CN102243161A - Multi-frequency electromagnetic measurement method for density and moisture content of grain - Google Patents

Abstract

The invention discloses a method of simultaneously measuring density and moisture content of grain based on a multi-frequency electromagnetic measurement technology. The method comprises the following steps of: firstly, measuring dielectric constants of a grain sample at different densities, moisture contents, temperatures and frequencies by a capacitance method, and establishing a relational model between the dielectric constants and the density and the moisture content; correcting model parameters according to the dielectric constant measured by an electromagnetic wave velocity method and the moisture content measured by an oven drying method, and establishing a parameter database of various grain varieties; and finally, substituting the electric constants of the grain in a grain bulk measured by the electromagnetic wave velocity method at two frequencies into the model, and solving the density and the moisture content of the measured grain. According to the measurement method provided by the invention, efficiency of detecting amount and quality of the grain can be improved, investment of labor power, material resources and financial capacity can be reduced and grain security can be ensured.

Description

The multi-frequency electromagnetic wave measurement method of a kind of grain density and moisture

Technical field

The present invention relates to a kind of method of measuring grain density and moisture in the grain depot, relate in particular to a kind of specific inductive capacity that utilizes and be subjected to the density of grain and the characteristic of moisture effects, in the parallel insertion grain heap of small sized wide-band short-wave antenna, carry out the method for grain density and moisture measurement by the electromagnetic wave of receiving and dispatching multiple frequency.

Background technology

Grain density is to calculate the significant data of grain weight.At present the method that adopts of density measure is a kind of sampling and measuring analogy estimation algorithm: sampling and measuring grain density, as liter weighing tester or 0.25 to 1 cubic metre of bulk container, carefully fill grain claim net weight, again divided by vessel volume, obtain sample rate; Sample rate multiply by correction factor and calculates grain heap average density; Correction factor wherein is the standard storehouse with same preservation condition, known volume and weight, the ratio of its grain heap average density and grain unit weight (or bulk container unit volume grain weight).Because the standard storehouse must be a storage grain of the same race under the identical storage condition, and can only be similar in the reality, so generally be to select the classification benchmark by experience.This measuring method precision is difficult to determine, and the complicated operation effort.

Grain moisture content content influence grain physics, chemistry and biological nature are the key indexs of grain quality.National standard is for being at present: GB/T5497-1985.105 ℃ of constant weight methods, constant temperature regularly oven drying method, tunnel type Oven Method and two-stage drying are wherein arranged.Corn content is measured and is carried out according to GB/T10362-1995.Oven dry check weighing method, Measuring Time is long, and real-time is poor, is applicable to that the laboratory accurately measures occasion more, is not suitable for extensive in-site measurement.

Therefore, many methods are suggested density measurement or moisture, as capacitance method, rays method, the sonic method of density measure, and the capacitance method of moisture measurement, near infrared method, microwave method etc.These methods respectively have its relative merits, and do not have a kind of method can measure the density and the moisture of grain simultaneously.

Summary of the invention

The objective of the invention is provides a kind of method of measuring grain density and moisture simultaneously based on multi-frequency electromagnetic ripple detection technique, and realize that the technical scheme of above-mentioned purpose is: a kind of method of measuring grain density and moisture simultaneously specifically may further comprise the steps:

S100. utilize capacitance measurement to go out the specific inductive capacity of grain samples when different densities, moisture, temperature, frequency, set up specific inductive capacity and density, water relation model;

S200. utilize the specific inductive capacity of velocity of electromagnetic waves method measurement and the moisture of oven drying method measurement to carry out corrected model parameter, set up different grain variety parameter databases after the correction;

In the specific inductive capacity substitution model of grain, solve the density and the moisture of tested grain when S300. utilizing two kinds of frequencies that the velocity of electromagnetic waves method measures.

Among the described step S100, the grain samples of from the grain heap, getting constant weight, put into the container of certain volume, change the density of grain by vibration container, change the moisture of grain by oven dry or air-humidification method, utilize electric impedance analyzer, drimeter, thermometer to carry out the relation of specific inductive capacity and frequency under different densities, moisture, the temperature.

