Ikram Rabbani Pakistan Studies Book Pdf confbron
This book will help CSS PMS Aspirants in the Pakistan affairs paper. This book is available to download in pdf in Urdu version free of cost.1. Field of the Invention The invention is related to a non-contact sensor for measuring body parameters, in particular for measuring an electric conductivity of a blood stream. 2. Description of the Prior Art Blood, e.g. the human blood, exhibits a very high electrical conductivity which has to be taken into consideration when it is determined whether an area of the blood stream is flowing or not. Usually a very high conductivity of the blood requires a very high contact area between sensor and blood. The electrical conductivity of the blood can be determined using an optical method, which is usually based on the use of so called Faraday-diodes. By illuminating the patient's arm with light the light intensity is modulated and measured by a receiver, e.g. a photo detector. This method has the disadvantage that the optical system has to be positioned near the patient and that the patients should be able to look at the optical system. Additionally this measurement method is less accurate because of the use of optical light which is influenced by other factors than the blood flow. It is also possible to determine the electrical conductivity of the blood stream by providing the blood stream with a very high alternating voltage at a predetermined frequency. The electrical conductivity of the blood is determined from the magnitude of the impedance of the blood stream in the defined frequency range. This method is usually not suitable for measuring the conductivity of the blood stream with great accuracy, since the magnitude of the impedance in the defined frequency range may vary if the blood flow is too low or too high, in particular in the case of fast blood flow. U.S. Pat. No. 5,076,032 shows a blood conductivity measuring device comprising an injection needle attached to an implantable piezoelectric transducer, which is vibrated by the transducer in order to penetrate the skin and the tissue down to the blood stream. The transducer is also vibrated to measure the mechanical impedance of the tissue penetrating the tissue and thereby detecting the blood flow, so that the measured impedance can be correlated with the conductivity of the blood. When using the known measuring device the measuring accuracy is rather low, since the penetration depth of the needle depends on the blood flow which varies during the measurement and since the measured impedance depends on the tissue thickness.