SAMTEC 1
Audio Magnetotelluric System

General

The Samtec 1 unit can be used through a fully automatic procedure (automatic ranging, stacking & preset frequencies), or through a manual mode where the operator maintains full control of the acquisition . Ease of use and quality measurements make Samtec 1 an efficient alternative to long line electrical soundings, and a powerful tool in deep exploration surveys for mining applications, groundwater investigations, geothermal exploration, and structural studies.

Ease of Use

Automatic mode allows the operator to introduce the station number, the number of stacks to be carried out, or the minimum quality of measurement wanted. Default values are available. Filtering, gain ranging and frequency scanning are automatic after selecting the start key. En frequencies per decad' are analyzed for a total of thirty-six frequencies in the frequency range. When several cycles of measurement are required at the same station, data storage is automatic at the end of each cycle and measurement proceeds automatically. The internal memory can store up to 780 measurements that correspond to 21 frequency soundings. After the operator has set up the grounded electric line and the magnetic sensor, a complete sounding can be carried out in less than ten minutes under good signal conditions.

The Samtec 1 receiver performs digital filtering through a Fourier Transform computation. For each frequency, F, keyed-in during manual mode, four frequencies are analyzed simultaneously: F, 1.5F 2F and 3F.

Stacking of measurements is carried out according to a selective process: Electric/magnetic field ratios are averaged through weight coefficients that depend on the coherency between the electric and the magnetic fields, or on the standard deviation of the resistivity. This weighted stacking allows the operator to lower the influence of a noisy measurement that is not supposed to correspond to a MT signal. A good quality measurement is reached in a shorter time through this procedure versus using a classical average of signals.

The electric line consists of three non polarizable electrodes, two electrode pre-amplifiers, two 10 n low noise special cables, and one differential pre-amplifier. The total internal noise of the electric line is lower than 50 nV/4Hz from 10 Hz to 7,500Hz.

The magnetic sensor consists of a flux feedback coil with a flat induction response of 100 mVy from 2Hz to 7,500Hz, and a shielded case internal measurement lower than 2 micro y/4Hz at higher frequencies. Calibration coefficients of the magnetic sensors are stored in ROM and automatically considered during data processing.

Specifications

Samtec 1 General:

Dimensions: 22 x 31 x 33cm

Weight: 8kg

Operating Temp. Range: -20OC to + 60°C

Power Supply: Nine 1.5V D size dry cells or 12V external battery

Magnetic Sensor (CMA):

Frequency Range: lHz-7,500Hz

Length: lm

Diameter: 9cm

Weight: 7kg

Two S ultaneous Measuring Channels:

Electric field (E), magnetic field (H)

Frequency Range: lHz to 7,500Hz

Automatic cycle for measurements in the whole frequency range

Visualization of E and H signals through galvanometers

Automatic and manual gain ranging

Digital Data Processing: Fourier Transform and cross spectra

Coherence and standard deviation parameters

Real time display of resistivity and quality coeffcient

Phase measurement between electric and magnetic field

Differential measurement for electric field

Non polarizable electrodes with low noise pre-amplifiers

Standard Components

Samtec 1 console, 20m long electric Ime, magnetic sensor, 3 non-polarizable electrodes with preamplifier, and instruction manuals.

Ordering Information

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