JP2002350364A - Microwave apparatus for measuring concentration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and in real tame measure the concentration of solid materials/suspended matters in an object to be measured even in the case of the occurrence of bubbling or the like in the object to be measured. SOLUTION: The microwave apparatus for measuring the concentration, which transmits one of two microwaves toward the object to be measured, mixes a received signal and the other microwave, detects the difference between phases and measures the concentration, is composed of a microwave generating means 30 that generates a linearly or circularly polarized microwave, and a microwave receiving means 31 that detects microwaves having an identical phase and being normal to the microwave transmitted from a sending side in the case of using the linearly polarized microwave, and having an identical rotating direction and a reverse rotating direction to the microwave transmitted from the sending side in the case of using the circularly polarized microwave.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concentration measuring device using microwaves for measuring the concentration of solids and suspended solids in an object to be measured.
The present invention relates to a microwave concentration measuring device capable of measuring the concentrations of pulp and other various substances in a paper to be measured in papermaking with high accuracy and in real time without interrupting the flow.

[0002]

2. Description of the Related Art Conventionally, as one method for measuring the concentration of an object to be measured, for example, a solid substance or a suspended substance in a measurement liquid, a part of the measurement liquid is sampled, and the measurement liquid is evaporated to remove residue. There is a primitive way of weighing. However, in such a method, it takes a long time for measurement, and it is difficult to achieve automation.

For this reason, various types of sensors have been put to practical use as densitometers. As one of them, for example, a densitometer using ultrasonic waves is used. However, this ultrasonic type densitometer has a problem that measurement cannot be performed when bubbles are present in the liquid.

Therefore, recently, in order to solve such a problem, a densitometer using a microwave as disclosed in, for example, Japanese Patent Application Laid-Open No. 4-238246 has been developed.

This microwave densitometer measures the concentration by measuring the phase delay of the microwave because the phase of the microwave causes a delay almost proportional to the concentration of the substance to be measured in the liquid to be measured. .

Hereinafter, an outline of a measurement method using this type of microwave densitometer will be described with reference to FIG.

FIG. 11 is a block diagram showing a configuration example of a conventional microwave densitometer of this type.

In FIG. 11, a microwave densitometer includes a transmitting / receiving antenna 62 and 64 disposed on a pipe 63 as a microwave antenna, a densitometer circuit 79 as a microwave circuit, and an arithmetic unit. 81.

An oscillator 55 generates two microwave signals 56 and 57 having a frequency f. One microwave signal 5
6 is amplified by an amplifier 58, and switches 59, 6
When 0 is in the state as shown in FIG. 11, the transmission signal 61 is sent to the antenna 62 arranged on the pipe 63 and sent out into the pipe 63 passing through the measurement liquid to be measured,
The signal is received by an antenna 64 disposed on a pipe 63 so as to face the antenna 62.

The reference oscillator 65 has a frequency f + slightly different from the frequency f of the microwave signals 56 and 57 of the oscillator 55.
It generates two reference signals 66 and 67 of Δf. The other microwave signal 57 and one reference signal 66 are connected to a mixer 68
To obtain a reference side heterodyne output 69 having a difference frequency Δf, which is converted by a comparator 70 into a reference side digital signal θ _FB 71 having a voltage of 0 as a threshold, and sent to a phase difference measuring means 72.

The received signal 73 from the antenna 64 is amplified by an amplifier 74 and the amplified received signal 73 is amplified.
And the other reference signal 67 are mixed by a mixer 75 and a measurement side heterodyne output 76 having a difference frequency Δf
Is converted into a measurement-side digital signal θ _REF 78 by the comparator 77 and sent to the phase difference measuring means 72.

The phase difference measuring means 72 has two digital outputs.
Force θ_FB71, θ_REF78 phase difference Φ_V Ask for. This place
Phase difference Φ_VAs shown in FIG.
And the signal θ_FB, Θ_REFPhase difference Φ_V
Asking.

Here, in the densitometer circuit 79 shown by the dotted line, the phase changes due to a change in the temperature inside the circuit or the like, which causes an error. Therefore, the switches 59 and 60 are set in FIG.
The phase difference Φ _R through the fixed reference 80 is measured by switching to the opposite side as shown in FIG. 4 and subtracted from the phase difference Φ _V to compensate for the above-mentioned error.

That is, the required phase difference Φ is Φ = Φ _V −Φ _R.

Here, an attenuator is used as the fixed reference 80 in order to reduce the microwave signal level to a level equivalent to that received by the antenna 64.

If data on the phase difference at the reference concentration (calibration curve data) is obtained in advance, the concentration of the substance to be measured in the measurement liquid is calculated by the arithmetic unit 81 from the obtained phase difference Φ based on the data. can do.

Here, if the density is D, the relationship with the phase difference is almost linear as D = aΦ + b (1). Analysis may be performed to determine a and b.

In a conductive medium (eg, water) as a measuring liquid, the relationship between microwave attenuation / phase lag and the medium's conductivity σ, dielectric constant, and temperature t is theoretically as follows. Become.

Microwave attenuation rate α (Neper / m) and phase change rate β (rad / s) of angular frequency ω (rad / s)
m) can be expressed as in equations (2) and (3).

[0020]

(Equation 1)

Here, σ is the conductivity, and ε _r ′ and ε _r ″ are the real and imaginary parts of the complex relative permittivity of the medium.

It is known that the effective dielectric constant changes when the concentration of sludge, pulp, or the like, which is a measurement substance, changes.
In particular, the correlation between the real part of the dielectric constant and the concentration is high.

