Photoplethysmography and its application in clinical physiological measurement

http://www.kresttechnology.com/krest-academic-projects/krest-major-projects/ECE/B-Tech%20Papers/67.pdf

ECG signal denoising and baseline wander correction based on the empirical mode decomposition

Oscillating-water-column wave energy converters and air turbines: A review

McDonaldʼs Blood Flow in Arteries

Photoplethysmography (PPG) is a noninvasive optical technique for detecting microvascular blood volume changes in tissues. Its ease of use, low cost and convenience make it an attractive area of research in the biomedical and clinical communities. Nevertheless, its single spot monitoring and the need to apply a PPG sensor directly to the skin limit its practicality in situations such as perfusion mapping and healing assessments or when free movement is required. The introduction of fast digital cameras into clinical imaging monitoring and diagnosis systems, the desire to reduce the physical restrictions, and the possible new insights that might come from perfusion imaging and mapping inspired the evolution of the conventional PPG technology to imaging PPG (IPPG). IPPG is a noncontact method that can detect heart-generated pulse waves by means of peripheral blood perfusion measurements. Since its inception, IPPG has attracted significant public interest and provided opportunities to improve personal healthcare. This study presents an overview of the wide range of IPPG systems currently being introduced along with examples of their application in various physiological assessments. We believe that the widespread acceptance of IPPG is happening, and it will dramatically accelerate the promotion of this healthcare model in the near future.

/pdf/photoplethysmography-revisited-from-contact-to-noncontact-2jla840amb.pdf

Photoplethysmography Revisited: From Contact to Noncontact, From Point to Imaging

This paper presents a non-contact inductive and capacitive coupled method of measurement of conductivity of liquids. The current through a pre-set column of liquid is established through induction. The voltage drop across the preset column of liquid is measured through capacitive coupled electrodes. The absence of contacting electrodes ensures that the method is free from effects due to contamination / corrosion of electrodes. The method proposed ensures that the measurement of the voltage drop across the column is independent of the values of the coupling capacitances of the capacitive coupled electrode. Hence, any deviation in the fabrication of the probe has negligible influence on the measured conductivity. Results obtained from a prototype unit built and tested show that the maximum relative error in the conductivity measurement is $ and the measured conductivity values are independent of the values of the coupling capacitors.

Inductive-Capacitive Coupled Probe for Non-Contact Measurement of Liquid Conductivity

This paper presents a new non-contact displacement sensor employing a combination of variable reluctance technique and Hall effect sensing. The sensor head is made of ‘E’ type soft ferromagnetic core, a permanent magnet and a couple of Hall sensors. The sensor head moves on two identical soft ferromagnetic elements. The final output of the sensor, obtained by determining the ratio of the difference and sum of the Hall sensor outputs, is proportional to the relative displacement between the sensor head and the soft ferromagnetic core elements. Since the output is insensitive to the actual value of the strength of the permanent magnet, any change in the magnetic strength of the magnet (either due to decay or misalignment) will not affect the performance of the proposed displacement sensor. Finite Element Analysis of the proposed sensor and the results from the subsequent linearization approach establishes the efficacy of the proposed sensor.

A novel variable reluctance-hall effect transduction technique based displacement sensor

Direct Digital Converter (DDC) suitable for resistive sensor elements connected in the form of bridge provides a digital output proportional to quantity being sensed. However, such a DDC requires that all the four sensor elements are to be identical. If there is a mismatch between the sensor elements (nominal values of the four resistances not equal) the error in the output of the DDC increases drastically. We now present a modified DDC that can tolerate mismatch between the four sensing elements of a bridge type resistive sensor. While the worst case error observed from the conventional DDC scheme rises from ± 0.07% to ± 1.32 % (simulation studies) for a very low mismatch of 0.03 %, the worst case error observed from the improved DDC scheme proposed here is only ± 0.24%.

A modified Direct Digital Converter for resistive sensors in bridge form

A novel signal conditioning circuit suitable for push- pull type capacitive transducers is proposed. The circuit developed is capable of providing a linear output over a wide range of values of the physical quantity being measured even when the transducer output has an inverse relationship with the measurand. The push- pull type capacitive transducer becomes an integral part of a relax- ation oscillator, the duty cycle ratio of the output of which becomes proportional to the measurand. The various sources of error in the circuit are analyzed, and quantitative expressions to estimate such errors are derived. Results obtained from tests on a prototype in- dicate that the circuit possesses very low errors. Index Terms—Capacitive transducer, relaxation oscillator, signal conditioning.

http://ieeexplore.ieee.org/iel5/19/4061067/04061093.pdf

Novel Signal Conditioning Circuit for Push-Pull Type

This paper presents a new technique based on comparison method of testing to distinguish an annealed magnetic sample from a non-annealed sample of same dimensions. In order to perform this test, a suitable magnetic fixture that can accommodate test samples of various inner and outer diameters has been developed and described in the paper. The paper also gives details of a virtual instrument that has been developed to perform the comparison method of testing for the annealed samples. Using the developed instrument, the samples can be tested after the manufacturing process without any further machining. The performance of the developed instrument has been verified by conducting measurements on different samples of known magnetic properties. The instrument developed distinguished the annealed samples from the non-annealed samples accurately.

V. Jagadeesh Kumar

Papers

Inductive-Capacitive Coupled Probe for Non-Contact Measurement of Liquid Conductivity

A novel variable reluctance-hall effect transduction technique based displacement sensor

A modified Direct Digital Converter for resistive sensors in bridge form

Novel Signal Conditioning Circuit for Push-Pull Type

Virtual instrument to measure the magnetic properties of annealed components