"Geophysical Sensor"
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Preliminary Patent Application

August 23, 1980
Coronado, California

Copyrighted © by The Townsend Brown family. All rights reserved.

This patent relates to a class of portable sensing devices believed to be useful in geophysical prospecting. It is based in principle on a phenomenon in physics not, as yet, fully understood; namely, "the anomalous variation in electrical resistivity of long wires." It is believed that such variations are caused by an incident penetrating radiation coming (in part) from rock formations deep within the earth.

In its practical application, the sensor comprises (in combination) a wirewound (preferably non-inductive) resistor, of extremely high resistivity (approx. 1 megohm), electrically-coupled to a low voltage battery and suitable readout (in the nano-ampere range).

The circuit shown in Fig. 1 represents the simplest form of the invention. Unfortunately, such a circuit is commonly used in measuring resistance and, therefore, probably not patentable per se. Certain additions to the circuit may provide patentability and, at the same time, increase its effectiveness and utility as a geophysical sensor. Such a circuit a shown in Fig. 2.

Here, a voltage divider is provided to reduce the battery voltage bellow the (1.5 volt) normal value. The advantage is as follows:

In the research (of this phenomenon) to date, it has been discovered that "long-wire" resistors, including also certain dielectric materials and semi-conductors, generate spontaneously a low-order counter-emf when conducting a current.

This counter-emf (believed to be produced by a penetrating incident radiation from an outside source) bucks the current from the battery causing what appears to be an increase in resistance. In certain instances, the counter-emf may equal or exceed the battery voltage, thus providing a null, or reversed, polarity. The technique of indicating the null position would provide increased sensitivity to the method and, since the use of a "null" is not utilized in conventional methods for measuring resistance, its use here may provide patentability.

In short, the indication and measurement of the shift in the null position would provide a measure of the intensity of sub-surface geophysical radiation. Such radiation (the nature of which has still not been determined in the on-going investigations) is believed to be, in large measure, emitted by or dependent upon rock composition or structure. Hence, the sensor may provide information useful in prospecting for oil or mineral deposits or in locating geo-thermal reservoirs.

In the design of such a sensor, it is important to use wires (metals or other materials) which have minimum temperature effects. Many commercially available resistors are so compensated. When not so compensated, a constant-temperature housing must be provided.

Also, non-inductive windings (of resistors) are indicated where possible. Otherwise, magnetic shielding may be necessary.


1. Method of observing penetrating radiation consisting in providing, in combination, a metallic conductor, a source of direct current, and current measuring means, connecting the same in series, and observing the departure from normal of the electrical conductivity of said conductor.

2. Method as in Claim 1 using semi-conducting materials as conductors.

3. Method as in Claim 1 using rocks as conducting materials.

4. Method as in Claim 1 using partially-conducting oils as conducting materials.

5. A geophysical sensor comprising a wire-wound resistor, a source of direct current and current measuring means.

6. A geophysical sensor comprising a temperature-compensated wire-wound resistor, a variable source of direct current and current-measuring means.

7. A geophysical sensor as in Claim 5 using semi-conducting materials in place of wire-wound resistors.

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