Circuit for Approximate Computation of Reciprocal of Time Delay to Maximum Cross Correlation

1971 ◽  
Vol 42 (5) ◽  
pp. 616-618 ◽  
Author(s):  
W. R. Tompkins ◽  
M. Intaglietta
Keyword(s):  
Time Delay ◽  
Cross Correlation ◽  
Approximate Computation

scholarly journals Time Delay Estimation in Two-Phase Flow Investigation Using theγ-Ray Attenuation Technique

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Robert Hanus ◽  
Marcin Zych ◽  
Leszek Petryka ◽  
Dariusz Świsulski
Keyword(s):  
Time Delay ◽  
Cross Correlation ◽  
Two Phase Flow ◽  
Time Delay Estimation ◽  
Delay Estimation ◽  
Phase Flow ◽  
Two Phase ◽  
Stochastic Signals ◽  
Difference Function ◽  
Combined Methods

Time delay estimation is an important research question having many applications in a range of technologies. Measurement of a two-phase flow in a pipeline or an open channel using radioisotopes is an example of such application. For instance, the determination of velocity of dispersed phase in that case is based on estimation of the time delay between two stochastic signals provided by scintillation probes. The proper analysis of such signals, usually in presence of noise, requires the use of advanced statistical signal processing. In this paper, the simulation studies of time delay estimation were carried out with the use of the following differential methods: average magnitude difference function, and average square difference function and proposed combined methods comprising the above-mentioned differential and cross-correlation functions are presented. Attached simulations have been carried out for models of stochastic signals corresponding to the signals obtained in gamma-ray absorption measurements of gas-liquid flow in a horizontal pipeline. The standard uncertainties of time delay estimations have been determined for each of the methods. Improved metrological properties have been stated in the combined methods in comparison with the classical cross-correlation procedure.

Experimental Comparison of GCC-Based Time Delay Estimation Methods for Ultrasonic Leak Detection in Compressed Air System

2012 ◽  
Author(s):  
Pingping Liao ◽  
Maolin Cai ◽  
Xiangheng Fu
Keyword(s):  
Standard Deviation ◽  
Time Delay ◽  
Cross Correlation ◽  
Leak Detection ◽  
Time Delay Estimation ◽  
Compressed Air ◽  
Delay Estimation ◽  
Estimation Methods ◽  
Experimental Comparison ◽  
Success Rates

Air leakage is one of the most significant energy waste factors in compressed air systems which account for about 10% of total industrial energy consumption. It is estimated that about 10%∼40% of the compressed air is wasted through leakage in most plants. A new ultrasonic leak detection method based on time delay estimation (TDE) is proposed to locate the compressed air leak for preventing energy waste in pneumatic systems. The accuracy of detection is highly dependent on the performance of the TDE method. Performances of six typical TDE methods based on generalized cross correlation (GCC) are compared, and these methods are the basic cross correlation (BCC), the Roth impulse response, the phase transform (PHAT), the smoothed coherence transform (SCOT), the WEINER processor, and the Hannan-Thomson (HT) processor. The experimental results show that: Firstly, the accuracy and precision of time delay estimation increases with the observation interval for all these methods. Secondly, the success rates of Roth, PHAT, SCOT and HT are much higher than that of BCC and WEINER, among which the HT processor performs best with a highest success rates closely followed by the PHAT processor. Thirdly, the HT processor which is a maximum likelihood estimator gives the minimum standard deviation of the time delay estimate; however, the standard deviations of all these GCC methods are very small. The HT processor outperforms other GCC methods in terms of success rate and standard deviation. Consequently, it is preferable to apply the HT processor for this particular purpose.

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