In the above equations (2) and (3),

(Equation 2) In other words, if the imaginary part of the dielectric constant is small and the conductivity is small,

(Equation 3) From α and β obtained by the above equations (4) and (5), the attenuation
Find the phase lag. Assuming that the transmission power is P ₀ and the microwave power traveling in the z direction is P, P = P ₀ exp (−2αz) (6), and the attenuation is 20αz / ln10 (dB).
The phase delay is βz (rad).

In the above-described method, the density is obtained by obtaining the phase delay. As shown in the above equation (5), ε _r ′
Ε _r ′ and β are proportional to
The concentration is determined from Note that α is not directly used for concentration measurement because α has a smaller degree of correlation than β.

[0025]

However, the above-mentioned conventional microwave densitometer has the following problems.

(A) When the temperature or conductivity of the measurement liquid changes, the amount of microwave attenuation by the measurement liquid changes significantly. The microwave is attenuated and the measurement side heterodyne output 76
Is small, the time of switching changes due to the influence of noise and drift when digitizing by the comparator 77, resulting in a measurement error.

(B) For the same reason as in (a) above, if the power of the received signal 73 changes, the phase changes due to the non-linearity of the electronic circuit, resulting in a measurement error.

(C) Although the influence of the temperature drift of the electronic circuit is compensated by a fixed reference, if the signal level of the heterodyne output 76 on the measurement side changes, the influence of the temperature changes. Can not.

(D) Since the density is determined by a phase change, if the phase of the received signal 73 exceeds 360 degrees, the density cannot be determined correctly. That is, the pipe diameter is large,
When the concentration of the measurement substance is high, the phase changes by 360 degrees or more, so that the concentration cannot be uniquely determined from the phase change. If the measurement is continuously performed, for example, “Japanese Unexamined Patent Publication No.
82606 ", the number of rotations can be determined in a front-to-back relationship. However, once empty, the correct concentration cannot be measured when the target is next filled.

(E) Microwaves are received through places other than in the liquid due to sneaking and guidance from the circuit wiring pattern, resulting in measurement errors.

(F) If bubbles are present in the measurement liquid, the measurement error may be reduced due to the microwave propagation path being lengthened or being received through a plurality of paths due to the reflection of the microwave. Occurs.

(G) When the temperature or conductivity of the measurement liquid changes, the phase of the microwave changes, causing an error. Therefore, it is necessary to determine the temperature and the electric conductivity to perform the correction, and for example, a method of measuring the electric conductivity has been proposed as disclosed in Japanese Patent Application Laid-Open No. 9-43181. However, it is difficult to put the conductivity sensor to practical use because dirt easily adheres to the conductivity sensor, and there are problems such as deterioration of measurement accuracy and maintenance work.

It is an object of the present invention to provide a low-cost, high-precision and real-time method for determining the concentration of solids and suspended solids in an object to be measured even when bubbles are generated in the object to be measured. To provide a microwave concentration measuring device.

[0034]

In order to achieve the above object, according to the first aspect of the present invention, one of the two microwaves is transmitted to the object to be measured and the signal received is transmitted to the object to be measured. In a microwave concentration measuring device that measures a phase difference by measuring a phase difference by mixing with a microwave, a microwave generating means for generating a linearly or circularly polarized microwave, and when the transmitting side is a linearly polarized wave, It is provided with microwave receiving means for detecting the same rotational direction and the opposite rotational direction when the transmitting side is circularly polarized and the transmitting side is circularly polarized.

According to the second aspect of the present invention, the first aspect is provided.
The microwave concentration measuring apparatus according to the invention is provided with correction means for calculating the amount of bubbles from the two signals and correcting the phase measurement value.

Therefore, in the microwave concentration measuring apparatus according to the first and second aspects of the present invention, the microwave to be transmitted is linearly or circularly polarized, and the microwave to be received is linearly polarized when the transmitting side is linearly polarized. In phase and at right angles to this, when the transmitting side is circularly polarized, detect the same rotation direction and reverse rotation direction, calculate the amount of bubbles from the two signals and correct the phase measurement value, so that in the liquid Even when there are bubbles, the concentration can be measured with high accuracy because the amount of the bubbles is measured to compensate for the influence.

According to a third aspect of the present invention, there is provided the microwave density measuring apparatus according to the first or second aspect, further comprising a phase difference measuring means having a phase counting means for counting a phase difference at a center position. I have.

Therefore, in the microwave density measuring apparatus according to the third aspect of the present invention, the same effect as that of the first or second aspect of the present invention is obtained, and the phase difference is counted at the center position, so that the measurement error can be obtained. Does not occur, and the concentration can be measured with high accuracy.

On the other hand, according to the invention of claim 4, the above-mentioned claim 1
In the microwave concentration measuring apparatus according to any one of claims 3 to 3, in a method of measuring by switching between a measured object and a fixed reference as a measurement value,
A fixed reference measuring means using a signal from an external transmitting antenna position is provided.

Therefore, in the microwave concentration measuring apparatus according to the fourth aspect of the present invention, in addition to the same operation as that of any one of the first to third aspects of the present invention, a signal from an external transmitting antenna position is transmitted. By measuring as a fixed reference, even when there is a phase change due to a temperature change or the like inside the circuit, the phase difference through the fixed reference is measured and compensated, so that the concentration can be measured with high accuracy.

