L-GM Earth Resistivity Meter

The L-GM Earth Resistivity Meter is at the core of Herbi, our Soil Moisture Migration Mapping, HDPE reservoir liner testing and other Electrical Resistivity Tomography Imaging conducted by groundwater imaging. It can be run on its own and with a computer running Geotest. It is operated either directly connected to up to 4 electrodes or using active electrode switchboxes that operate up to 255 electrodes in pre-programmed combinations. Individual switchboxes attach to electrode stakes while 16 channel switchboxes operate from a central location and attach to electrodes via multicore cable.

L-GM Earth Resistivity Meter

L-GM Earth Resistivity Meter

This instrument is remarkable in that it is lightweight, low cost and yet operates rapidly, precisely and in a very versatile manner. The low cost and power consumption opens up opportunities for its use in non-traditional markets for resistivity survey including some involving time lapse acquisition and telemetry.

Groundwater Imaging claim that the same L-GM Earth Resistivity Meter is most appropriately used in the following manners:

  • Within HERBI for waterborne substrate resistivity tomography.
  • With electrode stakes and remote electrode switch boxes for Electrical Resistivity Tomography.
  • With a soil sample holder for Laboratory soil resistivity measurements
  • With buried cables of closely spaced electrodes for time lapse moisture and salinity migration mapping. This may be coupled with capacitance probes. Watermark soil moisture sensors and temperature probes can be incorporated into tomography setups and operated directly from the Earth Resistivity Meter. The meter reads absolute calibrated moisture within the watermark sensors and also uses them as electrodes as part of the ERT setup measuring moisture change throughout an entire bulk of undisturbed soil. Ideally, monitoring costs are kept low using solar power and telemetry.
  • With buried cables of electrodes under and around reservoirs for early warning of reservoir liner failure and seepage. Such a setup ideally uses telemetry to manage monitoring costs.
  • With buried cables and telemetry for early warning of saline groundwater encroachment such as in coastal aquifers.
  • With a hand held ‘Resismeter’ set of short probes in a frame for soil root zone electrical resistivity sounding with or without GPS. In a similar manner, resistivity can be measured with the device between two push rods typically used for impromptu soil moisture investigation.
  • With a towed wet mat of electrodes for detecting tiny defects in HDPE liners.

Because this equipment can be used in so many diverse ways it is also complicated to thoroughly learn its operation. Fortunately there is good documentation and software specialization for most commonly used applications.

Groundwater Imaging Pty Ltd supply both training and L-GM and auxiliary equipment tailored to users requirements and conduct surveys when requested.


ActEle16 active electrode switchbox