Paweł Ligęza

Bio: Paweł Ligęza is an academic researcher from Polish Academy of Sciences. The author has contributed to research in topics: Anemometer & Flow velocity. The author has an hindex of 11, co-authored 38 publications receiving 270 citations.

Constant-bandwidth constant-temperature hot-wire anemometer.

Abstract: A constant-temperature anemometer (CTA) enables the measurement of fast-changing velocity fluctuations. In the classical solution of CTA, the transmission band is a function of flow velocity. This is a minor drawback when the mean flow velocity does not significantly change, though it might lead to dynamic errors when flow velocity varies over a considerable range. A modification is outlined, whereby an adaptive controller is incorporated in the CTA system such that the anemometer's transmission band remains constant in the function of flow velocity. For that purpose, a second feedback loop is provided, and the output signal from the anemometer will regulate the controller's parameters such that the transmission bandwidth remains constant. The mathematical model of a CTA that has been developed and model testing data allow a through evaluation of the proposed solution. A modified anemometer can be used in measurements of high-frequency variable flows in a wide range of velocities. The proposed modification allows the minimization of dynamic measurement errors.

Four-point non-bridge constant-temperature anemometer circuit

Abstract: A constant-temperature bridge is the basic circuit used to supply hot-wire anemometer probes. One disadvantage of such circuits is that the probe overheat ratio depends on the resistance of the supply cable. To eliminate these shortcomings, a four-point non-bridge constant-temperature circuit was worked out. In such a circuit, cable adjustment is not required. This circuit enables high-precision anemometric measurements, especially under the conditions of low probe resistance, low overheat ratio range, low velocity range and long probe supply cables.

A four-point constant-current/temperature controlled circuit for anemometric applications

Abstract: A four-point constant-current/temperature controlled circuit is an electronic system for supplying a resistance measuring sensor in two modes of operation: either in constant-current or in constant-temperature mode. This circuit is destined for anemometric applications. It is new nonbridge, four-point constant-current/temperature anemometer circuit. Separation of current and voltage leads of the sensor makes it possible to eliminate the effects of leads’ resistance on the preset value of sensor supply parameters. In such a circuit no cable adjustment is required. The value of sensor current or its resistance is set with digital signals. This article presents the design of the original measuring circuit and its principle of operation. Design of measuring circuit based on those principles is also presented. Attention is also given to its applications. The most important advantages of the new circuit are: both constant-current or constant-temperature modes of operation are available, precise digital control of sensor current or resistance can be performed, and four-point sensor operation in both modes is possible. It enables high-precision laboratory anemometric measurements, especially under the conditions of low sensor resistance, low overheat ratio range, and long sensor supply cables.

On unique parameters and unified formal form of hot-wire anemometric sensor model

Abstract: This note reviews the extensively adopted equations used as models of hot-wire anemometric sensors. An unified formal form of the mathematical model of a hot-wire anemometric sensor with otherwise defined parameters is proposed. Those parameters, static and dynamic, have simple physical interpretation and can be easily determined. They show directly the range of sensor application. They determine the metrological properties of the given sensor in the actual medium. Hence, the parameters' values might be ascribed to each sensor in the given medium and be quoted in manufacturers’ catalogues, supplementing the sensor specifications. Because of their simple physical interpretation, those parameters allow the direct comparison of the fundamental metrological properties of various sensors and selection of the optimal sensor for the given research measurement application. The parameters are also useful in modeling complex hot-wire systems.

Oscillation mechanics of the respiratory system: applications to lung disease.

Abstract: Since its introduction in the 1950s, the forced oscillation technique (FOT) and the measurement of respiratory impedance have evolved into powerful tools for the assessment of various mechanical phenomena in the mammalian lung during health and disease. In this review, we highlight the most recent developments in instrumentation, signal processing, and modeling relevant to FOT measurements. We demonstrate how FOT provides unparalleled information on the mechanical status of the respiratory system compared to more widely used pulmonary function tests. The concept of mechanical impedance is reviewed, as well as the various measurement techniques used to acquire such data. Emphasis is placed on the analysis of lower, physiologic frequency ranges (typically less than 10 Hz) that are most sensitive to normal physical processes as well as pathologic structural alterations. Various inverse modeling approaches used to interpret alterations in impedance are also discussed, specifically in the context of three common respiratory diseases: asthma, chronic obstructive pulmonary disease, and acute lung injury. Finally, we speculate on the potential role for FOT in the clinical arena.

