Ultrasensitive ratiometric capacitance dilatometer and related methods

Abstract

An ultrasensitive ratiometric capacitance dilatometer and related methods are described. The dilatometer (100) provides a capacitance measurement based on a ratiometric capacitance, or the capacitance ratio measured between two or more parallel plate capacitors (201; 202) of the dilatometer. In this regard, an absolute capacity bridge is not required, and even more advantageously, the effects of adsorbed gas are greatly reduced compared to conventional dilatometers. The ratiometric capacitance dilatometer provides a symmetrical configuration, which reduces the effects of temperature gradients. Moreover, certain embodiments provide a v-groove design, wherein a first parallel plate capacitor forms an angle with a second parallel plate capacitor of the dilatometer along a key centerline of the dilatometer cell, which improves manufacturability due to simpler grinding, metalizing and assembly.

Description

technical field [0001] The present invention relates to precision instruments called dilatometers, which are designed to measure dimensional changes in a sample due to changes in the environment of the sample; and more particularly, such dilatometers are configured for use in two or more parallel Ratiometric measurements between plate capacitors, and related methods, such instruments are referred to herein as "ratiocapacitance dilatometers". Background technique [0002] The coefficient of thermal expansion is a fundamental property of all materials; however, the ability to measure thermal expansion is not readily available in most laboratories, especially at cryogenic temperatures on the order of very low or a fraction of a degree Kelvin. [0003] Dilatometers are ultra-sensitive instruments used to measure dimensional changes in materials due to changes in their environment. Various applications for dilatometers can include: locating phase transitions in materials; predic...

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Problems solved by technology

[0013] Although an improvement over previous capacitive dilatometers of the copper alloy type (which themselves suffer from high thermal expansion), in practice several problems have been presented when using Neumeier cells in cryostats at low temperatures, such as: capacity is affected effects of gas adsorption; requires absolute capacitance measurements; and thermal gradients affect first-order accuracy (accuracyin1 st order)

[0014] Furthermore, in all these capacitive prior art units, the measurement is affected by gas adsorption and thermal gradients to the first order; and the measurement of the required absolute capacitance is difficult without very specialized and expensive instrumentation

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