Papers by Author: Lee Long Han

Abstract: . This study presents the dynamic calibration of pressure sensors using a developed liquid step wave generator. This approach is sufficient to display the transient response of pressure sensors in the time and frequency domains and it depends on the performance of pressure generators. In this study, the liquid step wave generator was developed via a reformed spool valve generating a liquid step wave with a short rise time that current generators have not achieved so far. A small sensing cavity, where maintains the liquid step wave, and a contact seal were adopted herein to limit the pressure transient of the fluid in the generator, such that the rise time and the bandwidth of the liquid step wave can reach 30.0 µs and 10.4 kHz. The experimental results not only display the performance of the liquid step wave generator, but also reveal the dynamic characteristics of three different test pressure sensors using the developed liquid step wave generator.

Abstract: One hydraulic pressure generator has been developed with a unique rotating valve and the waveform of generated waves is approximately square-like shape under the low rotating speed. The generated wave has advantages for research in the dynamic characteristics of hydraulic components. The unique rotating valve consists of a rotor and stator which have a number of rectangle grooves precisely milled on the peripheries of the rotor and stator as fluid channels. The rotating rotor alternately switches the fluid channels to open and close state, therefore the waveform is close to square in principle. The pressure transient on the generated wave plays a major role and influences dynamic performances of generated wave. For analyzing the performances of the generator, one sensitivity pressure transducer mounted on the outlet of the generator to measure waveform in time domain. In addition, through Fourier series expansion the spectrum of generated waves clearly indicates the harmonic components of generated waves. Results show the waveform is close to square-like under the low rotating speed in time domain. In the frequency domain, the spectrum of the generated wave demonstrates the bandwidth is abundant. Thus, the generator could be one kind of function generator to performing the calibration of the hydraulic components.

Abstract: The purpose of this paper is to analyze and compare the dynamic characteristics of various structure pressure sensors using the Improved Pressure Square Wave Generator (IPSWG). The developed IPSWG is a signal generator that creates pressure square waves as an excitation source. The dynamic characteristics of pressure sensor in hydraulic systems can be measured and evaluated effectively due to the high excitation energy. The method is also useful for dynamic testing and characterization for a high frequency range, which cannot be performed by the traditional methods, such as the hammer kit excitation, sweeping frequency pressure wave, and random frequency wave. Result shows that piezoelectric sensors (quartz) have a largest gain margin and overshoot. The strain gauge sensor has a smaller gain margin and overshoot. The piezoelectric sensor is more suitable for measuring dynamic pressure.