SU1516905A1 - Method of measuring moisture content of loose material - Google Patents

Abstract

This invention relates to a measurement technique and can be used in the production of chipboard. The purpose of the invention is to improve the measurement accuracy. The method consists in determining the moisture content of the bulk material (wood chips) by acting on the bulk material located in the measuring glass with division, mechanical vibrations. Oscillations occur in a membrane mounted in the bottom of the glass, connected to a vibrator connected to an electrical oscillator 5. The frequency of mechanical oscillations is changed to a value equal to the natural frequency of oscillation of the material under study. Humidity is determined by pre-obtained calibration dependence. 1 il.

Description

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The invention relates to the field of measurement technology and can be used to measure the moisture content of bulk materials, such as wood chips, in the production of wood particle boards.

The aim of the invention is to improve the measurement accuracy by eliminating the effect on the measurement result of the compaction of the bulk material in the sensor.

The method of measuring the moisture content of the bulk material consists in exposing the bulk material with the same particle size to mechanical oscillations, followed by determining the moisture content from the previously obtained calibration dependence. The frequency of mechanical vibrations is changed to a value different to the natural frequency of oscillation of the material under study. The moment of resonance response is determined, and the moisture content of the material is judged by the value of the resonant frequency. The drawing shows a functional diagram of an apparatus for implementing the method.

Bulk material 1 is located in a measuring glass 2 with a distance, in the bottom of which a membrane 3 is mounted, connected to a vibrator 4 connected to an oscillator 5 of electrical oscillations,

The method is carried out as follows.

The electrical oscillations arising in the oscillator 5 of the electrical oscillations are converted by the vibrator 4 into mechanical oscillations and transmitted to the membrane 3 embedded in the bottom of the measuring cup 2 with divisions. These mechanical vibrations are then transmitted to the layer of bulk material 1, which is poured onto the surface of membrane 3, and the bulk material I begins to vibrate. When the oscillation frequency that occurs in the oscillator 5 of the electrical oscillation changes, the oscillation frequency of the membrane 3 changes. At a certain oscillation frequency equal to the natural oscillation frequency of the bulk material, a resonant state of the system appears; the bulk material is maximum, as noted by the divisions from measuring cup 2,

A change in the moisture content of the bulk material changes the natural frequency of the bulk material in one direction or another. Investigators, the oscillations of the electric oscillations of the generator 5 determine the time of onset of resonance and, by the value of the resonant frequency, judge the moisture content of the material

With these measurements, the amplitude of the sticking, the generator in the jx generator 5, should be strictly constant. The method is applicable to bulk material, the particles of which have the same size. For example, it can be used to measure the moisture content of wood chips going to production of wood-shaving plates, since such chips have strictly lodged identical sizes,

The height of the bulk material filling is measured by divisions deposited on the outside of the measuring cup. The measuring cup is transparent, t, e, made of, for example, transparent plastic. During measurements, the layer boundary is clearly visible, but the boundary should be considered a continuous layer.

The power of electrical oscillations, supplied by the generator to the vibrator, is selected with a margin in order to exclude the damping of the membrane, the weight of the column being poured into the measuring cup of the bulk material. At the same time, a certain difference in the weight of the bulk material filling column with different fillings does not play a significant role in measuring 1 {and x,

The power of electrical oscillations, under the drive to the vibrator, is 50 W, the resonant frequency of the mechanical vibrations of the vibrator is 25 Hz, the height of the measuring cup is 110 mm. The height of the filling of the measured bulk material is taken to be approximately one fifth of the height of the measuring cup, namely 20 mm,

When measuring the moisture content of wood chips by the proposed method, a calibration of the moisture content of the studied wood chips from the resonant frequency is constructed. This calibration dependence determines the moisture content of the bulk material under investigation, wood chips,

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Example I. The actual moisture content of wood chips is 4.0% | The mechanical resonance of this wood chip corresponds to a frequency of 172 Hz. The wood chips measured by the proposed method are 4.1%. The absolute measurement error is 0.1%, the relative measurement error is 2.5%.

Example 2. The actual moisture content of wood chips is 4.7%. The mechanical resonance of this wood chip corresponds to a frequency of 143 Hz. The moisture content of the wood chip measured by the proposed method is 4.5%. The absolute measurement error is 0.2%, the relative measurement error is 4.3%.

Example 3. The actual moisture content of wood chips is 5.1%. The mechanical resonance of this wood chip corresponds to ca 16905

It is 130 Hz. The moisture content of wood chips measured by the proposed method is 5.3%, the absolute measurement error is 0.2%, the relative measurement error is 4.0%.

Claims (1)

Invention Formula A method for measuring the moisture content of a bulk material with the same particle size, which consists in influencing the bulk material of mechanical oscillations with subsequent determination of moisture content based on a previously obtained calibration dependence, characterized in that, in order to increase the measurement accuracy, the frequency of mechanical oscillations is changed to equal to the natural frequency of oscillation of the material under study, determine the time of onset of the resonance and judge the humidity of the material by the value of the resonant slots.