Electricmagnetometers

MDTEM64 Multi-channel Distributed TEM Surveying System

( Overview

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Transient electromagnetic methods (TEM) is an time domain artificial source EM surveying method built on the principle of electromagnetic induction. It uses ungrounded wire loops (magnetic source) and grounded wire loops (galvanic couple source) to project one-time pulses of magnetic field (henceforth known as one-time fields) underground. During the rest period between pulses, coils or grounded electrodes are used to observe two-time fields. Abundant surveying information of geological bodies can be extracted from analysis of these two-time fields. TEM is one of the most effective electromagnetic methods of geophysics surveying. It has a large surveying depth, high resolution, is easy to use, works quickly, has high noise suppression capability and produces effective results. It's no wonder it's become the forefront of shallow-earth electromagnetic methods. It is especially suited for underground water, metal ore and shallow structure surveying. Because this method does not require penetration of the ground, it has minimal environmental impact and can be performed in any location accessible to human labor. In particular, this method is most advantageous, in places such as deserts, gravel areas, volcanic rock areas where ground contact is poor (electrically). This system can be widely used for mineral resources surveying, mined-out area surveying, geological disaster investigation, water resources surveying and various types of engineering foundation surveying.

TEM is conducted in the gap between pulses. One time fields have several characteristics to note: they present small interference, their pulses are a composition of multiple frequencies, observations made at different times exhibit different primary frequencies, and the response time field travels through the earth at different speeds, allowing for different surveying depths. Because of this, TEM can differentiate between temporal and spatial information.

For the past ten years, both domestic and foreign time domain electromagnetic methodology has developed quickly, its expanding its applications. New technologies and systems emerge in large numbers. In terms of hardware, due to recent advances in electronic and computer technology, observation precision, noise suppression and data processing software have all seen huge improvements, achieving highly anticipated geological results.

Most Common Sources of EM Interference for TEM:
1. High frequency radio wave interference.
2. Industrial electromagnetic signal interference.
3. Natural field signal interference.

Properties of EM Interference:
1. Has broad-spectrum characteristics.
2. Has phase coherence within the scope of the local area.
3. Signal exhibits randomness.
4. The interference signal intensity has a high dynamic range.

Considering the characters of the noise, single channel TEM mostly relies on superposition of many sets of result to increase the SNR. However, in noisy regions, superposition up to 4096 times still wouldn't bring SNR to a desirable level. The result is low resolution on the surface and bad precision in deep layers. Parallel multi-channel TEM technology, on the other hand, can efficiently detect the pattern of noise, thus eliminate noise with filters. Hence greatly improve the resolution and the precision of surveying.

The targeting geological body is a 3D body and electromagnetic wave has body properties. 2D surveying in this case introduces large errors in the distortion of the field, while 3D surveying technology models the EM field much accurately.

Therefore Parallel multi-channel 3D TEM has become a necessity for modern geological surveying.

 
 

( Main Function

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TEM is widely used for detection metal mines, underground water, underground heat source, underground hollow space and tunnel construction.

 
 

( Main Features

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1. The entire system is light, has a fully industrialized design. The main unit casing is aluminum alloy with membrane keyboard. Easy to use.
2. The main unit contains 1 acquisition channel and a built-in low-power emitter designed for convenient hand-held data collecting.
3. Externally connected emitter allows for 2D and 3D TEM surveying.
4. Comes with EM-2A 2 channel acquisition station, can be set up as 16-64 channel system.
5. Fast set-up. Multiple channels working in parallel allows for identifying and excluding manmade and natural sources of electrical interference.
6. Uses a sampling rate and sampling length of 1 microsecond. Has relatively good capability for mid-depth and deep surveying, but has significantly higher resolution for shallow surveying.
7. Distributed design. GPS, radio, quartz clock synchronization methods.
 
 

( Pictures

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( Technical Specifications

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MDTEM64 Main STATION:
CPU: Intel(R) Atom® N270 1.6GHz
Ram: 1G
Hard drive: 160G
Monitor: 9 in, 1024*600
Keyword: Sealed thin pad
Port: USB
Data Format: GeoPen, USF (for V8)
Channel: 1
Synchronization: GPS, wireless, radio, quartz
Operating Environment:
User Interface: Mouse or keyboard
OS: Windows 2000
EM-2A Data Acquisition Unit:
Channel: 2
Sampling period: 1us、2 us、4 us、8 us、16 us、32 us
Impulse width: 10、20、40、80、160、320ms
Bandwidth: 0 ~ 200 kHz
Environment Requirements:
Operating Temperature: -10℃ ~ +50℃
Storage Temperature: -40℃ ~ +70℃
Operating Humidity: 0~95%
Simulator Filter:
High pass filter: user defined
Low pass filter: user defined
A/D resolution: 16bit
Noise suppression: over 80db
EMT1000 Source Emitter:
Input voltage: 24~48VDC, 220VAC, 50Hz
Output voltage: 48~96VDC, 48VAC, 96VAC, 144VAC
Maximum output current:: 40App
Signal type: Square wave
Transient off time: minimum 1.5us (pure resistive)
Impulse width: 10/20/40/80/160/320 ms
Synchronization precision: GPS 1us, GFSK 10us
Protection: output current protection, input voltage reversal protection
Main STATION:
Size: 340x290x180 mm
Weight: 10 Kg
Environment Requirements:
Operating Temperature: -20℃ ~ +50℃
Storage Temperature: -40℃ ~ +70℃
Operating Humidity: 0~95%
The operating environment:
User Interface: thin pad keyboard
MC- 25 Induction Coil:
Size: 500×500mm
Weight: 1.0Kg
Area: 25㎡
Packaging: PVC tubing
MC- 50 Induction Coil:
Size: 700×700mm
Weight: 1.5Kg
Area: 50㎡
Packaging: PVC tubing
MC- 100 Induction Coil:
Size: 1000×1000mm
Weight: 2.0Kg
Area: 100平方米
Packaging: PVC tubing
 
 

( Standard Software

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Main features:
1. Real display of multi-channel data plots and data integral plots
2. Automatic data file naming system for projects
3. Raw data are save for further editing and analysis
4. Parameters for data collection and processing can be changed interactively, independent of raw data
5. Parameters such as formatting and typewriting are saved with the raw data
6. All parameters are saved in the project automatically
Data editing software: Preprocessing and management of raw data in a simple user friendly interface.
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Postprocessing Software:

Export data collected on MDTEM64 into various format.

 
 

( Possible Extensions

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MDTEM64 Multi-channel Distributed TEM Surveying System optional peripherals:
index Name Model Quantity Comment
1 Signal generator EMT1000 1
2 Data receiver (2 channels per unit) EM2 32
3 Hub EMHUB 1
4 Main cable MC-L 1
5 Digital Cable (25m) EDC-25 32
6 End resistance 2
7 Induction coil MIC-100 64
8 Induction coil cable MCL-5 64
 
 

( Recommended Configuration

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MDTEM64 Multi-channel Distributed TEM Surveying System standard setup:
index Name Model Quantity Comment
Standard setup (coincided source and receiver coil)
1 Signal generator/Receiver MDTEM64 1
2 Device case BY-1 1
3 Induction coil (50*50cm)) MIC-25 1
4 Induction coil (70*70cm) MIC-50 1
5 Induction coil (100*100cm) MIC-100 1
6 Induction coil cable (5m) MCL-5 1
7 Antenna cable 400m 5
8 1KVA Generato 1
9 TEM Software 1