V. Jagadeesh Kumar

Bio: V. Jagadeesh Kumar is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Signal conditioning & Capacitive sensing. The author has an hindex of 15, co-authored 83 publications receiving 637 citations. Previous affiliations of V. Jagadeesh Kumar include Indian Institutes of Technology.

A linear Tunneling Magneto-Resistance angle transducer

Abstract: A new Tunneling Magneto-Resistance (TMR) based angle transducer realized with a novel Signal Conditioning (SC) scheme that accepts TMR angle sensing elements possessing sine/cosine output characteristics and provides a final output that changes linearly with the angle being sensed over a full-circle range (0–360°) is presented in this paper. The proposed scheme converts the angle being sensed by the TMR sensing elements into an equivalent phase shift of a sinusoid, whose amplitude is dictated by the flux produced by the permanent magnet employed in the transducer. The phase of the sinusoid is then converted as an output voltage that is dependent only on the phase angle and not on the magnetic strength. Thus even over a long period, over which the strength of the permanent magnet may decay, the accuracy of angle sensing is preserved. A prototype angle sensor, using a TMR IC, and proposed SC circuit has been built and tested. The output of the transducer was found to be linear across the entire 0–360°. The worst-case error observed for the transducer was less than ± 0.85 % of the full-scale while that for the SC unit alone was less than ± 0.1 %.

An auto-balancing signal conditioning scheme for non-contact measurement of conductivity of water

Abstract: This paper presents a signal conditioning approach to measure resistance and hence conductivity of water in an insulating tube through capacitively coupled electrodes. In the scheme presented, the electrodes are electrically insulated from water and measurement is taken through couple of capacitances formed between the electrode and water column. The capacitive coupling overcomes the problems of electrode polarization and contamination associated with conventional contact based approach of conductivity measurement of water. The large reactance of the coupling capacitors, compared to the resistance of the water column under measurement, is a challenge. Moreover, the variations in the coupling capacitor over time presents another challenge. The auto-balancing signal conditioning scheme presented here overcome these challenges by providing an output that is directly proportional to the resistance under measurement and is independent of the value of the coupling capacitors. Test results on a prototype of the proposed circuit show that the maximum error in the resistance measurement is less than 0.9 % and the output is independent of the coupling capacitors.

Validation of capillary electrophoresis method for determination of N-methylpyrrolidine in cefepime for injection.

Abstract: The present study relates to a new capillary electrophoresis method for the determination of N-methylpyrrolidine, an impurity considered to be toxic and also potential degradation impurity in cefepime hydrochloride drug substance. The newly developed capillary electrophoresis method for determining the content of N-methylpyrrolidine in cefepime for injection has been validated as per International Conference on Harmonization (ICH) guidelines to prove the selectivity, sensitivity, suitability, robustness, and ruggedness of the method. This simple, efficient, and rapid methodology may be used by pharmaceutical industry for routine analysis as well as during stability studies. The newly developed capillary electrophoresis method to determine the content of N-methylpyrrolidine in cefepime for injection requires 10 min for data acquisition, and uses an indirect UV photometry method to detect the analyte signal at 240 nm against the reference signal at 210 nm. The electrophoretic system is optimized to get stable base line, higher signal to noise ratio and peaks with narrow peak width. The method employs bare fused silica capillary with extended light path, effective length of capillary is 56 cm and inner diameter of capillary is 50 μm, 5 mmole of imidazole buffer adjusted to pH 5.1 with 3 molar acetic acid solution is used as background electrolyte. The sample is introduced in hydrodynamic mode employing pressure of 50 mbar for 5 s, and the desired separation is achieved with constant applied voltage of 25 kV at ambient temperature (~25°C).

Photoplethsymography for non-invasive diagnostics

Abstract: Photo-plethysmo-graphy (PPG) is a noninvasive method of obtaining a signal proportional to blood volume changes using light. From the initial trials seven decades back, the PPG technique has grown leaps and bounds and today its application has become indispensible not only during surgical procedures but also in patient monitoring in critical care environment. This paper traces the path of advancement of this technique and highlights the research outcomes of an "Indo German" collaborative research between Indian Institute of Technology Madras, Chennai, India and Technical University (RWTH) Aachen, Germany funded by ministry of science (BMBF), Germany, Research projects funded by Department of Science and Technology and Department of Biotechnology, Government of India.

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

Abstract: 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.