richard l. davis_ non-inductive resistance

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Richard DAVIS

Non-Inductive Resistor

AEC-NASA Tech Brief # 68-10267Moebius Resistor is Noninductive & Nonreactive

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Richard L. Davis: Non-Inductive Resistor (Moebius loop) http://www.rexresearch.com/davis/davis.ht

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Notes:

(1) If the terminals are not directly opposed, the resistor becomes inductive, with maximum inductance when the terminals areseparated by one-half the length of the loop.

(2) Inquiries concerning this invention may be directed to:

Sandia Office of Industrial Cooperation ~ Org. 3413Sandia Corp.P.O. Box 5800Albuquerque NM 87115Reference: B68-10267

Electronics Illustrated (November 1969, p. 76, 77, 117)

At Ultra-High Frequencies Electronic Components Take On Weird Shapes!

byJorma Hyypia

How can you squeeze troublesome inductance and reactance (resistance to changes in AC) out of a resistor? One way is to make aresistor in the shape of a Moebius loop --- a century-old mathematical oddity that is based on a geometric surface having only one sideand one edge.

Under ideal circumstances, a resistor should provide only resistance, a capacitor only capacitance and an inductor only inductance.Unfortunately, in high-frequency circuits (UHF and microwave) and especially in pulse applications such as radar, the design andoperation of such circuits is greatly affected by the unwanted reactance inherent in these components. The higher the frequency, themore critical these parasitic values are.

A unique solution to one of these problems (making low-value resistors non-reactive) has been found by Richard L. Davis, anelectronics engineer with the Sandia Laboratories in Albuquerque, NM. Davis reasoned that if current passing through a resistor could

be divided into two equal components whose electromagnetic fields cancel out, the reactance of the resistor would be small. Howcould such a resistor be made? The Davis solution was to add a simple Moebius twist to a ribbon- or wire-conductor resistor.

Kooky Loops ~

Perhaps the oldest way to visualize the construction (and operation) of a Moebius resistor is to make a coupe of Moebius loops fromlong strips of paper that are about an inch wide. First make the basic loop by joining (with tape) the two ends of a single strip after youhave given the strip a half twist. This loop has only one surface! Prove this by drawing a line along the full length of the strip right back


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Richard L Davis: Non Inductive Resistor (Moebius loop) http://www rexresearch com/davis/davis ht


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US Patent # 3,267,406

Non-Inductive Electrical Resistor(August 16, 1966)

Richard L. Davis

This invention relates to electrical resistors, particularly to non-inductive electrical resistors.

In high voltage, high frequency electronic circuits, especially in pulse applications such as radar, the design and operation of thesecircuits is greatly affected by unknown reactance in the circuit components themselves or in unwanted coupling between components.A large amount of time and money has been expended to develop components that display in these applications the particular electrical function for which it was designed. Under ideal circumstances, a resistor should essentially provide only resistance to thecircuit, a capacitor only capacitance, and an inductor only inductance.

This has been the problem in the resistor field and particularly low resistance resistors. Previously known low resistance resistors havedisplayed in high frequency and pulse applications some form of deleterious reactance or coupling with other components.

It is therefore an objective of this invention to provide a resistor which has no residual self-inductance or mutual inductance.

It is a further object to provide a resistor which is non-reactive at high frequencies.

Various other objects and advantages will appear from the following description of one embodiment of the invention, and the mostnovel features will be particularly pointed out hereinafter in connection with the appended claims.

This invention contemplates utilizing insulated resistive material in the form of a Moebius surface with electrical leads attacheddiametrically opposite each other to the resistive material as a non-inductive resistor.

For a better understanding of the invention, reference may be had to the accompanying drawings in which:

Figure 1 is a perspective view of one embodiment of this invention,


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Richard L Davis: Non-Inductive Resistor (Moebius loop) http://www rexresearch com/davis/davis ht


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Figure 2 is a cross-sectional view of the Moebius strip showing the location of the resistor, insulator and electrical leads, and

Figure 3 is a cutaway view of a section of a resistor which embodies this invention.

Richard L. Davis: Non Inductive Resistor (Moebius loop) http://www.rexresearch.com/davis/davis.ht

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In the embodiment of the invention illustrated in Figure 1 and Figure 2, non-inductive resistor 1 comprises non-conductive ribbon 2 of an insulative material such as Mylar (polyethylene terepthalate) on both sides of which resistive ribbons 3 and 4 have been applied.Resistive ribbons 3 and 4 can be made of a resistive material such as Tophet A (80 Ni, 20 Cr) or for very low resistance, aluminum.The combined ribbons, 2,3, and 4 are then twisted as shown at point 5 and resistive ribbon 3 connected to a resistive ribbon 4 such as

by soldering so as to form a Moebius strip. Resistive ribbons 3 and 4, when connected form a single Moebius surface. Electrical leads 6and 7 are then attached such as by soldering to diametrically opposite points 8 and 9 of resistive ribbons 3 and 4 to complete theresistor.

It is understood that the resistive ribbons 3 and 4 may be replaced by resistive wire such as Manganin (84 Cu, 12 Mn, 4 Ni) bifilar wirewherein the insulation normally provided would replace non-conductive ribbon 2. By bifilar wire, it is meant two parallel strands of wire covered by and separated by the same insulator. The spacing between the wires provided by the insulation should be maintainedwhen the respective wires are connected together to form the Moebius strip so as to have minimum reactance in the resistor.

In operation, a high frequency electrical current inserted across electrical leads 6 and 7 will travel in opposite directions between theleads through resistive ribbons 3 and 4. The electromagnetic fields generated by these currents thereby cancel each other resulting inan essentially non-inductive, non-reactive resistor as shown in Table 1.

Table 1 ~

Conductor Resistance (ohms) Reactance (200 kc) Resistive materialRibbon 12.7 0.0305 microhenries Tophet ARibbon 80 0.1 picofarad Tophet AWire 50.3 0.090 microhenries ManganinWire 62 0.069 picofarad Manganin

The Moebius resistor listed first in Table 1 was pulsed at 1000 volts and had a measured rise time of 0.1 microsecond.

c a d . av s: o duct ve es sto ( oeb us oop) ttp://www. e esea c .co /dav s/dav s. t

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richard l. davis_ non-inductive resistance

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