Today the third-generation of VECS equipment is used. It consists of sounding array and 3 meters.
Sounding array «GTE-10S»
Sounding array «GTE-10S» forms stabilized pulses of alternating polarity with set amplitude and duration that are transmitted into the ground through a circular electric dipole . The array has the following characteristics:
• 8 channels;
• Output voltage from 50 to 750 V (three work ranges: 50-250V, 150-500V, 300-750V);
• Range of output current from 8 to 160 A;
• Current stability of ± 1%;
• Maximum input power 80 kW;
• Powered by three-phase AC voltage 380/220 V from power supply with an isolated neutral of power not less than 100 kW;
• GPS Synchronization;
• Weight 300 kg, overall dimensions – two racks 550 × 500 × 940 mm;
• Protection against overload and overheating;
• LCD indication and file logging of voltage, current consumption, power per phase, total power and stabilization failures;
• Continuous monitoring of insulation resistance of the power supply circuit.
«CEI-7» receiver
Each measurement cycle of «CEI-7» receiver begins with calibration measurements performed in order to check the receiver’s operability and compensate temperature and time variations of the transient response in the measuring channel.
Next step is test measurement of the input signal used to tune certain measurement parameters for better quality of the recorded signal. These parameters are:
• Buffer amplifier coefficient;
• DAC output for input bias compensation;
• Optimal integrator transfer coefficients for all integration intervals.
Test and operational measurements are performed with the same algorithm described below. Input signal through the buffer amplifier is fed to the input of the integrator. The result of integration on a certain time period is coded by the ADC and read by the microcontroller. Read value is associated with the middle of the integration interval. Measurement time scale for this measurement channel is pseudo-logarithmic and determined by the sequence of integration intervals. Basic duration of the integration interval does not exceed 1/8 of the measurement time (20 points per decade). User can customize scale density – from 4 to 80 points per decade.
Further signal processing is carried out on a PC after data transmission via one of the interfaces. Depending on the computer and measurement conditions one of 3 interfaces – RS232, USB, or wireless BlueTooth can be chosen. The last one is the most suitable choice for the mobile solution with handheld computer.
There is an additional option for remote control when modem connection is utilized. In this case, it is possible to work with the receiver up to 1 km away from the host computer. Modem interface is also used for multichannel measurements, when receiver systems are placed remotely from the control computer. Multichannel interface allows one to perform up to five measurements simultaneously.
Control application for“CEI-7” receiver is designed for PC running Microsoft Windows operating system, including the newest Windows 7. Application with limited functionality is available for Pocket PC running Windows Mobile.