5TE Soil moisture, Temperature and Conductivity Sensors

5TE Soil moisture, Temperature and Conductivity Sensors Description：

User's Manual

The 5TE sensor determines soil moisture content, conductivity, and temperature at an oscillating frequency of 70MHz. The water content is determined by measuring the dielectric constant of the soil. The thermistor at the base of the triforked probe measures the soil temperature, and the conductivity is measured by screws in the middle of the surface of two of the probes. Background In 2006, Decagon developed 5TE by combining EC-5 and ECH2O-TE. Using the same theoretical basis as ECH2O-TE, 5TE can also measure soil moisture content, conductivity and temperature at the same time. The difference is that the 5TE uses stainless steel screws to determine the conductivity, while the ECH2O-TE uses gold-plated wire. In contrast, the 5TE is designed to be more robust and corrosion-resistant. In addition, 5TE uses a 5-point calibration of the dielectric constant, which is more accurate than the ECH2O-TE.

Measurement Theory

Volume moisture content 5TE The permittivity of the surrounding medium is determined by the principle of electromagnetic field. The sensor provides an oscillating electromagnetic wave of 70MHz, which charges the sensor according to the dielectric constant of the medium. The stored electricity is proportional to the dielectric constant and volumetric water content of the soil. The 5TE microprocessor measures the amount of charge and outputs the dielectric constant value. Temperature 5TE uses a thermistor mounted on the surface to measure temperature. It is located under the black plastic housing at the base of the forked probe, near one of the probes, and measures the temperature of the probe surface. 5TE normally outputs in °C, unless otherwise specified in the preferences file in the ECH2O DataTrac or ECH2O Utility program. It should be noted that if the black plastic housing at the base of the probe is in direct sunlight, the temperature reading will be very high. At the same time, direct sunlight can also seriously affect the service life of the sensor. It is recommended not to expose the plastic housing part to sunlight when installing the sensor.

EC

Electrical conductivity (EC) is an index used to characterize the ability of a substance to conduct current, and can be used to infer the content of polar molecules in a solution. The conductivity is determined by applying a changing current to the two electrodes to determine the impedance between the electrodes. The conductivity is equal to the reciprocal of the impedance multiplied by the unit constant (distance between electrodes/electrode area). 5TE determines EC using a dual probe array located on the stainless steel screws of two of the forked probes. The trace oil on the skin will greatly affect the accuracy of EC determination after contact with the screw. If this happens, please refer to the cleaning section at the end of the manual to clean the screws. 5TE measures the volume conductivity of the surrounding medium (bulk EC). The calibration values of bulk EC at the factory guarantee an accuracy of ±10% in the conductivity range of 0 to 7dS/m. This accuracy range fully meets most field, greenhouse and nursery measurements. However, the conductivity of soil with high salt content will be higher than the above calibration range. The measurement range of 5TE can be up to 23.1 dS/m bulk EC, when the bulk EC is higher than 7 dS/m, the user needs to calibrate. In addition, EC measurements above 7 dS/m are very sensitive to grease on the electrode surface. If you are measuring saline soil, be sure to read the sensor cleaning section at the end of the manual.

Data Acquisition Communication

When the excitation voltage is turned on, the 5TE is measured. Within the excitation time of 50ms, the 3 parameters were input in ASCII code. 1200 baud rate 8-bit asynchronous continuous output, none parity, one stop bit. Voltage range is 0-3.6V, transistor logic circuit. Power off during test interval. Three parameters are separated by Spaces in an ASCII data string. The data string ends with a carriage return. The first value is the original permittivity, the second is the original conductivity value, and the third is the original temperature value. The following shows how raw values are converted to standard unit values.

5TE Soil moisture, Temperature and Conductivity Sensors Specification：

Note: This product can be customized according to customer requirements interface (RS232/RS485), communication protocol (MODBUS), etc. In addition, the company has RS232/RS485 to SDI-12 module, which is convenient for customers to secondary development and debugging. Please click if necessarySDI-12 Converter to RS232 RS485