JPH1183757A - Microwave densitometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure concentration with high accuracy by reducing effects due to changes in conductivity and temperature and the induction of radio waves in the case where the diameter of a tube is large. SOLUTION: This densitometer is provided with a microwave oscillator 3 to generate microwaves in a plurality of frequencies, microwave transmitting and receiving parts 12 and 13 to selectively transmit microwaves in a plurality of frequencies generated from the microwave oscillator 3 and receive them via an object to be measured in a tube, a phase difference measuring means 23 to measure the first and second phase differences on the basis of microwaves in a plurality of frequencies through the use of the received reception signals, and a means 26 to determine phase rotation on the basis of the first and second phase differences. A phase lag is detected from the phase differences and phase rotation to measure the concentration of the object to be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave densitometer for measuring the concentration of a solid substance or a suspended substance in an object to be measured. The present invention relates to a microwave densitometer for measuring the concentration of pollutants and the concentration of various substances in a fluid such as paper pulp.

[0002]

2. Description of the Related Art An object to be measured, such as a solid substance in a liquid,
The most primitive method of measuring the concentration of a suspended substance is to measure the concentration of an analyte by sampling a part of the liquid and weighing the residue after evaporating the liquid. .

However, this measurement method requires a long time for measurement, and is difficult to automate. Therefore, various sensors related to densitometers have been put into practical use in view of shortening of measurement time and automation.

Conventionally, a densitometer using ultrasonic waves has been developed and used as one of the sensors. However, this ultrasonic densitometer has a problem that measurement cannot be performed when bubbles are present in the liquid.

[0005] In order to solve this problem, for example, a concentration meter using microwaves has been developed as disclosed in Japanese Patent Application Laid-Open No. Hei 4-238246. Hereinafter, an outline of the measuring method of the microwave densitometer will be described with reference to FIG.

This microwave densitometer measures the concentration of a liquid from the phase delay of the microwave based on the principle that the phase of the microwave is delayed almost in proportion to the concentration of the liquid.

More specifically, a microwave signal 61 having a frequency f generated by an oscillator 60 is amplified by an amplifier 62, and branched and output into a transmission signal 64 and a reference signal 65 by a distributor 63, of which the transmission signal 64 is transmitted. Transmitted to the device under test in the pipe 67 via the trust antenna 66,
The reference signal 65 is sent to a mixer 68.

A receiving antenna 69 installed on the opposite side of the pipe 67 receives a microwave passing through the device under test, and the received signal 70 is sent to another mixer 72 via an amplifier 71. Sent out.

At this time, the reference oscillator 73 outputs a frequency f + Δf slightly different from the microwave signal 61 having the frequency f.
Reference signals 74 and 75 are generated, respectively.
8, 72. As a result, the mixer 68 mixes the reference signal 65 and the reference signal 74, extracts the reference side heterodyne output 76 having the difference frequency Δf, and sends it to the phase difference measuring means 77.

On the other hand, another mixer 72 mixes the received signal 70 received by the receiving antenna 69 with the reference signal 75, takes out the measurement side heterodyne output 78 having the difference frequency Δf, and similarly extracts the phase difference. It is sent to the measuring means 77.

Here, the phase difference measuring means 77 takes in the reference side heterodyne output 76 and the measurement side heterodyne output 78, finds the phase difference Φ between these two outputs, and sends it to the arithmetic unit 79. The device 79 can calculate the density of the DUT from the phase difference Φ based on the reference phase difference if the phase difference at the reference density is determined in advance.

When the density is D, the relationship between the density D and the phase difference Φ is as follows: D = aΦ + b (1) Since the relationship is substantially linear, the phase difference is changed by changing the density. By measuring and performing regression analysis, a and b can be determined.

In a conductive medium (eg, water), the relationship between microwave attenuation / phase lag and the conductivity σ, dielectric constant, and temperature t of the medium is theoretically as follows. become.

