| 摘要 |
A single-rod measuring chain, especially for measuring pH, comprising a cylindrical glass tube which is closed at the top and bottom and in which there is an electrolyte. Arranged in the glass tube there is a measuring electrode and a reference electrode. Said electrodes are connected, by means of electrical connections, to electric terminals disposed at the upper end of the glass tube. Disposed at the lower end of the glass tube there is a diaphragm. A drawback of the known arrangements is that the diaphragm can be contaminated by the measuring medium and, for example, can be blocked by silt. As cleaning of the diaphragm is impossible, the measuring chain becomes unusable after a certain time. In the new arrangement, the glass tube in its lower section has an orifice which is closed by a sleeve encircling the glass tube. Said sleeve consists of a porous, electrically non-conductive material, for example porous polytetrafluoroethylene. The sleeve can be pulled off the glass tube and be cleaned and is then reusable, so that the service life of the measuring chain is not limited.
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