According to the fifth aspect of the present invention, the above first aspect is provided.
In the microwave concentration measuring apparatus according to any one of the fourth to fourth aspects of the present invention, a signal level control means for controlling a level of the mixed signal to be constant is provided.

Therefore, in the microwave density measuring apparatus according to the fifth aspect of the present invention, the same effect as that of any one of the first to fourth aspects of the present invention is obtained, and the level of the mixed signal is kept constant. In this way, errors do not occur even when the microwave attenuation is large due to the temperature and conductivity of the measured object, and when the measured signal level is small, the signal is amplified to improve the S / N ratio against noise. Therefore, the concentration can be measured with high accuracy.

According to a sixth aspect of the present invention, in the microwave concentration measuring apparatus according to any one of the first to fifth aspects of the present invention, a housing for measuring a temperature of a housing in which the measuring device main body is stored. Temperature measuring means, and a temperature control means for controlling the case temperature to be a constant value when the case temperature measured by the case temperature measuring means is equal to or less than a certain value,
When the case temperature measured by the case temperature measuring means is equal to or higher than a predetermined value, a correcting means for correcting the measured value by a preset correction value is provided.

Therefore, the microwave concentration measuring apparatus according to the sixth aspect of the present invention has the same effect as that of any one of the first to fifth aspects of the present invention. The temperature is controlled to a constant value, and when the temperature is equal to or higher than a certain value, the measured value is corrected by a preset correction value, so that even if the ambient temperature changes, Concentration can be measured,
Further, the circuit is simplified and the cost can be reduced.

[0045]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing a configuration example of a microwave concentration measuring apparatus according to the present embodiment.

In FIG. 1, a clock source 1 generates a reference signal (θ _REF ) 2 as a phase reference, which is a low-frequency signal.

The oscillator 3 constituting a part of the microwave generating means includes a PLL circuit (phased lock loop circuit), and includes a reference signal 2 from a clock source 1.
Is used as a synchronization signal for the PLL circuit, thereby generating a microwave having a frequency f (corresponding to one microwave in claims) in synchronization with the reference signal 2 from the clock source 1.

The microwave from the oscillator 3 is amplified by the amplifier 4, and when the switches 5 and 6 are in the illustrated state, the microwave is transmitted from the transmitting antenna 7 to the liquid to be measured in the pipe 8 and received. The signal is received by the antenna 9 and amplified by the amplifier 10 to obtain a received signal 12.

The reference oscillator 11 constituting a part of the microwave generating means includes a PLL circuit, like the oscillator 3, and uses the reference signal 2 from the clock source 1 as a synchronization signal of the PLL circuit. As a result, in synchronization with the reference signal 2 from the clock source 1, a microwave having a frequency f + Δf different from the frequency f of the microwave from the oscillator 3 by Δf (corresponding to the other microwave in the claims) is transmitted to the reference signal 1.
Occurs as 3.

The mixer 14, which is a microwave mixing means,
The received signal 12 and the reference signal 13 are mixed to obtain a frequency Δf
Is obtained. Although not shown, the heterodyne output 15 attenuates an unnecessary high frequency by a filter or the like as necessary, and amplifies the frequency Δf component.

The comparator 16 has a heterodyne output 1
5 is input and the measurement digital signal θ _FB 17 is output.

The phase difference measuring means 18 measures the phase difference by comparing the measurement digital signal 17 with the reference signal 2 from the clock source 1, and outputs the phase difference Φ.

Here, as the phase difference measuring means 18, in this embodiment, particularly, a phase counting means for counting the phase difference at a substantial center position of the phase difference is provided.

The arithmetic unit 19 calculates and outputs the density of the object to be measured from the phase difference Φ from the phase difference measuring means 18.

Next, in the microwave density measuring apparatus of the present embodiment configured as described above, a reference signal 2 is generated by a clock source 1 as a phase reference, and transmitted in synchronization with the reference signal 2. Two microwaves having different frequencies from each other are generated by the detector 3 and the reference oscillator 11, the signal 12 measured by one microwave and the other microwave 13 are mixed, and the heterodyne output 15 obtained by the mixing is mixed. Since the phase of the measured digital signal θ _FB 17 and the reference signal 2 from the clock source 1 are compared with each other, two mixers, which are means for mixing microwaves, are required in the conventional example of FIG. Can be reduced to one. That is, the mixer 68 in the conventional example of FIG. 11 can be omitted.

As a result, the expensive microwave circuit can be omitted, and the comparator circuit after the mixer (the comparator 70 in the conventional example of FIG. 11) can also be omitted. Therefore, the circuit becomes extremely simple, and the circuit is inexpensive and highly reliable. Becomes

That is, this is made possible by the fact that the two microwave oscillators 3 and 11 are controlled by the PLL circuit so as to be completely synchronized with the low-frequency clock source 1 which is not a microwave. This is because the low frequency of the signal from the clock source 1 can be used as a reference frequency.

Note that the reference signal θ _REF used for the phase difference measurement is
2 is used to obtain a relative value with respect to the measurement digital signal θ _FB 17, and the reference signal θ _REF 2 obtained from the fixed reference 20
The absolute value is obtained from the relative value of the measured digital signal θ _FB 17 and the measured value is calculated by comparing the absolute value with the calibration curve data prepared in advance.

On the other hand, in the microwave concentration measuring apparatus of the present embodiment, since the phase difference is counted at the substantial center position of the phase difference, no measurement error occurs and the concentration is measured with high accuracy. be able to.

FIGS. 2A to 2C are diagrams for explaining the operation of the phase counting means.