An attenuation rate α (Nepe of a microwave having an angular frequency ω)
r / m) and the phase change rate β (rad / m) can be expressed by the following equations (2) and (3). α = {Z ₀ / (2) ^1/2 ｝ · (σ + ωε ₀ ε ″ _r ) / [1+ [1 + ｛(σ / ωε ′ _r ε ₀ ) + (ε ″ _r / ε ′ _r )} ² ] ^{1 / 2} ] ^1/2 (2) β = ｛ω (μ _r ε ′ _r ) ^1/2 / c ₀ (2) ^1/2 ｝ · [1+ [1 + ｛(σ / ωε ′ _r ε ₀ ) + (Ε ″ _r / ε ′ _r )｝ ² ] ^1/2 ] ^1/2 (3) where σ is the conductivity, ε ′ _r and ε ″ _r are the actual values of the complex relative permittivity ε _r of the medium. Part and imaginary part. If the molecule is polar, such as water, the dielectric constant will be a function of frequency, as polarization will occur slowly when an electric field is applied. Assuming that a static relative permittivity is ε ′ _rs and a relative permittivity at a frequency ′ is ε ′ _r , ε _r = ε ′ _r −jε ″ _r = ε ′ _r + (ε ′ _rs −ε ′ _r ) / (1 + jωτ) (4) ε ′ _r = ε ′ _r + (ε ′ _rs −ε ′ _r ) / (1 + ω ² τ ² ) (5) ε ″ _r = ｛(ε ′ _rs −ε ′ _r) ) Ωτ｝ / (1 + ω ² τ ² ) (6) Here, τ is the time required for polarization.
ε ′ _rs and τ are functions of the temperature t (° C.), and it has been experimentally confirmed that pure water can be represented by the following approximate expression.

Ε ′ _rs = 88.195−0.40349 t + 0.65924 × 10 ⁻³ t ² ... (7) τ = 19.39 −0.6802 t + 0.95865 × 10 ² t ² −0.65303 × 10 ⁻¹⁷ exp (t) 8) Also, ε ′ _r = 4.9. Other constants are shown below.

Radio wave impedance Z ₀ = (μ ₀ / ε ₀ ) ^1/2 = 120 π Ω Vacuum permeability μ ₀ = 4 π × 10 ^-7 H / m Vacuum permittivity ε ₀ = 8.854 × 10 ^-12 F / m Speed of light in vacuum c ₀ = 3.00 × 10 ⁸ m / s Relative magnetic permeability μ _r of medium (water) = 1 Nearly, using the above constants and the like, the above equation (2)
After obtaining the attenuation rate α and the phase change rate β by the equation (3), the attenuation amount and the phase delay are obtained from the attenuation rate α and the phase change rate β.

Therefore, assuming that the transmission power is P ₀ and the microwave power traveling in the z direction is P, P = P ₀ exp (−2αz) (9), and the attenuation is (20αz / log10) ( db). The phase delay is βz (rad). As described above, the microwave attenuation / phase lag is a function of the dielectric constant of the medium,
It is also a function of frequency, medium conductivity, magnetic permeability and temperature.

[0018]

However, the conventional microwave densitometer has the following problems. (1) Since the concentration is obtained from the change in the phase, when the fluid to be measured has a high concentration or the pipe diameter is large, the reception signal 70
When the phase changes by one or more rotations, it is unclear how many times it has rotated, and the density cannot be determined. If the inside of the tube is always filled with the object to be measured and the phase is measured, the rotation speed can be obtained from the front-back relationship as shown in, for example, JP-A-8-82606. It becomes impossible to measure when it becomes empty. (2) As shown in the above equations (3) to (8), when the temperature or the conductivity of the device to be measured changes, the phase of the microwave changes and an error occurs. Therefore, it is necessary to measure and correct the temperature and the conductivity. For example, as disclosed in Japanese Patent Application Laid-Open No. 9-43181, a conductivity sensor is installed and the conductivity is measured.

However, it is difficult to put the conductivity sensor into practical use because dirt easily adheres to the conductivity sensor, and there is a problem in terms of deterioration of measurement accuracy and maintenance work. (3) When handling microwaves, there is a regulation under the Radio Law, and the electric field strength of leaked radio waves must be equal to or lower than a reference value, and the microwave transmission output cannot be increased without limit. However, when the diameter of the tube is large and the distance between the transmitting and receiving antennas is large, the amount of attenuation increases. Similarly, when the conductivity is large, the attenuation is large. As a result, the received microwave power is reduced, the measurement error is increased, or the measurement cannot be performed at all. (4) Due to the action of inducing microwave radio waves, microwaves are received through places other than in liquid, causing measurement errors. (5) The received signal 70 received by the receiving antenna 69 is amplified by the amplifier 71, and the received signal power and the ambient temperature at which the amplifier 71 is installed change at this time.
There is a problem that the phase of the output signal changes and an error occurs.

The present invention has been made in view of the above-mentioned circumstances, and has been developed in consideration of changes in conductivity and temperature.
An object of the present invention is to provide a microwave densitometer for measuring the concentration of a suspended substance with high accuracy.

