Septum stoppers are used to close the upper ends of tensiometers. This closure needs to be airtight, which is the case with septum stoppers. The SMS septum stoppers are made such that they fit tightly over the tops of the tensiometers. SMS septum stoppers are further improved with a thick layer of silicone inside the stopper. This allows the septum stoppers to be punctured repeatedly with a needle without causing an air leak in the stopper. With care the septum stoppers can be punctured 70 times before they need replacement.
To determine the soil water tension, a tensimeter is placed over the tensiometer. The tensimeter consists of a pressure transducer with attached needle. When placing the tensimeter over a tensiometer the needle penetrates the septum stopper on the tensiometer, allowing the pressure inside the tensiometer to be exposed to the pressure transducer through the needle. The measured pressure is shown on the attached handheld digital readout. Once the reading has been recorded, the tensimeter is removed from the tensiometer. For this system to work well, it is essential that the septum stopper remains airtight after each puncture. The SMS stoppers are designed to do this.
The septum stoppers need to be protected from exposure to light. This is best accomplished by placing a short piece of PVC pipe over the tensiometer with septum stopper. Cut a 6 cm (2.5 inches) long section of white PVC pipe (Sch 40 3/4 inch). Glue an end cap to one end of this section of pipe, and place it over the tensiometer.
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