A flexible polymer tube lab-chip integrated with microsensors for smart microcatheter.

Abstract: A flexible polymer tube lab-chip integrated with physical and biochemical sensor modules mounted on a flexible spiral structure for measuring physiological (temperature/flow rate) and metabolic data (glucose concentration) in a catheter application was designed, fabricated and characterized in this work. This new approach not only provides a unique way to assemble multiple sensors on both the inside and outside the flexible polymer tube using standard microfabrication methods while avoiding wiring and assembling problems associated with previous methods, but also maintains catheter inherent lumen potency for in situ drug delivery or insertion of medical tools. Three well-known sensors: temperature sensor (RTD), flow rate sensor (hot film anemometry) and glucose biosensor (amperometric sensor) have been successfully fabricated and fully integrated outside the spirally rolled polymer tube (ID = 500 μm, OD = 650 μm) of this demonstration device. The fabricated sensors showed good performances not only in a planar configuration but also in a spirally rolled configuration. This flexible micro tube lab-chip system provides a generic platform for developing patient-specific “smart” microcatheters that incorporate microsensors, microactuators, microfluidic devices and wireless signal communication modules that are tailored for the patients’ unique condition.

Hot-Wire Anemometer Based on Silver-Coated Fiber Bragg Grating Assisted by No-Core Fiber

Abstract: A novel hot-wire anemometer based on a silver-coated optical fiber Bragg grating (FBG) is proposed and experimentally demonstrated with the assistance of a short length of no-core fiber (NCF). The silver coating deposited on the surface of the FBG absorbs light of a pump laser, which is coupled into the fiber cladding by the NCF, to generate the heat, whereas air flow cools down the FBG by taking the heat away. A dynamic thermal equilibrium with a temperature codetermined by the pump laser power and airflow velocity can be reached. Bragg wavelength of the FBG changes with temperature thus is used to measure airflow velocity. Experimental results reveal that the highest resolution of ~ 0.0017 m/s is achieved and the measurement range covers 0-13.7 m/s.

Compact Anemometer Using Silver-Coated Fiber Bragg Grating

Abstract: An optical fiber thermal anemometer is proposed based on a silver film-coated fiber Bragg grating (FBG) assisted by a core offset fusion splice. Light from a pump laser propagating along the fiber is coupled into the fiber cladding by the splice and absorbed by the silver film to generate heat and increase the temperature of the FBG. Air flow cools down the FBG and its velocity can be measured by the Bragg wavelength shift of the FBG. Experimental results show that the proposed FBG thermal anemometer allows a high resolution of 0.022 m/s in a range up to 6 m/s.

A miniature fiber optic blood pressure sensor and its application in in vivo blood pressure measurements of a swine model

Abstract: Fractional flow reserve (FFR) is a promising technique in diagnosis of coronary artery stenosis. The technique is applied in coronary catheterization to measure the blood pressure (BP) difference across a coronary artery stenosis in the blood flow. In vivo BP measurement is the key element in FFR diagnosis. This paper describes the utilizing of a novel miniature fiber optic sensor to measure the BP of a swine model in vivo . A 25–50 kg Yorkshire swine model was used as the test target. A guiding catheter was introduced into the coronary artery, and blood pressure signals in aortic arch and right coronary artery were measured by the fiber optic sensor. A standard invasive manometry was used as the reference. Finally, a 2.25 mm balloon was inflated in the catheter to simulate the stenosis and the BP drop was recorded by the fiber optic sensor. The experiment demonstrates that the reported fiber optic sensor has the capability of measuring blood pressure in vivo and can be used for FFR technique.