JP2001074671A - Microwave densitometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a microwave densitometer having a structure hard to stain. SOLUTION: A measuring pipe 31 is constituted of an insulating pipe such as a plastic pipe or a glass pipe and a microwave transmission antenna 11 and a microwave receiving antenna 12 are arranged in opposed relationship. The measuring pipe 31 is covered with a metal pipe 34 and metal flanges 35, 36 are provided at both ends of the metal pipe. By constituting the measuring pipe 31 of an insulating material, it becomes unnecessary to provide a window hole on a metal measuring pipe to attach a window plate made of an insulating material to the window hole through a seal material and, since the inner surface of the measuring pipe has no unevenness or gap, the measuring pipe is hard to stain. The leak quantity of microwaves to the outside is reduced by covering the measuring pipe with the metal pipe and piping strength can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to, for example, sewage sludge,
The present invention relates to a microwave densitometer for measuring the concentration of solids in a liquid to be measured, including various suspended substances and mixed substances such as soluble substances, such as pulp, paint, and foodstuff raw materials.

[0002]

2. Description of the Related Art Conventionally, as an instrument for measuring the concentration of a suspended substance or the like in a liquid, an ultrasonic densitometer for measuring the attenuation rate of an ultrasonic wave to obtain a concentration, a transmission light attenuation rate or scattering using light. Optical densitometers that measure the light increase rate to determine the density have been widely used.

[0003] However, in the former case, when air bubbles are mixed in the fluid, the influence of the air bubbles is greatly affected and the measurement error increases.

[0004] On the other hand, the latter is greatly affected by the contamination of the optical window through which light enters or receives light, and the measurement error increases.

[0005] In recent years, a microwave densitometer has been developed and put into practical use as a densitometer which is hardly affected by bubbles and dirt.

FIG. 2 shows a configuration example of a microwave type densitometer.

As shown in FIG. 1, a microwave transmitting antenna 11 and a microwave receiving antenna 12 are arranged opposite to a measuring tube 1 through which a liquid flows, and microwaves are supplied from a microwave oscillator 13. ing.

Further, as a microwave passage path, the power splitter 14 to the transmitting antenna 11 to the liquid in the measuring pipe
Phase difference measuring circuit 1 through microwave receiving antenna 12
5 is formed, and a second path through which microwaves are introduced into the phase difference measurement circuit 15 through the power splitter 14 is also formed. Further, the output of the phase difference measurement circuit 15 is input to the density calculator 16.

The phase difference measuring circuit 15 calculates the phase difference from the phase delay of the microwave from the first path with respect to the microwave from the second path.

In this densitometer, microwaves (second paths) directly received from the microwave oscillator 13 via the power splitter 14 propagate in the liquid to be measured in the pipe (first paths). Path) phase delay θ2
Is compared with a phase delay θ1 of a microwave when the measuring pipe is filled with a reference fluid (for example, tap water which can be regarded as having a concentration of zero) and measured under the same conditions as the liquid to be measured.
From Δθ = (θ2−θ1), for example, the concentration is determined using a calibration curve as shown in FIG.

More specifically, the density is obtained by calculating the density X = a △ θ + b. Here, a is the slope of the calibration curve, and b is the intercept of the calibration curve. Usually, b = 0.

Next, FIG. 4 shows a transmitting antenna 11 to a measuring pipe (detector pipe) 1 in a conventional microwave type densitometer.
2 shows a mounting structure of the receiving antenna 12.

The measuring tube 1 is made of a metal pipe such as stainless steel, and has a window hole 1 for transmitting and receiving microwaves at a position opposed to the metal pipe with the pipe axis interposed therebetween.
7 and 18 are provided respectively, and window plates 19 and 20 made of an insulating material such as plastic are provided in the window holes 17 and 18, respectively.
It is hermetically attached to the measuring tube 1 via 2. Further, a microwave transmitting antenna 11 and a receiving antenna 12 are attached to the window plates 19 and 20, respectively.

In this manner, the metal pipe has a window hole 17,
The reason for providing 18 is that even if microwaves are to enter the inside from the outside of the metal pipe, the microwaves are absorbed by the wall of the metal pipe and cannot enter. Therefore, a window hole is provided in the metal pipe, and microwaves enter and receive inside through a window plate made of an insulating material attached thereto.

