SOIL MOISTURE meter - ThetaProbe ML2x

accuracy +/-1% service free easy attachment to a recorder stable in the temperature and salinity functions for measurements in the portable and stationary sets

DESCRIPTION

The sensor ThetaProbe ML2x is used for measurement of soil moisture volume with high accuracy (estimate 1%). The sensor’s work principle is based on a measurement of standing wave signal coefficient of frequency 100MHz in a tested material. The sensor’s ML2x construction assures its predominance over other solutions, assuring precision and measurement credibility at moderate costs. The sensor is simple in use: after attaching it to an indicator and inserting in soil, the soil moisture measurement takes place within few sensors.  

Calibration

Assuring full 1% accuracy requires running accurate sensor calibration using a two point gravimetric method with application of the same soil, in which later on the measurements are going to take place. In the conventional usages many users are satisfied with lower accuracy estimate 5%. At such case the factory sensors calibration is enough.

Applications

 The typical applications of the sensor ML2x include watering, hydrology, environment monitoring and forestry etc. If an examination of a soil’s moisture profile in a depth function is required, then it is possible to apply few of such sensors placed at various depths, just like displayed on the pictures at the side. The sensors can be buried in soil at depth maximally up to 5 m or can be inserted in the holes previously prepared using an adequate device (soil drill). In order to make the sensors’ inserting in the long holes easier, their casings can be extended with the screw-top pipes of length  50 or 100 cm.

In gardening and agriculture the sensors ML2x can be used for various soil types, compost and other bases. Because the sensors are very small, they can be used for measurement even in the flower pots or can be buried horizontally in the cases. For correct functioning they require to be covered with a soil layer of minimum 50 mm in thickness.

When producing compost the sensors ML2x can be immediately placed in the prepared material, where they can tolerate the temperatures up to +70°C.  Measurement accuracy in the scope of temperatures +40...+70°C equals +/-2%, but a material’s density and pollutions can worsen the measurement’s accuracy and influence in a negative way the sensor’s durability. The sensors ML2x can be used for controlling the action of watering, because of their accuracy, easiness in use and quickness in obtaining a measurement result. Because of it, it is possible to optymalize the time of watering as well as switch the sensor into an automatic watering control.

The long lasting environment monitoring and climate supervision programs require registering of the mutual dependencies between soil and atmosphere. Soil moisture is in such inquires seen as even more important element of which measurement is allowed by among other the sensors ThetaProbe ML2x. The great majority of automatic weather stations can be enriched by one or few sensors ML2x.

Measurement readout and registry

The sensor ML2x is powered by voltage 5...15V, consuming energy of approximately 20 mA. The measurement result is led out form the meter in a form of a constant voltage value from the interval  of 0...1V. This signal can be directly measured and registered by the data-loggers (recorders) adjusted to analogous voltage measurements.

In case of using the sensor ThetaProbe ML2x in a portable version, for momentary control of soil moisture, it is possible to use a specialized pocket readout panel HH2.

In case of using a sensor in a meteorological station, based on the devices LB-741 or LB-486 LAB-EL, the sensors ML2x can attached to them using an analogue-digital converter LB-920.

TECHNICAL DATA

Scope of work temperatures	-20..+70°C
Powering voltage	5..15 VDC
Energy consumption	20 mA
Scope of the output voltages	0..1 VDC
Overall dimensions