Another object of the present invention is to provide a microwave densitometer for measuring the concentration of solids and suspended solids in a liquid with high accuracy even when the pipe diameter is large or radio waves are induced. Is to do.

[0022]

Means for Solving the Problems In order to solve the above problems, the inventions corresponding to Claims 1, 3 and 4 are:
Measure the phase lag of the microwave passing through the DUT inside the tube,
In a microwave densitometer for measuring the concentration of the object to be measured, a microwave generating means for generating microwaves of a plurality of frequencies, and a microwave of a plurality of frequencies individually generated from the microwave generating means are selectively used. And a microwave transmitting / receiving unit for receiving the signal via the device under test in the tube, and a first and a second signal based on the microwaves of the plurality of frequencies using a reception signal received by the microwave transmitting / receiving unit. A phase difference measuring means for measuring a phase difference, and means for determining a phase rotation based on the first and second phase differences are provided.

As means for generating microwaves of a plurality of frequencies, one microwave oscillator is provided, and in addition to the case where microwaves of a plurality of different frequencies are selectively generated by changing the frequency setting, two A microwave oscillator is provided, and a microwave transmitting / receiving unit is connected to each of the two microwave oscillators via a switch. Microwaves having different frequencies are generated while turning on one of the switches, and are introduced into the microwave transmitting / receiving unit. . When two microwave oscillators are provided, two phase difference measuring means are provided corresponding to these oscillators, and different phase differences are measured based on microwaves having different frequencies.

[0024] By adopting such means, microwaves of two different frequencies are selectively transmitted, and the receiving side and the reference signal and the reference signal of the microwaves of the two different frequencies are used for measurement. The heterodyne output and the reference side heterodyne output are taken out, and the first and second phase differences based on the microwaves having different frequencies are measured from these two heterodyne outputs.
Using the two phase differences and the previously known phase difference when the concentration of each frequency is zero, the amount of change in the phase difference taking into account the rotational speed is determined, and the phase change rate of each frequency is determined. Since the phase rotation speed is determined using the amount and the phase difference change rate, even when the concentration is high or the pipe diameter is large, the phase rotation speed is accurately determined to determine the concentration of the DUT. Can be measured.

According to a second, third, and fourth aspect of the present invention, a microwave generating means for generating a microwave having a predetermined frequency, and a microwave generated from the microwave generating means, A microwave transmitting / receiving unit that receives through the device under test, a phase difference measuring unit that measures a phase difference using a received signal received by the microwave transmitting / receiving unit, and a voltage of a signal related to the received signal. Voltage measuring means to measure, and measure the amount of attenuation of the microwave received from the voltage measured by the voltage measuring means, calculate the conductivity of the object to be measured using the amount of attenuation, by this conductivity Correction means for correcting the phase difference. As described above, one microwave generating unit or two microwave generating units may be provided.

By taking such means, the measuring side heterodyne output measured by the voltage measuring means is measured, the attenuation of the received microwave is calculated, and the conductivity of the device under test is calculated from the attenuation. Is calculated and the phase difference is corrected, so that even if the conductivity of the DUT changes and the phase of the microwave changes, the conductivity is accurately calculated and the phase of the microwave is corrected, The concentration can be measured, and the measurement accuracy of the concentration can be improved.

According to a fifth aspect of the present invention, in addition to the configuration of the second aspect of the present invention, a temperature measuring means for measuring the temperature of the object to be measured in the tube is further provided. While measuring the amount of attenuation of the received microwave, the conductivity of the device under test is calculated from the amount of attenuation and the measured temperature, and the phase difference is corrected using the calculated conductivity. However, even if the temperature changes and the phase of the microwave changes, the conductivity is accurately calculated and the phase of the microwave is corrected, so that the concentration can be measured accurately and the measurement accuracy of the concentration can be improved. it can.

According to a sixth aspect of the present invention, there is provided a frequency converter for adding a received signal received by a microwave transmitting / receiving unit and a reference signal having a frequency slightly different from a predetermined frequency, and then distributing and extracting a mixed signal. By providing the means, it is possible to compensate for a phase change such as a temperature change by passing both the reception signal and the reference signal through a component of the same reception output line, for example, an amplifier.

According to a seventh aspect of the present invention, there is provided a terminating resistor having one end grounded, a selecting means for selecting an output line on the other end side of the terminating resistor, and an output line of the microwave receiving section, Induction correction for measuring the inductive component of the microwave from the output of the output line on the other end of the terminating resistor selected by the means, and correcting the phase difference obtained from the output of the output line of the selected microwave receiver. The provision of the means makes it possible to compensate for the influence of the induced component even when the microwave is received through a place other than the measured object by induction.