Among the described step S100, the data that measure are carried out definite relational model formula ε ' that multivariate statistics returns _r=[1+ (a-blog ₁₀F+cM-dMlog ₁₀F) ρ] ³Parameter a, b, c, d.ε ' in the formula _rBe specific inductive capacity; F is a survey frequency, the MHz of unit; ρ is a grain density, and unit is g/cm ³M is % for grain moisture content unit.

Among the described step S100, measure the aerial capacitance C of capacitive transducer earlier ₀, measure the capacitance C of capacitive transducer in grain again _x, then the specific inductive capacity of grain is:

Among the described step S200, carry out grain heap grain electromagnetic wave method measures at the silo scene, sampled measurements goes out grain moisture content simultaneously, go out grain moisture content and the model moisture contrasts by sampled measurements,, finally make error less than 0.3% by iterative computation, adjustment model parameter, obtain adjusted parameter, by different cultivars grain is measured, set up the parameter database of various grains, query calls when actual measurement.

Among the described step S200, utilize multi-frequency electromagnetic ripple dielectric constant measurement system to carry out the measurement of different frequency grain heap specific inductive capacity, utilize above-mentioned relation to set up the linear equation in two unknowns group, establish survey frequency and be respectively f ₁, f ₂The time specific inductive capacity that measures be respectively ε ' ₁, ε ' ₂, then system of equations is:

$\left\{\begin{array}{c}{\mathrm{\ϵ}}_1^{\′}={[1+(a-b{\log }_{10}{f}_1+\mathrm{cM}-\mathrm{dM}{\log }_{10}{f}_1)\mathrm{\ρ}]}^3\\ {\mathrm{\ϵ}}_2^{\′}={[1+(a-b{\log }_{10}{f}_2+\mathrm{cM}-\mathrm{dM}{\log }_{10}{f}_2)\mathrm{\ρ}]}^3\end{array}\right.$

Among the described step S200, measure electromagnetic wave velocity of propagation v in grain, then the specific inductive capacity of grain is:

In the formula, c is an electromagnetic wave velocity of propagation in a vacuum.

Among the described step S300, measure grain two frequency f ₁, f ₂The time DIELECTRIC CONSTANT ' ₁, ε ' ₂

The value of parameter a, b, c, d when corresponding grain variety of supplemental characteristic library inquiry and temperature;

According to formula

$\left\{\begin{array}{c}\mathrm{\ρ}=\frac{(c-d{\log }_{10}{f}_2)({\mathrm{\ϵ}}_1^{\′1/3}-1)-(a-b{\log }_{10}{f}_1)({\mathrm{\ϵ}}_2^{\′1/3}-1)}{(a-b{\log }_{10}{f}_1)(c-d{\log }_{10}{f}_2)-(a-b{\log }_{10}{f}_2)(c-d{\log }_{10}{f}_1)}\\ M=\frac{(a-b{\log }_{10}{f}_1)({\mathrm{\ϵ}}_2^{\′1/3}-1)-(a-b{\log }_{10}{f}_2)({\mathrm{\ϵ}}_1^{\′1/3}-1)}{(c-d{\log }_{10}{f}_2)({\mathrm{\ϵ}}_1^{\′1/3}-1)-(c-d{\log }_{10}{f}_1)({\mathrm{\ϵ}}_2^{\′1/3}-1)}\end{array}\right.$

Calculate the density p (g/cm of tested grain ³) and moisture M (%).

Advantage of the present invention: the present invention proposes a kind of method of measuring grain density and moisture simultaneously, can improve the efficient of grain quantity and quality testing, reduce the input of human and material resources, financial resources, guarantee grain security.Use multi-frequency electromagnetic ripple detection technique, can measure grain density and moisture simultaneously.The foundation of parameter database is convenient to inquire about, measure the grain density and the moisture of different cultivars.

Description of drawings

Fig. 1 is the process flow diagram that the present invention measures grain density and moisture;

Fig. 2 is formula 1 a parameter correction iterative process;

Fig. 3 is that the velocity of electromagnetic waves method is measured grain specific inductive capacity system schematic.

