Electromagnetic conductivity meters are utilised for many applications including; brown field site mitigation, environmental mapping, contaminated land remediation, archaeological prospection and precision agriculture.
Frequency Domain (or Slingram) EM systems are used to measure electrical and magnetic ground properties. Consisting of a transmitter and one or more receivers these instruments are suited for minerial exploration and geological mapping.
Time Domain (or Transient) EM systems record resistivity measurements to depths which are impractical using galvanic resistivity systems and are therefore ideally suited for mineral exploration and hydrology studies.
Electromagnetic geophysical equipment covers a broad range of devices. All these systems fall under two categories;
Frequency Domain Electromagnetic devices (FEDM)
Frequency Domain Electromagnetic devices induce electrical Eddie currents into the ground by sustaining an alternating Electromagnetic field at a well defined frequency, typically between 5kHz and 20KHz. The Eddy currents present a secondary magnetic field which is detected and recorded by the instrument. Field measurements consists of an inphase measurement and a quadrature measurement. The In phase response is the amplitude of the secondary EM field when the primary EM field is at maximum. The quadrature response is the amplitude of the secondary EM field when the primary EM field amplitude is zero. The quadrature response relates to the conductivity of the ground, reported in millisiemens per meter, and the In-phase to Magnetic Susceptibility. With FDEM the separation of the transmitter and receiver coil prominently dictate the depth as which the instrument prospects to.
Time Domain Electromagnetic devices (TDEM)
Time Domain Electromagnetic devices apply a current to a coil and terminate the current rapidly. The effect of terminating the current causes a change in the EM field which insights Eddy currents to form in the ground and in conductive objects. The device then measures the decay of magnetic field produced by the Eddy currents. The amplitude of the secondary magnetic field and decay rate offer incites into the electrical properties of the ground, generally reported in Ohm meters.
Due to the shear verity of these systems and their various applications we have divided them up into sub-categories to aid site navigation.