Optimization of a Single Tube Practical Acoustic Thermometer.

When designing a single tube practical acoustic thermometer (PAT), certain considerations should be addressed for optimal performance. This paper is concerned with the main issues involved in building a reliable PAT. It has to be emphasised that a PAT measures the ratio of the time delay between the single temperature calibration point (ice point) and any other temperature. Here, we present different models of the speed of sound in tubes, including the effects of real gases and an error analysis of the most accurate model with a Monte Carlo simulation. Additionally, we introduce the problem of acoustic signal overlap and some possible solutions, one of which is acoustic signal cancellation, which aims to eliminate the unwanted parts of an acoustic signal, and another is to optimize the tube length for the parameters of the gas used and specific temperature range.

Electrodermal activity patient simulator.

Electrodermal activity (EDA) is an electrical property of the human skin, correlated with person's psychological arousal. Nowadays, different types of EDA measuring devices are used in highly versatile fields-from research, health-care and education to entertainment industry. But despite their universal use the quality of their measuring function (their accuracy) is questioned or investigated very seldom. In this paper, we propose a concept of an EDA patient simulator-a device enabling metrological testing of EDA devices by means of a variable resistance. EDA simulator was designed based on a programmable light-controlled resistor with a wide resistance range, capable of simulating skin conductance levels (SCL) and responses (SCR) and was equipped with an artificial hand. The hand included electrically conductive fingers for attachment of EDA device electrodes. A minimal set of tests for evaluating an EDA device was identified, the simulator's functionality discussed and some testing results presented.

Design and Clinical Evaluation of a Non-Contact Heart Rate Variability Measuring Device.

The object of the proposed paper is to design and analyze the performance of a non-contact heart rate variability (HRV) measuring device based on ultrasound transducers. The rationale behind non-contact HRV measurement is the goal of obtaining a means of long term monitoring of a patient's heart performance. Due to its complexity as a non-contact measuring device, influential physical quantities, error source and other perturbations were thoroughly investigated. For medical purposes it is of utmost importance to define the target uncertainty of a measuring method from the side of physicians, while it is the role of scientists to realistically evaluate all uncertainty contributions. Within this paper we present a novelty method of non-contact HRV measurement based on ultrasound transducers operating at two frequencies simultaneously. We report laboratory results and clinical evaluations are given for healthy subjects as well as patients with known heart conditions. Furthermore, laboratory tests were conducted on subjects during a relaxation period, and after 1 min physical activity.

Temperature measurement of mineral melt by means of a high-speed camera.

This paper presents a temperature evaluation method by means of high-speed, visible light digital camera visualization and its application to the mineral wool production process. The proposed method adequately resolves the temperature-related requirements in mineral wool production and significantly improves the spatial and temporal resolution of measured temperature fields. Additionally, it is very cost effective in comparison with other non-contact temperature field measurement methods, such as infrared thermometry. Using the proposed method for temperatures between 800°C and 1500°C, the available temperature measurement range is approximately 300 K with a single temperature calibration point and without the need for camera setting adjustments. In the case of a stationary blackbody, the proposed method is able to produce deviations of less than 5 K from the reference (thermocouple-measured) temperature in a measurement range within 100 K from the calibration temperature. The method was also tested by visualization of rotating melt film in the rock wool production process. The resulting temperature fields are characterized by a very good temporal and spatial resolution (18,700 frames per second at 128 pixels×328 pixels and 8000 frames per second at 416 pixels×298 pixels).

A procedure for evaluation of non-invasive blood pressure simulators.

Non-invasive blood pressure (NIBP) simulators are used in clinical environment for quick checks of blood pressure monitors as a part of technical maintenance and health-care quality assurance system. They are also included in various tests within the procedures for testing NIBP monitors. In practice simulators are often subject to mechanical and electromagnetic shocks which could effect their measuring function. Our objective was to design a procedure for testing the reliability and quality of simulators in order to ensure reliable testing of NIBP monitors. Procedure for evaluation of NIBP simulators, consisting of a static and dynamic test, is proposed. Static test consisted of procedures derived from common electro-mechanical manometer calibration, while dynamic test included testing of repeatability of simulator's output. A commercial simulator was tested. Among others, the results indicated that evaluations of NIBP simulators should be performed regularly with a suitable time interval in order to track the metrological quality of the simulator in time. Acceptance criteria for a reliable simulator in both static and dynamic sense are proposed.

Infrared ear thermometers--parameters influencing their reading and accuracy.

Infrared ear thermometers (IRETs) are extensively used for measuring the temperature of a human body. For accurate measurements with IRETs they have to be calibrated regularly with an appropriate and traceable calibration system. Such systems are neither widely available nor are there many competent (accredited) laboratories which can provide traceability for IRETs. This paper describes some important influential parameters in the calibration and use of IRETs, which were observed during the extensive research on IRETs and have not been reported in the literature yet. IRET readings, and consequently also their most important metrological characteristics, accuracy and uncertainty of measurement, depend on these influential parameters. According to our findings, we would like to warn users of medical radiation thermometers, not only IRETs but also forehead thermometers and infrared temperature scanning systems, that they should be extremely careful in selection, maintenance and use of medical radiation thermometers. Measurement accuracy, as it is required by several technical standards, is hard to achieve with the majority of currently available medical radiation thermometers.

Bilateral comparison of blackbody cavities for calibration of infrared ear thermometers between NPL and FE/LMK.

The paper describes the comparison method and analyses the results of comparison in terms of agreement between the blackbody of the National Physical Laboratory (NPL), United Kingdom and four different blackbody cavities of the Laboratory of Metrology and Quality (LMK), at the University of Ljubljana, Faculty of Electrical Engineering (FE), Slovenia. Three cavity shapes are suggested in different standards as suitable for calibration of infrared ear thermometers (IRETs), while one cavity shape was proposed by the LMK. The agreement between blackbody cavities was determined with the help of platinum resistance thermometers. Two reference IRETs were used to check their stability and level of agreement between calibration results at different institutes and against different blackbody cavities. Measurements were performed with two IRETs, at the NPL in one cavity and at the LMK in four different cavities. The comparison was initiated to solve the problem of assuring proper traceability for IRETs and to present the solution to their users.

IR ear thermometers: what do they measure and how do they comply with the EU technical regulation?

Medical diagnostics and clinical practice rely extensively on test and measurement instrumentation. It is therefore of paramount importance that test and measurement instrumentation provides reliable data of sufficient stability, within appropriate limits of accuracy. At the same time the intended purpose of a particular measuring instrument has to be taken into account. The essential problem of every measuring instrument is that it measures and indicates basically what appears at the input of the measuring instrument, which might be significantly different from the real condition of a measurand. Namely, it is assumed that a measurand is stable, repeatable, and relatively unsusceptible to environmental influences. All these requirements are difficult to assure in a biological system and especially difficult in medical practice. Technology could easily provide high-resolution measurements, but due to natural instability of a measurand and various influential parameters the measurement uncertainty is inevitable. Sometimes even gross measurement errors are introduced. To achieve the expected accuracy for intended purpose is therefore much more demanding than merely relying on manufacturers' specifications. This paper describes and analyses the mentioned dilemmas in the case of widely used infrared ear thermometers, with their benefits and limitations, as well as with regard to the European technical regulation in the field of medical devices.