In FIG. 2, θ _REF is a reference signal 2 and θ _FB is a measurement digital signal 17. In the above-described conventional method, the rise time difference Φ ₁ was obtained. In), the average value of Φ ₁ and Φ ₂ is obtained.

That is, due to the DC component of the heterodyne output 15, drift, the threshold value of the comparator 16 is not strictly 0 [v], etc.
As shown in the _figure , when the ratio of “0” and “1” of θ _FB is different, an error occurs in the above-described conventional method, but by using the center method of the present embodiment, no error occurs and The concentration can be accurately measured. In particular, the effect is large when the attenuation of the microwave is large and the amplitude of the heterodyne output 15 is small.

As described above, in the microwave density measuring apparatus according to the present embodiment, the clock source 1 generates the low-frequency reference signal 2 as the phase reference, and the low-frequency reference signal 2 is synchronized with the low-frequency reference signal 2. Two microwaves having different frequencies are generated by PLL control, and a received signal obtained by passing one microwave through a measurement liquid is mixed with the other microwave, and the phase is compared with a reference signal 2 from a clock source 1. Therefore, the circuit can be simplified, and it can be inexpensive and highly reliable.

Since the phase difference is counted at the substantial center position of the phase difference, no measurement error occurs, and the density can be measured with high accuracy.

The present embodiment can be applied to a conventional example as shown in FIG.

(Modification of the First Embodiment)
In the microwave concentration measuring apparatus according to the present embodiment, a plurality of microwaves having the same frequency difference are generated as the oscillator 3 and the reference oscillator 11 according to the first embodiment.

That is, the oscillator 3 is set to the frequency f ₁ , f
₂ and a reference oscillator 11
Generate microwaves of frequencies f ₁ + Δf and f ₂ + Δf.

The phase difference measuring means 18 measures the phase difference based on the plurality of microwaves having the same frequency difference, switches and measures the microwaves from these, and detects the phase difference of 360 degrees or more. I try to measure.

Next, in the microwave concentration measuring apparatus of the present embodiment configured as described above, a plurality of microwaves having the same frequency difference are generated, switched and measured,
By measuring the phase difference of degrees or more, the phase becomes 36
Even when the angle changes beyond 0 degrees, the correct phase change amount can be obtained.

That is, in this example, two sets of frequencies f _1,
Generate f ₂ and f ₁ + Δf, f ₂ + Δf, and measure the phase difference in each combination. Then, from these two phase differences, the rotation speed of the phase change is obtained, and the phase change in the case of exceeding 360 degrees is obtained.

Here, the two phase differences are Φ ₁ and Φ ₂ . Further, it is assumed that the phase difference when the density is 0 is Φ ₁₀ and Φ ₂₀ for f ₁ and f ₂ , respectively, and that the phase difference changes as follows due to the change in the density.

F ₁ : Φ ₁₀ → Φ ₁ + 2πm (m is 0 or a positive integer) f ₂ : Φ ₂₀ → Φ ₂ + 2πn (n is 0 or a positive integer) m and n are rotation speeds.

The change amounts of the phase difference ΔΦ ₁ and ΔΦ _{2 are} as follows: ΔΦ ₁ = Φ ₁ + 2πm−Φ ₁₀ (7) ΔΦ ₂ = Φ ₂ + 2πn−Φ ₂₀ (8) Phase change at f ₁ and f ₂ Assuming that the rates are β ₁ and β ₂ , ΔΦ ₂ = (β ₂ / β ₁ ) · ΔΦ ₁ (9)

When the right side is subtracted from the left side of equation (9) and the above equations (7) and (8) are substituted, Φ ₂ + 2πn−Φ ₂₀ − (β ₂ / β ₁ ) · (Φ ₁ + 2πm−Φ ₁₀ ) = 0 (10) Actually, there is an error in the phase difference measurement value.
It is sufficient to substitute integers m and n into the left side of the equation (0), and obtain a combination of m and n whose values are within the allowable error value.

From these m and n, the phase difference change amounts ΔΦ ₁ and ΔΦ ₂ are obtained by the above equations (8) and (9), and the density is calculated.

Β ₂ / β ₁ is equal to f ₁ / f ₂ if ε _r ′ is the same according to the above equation (5). Since f ₁ and f ₂ take relatively close values, ε _r ′ generally does not change so much.

As described above, in the microwave concentration measuring device according to the modified example of the present embodiment, the transmitters 3 and 11 as the microwave signal sources generate a plurality of microwaves having the same frequency difference and switch them. Since the measurement is performed and the phase difference of 360 degrees or more is measured, when the phase changes beyond 360 degrees, even if a method such as the above-mentioned “Japanese Patent Application Laid-Open No. 8-82606” is not used, A correct phase change amount can be obtained.

Thus, the correct concentration can be measured even when the diameter of the tube is large, when the substance to be measured has a high concentration, or when the inside of the tube is once emptied and then filled with the measuring liquid.

Although the present embodiment has been described as a modification of the first embodiment, the present invention is not limited to this, and can be applied to the conventional example shown in FIG.

(Second Embodiment) FIG. 3 is a block diagram showing a configuration example of a microwave concentration measuring apparatus according to the present embodiment. The same parts as those in FIG. Are omitted, and only different portions will be described here.

That is, the basic configuration of the microwave density measuring apparatus of the present embodiment is the same as that of the conventional example described above, and the microwave generated by the oscillator 3 and the reference oscillator 11 is mixed by the mixer 22. Thus, the reference side heterodyne signal 23 is obtained, and the reference signal 25 is obtained by the comparator 24.

Although not shown, the measurement side heterodyne output 15 attenuates high frequencies with a filter or the like as necessary.
The frequency Δf component is amplified.

Further, a reference terminal 26 is provided adjacent to the transmission antenna 7. That is, a fixed reference measuring means using a signal from an external transmitting antenna 7 position is provided as a fixed reference.

Next, in the microwave density measuring apparatus of the present embodiment configured as described above, the phase difference passing through the fixed reference is measured and compensated, so that the temperature difference inside the circuit can be changed. Even when there is a phase change, the concentration can be measured with high accuracy.

In particular, the distance from the receiving antenna 9 to the entrance of the densitometer circuit, which is an electronic circuit, can be equal to the distance from the reference terminal 26 to the entrance of the densitometer circuit, which is an electronic circuit. For this reason, the fixed reference is the transmitting antenna 7
The phase delay due to the cable to the receiving antenna 9 can be compensated, and the phase delay due to the temperature change can be eliminated by the compensation of the phase delay, so that accurate measurement can be performed.

On the other hand, in the conventional example described above, since the fixed reference using the fixed attenuator is used, an error may occur when the temperature of the cable changes. That is, in the conventional example described above, since the phase is changed by a temperature change or the like of the internal circuit, by measuring the phase difference [Phi _R through the fixed reference had to compensate the phase variation by subtracting from the phase difference [Phi _V .

On the other hand, in the present embodiment, the reference terminal 26 is provided adjacent to the transmission antenna 7, and a signal received by the reference terminal 26 is used as a fixed reference. Then, by switching the switch 6 to the reference terminal 26 side, measuring the phase difference Φ _R through the fixed reference, and subtracting it from the phase difference Φ _V , the above-described error can be compensated.

In this embodiment, the reference terminal 26
Although the antenna for receiving the radio wave from the transmitting antenna 7 has been described as above, a unit for receiving a part of the power to the transmitting antenna 7 may be used.

As described above, in the microwave concentration measuring apparatus according to the present embodiment, the phase difference is measured and compensated by passing the fixed reference, so that there is a phase change due to a temperature change inside the circuit. Even in this case, the concentration can be measured with high accuracy.

Although the present embodiment has been described as a modification of the first embodiment, the present invention is not limited to this and can be applied to the conventional example shown in FIG.

(Third Embodiment) FIG. 4 is a block diagram showing a configuration example of a microwave concentration measuring apparatus according to the present embodiment. The same parts as those in FIG. Are omitted, and only different portions will be described here.

That is, the microwave density measuring apparatus of the present embodiment has the same basic configuration as the above-described conventional example, and the microwave generated by the oscillator 3 and the reference oscillator 11 is mixed by the mixer 22. Thus, the reference side heterodyne signal 23 is obtained, and the comparator 24 obtains the reference signal 25.

Although not shown, the measurement side heterodyne output 15 attenuates high frequencies with a filter or the like as necessary.
The frequency Δf component is amplified.

The frequency mixing means 28 generates the reference signal 1
The measurement is performed with three phases as a plurality of values. In particular, in this example, microwaves having two phases different by 90 degrees are produced and mixed by the mixer 14. This 90 degree phase difference is created by the hybrid 29.

The fixed reference 27 uses an attenuator.

Next, in the microwave density measuring apparatus of the present embodiment configured as described above, one microwave for obtaining the measurement side heterodyne output 15 is used as a plurality of phase values to measure the phase difference. Accordingly, even if there is a wraparound or an induction from the wiring pattern of the circuit, the measurement can be performed in a plurality of phases and compensated, so that the concentration can be measured with high accuracy.

Since the hybrid 29 is easily available, generation of a microwave having a phase of 90 degrees or an integral multiple thereof can be easily realized.

That is, in the phase measurement according to the present embodiment, as shown in FIG. 5A, phases Φ _I and Φ _Q differing by 90 degrees are measured, the average thereof is obtained, and this is used for density value calculation. Is the phase Φ.

In this method, assuming that the phase of the microwave passing through the measuring liquid has changed from a certain reference to +360 degrees, a typical example of the error characteristics of the phase Φ measured by experiment is shown in FIG. .

That is, due to a disturbance having a fixed phase, such as wraparound or induction from a circuit wiring pattern, Φ
_{Although I} and Φ _Q have sine component nonlinearity errors,
The error Φ obtained by averaging these Φ _I and Φ _Q is canceled out, and the phase Φ has good linearity.

Note that, in the present embodiment, two different by 90 degrees are used.
Two phases differed by 180 degrees, or 0 °, 90 °, 180 °, 270 °
May be measured.

In this embodiment, the phase of the reference signal is changed. However, a method of changing the phase of the received signal, or two mixers are provided, one of which is 0 ° and the other is 90 °. Alternatively, two sets of circuits may be provided.

As described above, in the microwave concentration measuring apparatus according to the present embodiment, compensation is performed by measuring at a plurality of phases. It is possible to measure the concentration with high accuracy. This is particularly effective when the received microwave power is small.

Further, since the phase is made 90 degrees or an integral multiple thereof, the circuit can be easily realized by the hybrid 29.

(Fourth Embodiment) FIG. 6 is a block diagram showing a configuration example of a microwave density measuring apparatus according to the present embodiment. The same parts as those in FIG. Are omitted, and only different portions will be described here.

