September 16, 2009
VTEM detects the Night Hawk Lake conductor from 705 m above.
Read the case study (PDF)
March 24, 2009
BENTON RESOURCES, ROYAL ROADS & GOLDEN DORY APPROVE 2009 PROGRAM FOR LONG RANGE NICKEL JOINT VENTURE, NEWFOUNDLAND – DRILL TARGETS IDENTIFIED
"... Among the targets selected for further work is a 600 metre long VTEM conductive anomaly described by Geotech Ltd. as “a relatively strong conductor consistent with massive sulphides”. This target has been selected for testing by diamond drilling, and it is anticipated that additional targets will be developed from results of the prospecting and ground geophysical surveys."
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VTEM | Airborne Gravity | AFMAG | Hummingbird | Hawk
VTEM Technologies
Features:
- 25 Hz up to 200 Hz base frequency
- Low base base frequency (30 Hz) provides better depth penetration and better discrimination of the conductive bodies by conductivity
- Big transmitter dipole moment up to 750,000 NIA
- Long transmitter pulse provides better conductor saturation and stronger response in all time channels
- Soft receiver suspension provides lower noise level
- Fixed concentric loop Tx/Rx geometry avoids data bias
- System parameters, such as wave-form, dipole moment may be adjusted to suit geophysical requirements
- Direct helicopter power used, no generator needed
History:
Over the past five years Geotech has undertaken an extensive development program to produce a much needed helicopter time-domain EM system. The experience of Geotech employees dating back to the original Input system development and beyond were called upon to produce a system that would overcome the inadequacies of the available technologies. In 2002 the first successful flights and patent applications took place. The final system metamorphosis took place in 2003. The resulting technology now offers a loop area of up to 500 square meters as well as improved early time response and a patent pending "on-time" measurement. This new system supersedes the earlier "Scorpion" and "Dream Catcher" Technology and has been dubbed the VTEM system.
Description:
The "VTEM" is the first Time Domain System to offer selectable transmitter wave-form types and associated configurable transmitting loop. Computer controlled power electronics and advanced signal processing software makes the system easily adjustable to different geophysical tasks, from shallow soil mapping to deep ore bodies search. The standard configuration is a 30 HZ base frequency with a three turn loop. Transmitter duty cycle is approximately 40% on time so we saturate the conductors more effectively. The standard wave-form is set as a trapezoid. The system is easily transportable worldwide and installation time is about half a day. A major feature of the system is the non-critical nature of the composite structure thus allowing field repairs on site even after a tree strike. This is important to assure the completion of jobs in remote areas without demobilization. All ancillary instrumentation such as data acquisition system and navigation system are of Geotech design thus assuring excellent control of survey reliability.
Specifications:
| Transmitter: | |
|---|---|
| Transmitter coil | Vertical axis |
| Pulse: | Trapezoid |
| Pulse width | 1 – 10 msec (selectable) |
| Base frequency | 25 – 200 Hz (selectable) |
| Peak dipole moment | up to 500,000 NIA |
| Max Loop area | 500 Square Meters |
| Max current | 250 amperes |
| Receiver: | |
|---|---|
| RX coils | Single Vertical axis |
| Sample rate | up to 200 kHz (selectable) |
| Interval recorded; | Total signal or up to 800 channels |
| Band width | up to 20 kHz |
| Spherical noise rejection | Digital, 3 levels |
| Industrial noise rejection | Digital, 50/60 Hz |
| Data recording | PCMCIA Flash Card |
EM System Noise at 30 hz:
± 0.01 pico volts per Amp meter4
± 1.3 nanoteslas per second
| Mechanical: | |
|---|---|
| Maximum airspeed | 120 km per hour |
| Flying height | 30 meters AGL |
| Temperature | -40 °C to + 45 °C |
| Power requirement; | 50 Amps at 28 VDC |
| Shipping length | 2.5 Meters |
| Weight | 350 kg |
| Installation/Assembly time | 4Hours |