• International journal of advanced smart convergence
• /
• v.11 no.4
• /
• pp.240-246
• /
• 2022

In order to measure the respiratory rate, one of the major vital signs, many devices have been developed and related studies have been conducted. In particular, as the number of wearers of respirators increases in the COVID-19 pandemic situation, studies have been conducted to measure the respiratory rate of the wearer by attaching an electronic sensor to the respirator, but most of them are cases in which an air flow sensor or a microphone sensor is used. In this study, we design and develop a system that measures the respiratory rate of the wearer using an air pressure sensor in a respirator. Air pressure sensors are inexpensive and consume less power than the other sensors. In addition, since the amount of data required for calculation is small and the algorithm is simple, it is suitable for small-scale and low-power processing devices such as Arduino. We developed an algorithm to measure the respiratory rate of a respirator wearer by analysing air pressure change patterns. In addition, variables that can affect air pressure changes were selected, and experimental scenarios were designed according to the variables. According to the designed scenario, we collected air pressure data while the respirator wearer was breathing. The performance of the developed system was evaluated using the collected data.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.11 no.2
• /
• pp.47-54
• /
• 2012

An oxygen sensor installed in vehicle exhaust systems enables to measure the amount of oxygen in the exhaust gas, in which the measured data are collected and analyzed in ECU(Engine Control Unit). The oxygen sensor is exposed to the high speed exhaust gas at high temperature circumstance, so that protection caps are required not only to protect the susceptible measuring part, but also to provide the real time measurement without time delay. In this study, a new oxygen sensor with one protection cap was proposed, and the CFD analysis was carried out in order to compare the performance characteristics, such as flow speed and ratio of AOA(Age of Air), for the conventional and new oxygen sensor. The numerical results of CFD analysis provided the flow speed of 1.34m/s and the ratio of AOA of 3.43. The similar features obtained from the numerical results showed that the new oxygen sensor guarantees the same performance characteristics of the conventional ones.

• Nuclear Engineering and Technology
• /
• v.47 no.7
• /
• pp.804-813
• /
• 2015

The electrical-impedance method has been widely used for void-fraction measurement in two-phase flow due to its many favorable features. In the impedance method, the response characteristics of the electrical signal heavily depend upon flow pattern, as well as phasic volume. Thus, information on the flow pattern should be given for reliable void-fraction measurement. This study proposes an improved electrical-conductance sensor composed of a three-electrode set of adjacent and opposite electrodes. In the proposed sensor, conductance readings are directly converted into the flow pattern through a specified criterion and are consecutively used to estimate the corresponding void fraction. Since the flow pattern and the void fraction are evaluated by reading conductance measurements, complexity of data processing can be significantly reduced and real-time information provided. Before actual applications, several numerical calculations are performed to optimize electrode and insulator sizes, and optimal design is verified by static experiments. Finally, the proposed sensor is applied for air-water two-phase flow in a horizontal loop with a 40-mm inner diameter and a 5-m length, and its measurement results are compared with those of a wire-mesh sensor.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.3 no.3
• /
• pp.58-65
• /
• 1995

In this study an air flow meter was developed for MPI engine using ultrasonic sensors. The major characteristcs of the ultrasonic flow meter are high speed response, flow direction recognition and linear output. The air flow rate measurements were conducted at upstream of the throttle and intake manifold. The characteristics of the ultrasonic flow meter are compared with those of the Bosch hot wire flow meter at both steady and unsteady engine conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.10a
• /
• pp.591-592
• /
• 2009

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.10
• /
• pp.876-883
• /
• 2007

Numerical simulations are conducted for the design of a micro thermal mass air flow sensor (MAFS), which consists of a microfabricated heater and thermopiles on the silicon-nitride ($Si_3N_4$) thin membrane structure. It is important to find the proper locations of these thermal elements in the design of MAFS with improved sensitivity. Three heating modes of the micro-heater are considered: constant temperature, constant power and heating pulses. The analyses are focused on the membrane temperature profile near the sensing section. Considered are the practical flow velocities, ranging from 3 m/s to 35 m/s, and the corresponding Reynolds numbers from 1000 to 10000. The results show that one of optimum sensing locations is about $100{\mu}m$ away from the microheater. It is concluded that the heating mode and configurations of thermal elements are the main factors for the MAFS with higher sensitivity.

• Journal of Biosystems Engineering
• /
• v.30 no.5 s.112
• /
• pp.312-317
• /
• 2005

A flow injection type biosensor was tested to confirm the performance of a batch and a continuous type flow injection unit. Reproducibility and consistence of the biosensor were investigated to determine the effect of pulsations and air bubbles, and the applicability of on-line monitoring. The air bubbles affected the performance of the sensor irrespective of the location, and also the pulsations of the pump influenced the performance of the sensor. The applicability of on-line motoring was accepted as the result of the repeated and long-term measurements.

• Journal of Sensor Science and Technology
• /
• v.9 no.4
• /
• pp.268-273
• /
• 2000

This paper represents a hot-film flow sensor which is compensated by a noble temperature compensation method using the initial unbalanced voltage. The resistance value of the sensor is determined by using the graph of the initial unbalanced voltage of an open-loop circuit against the air temperature. The compensation is accomplished by applying the unbalanced ratio of the resistors in the Wheastone bridge circuit. In the range of air temperature of $-20^{\circ}C{\sim}120^{\circ}C$, the error is about ${\pm}1%$.

• Nuclear Engineering and Technology
• /
• v.32 no.5
• /
• pp.433-445
• /
• 2000

The interfacial area concentration (IAC) is one of the most important parameters in the two-fluid model for two-phase flow analysis. The IAC can be measured by a local conductivity probe method that uses the difference of conductivity between water and air/steam. The number of sensors in the conductivity probe may be differently chosen by considering the flow regime of two-phase flow. The four sensor conductivity probe method predicts the IAC without any assumptions of the bubble shape. The local IAC can be obtained by measuring the three dimensional velocity vector elements at the measuring point, and the directional cosines of the sensors. The five sensor conductivity probe method proposed in this study is based on the four sensor probe method. With the five sensor probe, the local IAC for a given referred measuring area of the probe can be predicted more exactly than the four sensor probe. In this paper, the mathematical approach of the five sensor probe method for measuring the IAC is described, and a numerical simulation is carried out for ideal cap bubbles of which the sizes and locations are determined by a random number generator.

• Journal of Aerospace System Engineering
• /
• v.11 no.5
• /
• pp.20-27
• /
• 2017

The present paper describes the flow analysis of the flows around the multicopter for the selection of optimal position of air data sensor. For the flow analysis, the commercial fluid dynamics solver, STAR-CCM+ was used with polygon mesh and k-w SST turbulence modeling options. For the simulation of each rotating 4 propellers, unstructured overset mesh method was used. Hovering, forward flight, ascending and descending flight conditions are selected for the analysis and airspeed and flow angle errors were investigated using the CFD results. Through the flow field analysis, sensor location above one propeller diameter distance from the propeller rotating plane showed airspeed error less than 1m/s within the typical flight conditions of multicopter except descending.