Paper Information

Journal:   INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE (ENGLISH)   Winter 2003 , Volume 14 , Number 1; Page(s) 121 To 140.
 
Paper: 

A NOVEL TECHNIQUE TO IMPROVE THE ACCURACY OF ULTRASONIC FLOWMETERS.

 
 
Author(s):  AZHARI S.J., MIRHOSSEINI S.H.
 
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Abstract: 
Ultrasonic transit time flowmeters, despite their popularity suffer from the poor accuracy at low values of flow rates and small pipe diameters, where time delays in the range of nanoseconds are to be detected. To overcome this problem, a novel technique is presented in this paper. We have named it "Time Expansion Method, TEM" in which the information carried by phase angles of high frequencies are transferred to low frequencies phase angles, causing the width of the relevant time gate to be expanded. As a result, at a specified flow rate and/or pipe diameter, the system resolution and accuracy is increased. In other words, at a given resolution and accuracy, the lower flow rates inside the narrower pipes can be measured. The theory of the method is developed and its most important parameters are formulated. To practicaly study the method a prototype flowmeter was designed and successfully tested. By applying the innovative "Time Expansion Method" the flow rate information at a frequency of 2500 Khz (the working frequency of ultrasonic piezoelectric transducers) was transferred to the much lower frequency of 200Hz, expanding the related transit time 12500 times, resulting an identical improvement flowmeter sensitivity. Consequently a flowmeter with much less sophisticatied structure and expense can measure an original transit time difference of about 25 picoseconds which matches flow rate sensitivity of about 0.2mm/s or 5.5 lit/ h in a 4" (100-mm) pipe.
 
Keyword(s): TIME EXPANSION METHOD, TRANSITIME FLOWMETERS, ULTRASONIC FLOWMETERS.
 
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