The invention according to claim 8 and claim 9 is characterized in that a microwave transmitting section for generating a microwave, a microwave receiving section for receiving the generated microwave through an object to be measured in a tube, and A dielectric having a dielectric constant equivalent to that of the device under test is disposed between the portion in contact with the tube or the portion penetrating the tube and contacting the device under test, or the inside of the tube is smaller than the inner diameter of the tube. By arranging a microwave transmitting unit that generates microwaves so as to be small in distance and a microwave receiving unit that receives the generated microwaves through an object to be measured in the tube, the tube diameter is large. Even in such a case, the concentration can be measured by reducing the amount of attenuation, and the concentration can be measured by easily lowering the electric field strength below the reference value. The invention corresponding to claim 10 is the following, as a microwave:
By using the frequency of the ISM, the concentration of the measured object can be measured using a microwave with a strict regulation.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a block diagram showing an embodiment of a microwave densitometer according to the first to fourth aspects of the present invention.

This microwave densitometer is internally provided with two circuit blocks 1 and 2 having similar components.
Different frequencies f ₁ and f ₂ from these circuit blocks 1 and ₂
A microwave is generated to measure the concentration. One circuit block has substantially the same configuration as a conventional microwave densitometer except for piping, an antenna, and the like.

The circuit block 1 comprises an oscillator 3 for generating a microwave having a frequency f ₁ , an amplifier 4 and a distribution means 5.
Is provided to the reference signal 6 and the transmission signal 7 by the distribution means 5. The reference signal f ₁ is sent to the mixer 8, and the transmission signal 7 is transmitted through the switch 9 to the coupling means 10.
Sent to The switch 9 turns on only one of the circuit blocks 1 and 2.

Therefore, when the switch 9 of the circuit block 1 or the circuit block 2 is turned on, the transmission signal 7 of the frequency f ₁ or the transmission signal 11 of the frequency f ₂ passes through the coupling means 10 from the transmission antenna 12 to the pipe 13. The signal is transmitted to the device under test and received by the receiving antenna 14.

The received signal is distributed to the received signals 16 and 17 by the distribution means 15 and introduced to the mixers 18 of the circuit blocks 1 and 2. At this time, the frequency f ₁ slightly different from the frequency f ₁ is output from the reference oscillator 19 of the circuit block 1.
₁ + △ f ₁ is generated and introduced as reference signals 20 and 21 to mixers 8 and 18, respectively.

Accordingly, the mixer 18 mixes the reference signal f ₁ and the reference signal 20, takes out the reference side heterodyne output 22 having the difference frequency Δf ₁ , and sends it to the phase difference measuring means 23. On the other hand, the mixer 18
6 and the reference signal 21, and a measurement side heterodyne output 24 having a difference frequency Δf ₁ is taken out and sent to the phase difference measuring means 23 and the voltage measuring means 25.

The phase difference measuring means 23 obtains the phase difference Φ ₁ from the reference side heterodyne output 22 and the measurement side heterodyne output 24, and sends it to the arithmetic unit 26. Also,
The voltage measuring means 25 measures the voltage V ₁ of the measurement side heterodyne output 24 and sends it to the arithmetic unit 26.

The circuit block 2 also uses the same processing means to generate a phase difference Φ using a microwave having a frequency f _2.
2, the determined voltage V _2, and sends it to the arithmetic unit 26. Therefore, the arithmetic unit 26 calculates the phase difference Φ obtained as described above.
The density of the device under test is measured using ₁ , Φ ₂ and the voltages V ₁ , V ₂ . However, as for the phase differences Φ ₁ and Φ _2, there is a possibility that the phases are rotating.

Now, when the density is 0, the phase difference is the frequency f
_{It is} assumed that Φ ₁₀ and Φ ₂₀ are set for ₁ and f ₂ , respectively, and that the following changes are caused by the change in the concentration. f ₁ : Φ ₁₀ → Φ ₁ + 2πm (−1 ≦ m, m is an integer) f ₂ : Φ ₂₀ → Φ ₂ + 2πn (−1 ≦ n, n is an integer) Here, m and n are rotation speeds. Therefore, the change amounts of the phase difference △ Φ ₁ and △ Φ ₂ are as follows: ΔΦ ₁ = Φ ₁ + 2πm−Φ ₁₀ (10) ΔΦ ₂ = Φ ₂ + 2πn−Φ ₂₀ (11)

