TMS11A - Soil tensiometers
Characteristic properties
- Measuring range of suction pressures from 0 to -65 kPa
- Water level measurement (sensor flooding) from 0 to 3 m level
- Ceramic head with a diameter of 25 mm
- Filling the soil tensiometer built-in capillaries without removing the sensor from the measuring point
- Included in the set 4 input evaluation module TM4
- Automatic compensation of atmospheric air pressure in the evaluation module (soil tensiometer including cable connection can be flooded for a long time)
- Digital data output via RS485
- Output compatible with FIEDLER telemetry and recording units
Basic description
The TMS11A soil tensiometer is used to measure the suction pressure, which is caused by the action of capillary forces of water-unsaturated soil. For example, the suction pressure is overcome by the plants in obtaining moisture and also affects the transport of moisture and solutions through the soil.
The TMS11A soil tensiometer is also able to measure the hydrostatic pressure of the water column if the strain gauge head falls below the current groundwater level.
The ceramic head of the soil tensiometer with a defined pore size mediates the transfer of negative and positive pressures from around the tensiometer to the liquid inside the tensiometer. The value of the pressure in the liquid is measured by an accurate pressure sensor supplemented by a measuring transducer. Together with the soil temperature, the measured values are transmitted in digital form to the connected evaluation module TM4. Up to 4 TMS11A soil tensiometers can be connected to one TM4 module at the same time. The length of the connecting cable between the tensiometers and the module can be up to 15 m.
The TM4 evaluation module corrects the absolute pressure obtained from the soil tensiometer by the value of the atmospheric air pressure. The atmospheric air pressure sensor is located in the TM4 module. The resulting calculated vacuum-overpressure in the soil is transmitted to the connected recording unit (datalogger) via the RS485 bus.
Temperature compensated sensor
The core part of the TMS11A soil tensiometr is a very accurate absolute pressure sensor with a built-in temperature sensor. The sensor has already set temperature correction coefficients during its production, which eliminate its temperature dependence. The error of pressure measurement is thus less than 0.3 kPa in the whole measuring range and the long-term time stability of the sensor is better than 0.1 kPa / year.
Installing TMS11A
The TMS11A soil tensiometr has a diameter of 25 mm and is available in various lengths from 20 to 100 cm. The upper end of the tensiometer is terminated by a cable gland, through which a 3 m long communication cable is led out of the sensor. This cable can be extended to a maximum of 10 m.
In addition to the cable, filling and venting capillaries are also led out of the cable gland. After installation of the soil tensiometer to the required depth in the soil, it is therefore suitable for the upper end of the sensor to be permanently accessible precisely for the possibility of replenishing the tensiometer with deaerated water.
Technical parameters
Sensor head dimensions: diameter 25 mm, length 60 mm
Ceramic head air inlet value: - 65 kPa
Sensor body material: Tecaform
Sensor body dimensions: diameter 25 mm, optional length 200 to 1000 mm
Measurement of suction pressures in the range: 0 kPa to -65 kPa
Water level measurement (sensor flooding): 0 to 3 m water column
Pressure measurement accuracy: 0.3 kPa
Soil temperature measurement in the range: 0 to +50 ° C
Temperature measurement accuracy: 0.3 ° C
Filling system: detachable capillaries with a diameter of 1 mm, filling without removing the sensor
Power and communication cable: 4-core PUR cable, length 3 m, M12 connector
Sensor power supply: Unap 3.3 V DC / max 1 mA from TM4
Protection: IP67
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