EM3W Wireless EM Receiving Unit

( Overview

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The EM3W 3-channel EM receiving unit is a distributed EM signal acquisition system specifically designed for 3D EM surveying. It can be used for 3D artificial and natural sources EM surveying methods such as 3D controlled source audio magnetotelluric (3D-CSAMT), 3D audio magnetotelluric (3D-AMT), 3D time domain induced polarity (3D-TDIP), 3D spectral induced polarity (3D-SIP), 3D transient electromagnetic (3D-TEM), 3D earth-charging method, natural potential method monitoring. The system can have up to 256 EM3W acquisition station for a 3 to 768 channel 3D receiving system. When paired with a high power emitter, it is capable of various types of EM surveying work. The system composition is versatile and can be upgraded to various extents as required. It played a revolutionary role in areas such as geological surveying and oil surveying and an important tool in the step from 2D to 3D EM surveying.


( Main Function

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The EM3W EM Receiving Unit is a modularized EM signal acquisition system designed for 3D electromagnetic surveying. It comes with magnetic plugs, non-polarizing electrodes and is used for 2D and 3D audio magnetotelluric (2D, 3D-AMT) surveying. When conducting 2D or 3D AMT, this system avoids the hassles of data transmission cables without suffering in inter-node distance, automatically logs the coordinates of each node, is light and convenient to carry, and overcomes disadvantageous effects of the terrain. The system is especially adaptable for single-man operation, but is even more efficient when used in a team — each member need only carry the EM3W EM acquisition station and sensor. When performing AMT/MT data acquisition, one acquisition team is typically composed to two people with two EM3W devices working simultaneously — one of which is the electric channel station, the other being the magnetic channel station. In this manner, one team can complete about 20 data points of AMT acquisition per day. Of course, MT acquisition time depends on acquisition time. The built-in high precision GPS (timing error <30ns, positional accuracy 3m) can determine each electrode's specific coordinates and the magnetic bar's orientation, eliminating these measurement tasks from the workload. Position and time data is automatically recorded with the data. All data acquisition is started at UTC time on the minute, deliberately allowing multiple teams to share data for reference, and fully automating the task of processing together data taken at the same time.

In recent years, controlled source audio magnetotelluric (CSAMT) surveying has been widely used in various types of resource surveying, even seeing relatively good application results in engineering surveying. In current centralized devices, excessive cable length leads to EM interference, affecting data precision. Although wireless devices can more or less overcome the above deficiency, because radio and other systems often are affected by the terrain and work environment, they are often prevented from performed real-time data quality control. The EM3W 3 channel wireless telemetry acquisition station not only effectively overcomes both of the above issues, it is easy to set up and guarantees signals do not undergo electromagnetic degradation. It also allows the operator to monitor and evaluate the data in real-time. Experience shows this wireless telemetry system is highly suited for a team consisting of small numbers of technical operators and large numbers of ordinary laborers, allowing the work to be completed with lower labor costs. When making the CSAMT observation system, 5-30 EM3W acquisition stations for a 3D observation system. It can perform tensor, vector, and scalar CSAMT testing. Each EM3W can connect 3 electric or magnetic channels. Typically an observation system is composed of more electric channels than magnetic channels. During 3D observation, 4 components need be tested — these are the electrical and magnetic components, each in the x and y direction (Ex, Ey, Hx, Hy). The most optimal method of conducting such surveying consists of using a network made of 24 EM3W 3-channel units — 20 units for electrical observation (measuring Ex, Ex, and Ey) and 4 for magnetic (measuring Hx, Hy, Hz), for a total of 72 channels. The 24 units are then evenly divided into 4 groups to form a network. In this manner, one observation system can observe 1 square kilometer of 3D data. Field surveying systems are composed of the E60EM main unit, EM3W acquisition station and generator group, EMT30A emitter, magnetic sensor, non-polarizing electrodes and matching sensor connection cables, etc. E60EM main unit can do on-site supervision, control and monitor data, or can act as an off-site unit for remote supervision, control and monitoring through a wireless network. In 2D surveying, the E60EM's 10 channels can also do the job. Hence, the system can be upgraded or not as the situation requires.

The EM3W 3D EM Receiving Unit is a modularized EM signal acquisition system designed for 3D electromagnetic surveying. With the compatible EMT1000 mid-power emitter and receiver coil, it is used for 2D and 3D transient electromagnetic (2D, 3D-TEM) surveying. The system is versatile with many optional add-ons, and has played a revolutionary role in areas such as geological surveying, engineering surveying and advanced underground prediction, particularly in cases of difficult terrain. Regarding available widely-used large fixed-source equipment, traditional TEM uses point-by-point data acquisition, but the EM3W performs simultaneous acquisition to greatly increase work efficiency. A significant advantage is seen in the areas of metal ore surveying, underground water surveying, geothermal surveying, mined-out area investigation and general surveying — under the same conditions, a job that would take traditional methods several days to complete using this system can shorten to several hours.