Next, the phase change rate β at f ₁ and f ₂
Assuming that ₁ , β ₂ , the phase change rates β ₁ , β ₂ and the phase difference change amounts △ Φ ₁ , △ Φ ₂ can be expressed by the following relationship. ΔΦ ₂ = (β ₂ / β ₁ ) △ Φ ₁ (12) Then, after subtracting the right side from the left side of the equation (12) and setting the right side to 0, the equations (10) and (11) are changed to By substitution, Φ ₂ + 2πn−Φ ₂₀ − (β ₂ / β ₁ ) · (Φ ₁ + 2πm−Φ ₁₀ ) = 0 (13) is obtained.

Actually, there is an error in the measured value of the phase difference.
It is sufficient to substitute integers m and n into the left side of (13) and determine a combination of m and n that makes the measured phase difference fall within the allowable error value. Therefore, the phase change amounts △ Φ ₁ and △ Φ ₂ can be obtained from m and n by the equations (10) and (11).

Since the change in the phase of the microwave is affected by the conductivity of the part to be measured, the attenuation is obtained from the voltages V ₁ and V ₂ , the conductivity is calculated from the amount of attenuation, and the phase difference is calculated. to correct.

In this embodiment, the switches 9 of the circuit blocks 1 and 2 are selectively switched to generate different frequencies separately. If the wave isolation is good and it is acceptable to transmit and receive at the same time, it is possible to measure simultaneously.

In this embodiment, two oscillators are used to generate different frequencies. However, if a wide frequency range is used and the frequency stability is good, the frequency can be set using one oscillator. It can be realized by changing.
In this case, except to change the frequency setting,
It is the same as a conventional circuit, and can be greatly simplified. (Second Embodiment) FIG.
1 is a configuration diagram showing an embodiment of a microwave densitometer according to the invention of FIG.

This microwave densitometer is an ISM (Industrial
rial, Scientific, and Medical), an oscillator 27 for generating a microwave signal of a frequency f _ISM , an amplifier 28 for amplifying the microwave signal at a predetermined amplification factor, and transmitting the amplified microwave signal to a transmission signal and a reference signal. A splitter 29 for splitting and outputting the signal 30 is provided. The split and output transmission signal is transmitted to an object to be measured in a pipe 32 via a transmission antenna 31, and a reception antenna on the opposite side of the pipe 32 is provided. 3
3 to receive.

The reason for using the microwave of the frequency f _ISM of the _ISM is as follows. ISM is a specific frequency band used in the fields of industry, science, and medicine, and regulations on output power and electric field strength are relaxed internationally. In Japan, Article 65 of the Radio Equipment Regulations stipulates that no special regulations on electric field strength are stipulated. Incidentally, the frequency band of ISM is described as follows: 13.560 MHz ± 7 kHz 27.120 MHz ± 163 kHz 40.680 MHz ± 20 kHz 433.92 MHz ± 870 kHz (several European countries) 915 MHz ± 13 MHz (North America / South America) 2450 MHz ± 50 MHz 5.8 GHz ± 75MHz 24.125GHz ± 125MHz 34 is a reference oscillator for outputting a reference signal 35, 36 of slightly different frequencies f _ISM + △ f and the frequency f _ISM,
The reference signal 36 and the reference signal 30 are mixed by a mixer 37 and sent to a phase difference measuring means 39 as a reference side heterodyne output 38 having a difference frequency Δf.

On the other hand, the received signal 40 and the reference signal 35 received by the receiving antenna 33 are combined by the combining means 41, amplified by the amplifier 42, and divided by the distribution means 43 into the received signal 40 and the reference signal 35. , And mixed by the mixer 44, thereby taking out the measurement side heterodyne output 45 having the difference frequency Δf and sending it to the phase difference measuring means 39. By combining the received signal 40 and the reference signal 35 by the combining means 41, a phase change due to a temperature change or the like of the amplifier 42 is compensated.

After calculating the phase difference between the two heterodyne outputs by the phase difference measuring means 39, the arithmetic unit 46
To send to. If the phase difference at the reference density is obtained in advance, the arithmetic unit 46 can obtain the density of the DUT from the measured phase difference based on the phase difference data of the reference density.

In the microwave densitometer, a voltage measuring means 47 is provided on the output side of the mixer 44, and measures the voltage V of the heterodyne output 45 on the measuring side and sends it to the arithmetic unit 46. The arithmetic unit 46 has a measurement side heterodyne output 45.
Then, the attenuation of the received microwave is calculated using the voltage V, the conductivity of the measured object is calculated from the reduced quantity, and the concentration error due to the change in conductivity is corrected.