The above-mentioned microwave densitometer does not measure the attenuation rate of the microwave but measures the phase difference, and the window for receiving or receiving the microwave is transparent. Since it is not necessary, it is hardly affected by bubbles and dirt, and the concentration can be continuously measured.

[0016]

The microwave densitometer is a measurement method which is less susceptible to the adhesion of dirt as compared with the optical densitometer as described above. If dirt or foreign matter accumulates in gaps such as in the vicinity of a part or a sealing material, the effect may not be negligible.

Further, when applied to the food field, etc., a sanitary structure is required so that solids in the liquid to be measured do not remain and accumulate on the irregularities and gaps in the piping and are not putrefied. Therefore, a sanitary structure that does not have any irregularities or gaps on the inner surface of the pipe is required.

However, when a metal pipe is used as a measuring pipe as in the prior art, there has been a problem that irregularities and gaps are unavoidably formed in the microwave transmitting / receiving antenna mounting portion.

The present invention has been made in view of such a conventional point, and has a structure in which no irregularities or gaps are formed on the inner surface of the microwave transmitting / receiving means mounting portion in the measuring tube, and a structure in which dirt hardly adheres. It is an object to provide a wave densitometer.

[0020]

Means for Solving the Problems In order to solve the above-mentioned problems and to achieve the object, the invention according to claim 1 is characterized in that a microwave transmitting means and a microwave receiving means are opposed to each other with a measuring tube interposed therebetween. In a microwave type densitometer for measuring the concentration of a liquid to be measured in a measurement tube by using a microwave, the measurement tube is made of an insulating material.

As described above, by forming the measuring tube with an insulating material such as a plastic pipe or a glass pipe, a window hole is provided in a metal measuring tube as in the prior art, and an insulating material made of an insulating material is provided therein. There is no need to attach the window plate via a sealing material, and a structure in which there is no unevenness or gap on the inner surface of the measurement tube can be realized.

The invention corresponding to claim 2 is characterized in that, in the invention corresponding to claim 1, the outside of the measuring tube is covered with a shielding member for shielding microwaves.

As described above, the outside of the insulating measuring tube is
For example, by covering with a shielding member that shields microwaves, such as covering with a metal cover, there is an effect of reducing leakage of unnecessary radio waves (microwaves) from a measurement tube made of an insulator.

The invention corresponding to claim 3 is characterized in that, in the invention corresponding to claim 1, the outside of the measuring tube is covered with a reinforcing member.

As described above, the outside of the insulating measuring tube is
For example, by adopting a configuration of covering with a reinforcing member such as covering with a metal cover, there is an effect of increasing pipe strength.

According to a fourth aspect of the present invention, in the second or third aspect, flanges for connecting pipes are provided at both ends of the shielding member or the reinforcing member.

The provision of the flange has an effect of increasing the strength of the pipe.

[0028]

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

FIG. 1 is a block diagram showing a configuration of a microwave densitometer according to one embodiment of the present invention. The section showing the mounting structure of the measuring tube and the transmitting antenna and the receiving antenna is a cross section thereof.

In FIG. 1, reference numeral 31 denotes a measuring tube of a densitometer detector, which is an insulating pipe such as a plastic pipe or a glass pipe. The liquid to be measured flows inside the measuring tube 31. Reference numerals 32 and 33 denote antenna mounting portions made of an insulator provided at positions facing the outer surface of the measuring tube 31 respectively. The antenna 11 for microwave transmission is mounted on the antenna mounting portion 32, and the microwave is mounted on the antenna mounting portion 33. A receiving antenna 12 is attached. The antenna mounting portions 32 and 33 may be formed by bonding a member made of the same material as the measuring tube 31 to the measuring tube 31 or may be formed integrally with the measuring tube 31.

Reference numeral 34 denotes a metal pipe that covers the measurement pipe 31. Metal flanges 35 and 36 for connecting pipes are provided at both ends. The measurement tube 31 is also provided with flanges at both ends.

