JPS63247623A - Gamma-ray level gauge - Google Patents

Abstract

PURPOSE:To accurately correct concentration by a single ray source by arranging two detectors which detect gamma rays emitted by the single gamma-ray source at a specific three-dimensional angle so that the gamma rays detected by them differ in transmission distance in a body to be measured. CONSTITUTION:The gamma-ray source 10 is put in a shielded container 12 and arranged so as to emit gamma rays slantingly to the varying direction of the level of the body 16 to be measured in a vessel 14. Then the two detectors 20A and 20B are positioned in a spread 18 of the gamma-ray beam so that the gamma rays differ in transmission distance in the body 16. Signals from those detectors 20A and 20B are converted by electronic circuit parts 22A and 22B into DC currents, which are converted logarithmically by logarithmic converters 24A and 24B. Those signals are inputted to a computing element 26, which outputs a level value after concentration correction using a transmission expression and the relational expression between the transmission distance and level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gamma ray level meter for measuring the level of fluid in a vessel in a chemical plant or the like.

[Conventional technology]

As shown in Japanese Utility Model Application Publication No. 58-92628, a gamma ray level meter has a pair of gamma ray source and a detector arranged diagonally opposite to an object to be measured. When the level of the object to be measured changes, the intensity of the gamma rays reaching the detector deteriorates, so this is detected and the level is measured. The γ-ray transmission equation is expressed by equation (1).

1=Ioe″″μmpx, -a)
Here, E: γ-ray intensity Io when the transmission ratio is $1x: x
γ-ray intensity μm when = O: Mass absorption coefficient ρ: Density of the object to be measured . When the density ρ changes, the gamma ray intensity detected for the same gamma ray transmission distance changes, so correction is necessary.

For this reason, a separate pair of gamma ray source and detector for density correction is used.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology requires two radiation sources and two detectors, and has the problem that the measurement locations for level and density are different and accurate density correction cannot be performed.

An object of the present invention is to provide a gamma ray level meter that can perform accurate density correction using a single radiation source.

[Means for solving problems]

The above purpose is to use two detectors that detect gamma rays emitted from a single gamma ray source at a predetermined solid angle, so that the gamma rays detected by the two detectors have different transmission distances through the measured object. This is achieved by placing the

[Effect]

That is, if the transmission distances XI and XZ of the gamma ray through the object to be measured are made different, two transmission formulas are obtained, although there is one radiation source and one gamma ray. However, since there are three unknowns: density ρ and transmission distance Xlt Xi2,
In this state, ρ, xi, and XZ cannot be determined.

On the other hand, when considering the relationship between the transmission distances Xi, XZ and the level h, the two have a corresponding relationship, and the transmission distances xl, X2 can be expressed as functions of the level h. Therefore, by using the above two transmission equations and the relational expression between the transmission distance and the level, it is possible to obtain a density-corrected level value. Moreover, since the locations measured by γ-rays are almost the same, accurate density correction can be performed.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1, a gamma ray source 10 is housed in a sealed container 12, and is arranged so as to emit gamma rays obliquely with respect to the direction of change in the level of an object 16 to be measured within a vessel 14. Two detectors 20A are located in the gamma ray beam spread 18 and are arranged such that the gamma rays have different transmission distances through the object 16.

20B is installed. Signals from the detectors 20A, 20B are converted into direct current by electronic circuit units 22A, 22B, and logarithmically converted by logarithmic converters 24A, 24B. This signal is input to the calculator 26.

The density-corrected level value is output.

Next, density correction will be explained using FIG. 2.

If the transmission distance of the gamma ray through the measured object 16 is Xl, Xl,
The transmission formula of the γ-rays reaching each of the detectors 2OA and 20B is as follows.

Engineering z=I. , -pl″ρ8″ ・・・
(2) Iz=Ioze−”ρXZ,
,, (3) That is, although there is one radiation source and one gamma ray beam, two transmission systems can be obtained. However, there are three unknowns: density ρ, transmission distances Xl, and X2.

From the two transmission equations, the following equation ρX1. It is not possible to obtain each of ρ, Xl, and X2 only by obtaining ρx2.

p x1= n n (Ioz/Il)
-(4) μm p Xl: Q n (Ioz/It)
-(5) μm However, since Xl and Xl can be expressed as a level h function if the geometric conditions shown in Fig. 2 are determined, this can be expressed as (4
), ρ and h can be found by substituting into equation (5). If the change in the irradiation angle of γ-rays for the detectors 20A and 20B is θ and θ2, then sin θ1 sin θ2 is obtained, where a is the distance between the vessel 14 and the γ-ray source 10, and h is the distance between the liquid level and the γ-ray source 10. It is.

Equation (2) will be introduced as follows.

Since b: (b+x1) = C: h h-cb, and Xi'', by substituting these, formula (6) is obtained. (
The same applies to equation 7).

Substituting equations (6) and (7) into equations (4) and (5) to find ρ, we get μrn (h-atanθ1) μ1Il (h-atanθ2) (8) From equations (9), we get h. If we find it...(10) Similarly, if we find ρ from equations (8) and (9)...(
11) is obtained. In equations (10) and (11), a,
Since θ1゜θ2 are values given by geometric conditions, the level h and density ρ can be determined by measuring the γ-ray intensities II and I2.
can be found. However, the measurement range of the level meter is 0% for the level where Xl:O is achieved and 100% for the level where Xi is maximum. Therefore, the level meter outputs H=h-C (12). That is, the geometric conditions may be determined so as to obtain the necessary measurement range.

〔Effect of the invention〕

According to the present invention, simultaneous changes in liquid level and density can be measured using a single radiation source. Moreover,
Since the γ-ray paths are almost the same, accurate density correction can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the invention, and FIG. 2 is a principle diagram explaining the invention.

Claims (1)

[Claims] 1. It has a single gamma ray source and two detectors, and the single gamma ray source and the two detectors are diagonally opposed to the object to be measured, and the two detectors are A gamma ray level meter characterized in that the gamma ray level meter is arranged such that the distance through which the detected gamma rays pass through the object to be measured is different.