The pipe 32 is provided with a temperature measuring means 48 for measuring the temperature t of the object to be measured. The temperature measuring means 48 measures the temperature t of the object to be measured and corrects a concentration error caused by a temperature change.

Hereinafter, an example of obtaining the conductivity σ and the corrected density D from the voltage V and the temperature t will be described. Now, assuming that the inner diameter of the pipe 32 is z, the voltage when there is no attenuation is V ₀ , and the attenuation rate is α, V = V ₀ exp (−αz) ∴α = (1 / z) ln (V ₀ / V) ... (14) Also, the conductivity σ, the attenuation rate α, and the temperature t
And σ = a ₀ + a ₁ α + a ₂ t + a ₃ αt + a ₄ α ² + a ₅ t ² (15), and the temperature t and the conductivity σ are obtained by the thermometer and the conductivity meter during calibration.
The measurement of the attenuation rate α when changing while measuring is repeated many times, and the coefficient a _i is obtained by regression analysis.

Then, at the time of measurement, the conductivity σ is obtained from the attenuation rate α and the temperature t according to the equation (15). On the other hand, the conductivity sigma and temperature t and the phase change amount △ for and [Phi _{is, △ Φ = a 0 + a} 1 D + a 2 σ + a 3 t + a 4 Dσ + a 5 Dt + a 6 σt + a 7 D 2 + a 8 σ 2 + a 9 t 2 ...... (16) After that, the amount of phase change when the concentration, conductivity, and temperature are changed at the time of calibration is measured many times, a coefficient a _i is obtained by regression analysis, and a solution for D in the above equation (16) is obtained. .

At the time of measurement, the corrected density is obtained by substituting ΔΦ, the conductivity σ and the temperature t obtained by the above equation (15) into the solution of D. Next, as another density measurement example, the following simultaneous equations are established for the phase change amount △ Φ and the attenuation rate α obtained by the above equation (14).

[0054] _{△ Φ = a 0 + a 1} D + a 2 σ + a 3 t + a 4 Dσ + a 5 Dt + a 6 σt + a 7 D 2 + a 8 σ 2 + a 9 t 2 ... (17a) α = b 0 + b 1 D + b 2 σ + b 3 t + b 4 Dσ + b _{5 Dt + b 6 σt + b} 7 D 2 + b 8 σ 2 + b 9 t 2 ... (17b) and, at the time of calibration is to measure a number of times and the phase shift amount and the attenuation when varying the concentration and electric conductivity and temperature, respectively Regression analysis is performed to find coefficients a _i and b _i . The obtained coefficient is substituted into the equation (17b) to obtain a solution of the conductivity σ. A solution for D in the above equation (17a) is obtained.

At the time of measurement, the attenuation rate α and the temperature t are obtained by substituting into the solution of the conductivity σ.
And the temperature t are substituted into the solution of D to obtain a corrected density. Further, as another example of concentration measurement, the phase change amount △ Φ
The following simultaneous equations are established with respect to the damping rate α obtained by the above equation (14).

[0056] _{△ Φ = a 0 + a 1} D + a 2 σ + a 3 Dσ + a 4 D 2 + a 5 σ 2 ... (18a) α = b 0 + b 1 D + b 2 σ + b 3 Dσ + b 4 D 2 + b 5 σ 2 ... (18b) in this case During calibration, the coefficients a _i and b _i are determined by changing the temperature in sufficiently fine steps, and a table is created for each temperature. At the time of measurement, a table of coefficients a _i and b _i is selected according to the temperature t, and the conductivity σ and the corrected concentration D are calculated by solving the simultaneous equations.

As described in the above density measurement example,
A corrected density can be obtained by substituting the conductivity into a previously calculated phase change amount equation. They are,
As in the case of the first embodiment, the present invention can be similarly applied to a case where a plurality of frequencies are used.

In the microwave densitometer according to the embodiment, switches 50 and 51 are inserted between the receiving antenna 33 and the coupling means 41 and between the terminating resistor 49 and the coupling means 41, respectively. One of the switches 50
Alternatively, only 51 is turned on. The switch 51 side is installed near the pipe 32 by the terminating resistor 49.

When the switch 51 of the switches 50 and 51 is turned on, the component due to the induction of the microwave is measured, and the phase can be corrected by subtracting from the intensity and phase of the microwave when the switch 50 is turned on.