Concrete embodiment

Concrete grammar of the present invention is as follows: the grain samples of getting constant weight from the grain heap, put into the container of certain volume, change the density of grain by vibration container, change the moisture of grain by oven dry or air-humidification method, utilize electric impedance analyzer, drimeter, thermometer to carry out the relation of specific inductive capacity and frequency under different densities, moisture, the temperature.

The data that measure are carried out parameter a, b, c, the d of definite relational model formula (1) of multivariate statistics recurrence.

ε′ _r＝[1+(a-blog ₁₀f+cM-dMlog ₁₀f)ρ] ³ (1)

ε ' in the formula _rBe specific inductive capacity; F is a survey frequency, the MHz of unit; ρ is a grain density, and unit is g/cm ³M is % for grain moisture content unit.

Utilize multi-frequency electromagnetic ripple dielectric constant measurement system to carry out the measurement of different frequency grain heap specific inductive capacity, utilize above-mentioned relation to set up the linear equation in two unknowns group.If survey frequency is respectively f ₁, f ₂The time specific inductive capacity that measures be respectively ε ' ₁, ε ' ₂, then system of equations is:

$\left\{\begin{array}{c}{\mathrm{\ϵ}}_1^{\′}={[1+(a-b{\log }_{10}{f}_1+\mathrm{cM}-\mathrm{dM}{\log }_{10}{f}_1)\mathrm{\ρ}]}^3\\ {\mathrm{\ϵ}}_2^{\′}={[1+(a-b{\log }_{10}{f}_2+\mathrm{cM}-\mathrm{dM}{\log }_{10}{f}_2)\mathrm{\ρ}]}^3\end{array}\right.---\left(2\right)$

Try to achieve the density p (g/cm of grain by the group of solving an equation ³) with moisture M (%) be:

$\left\{\begin{array}{c}\mathrm{\ρ}=\frac{(c-d{\log }_{10}{f}_2)({\mathrm{\ϵ}}_1^{\′1/3}-1)-(a-b{\log }_{10}{f}_1)({\mathrm{\ϵ}}_2^{\′1/3}-1)}{(a-b{\log }_{10}{f}_1)(c-d{\log }_{10}{f}_2)-(a-b{\log }_{10}{f}_2)(c-d{\log }_{10}{f}_1)}\\ M=\frac{(a-b{\log }_{10}{f}_1)({\mathrm{\ϵ}}_2^{\′1/3}-1)-(a-b{\log }_{10}{f}_2)({\mathrm{\ϵ}}_1^{\′1/3}-1)}{(c-d{\log }_{10}{f}_2)({\mathrm{\ϵ}}_1^{\′1/3}-1)-(c-d{\log }_{10}{f}_1)({\mathrm{\ϵ}}_2^{\′1/3}-1)}\end{array}\right.---\left(3\right)$

Go out grain moisture content and the model moisture contrasts by sampled measurements,, finally reach error minimize, obtain adjusted parameter by continuous iterative computation, adjustment model parameter.By different cultivars grain is measured, set up the parameter database of various grains, query calls when actual measurement.

The method that electric impedance analyzer is measured the grain specific inductive capacity is a capacitance method, measures the aerial capacitance C of capacitive transducer earlier ₀, measure the capacitance C of capacitive transducer in grain again _x, then the specific inductive capacity of grain is:

${\mathrm{\ϵ}}_r^{\′}=\frac{C_x}{C_0}---\left(4\right)$

The method of multi-frequency electromagnetic ripple dielectric constant measurement systematic survey grain specific inductive capacity is the velocity of electromagnetic waves method, measures electromagnetic wave velocity of propagation v in grain, and then the specific inductive capacity of grain is:

${\mathrm{\ϵ}}_r^{\′}={\left(\frac{c}{v}\right)}^2---\left(5\right)$

In the formula, c is an electromagnetic wave velocity of propagation in a vacuum.

Below in conjunction with drawings and Examples the present invention is described in further detail.

