What do I measure ?

The total soil water suction in the tensiometer tube (also known as soil water potential or hydraulic charge)


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…

The SKT 850 pressure sensor is built for field use and has a 0 to -999 HPa (mbar) measuring range.

The SKT 850 sensor has its own temperature correction (-10°C /+50°C).

The sensor is light (60 grs) and small.

The SKT 850 sensor is compact, waterproof and is built for outdoor as well as indoor use.

The SKT 850 sensor will be strongly fixed to any tensiometer.

The SKT 850 sensor exists in two versions : differential voltage or current loop output (4-20 mA).

You can choose between ordering the sensor alone or fixed to a tensiometer (all lengths are possible). Please, consult us.

Key Advantages

MONITORING (by connection to a data logger)

Electronic sensor sensitive to frost & to overpressure (ex : if the operator pushes too hard on the silicone stopper)


Measuring range : 0 Hpa to -999 Hpa.
Accuracy : better than 1% of full scale.
Pressure sensor : differental pressure type with integrated temperature compensation.
Offset : factory calibrated. Each sensor is delivered with an individual calibration certificate.
Measuring process : by putting the sensor’s inlet into the tensiometer’s tube. The sensor can be fastened to any existing tensiometer (manufactured by SDEC France or any other manufacturer).
Also fixable : on a TENSIONIC tensiometer tube (let us know when ordering).
Fastening system : stainless steel clamp collar.
Output : On cable across nickel stuffing box.
Power supply : direct current; +6 to +15 Volts.
Electric protection : the sensor is electronically protected against polarity reverse (SKT 850C2 model).
Temperature compensation : -10°C to +50°C.
Sensor case : The case is made out of PVC and special resin. The case is waterproof (IP67).
Dimensions : Ø = 50 mm x 40 mm.
Weight : 185 gramms.
Operating temperature : -10°C à + 50°C.
Storage temperature : -20°C à + 60°C.

The standard set

The SKT 850 is delivered either alone or fixed to a tensiometer tube (SMS model, ref. SMS 2000 or SMS 2000S, or TENSIONIC) if you choose to order them together.

You also need

Tensiometer tubes. You can choose between the standard tensiometer tubes (ref. SMS) and, the microtensiometers with flexible tubes. Anti-frost liquid must be added to the water to protect the sensor.

Is the measurement taken in air or water ? 

The tensiometer tube is full of water but there is some air captured underneath the stopper. The part which is connected to the pressure sensor is meant to measure the air pressure in the tube and must therefore dip into this air and not into water.

How is the sensor powered ? 

By the battery supply of the datalogger.

Are the tensiometer tubes included when ordering the sensors ? 

The price of the sensor doesn’t include the tensiometer tube. But you can either order the sensor alone or fixed to a tensiometer tube.

Which type of output should I choose ? 

You can choose between a differential voltage or current loop output. This choice depends on you data logger input. Usually, for cable length lower than 50 m, we recommend the choice of a voltage output (requires a stabilized power supply). For cable length longer than 50 m, you must choose a current loop output (suitable for cables of hundreds of meters).

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