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The hygroscopic and electrical resistance characteristics of lithium chloride are investigated. Then an evaluation is made of the lithium chloride characteristics that would be suitable in development of a dew point hygrometer with measurement accuracy of + 0. 3 c. The development of a 12 volt battery-powered hygrometer is presented with circuit details and performance characteristics. Lithium chloride phase transition hygrometers tend to oscillate under certain conditions. A damping control is presented as part of the circuit details and recordings of the response characteristics and effectiveness of damping are presented showing effective control of the oscillations with a wide range of humidity transients.

Stratospheric water vapor plays an important role in the Earth system, both through its role in stratospheric ozone destruction and as a greenhouse gas contributing to radiative forcing of the climate. Highly accurate water vapor measurements are critical to understanding how stratospheric water vapor concentrations will respond to a changing climate. However, the past disagreement among water vapor instruments on the order of 1 – 2 ppmv hinders understanding of the mechanisms which control stratospheric humidity, and the reliable detection of water vapor trends. In response to these issues, we present a new dual axis water vapor instrument that combines the heritage Harvard Lyman-\(\alpha\) hygrometer with the newly developed Harvard Herriott Hygrometer (HHH). The Lyman-\(\alpha\) instrument utilizes ultraviolet photo-fragment fluorescence detection, and its accuracy has been demonstrated though rigorous laboratory calibrations and in situ diagnostic procedures. HHH employs a tunable diode near-IR laser to measure water vapor via direct absorption in a Herriott cell; it demonstrated in-flight precision of 0.1 ppmv (1-sec) with accuracy of 5%±0.5 ppmv. We describe these two measurement techniques in detail along with our methodology for calibration and details of the measurement uncertainties. We also examine the recent flight comparison of the two instruments with several other in situ hygrometers during the 2011 MACPEX campaign, in which five independent instruments agreed to within 0.7 ppmv, a significant improvement over past comparisons. Water vapor measurements in combination with simultaneous in situ measurements of \(O_3\), CO, \(CO_2\), HDO, and HCl are also used to investigate transport in the Tropical Tropopause Layer (TTL). Data from the winter 2006 CR-AVE campaign and the summer 2007 TC4 campaign are analyzed in a one-dimensional mixing model to explore the seasonal importance of transport within the TTL via slow upward ascent, convective injection, and isentropic transport from the midlatitude stratosphere. The model shows transport from midlatitudes to be significant in summer and winter, affecting ozone concentrations and therefore the radiative balance of the TTL. It also shows significant convective influence up to 420 K potential temperature in both seasons, which appreciably increases the amount of water vapor above the tropopause. / Engineering and Applied Sciences

Atualmente, há diversos modelos de instrumentos termohigrômetros, utilizados em grande variedade de aplicações nas organizações, cujas medições de temperatura e umidade relativa se fazem necessárias. Nas atividades referentes ao desenvolvimento, fabricação e utilização desses instrumentos, há a necessidade de inspeções funcionais neles, para avaliações sobre as medições proporcionadas. De forma pertinente ao exposto, neste trabalho, é apresentada abordagem sobre os elementos do projeto conceitual de um sistema que utiliza visão computacional para apoio à realização da inspeção de tipo específico de termohigrômetro digital, em operações que envolvem a leitura e o registro das medidas indicadas no instrumento, como parte do procedimento adotado para a inspeção em questão. O tipo de termohigrômetro digital abordado é caracterizado: por ser de indicação digital em única face do invólucro; possuir mostrador de cristal líquido com dígitos de sete segmentos e notação em ponto decimal; apresentar em regiões distintas os dados das medições simultâneas de temperatura e umidade relativa; por não dispor de recursos de comunicação para aquisição dos dados das medições. O projeto conceitual do sistema abordado é caracterizado por explorar conceitos da aplicação de recursos de aquisição de imagens e reconhecimento óptico de caracteres, com a finalidade de dispor imagens e dados em meios computacionais, de forma automatizada, para auxiliar as operações de leitura e registro das medidas indicadas no termohigrômetro sob inspeção, sendo as informações resultantes acessíveis por outros sistemas computacionais. Os componentes para experimentos apresentaram resultados satisfatórios nos testes práticos, validando os princípios de funcionamento dos elementos implementados, do sistema de inspeção e da aplicação. Os objetivos propostos foram atingidos, haja vista que os estudos expostos permitem oferecer contribuição para as atividades referentes ao desenvolvimento, fabricação e utilização de termohigrômetros do tipo em questão, com ênfase para o âmbito daquelas relacionadas aos segmentos das aplicações de sistemas computacionais, voltadas para automatizações de processos de inspeção desse tipo de instrumento, para as quais possam ser estendidos os conceitos abordados. / Currently, there are many thermo hygrometer instruments that are used in several applications in organizations in which measurements of temperature and relative humidity are required. In order to verify the measurements provided by these instruments, it is necessary to perform functional inspection tests in them, in development, manufacture and usage activities, in order to verify the measurements provided by these instruments. In this paper, an approach of the elements used in a conceptual system using computer vision to support digital thermo hygrometer inspection is presented. The computer vision is used in operations that involve reading and recording of measurements in the instrument as part of the procedure adopted for their inspection. The kind of digital thermo hygrometer addressed in this paper is a digital instrument, with a liquid crystal display using seven-segment digits and a decimal point notation, which shows simultaneous measurements of temperature and relative humidity in different locations of its display, and which doesnt have communication resources for reading the measurement data. The system conceptual design explores concepts that use resources for acquiring images and for optical character recognition, in order to automatically provide images and data in a computer media, and assist the operations of reading and recording measures indicated by the thermo hygrometer. The resulting information can be accessible by other computer systems. The components used for experiments presented satisfactory results in practical tests, validating the principles of operation of the implemented elements of the inspection system and application. The proposed objectives were achieved, given the fact that the studies exposed here make it possible to offer assistance to activities related to the development, manufacture and use of thermo hygrometers of the type in question, with emphasis on those related to the scope of segments of applications for computing systems oriented to the automation of inspection processes of this type of instrument, for which the concepts covered may be extended.