As shown in Figure 1, a kind of method of measuring grain density and moisture simultaneously specifically may further comprise the steps:

Relational model is set up

Pile the center and choose 5 points all around from grain, 50 centimeters under each orders the grain face, grain is piled high 1/2 place, and apart from grain heap bottom 50 centimeters skewer sample thiefs, the sample size that each some skewer is got is basic identical, and all the even back of sample mix is as a sample measurement.The sampling total quantity should be greater than the splendid attire quantity of specimen holder.

Sample in the specimen holder is changed the density of grain by mechanical vibration, change the moisture of grain by the method for humidification and oven dry, utilize drimeter to measure grain moisture content, the dielectric constant measurement of grain when utilizing electric impedance analyzer to carry out different frequency is used the indoor and grain samples temperature of thermometer measure simultaneously.

The method of utilizing multivariate statistics to return is handled experimental data, obtains the value of parameter a, b, c, d in the formula (1).

Parameter correction

Because the foundation of model is based on capacitance method, its parameter of determining can only be as a reference of electromagnetic wave method, therefore also need carry out electromagnetic wave method experiments of measuring at the silo scene, sampled measurements goes out grain moisture content simultaneously, by continuous iterative computation, adjustment model parameter, finally reach error minimize.

Iterative process as shown in Figure 2, step is as follows:

The initial model parameter determines by capacitance method that specific inductive capacity, parameter a, b, c, d that the electromagnetic wave method is measured are input in the model, just can calculate the moisture of master pattern.

By the moisture of oven drying method measurement grain samples, comparison model moisture and the error of surveying moisture.If error size does not satisfy the requirement of precision, then adjust parameter, calculate comparison again.

By iterative process, constantly adjust the parameter initial value, reduce model moisture and the mean square deviation of surveying moisture.Iteration finishes when the accuracy requirement satisfied, can obtain adjusted model parameter.

By different cultivars grain is measured, set up the parameter database of various grains, query calls when actual measurement.

Actual measurement

Go out grain two frequency f with multi-frequency electromagnetic ripple dielectric constant measurement systematic survey ₁, f ₂The time DIELECTRIC CONSTANT ' ₁, ε ' ₂

Parameter a, b, c, d when corresponding kind, relevant temperature in the query argument database.

Calculate the density p (g/cm of tested grain according to formula (3) ³) and moisture M (%).

Velocity of electromagnetic waves method is as shown in Figure 3 measured grain specific inductive capacity system, is made up of signal source, small sized wide-band short-wave antenna, signal pickup assembly and portable computer.Signal source produces the electromagnetic wave of changeable frequency, is sent to emitting antenna through concentric cable.After by emitting antenna electromagnetic wave being launched, the receiving antenna of two root distance emitting antenna different distance is converted to electric current with the electromagnetic wave signal that receives and sends into signal pickup assembly through concentric cable.In portable computer, carry out signal Processing then, calculate the grain dielectric constant values.Measuring process is as follows:

The flagpole antenna that is respectively applied for the sending and receiving electromagnetic wave signal among the parallel insertion grain heap of certain distance, is located at the following certain position of grain face, and keeps upper and lower end concordant.

Measure antenna 1 and antenna 2 distance respectively, the record measurement data to emitting antenna.

Carry out measuring system according to Fig. 3 and connect opening signal source, signal pickup assembly and computer power supply.

Change the output wave frequency, the signal that two receiving antennas receive when gathering different frequency with signal pickup assembly, and be stored in the portable computer.

In portable computer, carry out signal Processing, the velocity of propagation of electromagnetic wave in grain when calculating different frequency, and then grain dielectric constant values when calculating different frequency by formula (5).

Claims (8)

1. the multi-frequency electromagnetic wave measurement method of grain density and moisture is characterized in that:

S100. utilize capacitance measurement to go out the specific inductive capacity of grain samples when different densities, moisture, temperature, frequency, set up specific inductive capacity and density, water relation model;

S200. utilize the specific inductive capacity of velocity of electromagnetic waves method measurement and the moisture of oven drying method measurement to carry out corrected model parameter, set up different grain variety parameter databases after the correction;

In the specific inductive capacity substitution model of grain, solve the density and the moisture of tested grain when S300. utilizing two kinds of frequencies that the velocity of electromagnetic waves method measures.