That is, the microwave density measuring apparatus according to the present embodiment has the same basic configuration as that of the above-described conventional example. It is attenuated to amplify the frequency Δf component.

The transmitting antenna 30, which is a microwave generating means, has a function of transmitting linearly or circularly polarized microwaves.

Further, a second terminal 32 is provided on a receiving antenna 31 which is a microwave receiving means, and a switch 33 is provided.
From the state shown in FIG. 6 to the second terminal 32 side, and when the transmitting side is linearly polarized, receives a microwave having the same phase as the transmitting microwave and a microwave orthogonal to the microwave having the same phase. When the transmitting side is a circularly polarized wave, a microwave in the same rotation direction as the transmission microwave and a microwave in the reverse rotation direction to the transmission microwave are received.

When the object to be measured is the liquid to be measured, if there are bubbles in the liquid to be measured, the microwaves are reflected on the bubbles, and the direction of the plane of polarization and the direction of rotation change. The multiple reflected microwave is received by the second terminal 32.

Here, the amount of microwaves reflected multiple times is
Since there is a positive correlation with the amount of bubbles, the arithmetic unit 19 calculates the amount of bubbles from the two signals to correct the phase measurement value.

Next, in the microwave concentration measuring apparatus of the present embodiment configured as described above, the microwave to be transmitted is linearly or circularly polarized, and the microwave to be received is linearly polarized on the transmitting side. In this case, receive microwaves in phase and at right angles to it, and if the transmitting side is circularly polarized, receive microwaves in the same and opposite rotation directions, and calculate the amount of bubbles from the two signals. By correcting the phase measurement value, even if there are bubbles in the measurement liquid, to measure the amount of bubbles and compensate for the effect,
The concentration can be measured with high accuracy.

That is, in the case of linear polarization and circular polarization, the amount of reflection can be measured as the intensity of the microwave detected at the second terminal 32 of the receiving antenna 31. Also,
If the characteristics of the amount of bubbles, the intensity of the received microwave, and the phase change are determined in advance, the amount of bubbles can be measured to compensate for the influence on the phase.

Hereinafter, such a point will be described more specifically.

The transmitting antenna 30 and the receiving antenna 31 have common parts, and the basic configuration is shown in FIG.

In FIG. 7A, the substrate 34 is made of a dielectric (dielectric constant).

The pattern 35 is a square solid pattern on the front side, and is a thin film metal. The length of one side is λ /
(The lambda wavelength) 2 is, but since the substrate 34, lambda is shortened compared to the wavelength in vacuum to 1 / √ε _r. The pattern 35 is provided with terminals 36 and terminals 37.

Here, the terminal 36 is located below the center of the pattern 35 at about 1/3 of the distance from the center to the side. Further, the terminal 37 is located on the right side of the center of the pattern 35 at a position which is about 1/3 of the distance from the center to the side.

The pattern 38 is a solid ground pattern on the back side (this is also a thin-film metal) and has holes only where the leads of the terminals 36 and 37 pass.

The transmitting antenna 30 and the receiving antenna 31
The terminals 36 and 37 are installed so as to face each other correctly (lines connecting the center of the antenna and the terminal 36 are parallel to each other).

When transmitting linearly polarized waves from the transmitting antenna 30, the terminal 37 need not be provided, and power may be supplied only to the terminal. When transmitting a circularly polarized wave from the transmission antenna 30, as shown in FIG.
A microwave 42 having a phase difference of 0 degrees is created,
1 is supplied to the terminal 36 and the microwave 42 is supplied to the terminal 37.
Although the hybrid 40 has four terminals, the other one is terminated by a terminating resistor 43.

When linearly polarized waves are used, the plane of polarization of a microwave reflected and received by an object in a measured object is different from that of a transmitted microwave. In the receiving antenna 31, a component on the same polarization plane as the transmission microwave is received from the terminal 36, and a component on a polarization plane orthogonal to the transmission microwave is received from the terminal 37. In this case, the terminal 37 corresponds to the second terminal 32.

When circularly polarized waves are used, the rotation direction of the circularly polarized microwaves reflected and received by the object in the object to be measured is opposite to that of the transmitted microwaves. That is, as shown in FIG. 7C, the receiving antenna 31 combines the microwaves received at the terminals 36 and 37 into the hybrid 44 and combines them. Note that FIG. 7C is shown as a perspective view so as not to change the rotation direction on the drawing.

Here, as shown in FIG. 7B, on the transmitting side, as shown in FIG. 7B, if a microwave having a phase delayed by 90 degrees with respect to the terminal 36 is supplied to the terminal 37, the rotation direction is the same as that of the transmitting microwave. Is received, the terminal 37 side is connected to the terminal 36
90 degrees behind the side. In the case of the wave in the reverse rotation direction, the phase of the terminal 36 is delayed by 90 degrees with respect to the terminal 37 when received.

Therefore, when synthesized by the hybrid 44,
If the output of the terminal 45 is a wave in the same rotation direction as the transmission microwave, the two inputs are strengthened because the phase is matched. Only waves in the same rotation direction as the transmitted microwave are output.

On the other hand, from the terminal 46, only the transmission microwave and the wave in the reverse rotation direction are reinforced and output. In this case, the terminal 46 corresponds to the second terminal 32.

As described above, in the microwave concentration measuring apparatus according to the present embodiment, the amount of bubbles is measured to compensate for its influence. It is possible to measure the concentration at a time.

