Patent ID: 7885783

Claim:
A remaining gas amount calculating device comprising: a gas container holding a specified gas; a decompression device arranged to depressurize the gas delivered from the gas container, the decompression device including a decompression device body having an inlet side and an outlet side; a gas pressure measuring device arranged to measure a pressure of the depressurized gas depressurized by the decompression device; and a remaining gas amount calculating device arranged to determine an amount of gas remaining in the gas container by calculating a pressure of the gas in the gas container based on the pressure measured with the gas pressure measuring device; wherein the decompression device is arranged such that the relationship between the pressure at the inlet side of the decompression device body through which the gas is provided and the pressure at the outlet side of the decompression device body through which the depressurized gas is delivered is a monotonical relationship so that when the inlet side pressure increases the outlet side pressure also increases and when the inlet side pressure decreases the outlet side pressure also decreases.