Variable external capacitor for NMR probe
First Claim
1. A variable external capacitor in a nuclear magnetic resonance probe comprising:
- a housing including an external capacitor member and a current-conducting ring insulated from said external capacitor member, said housing defining a capacitor cavity;
an internal capacitor member disposed at least partially inside said capacitor cavity and spaced from said external capacitor member by a distance, said internal capacitor member movable within said capacitor cavity to vary said distance, said internal capacitor member insulated from said external capacitor member;
a current-conducting rail connected between said ring and said internal capacitor member; and
a current-conducting plunger connected to said internal capacitor member and said rail, said plunger adjustable to move said internal capacitor member in said capacitor cavity.
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Accused Products
Abstract
A variable external capacitor produces greater functionality for NMR probes by reducing the size of components and efficiently arranging the components. The variable external capacity has a cavity that allows adjustment tools to be extended through the variable external capacitor to adjust additional components that may be stacked above the variable external capacitor. The cavity may be used to house reactance such as a fixed capacitor or inductor connected in parallel with the variable external capacitor. The variable external capacitor includes a polytetrafluoroethylene housing configured to minimize its size and reduce lead lengths of the NMR circuit. A silver deposit plate on the polytetrafluoroethylene housing constitutes a stationary capacitor plate. A drum disposed inside the cavity and movably spaced from the stationary capacitor plate functions as a movable capacitor plate. An anti-rotation rail supports the drum to prevent rotation. The drum includes internal threads that cooperates with threads provided in a plunger for adjustment of the drum in a translational direction. The plunger is supported by the rail and extends outside the cavity of the polytetrafluoroethylene housing for rotational adjustment. An insulator spaces the plunger and the drum from the stationary capacitor plate. The insulator and plunger provide a through passageway for an adjustment tool to extend therethrough. Alternatively, the space inside the insulator and plunger may be used to house a capacitor or inductor electrically supported by a current-conducting stick and connected in parallel with the variable external capacitor. A capacitor stick shifts the capacitance of the variable external capacitor, while an inductor stick forms a parallel LC resonant circuit. The structure provides the flexibility of choosing a stick to form a desirable circuit element for increased functionality of the NMR probe.
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Citations
30 Claims
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1. A variable external capacitor in a nuclear magnetic resonance probe comprising:
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a housing including an external capacitor member and a current-conducting ring insulated from said external capacitor member, said housing defining a capacitor cavity; an internal capacitor member disposed at least partially inside said capacitor cavity and spaced from said external capacitor member by a distance, said internal capacitor member movable within said capacitor cavity to vary said distance, said internal capacitor member insulated from said external capacitor member; a current-conducting rail connected between said ring and said internal capacitor member; and a current-conducting plunger connected to said internal capacitor member and said rail, said plunger adjustable to move said internal capacitor member in said capacitor cavity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A variable external capacitor comprising:
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a variable capacitor having a stationary capacitor component, a movable capacitor component movable relative to said stationary capacitor component, and a dielectric disposed between said stationary capacitor component and said movable capacitor component, said dielectric and said stationary capacitor member defining an internal cavity; a reactance disposed at least partially within said internal cavity and connected between said stationary capacitor component and said movable capacity component; and a retractable rod connected to said reactance and said movable capacitor component, said rod adjustable to move said movable capacitor component relative to said stationary capacitor component and to retrieve said reactance from said internal cavity. - View Dependent Claims (15, 16, 17, 18, 19)
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20. An adjustable external capacitor comprising:
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a variable capacitor having a cavity; a reactance releasably disposed within said cavity and electrically connected across said variable capacitor; and a means for adjusting the capacitance of said variable capacitor. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification