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PROTEM Digital TEM Receiver
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Features
  • Provides 24 bit resolution, a system bandwidth of 500kHz, microsecond sampling gates, and simultaneous XYZ component measurements.
  • When used with a 3-component coil mineral surveys are greatly accelerated.
  • Quick and accurate checks on geoelectric sounding data for lateral variations in conductivity.
General

It is well known that there is a tradeoff between depth of exploration and target definition in terms of conductivity, extent and orientation. Greatest depth is obtained with large fixed loop Turam-type systems that generate large half space responses. This fact, along with current gathering, makes target detection difficult. Better spatial resolution is obtained with a moving transmitter configured with short intercoil spacing, but this configuration is limited to shallower exploration depths. These variations in survey requirements make system flexibility an important design consideration.

Time Domain systems are routinely employed for general geological exploration such as searching for freshwater aquifers in bedrock fractures, and mapping gro.undwater contaminant plumes. Mapping shallow depths requires a very wide bandwidth and many narrow sampling gates.

Recognition of these diverse requirements led to the development of the extremely flexible Protem time domain system. The digital, 3-channel receiver is used with any of the three TEM transmitters and choice of receiver coils to cover all applications. With its 23 bit resolution, system bandwidth of 500kHz, microsecond sampling gates and simultaneous XYZ component measurements, the Protem receiver provides the ultimate in time domain capability. Used with a 3-component coil, mineral surveys are greatly accelerated with more data in either the fixed loop or slingram mode. Three component measurements make possible quick and accurate checks on geoelectric sounding data for lateral variations in conductivity. This could invalidate a layered-earth interpretation.

The latest addition to the PROTEM receiver enables the selection of either 20 gates per base frequency covering 2 decades of time, or 30 gates for a 3 decade range. If 3 decades of time are required to cover the decay then this selection saves switching frequencies and repeating the measurement; or if only 2 decades are required, using the 20 gate range reduces the measurement time by a factor of 10. A further receiver improvement enables automatic measurements during the on-time in addition to the standard off-time measurements.

Specifications

Measured Quantity: Rate of decay of induced magnetic field along 3 axes, in nV/mē
EM Sensor: Air-cored coils
Channels: 1 channel used sequential for 3 components or 3 channels for 3 components simultaneous operation
Time Gates: 20 gates covering 2 time decades 30 gates covering 3 time decades
Dynamic Range: 23 bits (132 dB)
Frequency: 0.3, 0.75, 3, 7.5, 30, 75 and 285 Hz or 0.25, 0.625, 2.5, 6.25, 25, 62.5 and 237.5Hz
Integration Time 2,4,8,15,30,60,120 or 240s
Display: 240 x 64 dot graphic LCD
Data Handling: Solid-state memory for 3300 data-sets. RS-232 output
Synchronization: Reference cable or optionally, highly stable quartz crystal
Power Supply: 12V rechargeable battery for 8 hrs continuous operation
Dimensions: 34 x 38 x 27cm
Weight: 15 kg

Standard Components

Instrument console, shipping case and instruction manual.