Induced polarization system and method for geological investigation having a stable waveform

Claim 2

An improved transmitter for an induced polarization system for performing subsurface earth investigations or the like, comprising a power supply for generating an AC power signal, conversion means responsive to said power signal for deriving a transmitter output signal having a preselected waveform and amplitude which is independent of any load on said transmitter, transducer means responsive to the magnitude of the current of said transmitter output signal for providing a functionally related voltage, a comparator for deriving a comparison signal which is functionally related to said voltage from said transducer means and a reference voltage, integrating means responsive to said comparison signal for deriving a functionally related adjustment signal, and line control means responsive to said power supply and said adjustment signal for deriving and applying phase-dependent actuating signals to said conversion means.

Claim 3

The transmitter described in claim 1, wherein said conversion means is a polyphase cycloconverter comprising a primary thyristor circuit responsive to said power supply and said actuating signals from said line control means, a secondary thyristor circuit responsive to said primary thyristor circuit for generating said transmitter output signal as a phase-dependent function of said power supply and said actuating signals from line control means, and a step-up transformer coupling said primary thyristor circuit to said secondary thyristor circuit.

Claim 4

The transmitter described in claim 2, wherein saId cycloconverter and generator are interconnected by three separate conductors and wherein said primary thyristor circuit includes a first SCR stage having a first pair of oppositely arranged SCR units interconnected to one of said three separate conductors, a second SCR stage having a second pair of oppositely arranged SCR units interconnected to another of said three separate conductors, and a third SCR stage having a third pair of oppositely arranged SCR units interconnected to a further different one of said three separate conductors.

Claim 5

The transmitter described in claim 3, wherein said line control means includes a first line control circuit actuated by said integrating means for providing firing signals to said first pair of SCR units in said first SCR stage, a second line control circuit actuated by said integrating means for providing firing signals to said second pair of SCR units in said second SCR stage, and a third line control circuit actuated by said integrating means for providing firing signals to said third pair of SCR units in said third SCR stage.

Claim 6

The transmitter described in claim 4, wherein each of said line control circuits includes a first line voltage comparator means interconnected with said integrator means and one of said three separate conductors for deriving a first gating signal, a second line voltage comparator means interconnected with another of said three separate conductors and a reference voltage for deriving a second gating signal, a third line voltage comparator means interconnected with said another conductor connected to said second line voltage comparator means and a further different one of said three separate conductors for deriving a third gating signal, first line gating means responsive to said first, second and third gating signals for deriving and applying firing signals of a first time-dependency to one of said SCR stages of said primary SCR circuit, and second line gating means responsive to said first, second and third gating signals for deriving and applying firing signals of a second time-dependency to said one SCR stage of said primary SCR circuit.

Claim 7

The transmitter described in claim 5, wherein each of said line control circuits further includes a rectifier and attenuator circuit interconnected between said first line voltage comparator means and said one of said three separate conductors, a first inverter means coupled to said second line voltage comparator means for inverting said second gating signal applied to said first and second line gating means, and a second inverter means coupled to said third line voltage comparator means for inverting said third gating signal applied to said first and second line gating means.

Claim 8

The transmitter described in claim 6, wherein said first and second line gating means in each of said line control circuits comprise a first NAND gate having a first input coupled to said first gating signal, a second input coupled between said second line voltage comparator means and said first inverter means, and third input coupled between said third line voltage comparator means and said second inverter means, a second NAND gate having a first input coupled to said first gating signal, a second input coupled to the output of said first inverter means, and a third input coupled to the output of said second inverter means, a first power amplifier for generating a firing signal of a first phase dependency, a second power amplifier for generating a firing signal of a second phase dependency, a third NAND gate having one of a pair of inputs coupled to the output of said first NAND gate and having its output coupled to said first power amplifier, a fourth NAND gate having its output coupled to the other input of said third NAND gate and having one of a pair of inputs coupled to the output of said third NAND gate and its other input coNnected between said second line voltage comparator and said first inverter, a fifth NAND gate having one of a pair of inputs connected to the output of said second NAND gate and its output coupled to said second power amplifier, and a sixth NAND gate having its output coupled to the other input of said fifth NAND gate and having one of a pair of inputs coupled to the output of said fifth NAND gate and its other input connected to the output of said first inverter means.

Claim 9

The transmitter described in claim 7, wherein said first and second power amplifiers in each of said line control circuits are connected to different ones of said SCR stages in said primary SCR circuit to actuate selected ones of said SCR units therein.

Claim 10

The transmitter described in claim 3, including polarity control means coupled to said secondary SCR circuit of said polyphase cycloconverter for determining the polarity of said transmitter output signal.

