF)
Max. transmit voltage: 6000V AC
Max. transmit current: 800A
Adjustable by 0.5μF increments for fine tuning

System will not operate unless tuning cover is securely closed
Rapid discharge (time constant ~ 1s)
Keyed access to high-voltage contacts

Software and Accessories

High voltage environmental-rated connectors with carrying case
GMR data acquisition software
GMR noise cancellation software
GMR 1D inversion software

GMR 2D inversion software
#8 AWG, 4kV polyurethane insulated
#10 AWG, 4kV polyurethane insulated

Expansion Options

4-channel Transmit/Receive Expansion Module (for accelerated 2D imaging)
4-channel Receive Expansion Module
Two parallel DC DC Converters (for extended pulse output)
16uF Tuning Expansion Module (for use at low Earth latitudes)
Custom ATA shipping cases