DUALEM instruments rapidly measure the conductivity and magnetic susceptibility of the ground, with multiple coil orientations and separations built into a single sensor, DUALEM instruments are the most advanced in their class.
DUALEM instruments operate by electromagnetic induction, so no contact with the ground is needed, which enables surveying at moderate speed over uneven or electrically resistive terrain. Terrain that has been surveyed using DUALEM instruments includes forests, recent volcanic flows, and multi-year ice. The patented DUALEM dual-geometry array simultaneously measures conductivity and susceptibility to two distinct and easily quantified depths.
The DUALEM-1S dual-geometry sensor has a 1 metre separation between its transmitter and dual receivers, so its dual depths of conductivity measurement are 0.5 and 1.5 metres (by the 70-% cumulative-sensitivity standard). For metal detection, the DUALEM-1S can detect a steel drum at depths beyond 1 metre.
The compact size of the DUALEM-1S makes it ideal for towing on a sled for optimum spatial and geophysical resolution, and for integrating with other sensors.
The DUALEM-2 has 2 metre separation between its transmitter and dual receivers, so its dual depths of conductivity measurement are 1 and 3 metres (by the 70-% cumulative-sensitivity standard). For metal detection, the DUALEM-2 can detect a steel drum to 2 metres depth.
The double shoulder-harness, smooth tubular design and moderate weight make the DUALEM-2 practical for prolonged surveys by a single operator. The DUALEM-2 is also convenient to pull on a sled at the ground surface to maximize sensitivity and spatial resolution.
The DUALEM-4 has 4 metre separation between its transmitter and dual receivers, so its dual depths of conductivity measurement are 2 and 6 metres (by the 70-% cumulative-sensitivity standard). For metal detection, the DUALEM-4 can detect a steel drum to depths greater than 3 metres.
Some users pull the DUALEM-4 on a cart behind a quad cycle or motor vehicle.
The DUALEM-421S sensor has dual-geometry receivers at separations of 1, 2 and 4 metres from the transmitter, which provide six simultaneous depths of conductivity sounding, six simultaneous depths of susceptibility sounding, and detection of metal.
The variety of sounding depths makes the DUALEM-421S ideal for the analysis of the thickness, conductivity and susceptibility of layering in the top several metres of the earth. Towing on a sled optimizes spatial and geophysical resolution, but a low cart is also a suitable platform for surveying.
DUALEM instruments are calibrated precisely and permanently at the factory using a patented technique, eliminating problematic ad hoc calibrations in the field.
Precise calibration, base-level stability, high sensitivity and advanced digital signal processing give the instruments unmatched accuracy.
DUALEM instruments provide output to their RS-232B port in either NMEA0183-standard or DUALEM format. As NMEA0183 is the standard for GPS communication, a wide variety of GPS loggers and software can record DUALEM measurements and integrate them with GPS positions.
Depending on your application, Dualem instruments are available on 1, 2 and 4 metre booms. They can also have multiple separations enabling a complete soil profile to be captured in 1 pass. For example a Dualem-421S measures conductive at 0.5, 1, 1.5, 2, 3 and 6 metres in one pass.
Alpha Geoscience can assist in data logging or data merging solutions.