Showing papers by "V. Jagadeesh Kumar published in 2006"
24 Apr 2006
TL;DR: The design and development of a virtual instrument for the measurement of haemodynamic parameters namely, pulse rate and oxygen saturation in arterial blood based on the popular photoplethysmographic (PPG) principle is presented.
Abstract: This paper presents the design and development of a virtual instrument for the measurement of haemo-dynamic parameters namely, pulse rate and oxygen saturation in arterial blood based on the popular photoplethysmographic (PPG) principle. A clip-on sensor, housing red and infrared (IR) light emitting diodes and suitable photo detectors is developed. The sensor is interfaced to a PC utilizing the audio channel of the sound card, thus dispensing with expensive analog to digital converter hardware. Since the frequency response of the audio channel is not suitable for the PPG waveforms of red and IR, FM modulation and demodulation are employed. An empirical relationship is developed for the computation of the oxygen saturation in arterial blood using the red and IR PPG data and the well-known and well-established extinction coefficients of haemoglobin with and without oxygen. Data acquisition and processing are accomplished under LabVIEW virtual environment.
27 citations
27 Mar 2006
TL;DR: In this paper, a switched capacitor, triple slope digital converter suitable for differential capacitive sensors is presented, which is dependent only on a pair of d.c. reference voltages and the clock frequency.
Abstract: A high accuracy switched capacitor, triple slope digital converter suitable for differential capacitive sensors is presented. The proposed technique accepts differential capacitive sensors possessing either linear or inverse characteristics and provides a linear capacitance to digital conversion. The output is dependent only on a pair of d.c. reference voltages and the clock frequency. Detailed analysis of the proposed scheme establishes that the sensitivity of the scheme to parameter variations is minimal. A prototype implemented and tested for a typical differential capacitive transducer of full-scale ±250 pF gave a worst-case error less than 0.05%.
23 citations
24 Apr 2006
TL;DR: A capacitance to digital converter that directly translates the changes in a differential type capacitive sensor to a proportional digital value is described in this article, which employs a suitably modified, dual-slope, analog to digital conversion technique.
Abstract: A capacitance to digital converter that directly translates the changes in a differential type capacitive sensor to a proportional digital value is described in this work. The proposed method employs a suitably modified, dual-slope, analog to digital conversion technique. Error analysis and results obtained from a prototype built around a micro-controller establish the efficacy of the proposed method.
9 citations
24 Apr 2006
TL;DR: In this article, a virtual instrument that determines the errors of an instrument transformer using a quasi-balance technique is proposed, operating on the secondary quantities of the test and standard transformers.
Abstract: Instrument transformers, namely, current and voltage (potential) transformers are characterized by their ratio and phase errors. A novel virtual instrument that determines the errors of an instrument transformer using a quasi-balance technique is proposed in this paper. Operating on the secondary quantities of the test and standard transformers, two independent quasi-balance conditions are obtained. The errors of the test transformer are then determined using the two quasi-balance settings alone. The method inherently possesses all the advantages of an ac bridge but dispenses with the tedious iterative balancing. A prototype unit built and tested establishes the practical viability of the proposed technique.
5 citations