| 摘要 |
A method of, and apparatus for, liquid sampling by way of a self contained unit provides for: 1) the periodical coupling of a pressurisable sample chamber to a source of sub-atmospheric pressure to cause a bulk sample of liquid for sampling to be drawn into the chamber from a body of liquid by a first passage; 2) the retention of a sample volume thereof in the chamber while allowing surplus liquid from the bulk sample to drain from the chamber by way of the first passage; and 3) allowing the retained sample volume to pass out of the chamber by way of a second passage under the control of a delivery valve wherein the periodical coupling of the sample chamber to a source of sub-atmospheric pressure is undertaken by way of a valve system comprising first and second flexible tubes, the first flexible tube linking a source of air at atmospheric pressure to the chamber and the second tube linking a source of air at sub-atmospheric pressure to the chamber: and a first clamping device in the form of a cam which can, depending on the disposition of the cam, alternately: i) distort the first tube to prevent the chamber communicating with the sub-atmospheric source while allowing the chamber to communicate with the atmospheric source by way of the second tube; ii) distort the first tube to prevent the chamber communicating with the atmospheric source while allowing the chamber to communicate with the sub-atmospheric source by way of the second tube. |