Incidentally, as described with reference to FIG. 3, assuming that the intensity of the received signal 52 is V _t , the phase is Φ _t , the intensity V _i of the induced signal 53 is Φ _i, and the phase is Φ _i , the intensity of the true received signal 54 is V _r and phase Φ _r can be obtained from the following equations.

V _r = (V _t ² + V _i ² -2 V _t V _i (cos Φ _t cos Φ _i + sin Φ _t sin Φ _i ) ^1/2 (19) Φ _r = arc tan ｛(V _t sin Φ _{t -V i sin Φ i) /} (V t cos Φ t -V i sin Φ i)} ... (20) Next, a diagram FIG. 4 shows a cross-section of the receiving portion to enlarge the pipe 32.

In this microwave densitometer, the distance is shortened by interposing a dielectric 55 having the same dielectric constant as the measured object between the transmitting antenna 31 and the measured object in the pipe 32. So that microwaves pass smoothly near the tube wall. Similarly, the receiving antenna 33
By interposing a dielectric 56 having a dielectric constant equivalent to that of the device under test between the device and the device under test in the pipe 32, reflection is reduced and microwaves passing through the device under test are properly received. It is a configuration to do.

With this configuration, the piping 3
The effect of the second wall can be removed, and a concentration dependent only on the measured object can be measured. In addition, as a microwave transmitting and receiving unit,
As shown in FIG. 5, a transmission / reception unit 59 including a transmission antenna 57 and a reception antenna 58 is installed in the pipe 32 so as to have a distance smaller than the inner diameter of the pipe 32. With such a configuration, the amount of microwave attenuation can be reduced, and the concentration of the DUT can be measured with high accuracy.

[0064]

According to the first, third and fourth aspects of the present invention, by generating microwaves of a plurality of frequencies and measuring the rotation of the phase, the phase can be changed when the concentration is high or when the tube diameter is large. Also in the case of rotation, the rotation can be grasped and the density can be accurately obtained.

According to the second to fifth aspects of the present invention, the influence of the conductivity is measured by measuring the attenuation of the received microwave, calculating the conductivity from the attenuation, and correcting the concentration by the conductivity. The concentration can be measured with high accuracy without receiving it.

Further, by measuring the amount of attenuation of the received microwave, calculating the temperature of the object to be measured, and correcting the concentration based on the temperature, the concentration can be measured with high accuracy without being affected by a change in temperature.

According to the sixth aspect of the present invention, the received signal and the reference signal are added, then distributed and mixed to obtain a measurement-side heterodyne output. The concentration can be measured with high accuracy without receiving it.

According to the seventh aspect of the present invention, the reception signal output line is switched to select the terminating resistor side and the amount of induction is measured, so that the influence of unnecessary reception signals can be eliminated. According to the eighth and ninth aspects of the invention, in order to increase the amount of received radio waves, a dielectric having a dielectric constant equivalent to that of an object to be measured in the tube is disposed at a portion in contact with the tube, thereby reducing microwave reflection. It is possible to achieve the same function as a distance smaller than the inner diameter of the pipe. In addition, by installing the transmitting / receiving unit at a distance smaller than the inner diameter of the tube, the amount of microwave attenuation can be reduced, and the concentration can be measured with high accuracy. Claim 10
According to the invention, by transmitting a high-output microwave using the frequency of the ISM, a sufficient reception signal can be obtained, and the concentration can be measured with high accuracy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a microwave densitometer according to the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the microwave densitometer according to the present invention.

FIG. 3 is an explanatory diagram for obtaining a true reception signal from a reception signal and a signal by induction.

FIG. 4 is an enlarged view showing an example of installation of a transmitting / receiving antenna on a pipe.

FIG. 5 is a configuration diagram in which a transmission / reception unit is arranged in a pipe.

FIG. 6 is a configuration diagram of a conventional microwave densitometer.

