Method of detecting residual quantity of gas in cassette type gas cylinder and apparatus thereof

PCT No. PCT/JP95/01524 Sec. 371 Date Apr. 2, 1996 Sec. 102(e) Date Apr. 2, 1996 PCT Filed Aug. 1, 1995 PCT Pub. No. WO96/04512 PCT Pub. Date Feb. 15, 1996A gas cylinder joined to a gas appliance. Based on the knowledge that a resonance frequency of cassette type gas cylinder does not vary with a residual quantity of gas therein a transmitter and a receiver are placed in positions opposed to a weld zone of the trunk portion of the gas cylinder and which permits an output voltage of the receiver with respect to a residual quantity of the gas to be detected at a specific resonance frequency of the gas cylinder. The resonance frequency is not lower than a predetermined level, the residual quantity of a liquefied gas in the cylinder being detected by transmitting the specific resonance frequency signal from the transmitter and detecting a reception output of not lower than a predetermined level by the receiver. This enables a residual quantity of the gas in the liquefied gas containing cassette type gas cylinder to be detected reliably from the outside.