Geometrics OhmMapper

OhmMapper TR System

The new Geometrics OhmMapper is a capacitively coupled resistivity meter that measures the electrical properties of rock and soil without cumbersome ground stakes used in traditional resistivity surveys. A simple coaxial-cable array with transmitter and receiver sections is pulled along the ground either by a single person or attached to an all-terrain vehicle. Data collection is many times faster than systems using conventional DC resistivity. Watch our new "Intro to OhmMapper" video below.

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Features

- Full dipole-dipole resistivity profile can be done in a fraction of the time taken for traditional resistivity measurement.
Operates over frozen ground, ice, concrete, and other areas where grounded dipole measurements are difficult to make.

- Data is logged to Geometrics DataMapper logging console for easy tracking and positioning of resistivity data.
Post acquisition processing is facilitated with Geometrics DataMap software for editing of data, positioning of data, and creating output compatible with third-party mapping and processing software.

Configurations

The OhmMapper consists of the transmitter electronics and batteries along with two transmitting dipole cables. The transmitter is towed via the nonconductive tow link connecting it to the receiver. The receiver consists of the transmitter electronics, batteries, and dipole cables. The received voltage level is converted to a digital signal in the receiver and transmitter to the data logger worn by the operator. The operator carries the data-logging console (DataMapper) at his waist.

Specifications

- Operating principle: Constant-current capacitively-coupled, dipole-dipole resistivity

- Operating range: Less than 1 OhmMeters to greater than 100,000 OhmMeters

- Cycle Rate: Signal sample and data logging rate at 2 times per second

- Data Storage: 2 Mbytes of nonvolatile RAM

- Audio Output: Metronome, signal amplitude, disconnect

- Visual Output: 320 by 200 graphic LCD display, daylight visible with selectable outputs for:

- Data Display: 5 line profiles of resistivity

- Internal Clock: Resolution of 0.1 drift <1 second/day.

- Weight: Console: 1.6 kg

- Transmitter: 2 kg

- Receiver: 2 kg

- Battery pack/Harness: 1.6 kg

- Array Depressor Weight: 3 kg (estimate)

Transmitter specifications

- Frequency under 18 kHz

- Output current: variable from 16 mA to 0.25 mA

- Receiver Specifications:

- Dipole lengths: 5 m, 10 m, 15 m, 20 m, longer lengths optional

- Input Specifications: 5 Mhos

- Measured Voltage Accuracy: 1%

- Input Voltage Range 0-2 V RMS

- Power Line Rejections: >100 dB

Survey Types

- Continuous, constant-offset dipole-dipole resistivity. (Multi-line with constant transmitter-receiver spacing for plan-view mapping.)

- Variable-offset, dipole-dipole resistivity. (Variable transmitter-receiver spacing for multiple passes on a single profile line to create a pseudosection.)

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