(Fifth Embodiment) FIG. 8 is a block diagram showing a configuration example of a microwave concentration measuring apparatus according to the present embodiment, and the same parts as those in FIG. Are omitted, and only different portions will be described here.

That is, the microwave density measuring apparatus according to the present embodiment has the same basic configuration as that of the above-described conventional example. It is attenuated to amplify the frequency Δf component.

Further, a variable gain amplifier 47 and a voltage measuring means 48, which are signal level control means, are provided. The gain of the variable gain amplifier 47 is controlled based on the value measured by the voltage measuring means 48.
To keep the amplitude (level) constant.

Next, in the microwave concentration measuring apparatus of the present embodiment configured as described above, since the output amplitude is made constant by the variable gain amplifier 47, the temperature and the conductivity of the liquid to be measured are changed. Even when the microwave attenuation is large, the comparator 1
No error occurs due to the change of the switching time of No. 6.

When the measured signal level is low,
Since the signal-to-noise ratio can be improved by amplifying the signal, the concentration can be measured with high accuracy.

As described above, in the microwave concentration measuring apparatus according to the present embodiment, the level of the mixed signal is controlled to be constant. Even if the attenuation is large, no error occurs, and when the measured signal level is small, the signal can be amplified to improve the S / N ratio against noise, so that the concentration can be measured with high accuracy.

(Sixth Embodiment) FIG. 9 is a block diagram showing a configuration example of a microwave concentration measuring apparatus according to the present embodiment. The same parts as those in FIG. Are omitted, and only different portions will be described here.

That is, the microwave density measuring apparatus of the present embodiment has the same basic configuration as that of the above-described conventional example. It is attenuated to amplify the frequency Δf component.

The densitometer circuit 49 indicated by the broken line is housed in the same housing. In this case, a case thermometer 50 as a case temperature measuring means is installed, and the case temperature is measured by the case thermometer 50. When the case temperature is equal to or less than a predetermined value, The heater temperature is controlled by a heater control circuit 51 and a heater 52 as temperature control means installed in the housing so that the housing temperature becomes a constant value.

Further, when the circuit temperature becomes higher than a certain value due to the internal heat generation of the densitometer circuit 49 or the environmental temperature,
The arithmetic unit 19 corrects the measured value based on a preset correction value.

Next, in the microwave concentration measuring apparatus of the present embodiment configured as described above, the circuit temperature is controlled or corrected to be constant, so that even if the ambient temperature changes, Prevent phase change due to change,
The concentration can be measured with high accuracy.

Further, from the state where the temperature at the time of power-on is low,
A stable state can be obtained quickly.

Further, when cooling is performed when the temperature rises, the circuit becomes complicated, the control is not easy, and the cost of cooling parts increases, but the measured value is corrected by the arithmetic unit 19 at 19. By doing so, the circuit can be made simple and low in cost.

As described above, in the microwave concentration measuring apparatus according to the present embodiment, when the housing temperature is equal to or lower than a certain value, the temperature is controlled so as to be constant, and when the temperature is equal to or higher than the certain value. The measurement value is corrected by the correction value set in advance, so that even if the ambient temperature changes, the concentration can be measured with high accuracy, the circuit is simplified, and the cost is reduced. It becomes possible to.

(Seventh Embodiment) FIG. 10 is a block diagram showing a configuration example of a microwave concentration measuring apparatus according to the present embodiment. The same parts as those in FIG. Are omitted, and only different portions will be described here.

That is, the microwave density measuring apparatus according to the present embodiment has the same basic configuration as that of the above-described conventional example. It is attenuated to amplify the frequency Δf component.

Further, based on the signal level measured by the voltage measuring means 48 and the temperature of the measuring liquid measured by the thermometer 53, the phase change due to the temperature and the signal level of the measuring liquid is corrected to calculate the concentration. .

Further, a correction value of the conductivity and the phase of the measurement liquid is calculated from the signal level and the temperature of the measurement liquid, and a phase change due to the conductivity is corrected to calculate the concentration.

Here, the phase calculation including the correction operation has many variables, and the relation between them and the phase cannot be easily expressed by a mathematical expression. Therefore, the phase calculation including the correction operation is realized by the neural network 54 as the correction value calculation means. With the learning function of the neural network 54, each variable and the actual concentration
Temperature and the like are set and learned by actual measurement, and correction calculation and phase calculation are performed.

Next, in the microwave density measuring apparatus of the present embodiment configured as described above, the correction values of the conductivity and the phase of the measurement liquid are calculated from the level of the received signal and the temperature of the measurement liquid. Accordingly, the concentration can be measured with high accuracy even when the attenuation of the microwave is large due to the temperature and conductivity of the measurement liquid or when the phase of the microwave changes due to the temperature of the measurement liquid.

That is, when the conductivity of the object to be measured changes due to, for example, the incorporation of salt or the like, the above equation (2) is used.
As shown in equation (4), the attenuation rate α changes greatly.

On the other hand, when the temperature of the measurement liquid changes, there is a change in the relative dielectric constant ε _r. Therefore, the concentration is corrected by measuring the temperature and performing a predetermined correction.

The phase difference Δθ is as follows: Δθ = {θ ₂ −k (T−T ₀ ) −γ (E−E ₀ )} − θ ₁ (11) where θ ₂ : phase of the object to be measured θ ₁ : reference during measurement phase k of water: liquid temperature correction factor T: liquid temperature T _0: temperature of the reference gamma: conductivity correction coefficient E: attenuation of the object E _0: attenuation concentration X of the reference water, X = a × Δθ + b (12) where: a: proportional constant b: bias As the conductivity changes, the attenuation rate α greatly changes as described above. Since there is also the effect of the change in ε _r ,
Is selected by creating a table by changing ε _r .

