| 摘要 |
PROBLEM TO BE SOLVED: To obtain a variable-volume apparatus by which the volume of a voluminous body to be measured can be measured and a leakage tester can be calibrated with high accuracy and efficiently by a method wherein a piston inserted into a cylinder is moved freely between two stop positions to obtain a volume change of a prescribed amount. SOLUTION: A piston 120 is stopped in a stop position I with reference to a cylinder 110. Compressed air under the known same pressure P0 is supplied to a voluminous body 10, to be measured, and a reference volume body 20. Then, the volume V0 of the voluminous body 10 to be measured becomes a value obtained by adding a volume between the piston 120 and the cylinder 110 to the volume of a connection passage 111. Then, when the piston 120 is moved to a stop position II, the volume between the cylinder 110 and the piston 120 is increased byΔV, and the pressure of the voluminous body 10 to be measured is changed to P0-ΔP, and its volume is changed to V0+ΔV. Then, when the volume V0 is known, a gas-pressure change amountΔP is found based on the volume V0, the pressure P0 and the volume change amountΔV, and a differential pressure gage 30 is calibrated. On the contrary, when the volume V0 is unknow, the volume V0 is found based on the known voluminous body pressure P0, the volume change amountΔV and the gas-pressure change amountΔP which is read out from the differential pressure gage 30.
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