2. according to the described method of claim 1, it is characterized in that:

Among the described step S100, the grain samples of from the grain heap, getting constant weight, put into the container of certain volume, change the density of grain by vibration container, change the moisture of grain by oven dry or air-humidification method, utilize electric impedance analyzer, drimeter, thermometer to carry out the relation of specific inductive capacity and frequency under different densities, moisture, the temperature.

3. according to claim 1 or 2 described methods, it is characterized in that:

Among the described step S100, the data that measure are carried out definite relational model formula ε ' that multivariate statistics returns _r=[1+ (a-blog ₁₀F+cM-dMlog ₁₀F) ρ] ³Parameter a, b, c, d.ε ' in the formula _rBe specific inductive capacity; F is a survey frequency, the MHz of unit; ρ is a grain density, and unit is g/cm ³M is % for grain moisture content unit.

4. according to the described method of claim 3, it is characterized in that:

Among the described step S100, measure the aerial capacitance C of capacitive transducer earlier ₀, measure the capacitance C of capacitive transducer in grain again _x, then the specific inductive capacity of grain is:

5. according to the described method of claim 1, it is characterized in that:

Among the described step S200, carry out the electromagnetic wave method measures at the silo scene, sampled measurements goes out grain moisture content simultaneously, go out grain moisture content and the model moisture contrasts by sampled measurements,, finally make error less than 0.3% by iterative computation, adjustment model parameter, obtain adjusted parameter, by different cultivars grain is measured, set up the parameter database of various grains, query calls when actual measurement.

6. according to claim 1 or 5 described methods, it is characterized in that:

Among the described step S200, the measurement of grain heap specific inductive capacity utilizes above-mentioned relation to set up the linear equation in two unknowns group when utilizing multi-frequency electromagnetic ripple dielectric constant measurement system to carry out different frequency, establishes survey frequency and is respectively f ₁, f ₂The time specific inductive capacity that measures be respectively ε ' ₁ε ' ₂, then system of equations is:

$\left\{\begin{array}{c}{\mathrm{\ϵ}}_1^{\′}={[1+(a-b{\log }_{10}{f}_1+\mathrm{cM}-\mathrm{dM}{\log }_{10}{f}_1)\mathrm{\ρ}]}^3\\ {\mathrm{\ϵ}}_2^{\′}={[1+(a-b{\log }_{10}{f}_2+\mathrm{cM}-\mathrm{dM}{\log }_{10}{f}_2)\mathrm{\ρ}]}^3\end{array}\right.$

7. according to the described method of claim 6, it is characterized in that:

Among the described step S200, measure electromagnetic wave velocity of propagation v in grain, then the specific inductive capacity of grain is: In the formula, c is an electromagnetic wave velocity of propagation in a vacuum.

8. according to the described method of claim 1, it is characterized in that:

Among the described step S300, measure grain two frequency f ₁, f ₂The time DIELECTRIC CONSTANT ' ₁, ε ' ₂

The value of parameter a, b, c, d when corresponding grain variety of supplemental characteristic library inquiry and temperature;

According to formula

$\left\{\begin{array}{c}\mathrm{\ρ}=\frac{(c-d{\log }_{10}{f}_2)({\mathrm{\ϵ}}_1^{\′1/3}-1)-(a-b{\log }_{10}{f}_1)({\mathrm{\ϵ}}_2^{\′1/3}-1)}{(a-b{\log }_{10}{f}_1)(c-d{\log }_{10}{f}_2)-(a-b{\log }_{10}{f}_2)(c-d{\log }_{10}{f}_1)}\\ M=\frac{(a-b{\log }_{10}{f}_1)({\mathrm{\ϵ}}_2^{\′1/3}-1)-(a-b{\log }_{10}{f}_2)({\mathrm{\ϵ}}_1^{\′1/3}-1)}{(c-d{\log }_{10}{f}_2)({\mathrm{\ϵ}}_1^{\′1/3}-1)-(c-d{\log }_{10}{f}_1)({\mathrm{\ϵ}}_2^{\′1/3}-1)}\end{array}\right.$

Calculate the density p (g/cm of tested grain ³) and moisture M (%).

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