Claim 11

The transmitter described in claim 9, wherein said polarity control means includes a supply of actuating pulses, a first bistable multivibrator responsive to said supply of actuating pulses and having a pair of outputs, a second bistable multivibrator having a pair of inputs coupled to corresponding ones of said pair of outputs of said first bistable multivibrator and also having a pair of outputs, a first plurality of power amplifiers having outputs coupled to said secondary SCR circuits, a second plurality of power amplifiers having outputs coupled to said secondary SCR circuit, and mode and gating circuitry responsive to said first and second bistable multivibrators for selecting and actuating said first and second pluralities of power amplifiers.

Claim 12

The transmitter described in claim 10, wherein said mode and gating circuitry in said polarity control means further includes a first NAND gate having one of a pair of inputs connected to a source of reference voltage and the other input coupled to one of said pair of outputs of said first bistable multivibrator, a second NAND gate having its output coupled to said first plurality of power amplifiers and having one of three inputs coupled to the output of said first NAND gate and another of said three inputs coupled to one of said pair of outputs of said second bistable multivibrator, and a third NAND gate having its output coupled to said second plurality of power amplifiers and having one of three inputs coupled to the output of said first NAND gate and another of said three inputs coupled to the other of said pair of outputs of said second bistable multivibrator, and inhibiting means for applying an inhibiting signal to a further one of said three inputs of each of said second and third NAND gates during a preselected limited time interval.

Claim 13

The transmitter described in claim 11, wherein said inhibiting means comprises a monostable multivibrator having its input coupled to one of the outputs of said first bistable multivibrator and having its output coupled to said further one of said three inputs of each of said second and third NAND gates.

Claim 14

The transmitter described in claim 12, wherein said mode and gating circuitry in said polarity control means further includes mode programming means adapted when in one of two preselected conditions to program said secondary SCR circuit to provide a time domain transmitter output signal and when in the other of said two preselected conditions to program said secondary SCR circuit to provide a frequency domain transmitter output signal.

Claim 15

The transmitter described in claim 13, wherein said mode programming means further includes another different reference voltage source, switch means for selecting and coupling one of said reference voltage sources to said one of said pair of inputs of said first NAND gate.

Claim 16

The transmitter described in claim 3, wherein said secondary SCR circuit of said polyphase cycloconverter further includes a first full-wave polyphase bridge rectifier circuit, and a second full-wave polyphase bridge rectifier circuit connected in inverse parallel with respect to said first full-wave polyphase bridge rectifier circuit.

Claim 17

The transmitter described in claim 15, further including polarity control means interconnected to actuate said first and second full-wave polyphase bridge rectifier circuits to receive and conduct signals from said primary SCR circuit.

Claim 18

The transmitter described in claim 16, wherein said first full-wave polyphase bridge rectifier is composed of a first plurality of SCR units responsive to said polarity control means for receiving and conducting signals from said primary SCR circuit, and wherein said second full-wave polyphase bridge rectifier circuit is composed of a second plurality of SCR units responsive to said polarity control means for receiving and conducting signals from said primary SCR circuit.

Claim 19

The transmitter described in claim 17, wherein said polarity control includes a first plurality of power amplifiers coupled to said first plurality of SCR units, a second plurality of power amplifiers coupled to said second plurality of SCR units, and gating and mode programming means for selectively actuating said power amplifiers to cause said SCR units to provide a transmitter output signal of preselected amplitude and wave form.

Claim 20

An improved transmitter for an induced polarization system for performing subsurface earth investigations or the like, comprising a power supply for generating an AC power signal, conversion means responsive to said power signal for deriving a transmitter output signal, monitoring means responsive to said transmitter output signal for producing a control signal having a waveform functionally related at all instances of time to predetermined time dependent instantaneous amplitude characteristics and line control means responsive to said control signal and to said AC power signal for deriving and applying phase-dependent actuating signals to said conversion means for regulating the waveform of said transmitter output signal according to said predetermined characteristics.

Claim 21

An improved transmitter for an induced polarization system for performing subsurface earth investigations or the like, comprising a power supply for generating an AC power signal, conversion means responsive to said power signal for deriving a transmitter output signal, monitoring means responsive to said transmitter output signal for producing a control signal having a waveform functionally related at all instances of time to predetermined time dependent instantaneous amplitude characteristics and line control means responsive to said control signal and to said AC power signal for deriving and applying phase-dependent actuating signals to said conversion means for regulating the waveform of said transmitter output signal according to said predetermined characteristics.

Claim 22

The apparatus described in claim 19, wherein said conversion means generates said transmitter output signal as a function of said phase-dependent actuating signals derived by said line control means and said control signal produced by said monitoring means.

Claim 23

The apparatus described in claim 20, wherein said monitoring means further comprises transducer means responsive to said transmitter output signal for providing a functionally related transducer voltage, and a comparator means for deriving a comparison signal which is a function of said voltage from said transducer means and a reference voltage.

Claim 24

The apparatus described in claim 21, wherein said transducer means provides said transducer voltage as a function of the magnitude of the current of said transmitter output signal.

Claim 25

The apparatus described in claim 22, wherein said monitoring means further comprises integrating means for actuating said line control means as a function of said comparison signal.