Development and validation of an acoustic-electrical joint testing system for hydrate-bearing porous media

Acoustic and electrical properties are fundamental and important physical properties to characterize hydrate-bearing sediments. A new experimental system called Ultrasound Combined with Electrical Impedance was developed for jointly testing the ultrasonic wave parameters and electrical impedance of hydrate-bearing porous media in the hydrate formation and decomposition processes. The Ultrasound Combined with Electrical Impedance system features its novel ultrasonic-electrical compound sensors and sensor array, fully controllable instruments, variety of sampled data, and flexible working modes. Experiment was carried out with methane gas as the hydrate former, meanwhile the acoustic/electrical parameters were derived. The acoustic/electrical properties were characterized with the aid of typical models such as the time-average equation, Wood’s equation, weighted equation, and Archie’s formula. It has been shown by the results that key parameters such as the sound velocity and electrical impedance can be used to characterize the acoustic and electrical properties of hydrate-bearing sediments conjointly, demonstrating the applicability of the proposed Ultrasound Combined with Electrical Impedance system. The wavelet-analysis based denoising approach and singularity detection method are effective denoising methods to filter the ultrasound signals and to identify the arriving time of the ultrasonic wave. The weighted equation and Archie’s formula with a segmented regression method are recommended for modeling the relations between the hydrate saturation and sound velocity/impedance modulus, respectively.

Study on Measuring the Resonant Frequency of Air Core Transformer on Mass Spectrometer with a Test Coil

Air core transformer is an essential part of mass spectrometer. Test coil is often used to measure its resonant frequency with the advantages of easy installation and high sensitivity. However, the influence of test coil while it is installed close to the working coils on the transformer is not studied before. To reveal the influence of test coil and determine the right position to install, two experiments using test coil and opened probe respectively for the measurement are conducted. Since the opened probe has little load effect on the original transformer impedance system, it can be used to validate the influence of test coil. By comparing the two experimental results, we find that the right position to install the test coil is on the further side of the primary coil to the secondary coil. This work allows us to integrate the test coil with the air core transformer to monitor the resonant frequency in real-time.