As a result, Δθ is obtained by the equation (11), and a and a which are obtained in advance by the equation (12).
Calculate the concentration by b.

Further, since the calculation of the correction value is performed by the neural network 54, the correction calculation can be easily realized.

As described above, in the microwave concentration measuring apparatus according to the present embodiment, the phase change due to the change in the temperature, conductivity, and signal level of the measurement liquid is corrected. Even when the attenuation of the microwave is large or the phase of the microwave changes depending on the temperature of the liquid to be measured, the concentration can be measured with high accuracy.

Further, since the correction value is calculated by the neural network 54, the correction calculation can be easily realized.

It is to be noted that, by appropriately combining a plurality of embodiments other than the above-described embodiments, it is possible to realize a higher-performance microwave concentration measuring apparatus.

[0156]

As described above, according to the microwave concentration measuring apparatus of the present invention, even when bubbles are generated in the object to be measured, the concentration of solids and suspended substances in the object to be measured is improved. Can be obtained with high accuracy and in real time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a microwave concentration measuring device according to the present invention.

FIG. 2 is a view for explaining the operation of the microwave concentration measuring device according to the first embodiment.

FIG. 3 is a block diagram showing a second embodiment of the microwave concentration measuring device according to the present invention.

FIG. 4 is a block diagram showing a third embodiment of the microwave concentration measuring device according to the present invention.

FIG. 5 is a view for explaining a calculation method in a case where the phase of one microwave is measured as two values that differ by 90 degrees in the microwave concentration measuring apparatus according to the third embodiment.

FIG. 6 is a block diagram showing a fourth embodiment of the microwave concentration measuring device according to the present invention.

FIG. 7 is a diagram showing a configuration example of an antenna in the microwave density measurement device according to the fourth embodiment.

FIG. 8 is a block diagram showing a fifth embodiment of the microwave concentration measuring device according to the present invention.

FIG. 9 is a block diagram showing a sixth embodiment of the microwave concentration measuring device according to the present invention.

FIG. 10 shows a seventh embodiment of the microwave concentration measuring apparatus according to the present invention.
FIG. 2 is a block diagram showing an embodiment.

FIG. 11 is a block diagram showing a configuration example of a conventional microwave concentration measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Clock source, 2 ... Reference signal, 3 ... Oscillator, 4 ... Amplifier, 5 ... Switch, 6 ... Switch, 7 ... Transmitting antenna, 8 ... Piping, 9 ... Receiving antenna, 10 ... Amplifier, 11 ... Reference oscillator, Reference numeral 12: Received signal, 13: Reference signal, 14: Mixer, 15: Heterodyne output, 16: Comparator, 17: Measurement digital signal, 18: Phase difference measuring means, 19: Computing device, 22: Mixer, 23: Reference Side heterodyne signal, 24 ... Comparator, 25 ... Reference signal, 26 ... Reference terminal, 27 ... Fixed reference, 28 ... Frequency mixing means, 29 ... Hybrid, 30 ... Transmit antenna, 31 ... Receive antenna, 32 ... Second terminal 33, switch, 34, substrate, 35, pattern, 36, 37, terminal, 38, pattern, 39, transmission microwave, 40, hybrid 41, microwave, 42, microwave, 43, terminal resistance, 44, hybrid, 45, 46, terminal, 47, variable gain amplifier, 48, voltage measuring means, 49, concentration meter circuit, 50, housing Thermometer 51: heater control circuit 52: heater 53: thermometer 54: neural network

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Katsusen Shimokawa 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Fuchu plant of Toshiba Corporation

Claims (6)

[Claims] 1. A microwave density measurement for measuring a density by mixing a signal received by transmitting one of two microwaves to an object to be measured and another microwave to measure a phase difference and measure a density. In the device, a microwave generation means for generating linearly or circularly polarized microwaves, and in-phase and at right angles thereto when the transmitting side is linearly polarized, and in the same rotation direction and reverse rotation when the transmitting side is circularly polarized. A microwave concentration measuring device, comprising: microwave receiving means for detecting a direction. 2. The microwave density measurement apparatus according to claim 1, further comprising a correction unit that calculates an amount of bubbles from two signals and corrects a phase measurement value. apparatus. 3. The microwave density measuring apparatus according to claim 1, further comprising: phase difference measuring means having phase counting means for counting a phase difference at a center position. Wave density measurement device. 4. The method according to claim 1, wherein
In the microwave concentration measuring apparatus according to the item, in a method of measuring by switching between the measured object and a fixed reference as a measurement value, as the fixed reference, a fixed reference measuring means using a signal from an external transmitting antenna position A microwave concentration measuring device comprising: 5. The method according to claim 1, wherein
The microwave density measuring apparatus according to any one of the preceding claims, further comprising signal level control means for controlling the level of the mixed signal to be constant. 6. The method according to claim 1, wherein
In the microwave concentration measuring device according to the item, a housing temperature measuring means for measuring the temperature of the housing in which the measuring device main body is stored, wherein the housing temperature measured by the housing temperature measuring means is a certain value or less. In the case, temperature control means for controlling the case temperature to be the constant value, and when the case temperature measured by the case temperature measuring means is equal to or more than a certain value, the temperature is corrected by a preset correction value. A microwave density measuring apparatus, comprising: a correcting unit that corrects a measured value.