The transmitting antenna 11 and the receiving antenna 1
Microwave oscillator 1 of microwave signal system connected to 2
3, the power splitter 14, the phase difference measuring circuit 15, and the density calculator 16 are the same as in the conventional configuration.

Next, the operation of the embodiment configured as described above will be described. The microwave is supplied from the microwave oscillator 13 to the transmitting antenna 11 attached to the antenna attaching portion 32 of the measuring tube 31 via the power splitter 14, and the receiving antenna 12 arranged opposite to the transmitting antenna 11 is used to supply the microwave inside the measuring tube 31. There is a first path that receives the microwave signal transmitted through the liquid to be measured and sends the signal to the phase difference measurement circuit 15. Further, there is a second path in which the microwave from the microwave oscillator 13 is directly sent to the phase difference measuring circuit 15 via the power splitter 14.

Then, the phase difference measuring circuit 15 determines the phase delay of the microwave from the first path with respect to the microwave from the second path. The concentration calculator 16 measures the phase delay θ2 of the microwave propagating in the liquid to be measured in the measuring tube 31 and the reference fluid (for example, tap water which can be regarded as having a zero concentration) in the measuring tube 31 in advance. The microwave is compared with the phase delay θ1 of the microwave measured under the same conditions as the target liquid, and the concentration is calculated from the phase difference Δθ = (θ2−θ1) using a calibration curve as shown in FIG. That is, the density is obtained by performing the calculation of the density X = a △ θ + b. Here, a is the slope of the calibration curve, and b is the intercept of the calibration curve. Usually, b = 0.

Here, the measuring tube 31 is made of an insulating pipe such as a plastic pipe or a glass pipe, so that microwaves can pass therethrough. Therefore, it is not necessary to provide a window hole in a metal measurement tube as in the related art and attach a window plate made of an insulating material therethrough via a sealing material, so that there is no unevenness or a gap on the inner surface of the measurement tube 31. Accordingly, since dirt and foreign matter do not adhere to or accumulate in the unevenness or gap as in the related art, a sanitary-type detector for application to, for example, the food field can be easily configured.

The metal pipe 34 functions to reduce the amount of the microwave incident into the measuring tube 31 from leaking from the portion other than the receiving antenna 12 mounting portion to the outside as unnecessary radio waves and to increase the strength of the piping. I have.

Further, flanges 35 and 36 provided at both ends of the metal pipe 34 for connecting pipes serve to increase the strength of the pipes.

[0038]

As described above, according to the present invention, it is not necessary to provide a window hole in the measuring tube and attach a window plate made of an insulating material via a sealing material. Since a structure that cannot be realized can be realized, dirt hardly adheres and foreign matter does not accumulate, so that it is possible to realize a microwave type densitometer which is hardly affected by dirt and can easily realize sanitary specifications.

[Brief description of the drawings]

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

FIG. 2 is a basic configuration diagram for explaining a microwave densitometer.

FIG. 3 is a diagram for explaining a calibration curve for obtaining a concentration X from a phase difference Δθ.

FIG. 4 is a cross-sectional view showing a mounting structure of a transmitting antenna and a receiving antenna to a measuring tube in a conventional microwave densitometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Transmission antenna 12 ... Reception antenna 13 ... Microwave oscillator 14 ... Power splitter 15 ... Phase difference measurement circuit 16 ... Concentration calculator 31 ... Measurement tube 32,33 ... Antenna mounting part 34 ... Metal pipe 35,36 ... Flange

Continued on the front page (72) Inventor Etsumi Suzuki 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Fuchu factory, Toshiba Corporation

Claims (4)

[Claims] 1. A microwave type densitometer in which a microwave transmitting means and a microwave receiving means are opposed to each other with a measuring tube interposed therebetween, and wherein the concentration of a liquid to be measured in the measuring tube is measured by microwaves. A microwave densitometer characterized by comprising an insulator. 2. The microwave densitometer according to claim 1, wherein the outside of the measuring tube is covered with a shielding member for shielding microwaves. 3. The microwave densitometer according to claim 1, wherein the outside of the measuring tube is covered with a reinforcing member. 4. The microwave type densitometer according to claim 2, wherein flanges for connecting pipes are provided at both ends of said shielding member or said reinforcing member.