SU1543332A2 - Device for determining moisture content of soil - Google Patents

Abstract

This invention relates to a measurement technique. The purpose of the invention is to increase the reliability of measurement results. The device contains channels for measuring humidity, measuring precipitation, measuring radiation evaporation, as well as circuit elements defining the choice of channel used to estimate moisture content depending on the ratio of the current humidity value and the specified value of critical humidity. The purpose of the invention is achieved by taking into account the dependence of the evaporation rate on the current value of soil moisture. 1 il.

Description

The invention relates to a measurement technique and can be used to determine the moisture content of soil by electrical methods.

The purpose of the invention is to increase the reliability of soil moisture measurement results.

The drawing shows a diagram of a device for determining the moisture content of a soil.

The device includes a quartz oscillator 1, a measuring resonant circuit 2, with modeling and compensating elements, an amplitude detector 3, a phase-sensitive amplifier k with variable gain, a resonance indicator 5, a measuring potentiometer 6, a modulator 7, a precipitation meter 8, a conversion unit 9 of a signal of a precipitometer, first adder

10, switch 11, memory 12, second adder 13, block 14 for generating a gain control signal of a phase-sensitive amplifier, radiation sensor 1 |, block 16 for converting a signal of a radiation sensor, integrator 17, relay element 16, recorder 19i comparison unit 20, block 21 (versus setpoint, relay element 22, switch 23, block 2k of the signal conversion corresponding to the evaporation rate.

The device works as follows.

Previously, in block 21, a setpoint is set to the comparison with the setpoint, equal to the critical soil moisture WHP. The signal corresponding to the value

N)

soil moisture is supplied from the output of the measuring potentiometer 6 to the input of the comparison unit 21 with the setpoint. At the same time, if the measured humidity is greater than the critical humidity W, then the output of block 21 versus the set point does not contain a signal, the relay element 22 is open, and through the switch 23 provides direct communication between the conversion unit 16 and the integrator 17.

If, however, the measured value of soil moisture is less than the critical humidity, the signal appearing at the output of block 21 compared with the setpoint triggers the relay element 22, which provides a link between the signal of the radiation sensor and the signal converting unit 2, corresponding to the intensity of at the same time breaking the direct connection of the radiation sensor signal unit 16 with the integrator 17.

The 2k signal conversion unit corresponding to the evaporation rate converts the signal from the block 16 into a signal corresponding to the evaporation under conditions when the soil moisture is less critical, in accordance with the relation:

f (R) W W - W5

w w.

Wj

w w,

Where

E - K wkp evaporation rate; radiation balance; critical humidity; the humidity of the head of tribute; current humidity value.

four

% - W The signal from the output of the signal conversion unit, which corresponds to the evaporation rate, comes with a minus sign to the input of the integrator 17. The pro-v integrated differential meter of the flowmeter and the balance meter, corresponding to the current soil moisture, is fed to the input of the comparison unit 20. If the difference between the integrator signal and the signal from the measuring potentiometer does not exceed the specified value,

0

P

five

0

five

0

then the output of the comparator unit is zero, and the relay element is in the open state. The recording device in this case is disconnected from the integrator output. In this case, it is necessary to use the readings of the measuring potentiometer. If the difference between the signals exceeds a predetermined value, then the output voltage of the comparison unit turns on the relay element and the recorder 19 is connected to the output of the integrator and the moisture reserve is judged by its readings.

The use of this device in automated irrigation control systems, where operational control over the moisture regime of the floor is required, improves the quality of operation of such systems. This is achieved by increasing the reliability measured by the device under conditions when the soil moisture is below the critical, since it takes into account that in this case the evaporation rate depends not only on the radiation balance, but also on the soil moisture.

Claims (1)

Invention Formula A device for determining the moisture content of the soil according to ed. No. 80286 4, characterized in that, in order to increase the reliability of the measurement results, a comparison block with a setpoint, a relay element, a switch, a signal conversion unit corresponding to the evaporation rate are additionally introduced, the input of the comparison block with the setpoint is connected to the output of the measuring potentiometer, and the output through the relay element is connected to one of the switch inputs, the switch and the signal conversion unit corresponding to the evaporation intensity are connected in series and interconnected Radiation sensor output transducer and the input of the integrator, and a second output connected to the switch, the input of the integrator.