Accuracy and Precision Improvement of Temperature Measurement Using Statistical Analysis/Central Limit Theorem.

This paper describes a method for increasing the accuracy and precision of temperature measurements of a liquid based on the central limit theorem. A thermometer immersed in a liquid exhibits a response with determined accuracy and precision. This measurement is integrated with an instrumentation and control system that imposes the behavioral conditions of the central limit theorem (CLT). The oversampling method exhibited an increasing measurement resolution. Through periodic sampling of large groups, an increase in the accuracy and formula of the increase in precision is developed. A measurement group sequencing algorithm and experimental system were developed to obtain the results of this system. Hundreds of thousands of experimental results are obtained and seem to demonstrate the proposed idea's validity.

Respiratory Rate Detection by a Time-Based Measurement System / Detección de frecuencia respiratoria mediante un sistema de medida basado en el tiempo

Abstract: This paper proposes a system that converts a time-modulated signal from a resistive sensor into a digital signal with the goal to estimate the respiratory rate of a subject. To detect breathing, a known method based on a nasal thermistor, which detects temperature changes near the nostrils, is used. In this work, the thermistor mounted in a Wheatstone bridge, forms a RC circuit which is connected directly to a microcontroller, without using any analog circuit or analog-digital converter. Thus, whenever the subject breathes, it causes a fractional change in resistance x (∆R/R 0) on the thermistor, and this produces a time-modulated signal that is directly digitized with the microcontroller. Measurements were made on 23 volunteers, obtaining changes of x > 0.01. The temperature resolution was 0.2 °C, and the time response was 0.8 s, mainly limited by the thermistor properties; these features were enough to obtain a well-defined waveform of the breathing, from which was easy to estimate the respiratory rate by a compact, low cost and low power consumption system. Unlike interface circuits based on voltage or current amplitude, with this kind of interface, the self-heating of the sensor is avoided since the thermistor does not require any voltage or bias current.

Resumen: Este trabajo propone un sistema que convierte una señal modulada en tiempo, proveniente de un sensor resistivo, en una señal digital con el fin de estimar la frecuencia respiratoria de un sujeto. Para detectar la respiración se utilizó el método basado en un termistor nasal, el cual detecta los cambios de temperatura cerca de las fosas nasales. En este trabajo, el termistor, montado en un puente de Wheatstone, forma un circuito RC que se conecta directamente a un microcontrolador, sin necesidad de usar ningún circuito analógico, ni conversor analógico-digital. Así, cada vez que el sujeto respire, provoca un cambio fraccional de resistencia x (∆R/R 0) en el termistor, y esto produce una señal modulada en tiempo que se digitaliza directamente con el microcontrolador. Se hicieron medidas en 23 voluntarios, obteniendo cambios de x > 0.01. Se obtuvo una resolución en temperatura de 0.2 °C y un tiempo de respuesta de 0.8 s, limitado principalmente por las propiedades del termistor utilizado. Estas características demostraron ser suficientes para obtener una forma de onda de la respiración bien definida, de la cual es sencillo estimar la frecuencia respiratoria mediante un sistema compacto, de bajo costo y bajo consumo de energía. A diferencia de los circuitos de interfaz basado en la amplitud de tensión o corriente, con este tipo de interfaz se evita el autocalentamiento del sensor, ya que el termistor no requiere ningún voltaje o corriente de polarización.

Evaluation of manometric temperature measurement, a process analytical technology tool for freeze-drying: Part I, product temperature measurement.

This study examines the factors that may cause systematic errors in the manometric temperature measurement (MTM) procedure used to evaluate product temperature during primary drying. MTM was conducted during primary drying using different vial loads, and the MTM product temperatures were compared with temperatures directly measured by thermocouples. To clarify the impact of freeze-drying load on MTM product temperatures, simulation of the MTM vapor pressure rise was performed, and the results were compared with the experimental results. The effect of product temperature heterogeneity in MTM product temperature determination was investigated by comparing the MTM product temperatures with directly measured thermocouple product temperatures in systems differing in temperature heterogeneity. Both the simulated and experimental results showed that at least 50 vials (5 mL) were needed to give sufficiently rapid pressure rise during the MTM data collection period (25 seconds) in the freeze dryer, to allow accurate determination of the product temperature. The product temperature is location dependent, with higher temperature for vials on the edge of the array and lower temperature for the vials in the center of the array. The product temperature heterogeneity is also dependent upon the freeze-drying conditions. In product temperature heterogeneous systems, MTM measures a temperature close to the coldest product temperature, even, if only a small fraction of the samples have the coldest product temperature. The MTM method is valid even at very low product temperature (-45°C).

Evaluación de lss pérdidas térmicas en calorimería isoperibólica. importancia de los alrededores en la obtención de constantes instrumentales / Evaluation of the thermal leakage in isoperibolic calorimetry. importance of the environs in the obtaining of instrumental constants

Para tres unidades calorimétricas con aislamientos en PVC, nailon y metálico se determina la constante de fugas térmicas, K, con valores de 6,50 x 10-3, 6,37 x 10-5 y 2,52 x 10-4 s-1, respectivamente. Se determina la capacidad calorífica del sistema con agua para cada una de las unidades calorimétricas y se obtienen valores para esta constante de 442,1 J °C-1 para la celda con aislamiento en PVC, 206,7 J °C-1 para la celda con aislamiento de nailon y 408,2 J °C-1 para la celda con aislamiento metálico. Se establece la influencia de la magnitud del efecto térmico en las pérdidas térmicas y en la constante de fugas térmicas, para trabajos eléctricos entre 0,5 y 3,4 kJ. Se determina la entalpía de solución para el sistema propanol-agua, con resultados similares para las tres unidades calorimétricas del orden de 10,7 kJmol-1 .

For three calorimetric units with isolations in PVC, nylon and metal, the heat leakage constant, K, is determined, giving values of 6.50 x10-3, 6.37 x10-5 and 2.52 x 10-4 s-1 respectively. The heat capacity of the system with water for each one of the calorimetric units was determined and values obtained for this constant are of 442.1 JC-1 for the cell with insulation in PVC, 206.7 JC-1 for the cell with insulation of nylon and 408.2 JC-1 for the cell with metallic insulation. The influence of the thermal effect magnitude in the thermal losses and the heat leakage constant, for electrical works between 0.5 and 3.4 kJ is established. Solution enthalpy for the system propanol- water was determined, with similar results for the three calorimetric units of the order of 10.7 kJmol-1.