RU2716865C1 - Device for measuring moisture content of loose substance - Google Patents

Abstract

FIELD: measuring equipment.SUBSTANCE: invention relates to measurement equipment and can be used for measurement of moisture content of loose substances. Device for measuring moisture content of loose substances comprises a housing, a receiver – a capacitive humidity converter, consisting of two equal sections and containing a common electrode and two active electrodes of equal areas, an electrical measuring circuit, wherein one of active electrodes is divided into several electrodes with independent leads.EFFECT: high accuracy and reliability of measurement results.1 cl, 3 dwg

Description

The invention relates to measuring technique and can be used to measure the moisture content of bulk substances, for example, grain.

A device for the operational measurement of moisture content of the grain is known - US patent No. 3.794.911, publ. in "Inventions Abroad", No. 4, 1974. The device is a capacitive moisture meter and contains a receiver - a capacitive humidity transducer, an electrical measuring circuit with a processor and registration of reference data and grain sample moisture, a mechanism for fixing the weight of the sample.

The main disadvantage of the device is the design complexity, the dependence of the measurement results on dielectric loss, active resistance.

A device for measuring the moisture content of bulk substances is known - copyright certificate No. 815600, publ. in the “Bulletin of inventions and discoveries”, No. 11, 1981. The device comprises a horizontal cylindrical body, a press device with a piston, a weighing device, a capacitive moisture transducer — a receiver of the substance under study, a capacitive weight transducer, and instrumentation.

The main disadvantage of the device is the design complexity, the dependence of the measurement results on dielectric loss, active resistance.

A device for measuring the moisture content of bulk substances is known - Copyright certificate No. 2130606, publ. 05/20/99, Bull. No. 14 (Prototype). The device contains a housing, the receiver is a capacitive humidity transducer, an electrical measuring circuit. The capacitive transducer is made in the form of a rectangular capacitance, bounded on two sides by flat electrodes, divided by a common electrode into two equal sections, one of which is divided into two sections, one of which is filled with a material with a dielectric constant equal to the dielectric constant of dry grain.

A capacitive transducer, also known as a receiver of an analyte, is a differential capacitor. When the receiver is filled with dry matter, the differential electric capacitance is close to 0, since in the first and second sections it is one substance, and the dielectric constant in the third section is close to the dry matter permeability, the effect of dielectric losses and active resistance on the side active electrodes is equal. Capacitive difference characterizes the degree of moisture of the test substance.

The third section with constant dielectric constant can be pressed against the active electrode. In this case, the efficiency of neutralizing the influence of dielectric losses and active resistance is 20-30%. When installing the third section to the common electrode, this efficiency increases and practically only the linear part of the dependence of the influence of dielectric losses and active resistance on humidity remains (Fig. 1). Horizontal (see Fig. 1) shows the distance of the third section from the active electrode in cm. The electrical signal on the active electrode in the first centimeters non-linearly depends on this distance. Further, the nonlinearity is smoothed.

The main disadvantages are incomplete neutralization of the influence of dielectric losses and active resistance, as well as a decrease in the difference signal, which leads to the need for additional amplification of this signal.

The aim of the present invention is to completely neutralize the effects of dielectric loss and active resistance with increasing accuracy and measurement performance.

This goal is achieved by the fact that in the device for measuring the moisture content of bulk solids containing a housing, the receiver is a capacitive humidity transducer consisting of two equal sections, a common electrode and two active ones with independent leads, a measuring electric circuit, one of the active electrodes is divided into several electrodes without changing the total area.

With this design, the sum of the measured signals from the individual parts of the cut electrode is greater than the signal from the whole electrode, and the difference depends on the number of cuts (Fig. 2). In this case, the influence of dielectric losses and active resistance is completely neutralized.

Such a capacitive converter, which is also the receiver of the substance under study, is a differential capacitor with equal active electrodes in area, but not equal electrical signals. Since the influence of dielectric losses and active resistance is determined by the area of the electrodes, they are compensated in the differential circuit. Due to the different capacitances, the electrical signal from the whole electrode and the sum of the electrical signals from the cut parts of another active electrode are not equal. The sum of the electrical signals from the sliced parts is greater than the electrical signal from the whole electrode, and this difference increases with the number of cuts. It affects the effect of unequal areas of the chopped parts and the whole electrode. The current density of the cut parts is greater than on the whole electrode. In addition, the effect of the near-electrode capacitances of the whole electrode and the total from the cut parts of another electrode is also not the same. The total near-electrode capacitance is greater.

In FIG. 3 shows a diagram of a device. 1 - a receiver of two equal sections, 2 - a common electrode, 3 - a whole active electrode, 4 - chopped parts of the second active electrode, 5 - electrical measuring circuit. The whole device is made in one case.

Humidity measurement is performed as follows. Fill the receiver 1 with the test sample. The inputs of the microcontroller of the measuring electric circuit 5 receive analog signals from the terminals of the cut parts 4 and the whole electrode 3. They are converted into digital signals, the humidity calculated in the processor program, the result is displayed on the recorder screen. The working equations for calculating humidity are obtained as a result of calibration measurements and calculations.

Claims (1)

A device for measuring the moisture content of bulk solids, containing a housing, a receiver - a capacitive humidity transducer, consisting of two equal sections and containing a common electrode and two active electrodes of equal areas, an electrical measuring circuit, while one of the active electrodes is divided into several electrodes with independent leads.

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