| 摘要 |
PROBLEM TO BE SOLVED: To suppress the occurrence of measuring errors due to interference of the acoustic wave emitted from a loudspeaker with the other environmental noises, by eliminating the use of the loudspeaker sound source emitting the acoustic wave while changing the frequency in conventional technique. SOLUTION: A Helmholtz resonator is comprised of a gas phase section 4 above the liquid level 3 of fuel 2 stored in a fuel tank 1 and an acoustic tube 5. Operating sound of a fuel pump 6 is introduced into air in the resonator to vibrate it. This vibration is detected with a microphone and is converted to the electric signal. This signal is amplified with a micro-amplifier 8 and spectral analysis is carried out at a frequency analysis device 9 using FFT analyzer. Since the maximum value of spectrum is the Helmholtz resonance frequency of the resonator, volume of the gas phase section 4 is derived based on the resonance frequency and the fuel remaining quantity can be computed by subtracting that volume from the whole volume of the tank 1. COPYRIGHT: (C)2007,JPO&INPIT
|
