What do I measure ?

With a pressure sensor (either hand held or fixed to the tube), you can measure the total soil water suction



Precise management of irrigations.
Management of adjusted water stress levels for seed production.
Studies on water bulbs in soils.
Water stress management for modeling.
Checking water potential levels before starting a soil solution sampling campaign.
Following water percolation periods.
Water potential measurements in unsaturated soils.
Soil water caracteristic curves.
Studies on water flows : percolation…
Studies on water ressources : refilling of the water table

The SMS series tensiometric tubes are designed to be used with the electronic hand held meter, ref. SMS 2500S. SDEC France’s tensiometer tubes are also compatible with all other tensimeters on the market (compatible outer diameter).

The functioning principle of the SMS tensiometer tubes is based on the use of a hypodermic needle to measure the suction in the tube through a special septum type stopper. To make the measurement, the meter is set on the top of the tensiometric tube. A special silicon stopper is used to close the tube. It is filled with a synthetic compound with self-sealing properties. The meter uses the needle to pierce the stopper at the top of the tube, and measures the vacuum (suction) inside. Due to its special design, the stopper remains airtight (it can stand up to 500 piercings without leaking). The porous ceramic SDEC 2150 used on the SMS series tensiometric tubes enables it to make measurements over -850 mbar. No air will be able to enter in this range of vacuum, thanks to the excellent porousness characteristics of SDEC ceramics.

The main interest, therefore, of this technique, lies in the multiplication of the tensiometric measurements at a low cost, since only one electronic meter is needed for many tubes. This technique is well adapted to agricultural research, and soil science in particular.

Key Advantages



Tensiometer tube : U.V resistant transparent P.V.C.
Tube dimensions : inside Ø = 15,4 mm. outside Ø = 21,5 mm.
Weight : 150 to 550 grams (depending on the length of the tube).
Porous ceramic cup : SDEC 2150
Air entry value : 1,5 Bar.
Hydraulic conductivity : 5,5 . 10-7cm.s-1.
Connection ceramic/tube : with special glue under vacuum.
Stopper : silicone with special stuffing (TECSIL 2034).
Life time of stopper : More than 500 punctures.

The standard set

The SMS 2000 tubes are delivered equiped with a porous ceramic glued on the PVC tube and a specific silicone stopper. The pressure sensor must be ordered separately.

You also need

. A pressure transducer to measure the soil water succion, either hand held, ref. SMS 2500S,or electronic, ref. SKT 850 . An auger to install the tube in the soil, ref. STM 21600 . A preparation syringe, ref. STM 21750

 Do the tensiometer tubes need to be prepared ? 

As all tensiometers, these tubes have a porous ceramic cup glued on the bottom. Before placing them into the soil, the ceramic must be saturated with gasless water. This can be done with a vacuum syringe, type STM 21750.

 Does the needle create an air leak ? 

A negligible amount of air can enter the SMS tensiometer tube when poking through the silicon stopper but without consequences on the measurement. After taking out the pressure sensor, the silicon stopper will seal back leaving a perfectly airtight tube. It can stand more than 600 pockings.

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