[Explanation of symbols]

 1, 2, circuit block 3, 27, oscillator 5, 29, distribution means 9, 50, 51, switch 8, 18, 37, 44, mixer 10, coupling means 19, 34, reference oscillator 23, 39, phase difference Measuring means 25, 47 Voltage measuring means 26, 46 Computing device 48 Temperature measuring means 49 Terminating resistor 55, 56 Dielectric

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Katsusen Shimokawa 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation Fuchu Plant

Claims (10)

[Claims] 1. A microwave densitometer for measuring a phase delay of a microwave passing through an object to be measured in a tube and measuring the concentration of the object to be measured. A microwave transmitting / receiving unit for selectively transmitting microwaves of a plurality of frequencies individually generated from the microwave generating means and receiving the microwaves via the object to be measured in the tube; and receiving the microwaves by the microwave transmitting / receiving unit. Phase difference measuring means for measuring first and second phase differences based on microwaves of the plurality of frequencies using a received signal; and determining phase rotation based on the first and second phase differences. Means, and a microwave densitometer comprising: 2. A microwave densitometer for measuring a phase delay of a microwave passing through an object to be measured in a tube and measuring the concentration of the object to be measured, wherein: a microwave generating means for generating a microwave having a predetermined frequency; A microwave transmission / reception unit that receives a microwave generated from the microwave generation unit via the device under test in the tube; and a phase difference is measured using a reception signal received by the microwave transmission / reception unit. Phase difference measuring means, voltage measuring means for measuring the voltage of the signal related to the received signal, and measuring the attenuation of the microwave received from the voltage measured by the voltage measuring means, using this attenuation Correction means for calculating the conductivity of the object to be measured and correcting the phase difference using the calculated conductivity. 3. The microwave densitometer according to claim 1, wherein when one microwave generating means is provided, the frequency is changed to selectively generate microwaves having a plurality of different frequencies. . 4. When two microwave generating means for generating microwaves of different frequencies are provided, a microwave transmitting / receiving unit is connected to each microwave generating means via a switch, and these switches are selectively turned on. 22. The microwave densitometer according to claim 1, wherein microwaves having different frequencies are transmitted as transmission signals to a microwave transmission / reception unit. 5. A microwave densitometer for measuring a phase delay of a microwave passing through an object to be measured in a tube and measuring the concentration of the object to be measured, wherein: a microwave generating means for generating a microwave having a predetermined frequency; A microwave transmission / reception unit that receives a microwave generated from the microwave generation unit via the device under test in the tube; and a phase difference is measured using a reception signal received by the microwave transmission / reception unit. Phase difference measuring means, voltage measuring means for measuring a voltage of a signal related to the received signal, temperature measuring means for measuring the temperature of the device under test in the tube, and a receiving micro from a voltage measured by the voltage measuring means. While measuring the amount of attenuation of the wave, calculating the conductivity of the device under test from the amount of attenuation and the measured temperature, and correcting the phase difference using the calculated conductivity. Means, and a microwave densitometer comprising: 6. A microwave densitometer for measuring a phase delay of a microwave passing through an object to be measured in a tube and measuring a concentration of the object to be measured, wherein: a microwave generating means for generating a microwave having a predetermined frequency; A microwave transmission / reception unit that receives a microwave generated from the microwave generation means via an object to be measured in the tube; and a reception signal received by the microwave transmission / reception unit and the predetermined frequency. Frequency conversion means for adding a reference signal of a different frequency and then extracting a distributed and mixed signal; and phase difference measuring means for measuring a phase difference using the distributed and mixed signal. Microwave densitometer. 7. A microwave densitometer for measuring a phase delay of a microwave passing through an object to be measured in a tube and measuring a concentration of the object to be measured, wherein: a microwave generating means for generating a microwave having a predetermined frequency; A microwave transmitting / receiving unit that receives a microwave generated from the microwave generating means via the device under test in the tube, a terminating resistor having one end grounded, and an output line on the other end side of the terminating resistor. Selecting means for selecting an output line of the microwave receiving unit, and measuring an inductive component of the microwave from an output of the other end side output line of the terminating resistor selected by the selecting means,
A microwave densitometer comprising: an induction correction unit configured to correct a phase difference obtained from an output of the selected output line of the microwave reception unit. 8. A microwave densitometer for measuring a phase delay of a microwave passing through an object to be measured in a tube to measure the concentration of the object to be measured. A microwave receiving unit that receives microwaves through the DUT in the tube, and a dielectric equivalent to the DUT between a portion that contacts the tube or a portion that penetrates the tube and contacts the DUT. A microwave densitometer characterized in that a dielectric material having a ratio is arranged. 9. A microwave densitometer for measuring a phase delay of a microwave passing through an object to be measured in a tube and measuring the concentration of the object to be measured, wherein the distance is smaller than the inner diameter of the tube in the tube. A microwave densitometer comprising: a microwave transmitting unit for generating microwaves; and a microwave receiving unit for receiving the generated microwaves via an object to be measured in a tube. 10. As a microwave having a predetermined frequency,
10. The microwave densitometer according to claim 2, wherein an ISM frequency is used.