The EM3W-TIP and EM3W-SIP Receiving Unit is a modularized EM signal acquisition system designed for 3D electromagnetic surveying. With the EMT30A or EMT6000 high power emitter, magnetic plugs, non-polarized electrodes, it is used for 2D and 3D Induced Polarity (2D/3D-TDIP/SIP) surveying. It avoids the hassles of cables, has unlimited inter-node distance, automatically stores measurement positions, is especially suited for single-man operation, but if used in a multi-man team, each person need only carry the EM3W EM acquisition station and sensor, is light and portable, and overcomes the difficulties of complex terrain. The E60EM main unit can provide on-site supervision, control and data monitoring, but can also perform these tasks remotely via a wireless network. Each acquisition station (EM3W) can wirelessly transfer data, completely breaking free of any limitations imposed by using cables. This setup can also complete spectral induced polarity (SIP) and high density electric field induced polarization (IP) surveying. When conducting SIP observations, this wireless acquisition station layout is even more suited for the oft-used dipole-dipole observation mode, allowing for easy and efficient data acquisition via the scrolling technique. For time-domain IP surveying, the operator can select the 2D or 3D system to raise work efficiency as the situation demands, even having the option of simultaneous multi--region surveying.


( Main Features

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1.High precision, ultra-wide bandwidth: 3 built-in 24 bit high precision acquisition channels, each with ultra-wide bandwidth and dynamic range. The device has high input resistance and can be set as either electric channel or magnetic channel.

2.High precision timing synchronization: built-in high sensitivity, high precision timing GPS (timing error <30ns, positional accuracy 3m).

3.Huge storage capacity: built-in micro SD card (512-16 GB) data storage, satisfying all sorts of long term EM data acquisition and storage. Windows FAT16/32 formatting system, compatible for use on PC. File naming done automatically by methodology, acquisition time, and device number. Data format in international standard USF EM data format, for ease of customer use in processing software.

4.Versatile acquisition methods: each acquisition station has a unique 64 bit identification number. Multiple networks under the control of the main unit perform parallel acquisition. Alternatively, a single unit (independent of the main unit) can operate under manual control. To avoid data loss, each data record includes the location of the acquisition station, recording time, and other parameters. The main unit can at any time query each station's operation status and monitor the data quality.

5.Wireless network: the built-in wireless communication module uses Digi's wireless network module and is compatible with up to over 60,000 nodes, with an inter-node distance of up to 3200m. Using this to link to the main unit allows the main unit to monitor the operation status and data quality as well as send acquisition commands. Substations can also send compressed data samples. Originally stored in SD cards, the data can be played back after leaving the site. Data playback can be by reading the SD card, or by wireless transmission.

6.Light and sturdy: the system features a hand-held design, is wind and dirt resistant, is the size of a cell phone, has a built-in swappable lithium battery, and has a gross weight of 250 g. It can be held, clipped to your waist, or placed in your pocket. It is extremely sturdy, able to survive a 10m drop on dirt. This module greatly reduces the workload when working in mountainous terrain, improving overall working efficiency.

7.High work efficiency: We performed a large-scale set-source TEM surveying experiment using 1 man on 1 station with 40m cable separation, 20m node separation, 12.5Hz baseband, super-positioned 256 times - The device can complete 20-30 data points per hour, or a 400x480m region per day. Three or four such devices can work simultaneously to complete three or four times the area per day, reaching an efficiency dozens of times higher than other existing devices to meet the requirements of high density mineral surveying.

8.Intelligent design: The device is a turnkey product. It is designed to be highly fool-proof so hence has low requirements on the operator's technical background; an average person can conduct the entire field survey with a small amount of training. Since this is a turnkey product, the device also conducts intelligent determination of the data quality, using audio and visual means to inform the operator of data fitness.

9.System modularization: Composed of the E60EM, EM3W, and various types of emitters, this set of combined surveying equipment is capable of completing complex EM surveying, yet individually each piece stands as an independent system — the E60EM main unit and each EM3W station is a standalone instrument capable of transient EM surveying, short-conductor induced polarity surveying and conductivity surveying, thus being especially suited for projects requiring multiple EM surveying methods in one area.


( Pictures

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( Technical Specifications

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1 Number of channels: 3
2 Gain: 1-64
3 Dynamic range: 126db
4 A/D conversion: △∑ 24bit
5 Number of base frequencies: 18 (50Hz/60Hz suppression)
6 Scanning Period: 5 min
7 Battery capacity: 7.2V/1.6Ah, 10 hours operating time, 50 hours standby
8 Operating Environment: -20 to 65 deg C, rainproof
9 Weight: 250g
10 Synchronization: 30ns precision by GPS
11 Data Storage: micro SD 4~32GB
12 Activation: manual, wireless, preset
13 Save file: time of creation
14 Wireless: maximum 1024 units, maximum 300m apart

( Standard Software

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( Possible Extensions

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( Recommended Configuration

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