Sensors & Transducers Journal

    (ISSN 1726- 5479)

Vol. 83, Issue 9, September 2007, pp.1521-1526

Study of a Modified Anemometer Type Flow Meter

S. C. Bera, ^*B. Chakraborty and D. N. Kole

Instrumentation Engineering Section, Applied Physics, University of Calcutta

92, Acharya Prafulla Chandra Road, Kolkata - 700 009, W.B. India

^*Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, West Bengal, India

E-mail: baduchak@yahoo.co.in

Received: 8 August 2007   /Accepted: 17 September 2007   /Published: 24 September 2007

Abstract: Flow rate of a fluid through a pipe line is one of the most important variables that are required to be measured and controlled in a process plant in order to obtain better quality product with lesser cost of production. There are various effects, like the effect of energy associated with a flowing fluid through a pipeline, Doppler effect and effect of speed of the fluid suction pump on the flow rate etc. have been utilized in designing the various flow meters. In the anemometer type flowmeter the cooling effect of a flowing fluid on a temperature sensitive resistance, thermister or p-n junction diode is utilized. It has been observed that the transducer output using these flow sensors varies non-linearly with flow rate and hence requires a linearization part in the instrumentation system. In the present paper a modified p-n junction cooling technique has been used to design a flow sensor, which gives an output, varying linearly with flow rate. In the actual installation, the flow head consists of a flow tube made of insulating material like PVC of specified diameter and length with flange joints at both ends. At the middle portion of the flow tube four identical p-n junction diodes with metallic-dissipating surfaces are placed in the same diametrical plane at right angles to each other. The four diodes are arranged to form a bridge configuration supplied with an AC voltage. The rectified DC output voltage across a series resistance is suitably processed. The principle of operation of the flow sensor has been explained in this paper. The flow head with the proposed flow transducer has been fabricated, functionally tested and the experimental results are reported in the paper. From these experimental data it has been observed that the transducer output follows a linear curve as explained theoretically.

Keywords: Anemometer, Flow sensor, p-n junction diode

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