SU1408213A1 - Method of measuring mass surface density or thickness - Google Patents

Description

about

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The invention relates to methods for measuring thickness using elementary particle streams, and is intended for use in ferrous metals to control hot rolled products.

The purpose of the invention is to improve the accuracy of calibration.

FIG. 1 shows a block diagram of a device implementing the method; in fig. 2 shows the dependence of 1n (Cd) on the surface density or thickness d,

The gamma-radiation source of the radiation source unit 2 and the detection unit 3 are located on opposite sides of the sheet material 4, which is not permanently located in the measuring gap between the source unit 2 and the detection unit 3. In block 2 of the non-source of radiation, a calibration absorber 5 is installed, which can be placed in the path of the radiation flux towards the detecting unit 3. The output of the latter, operating in proportional analog mode; connected to the input of the adder 6, on. the second input of which is supplied with a reference signal from a tunable voltage source 7. The adder b of the adder is connected to the input of the converter 8 voltage frequency, which performs a direct proportional controlled conversion of the input signal to the frequency. From the output of the converter 8, the frequency signal is fed to the input of the computing device 9, the output of which is connected to the input of the display unit 10. Computing device 9 comprises means for converting a frequency signal from block 8 into a signal thickness. Between the detecting unit 3 and the adder, a coupling unit 1I is turned on,

In addition, to implement the method, a set of (three) standard absorbers of known thickness, made of a uniform material, is used, which allows to obtain the required thicknesses.

I

The device works as follows

In the absence of sheet material, reference absorbers with trm at least d, d, d lying in the p measuring range of the thickness gauge (hfg 2)} are alternately placed into the measuring gap and determined after conversion to the HC-link and the detector signal corresponding to analog signal values r f p

L 5 3

The dependence of the transmitted radiation intensity I on the thickness d of the sheet material, taking into account multiple scattering, can be represented as

1.1 „e-:„ „and-), (O

where 1 ,, is the intensity of the incident radiation;

1l is the linear attenuation coefficient of the radiation;

p is the density of the sheet material;

c / is a parameter that takes into account multiple scattering. After transformation receive

- (Upci

, (lc) e ..

(2)

From (2) it follows that the effect of scattered radiation is reduced to a constant for a given measurement geometry, the addition to the exponential function of thickness. Subtracting 1p (from I, the dependence is reduced to an exponential form;

: 1-1 s () 1 (1-0) e

-.ro

3)

Denoting the corresponding electric signals of the meter by C (l), Uj (+ I, o), Codo), / bo (f) and x (pd), we obtain the following correlation:

C-Uo (Co-Uo) e

- HP 1

(four)

The determination of the coefficient is as follows. For three graduation samples, two ratios are determined.

ln (Ci-U) -ln (Ci-y)

ln (Ci-U) -ln (C3 + U)

(five)

where and is the voltage of the source 7 voltage.

Addition of signals C, C, C with voltage (-U) is made in adder b. The selection method determines the value at which the indicated ratios are equal, Plot the values of the splashes and determine the coefficient

PC

ln (, d, -dj

ln Ci + Uo) -ln (C3 + y)

d.-d

in this case, the linear dependence of In (C-Up) on thickness is provided. ,

Then, the radiation flux 1 is recorded in the absence of an absorber in the measuring gap and, at the output of the adder 6, taking into account the previously determined value of U, the value of the summation signal Cg-U corresponding to the absorber thickness is obtained.

Using the obtained linear character of the change in ln (C-Uj,) from the thickness, the maximum value of the measured thickness is determined (Fig. 2)

In (Cc-Uo)

MdkC

Ro

and, entering into the measuring gap a reference absorber with a thickness of d ц ,, ,, receives a signal C, -U., Value

, TT "M" KS

Cj and. placed in the memory computationally (KS

9. The C + Uo signal in the frequency converter is linearly converted into a frequency, so that the frequency corresponding to the signal Cj (((. satisfies the condition

cf wKC-W

where the specified measurement time, and the frequency fp corresponding to the signal C (, - U, provides the necessary static error when a given number of pulses are set (, | j. thereby establishes a linear relationship between the frequency f corresponding to the thickness of the sheet being measured and the analog signal

f. ,-and").

Co-Cd

Max

Hence, -t, and the thickness is determined from the ratio

d - 1- InN / Nj ,. Ro

Thus, the invention makes it possible to increase the accuracy due to the lateralization of the calibration dependence, taking into account the multiple scattering of radiation in the controlled material. Formula of invention

The method of measuring the mass surface density or ON

pre-irradiation of at least three samples with known values of mass surface

density or thickness d

1 t

registering the transmitted radiation and converting it into analog signals

rolls C,

C, respectively, opreJ, At Vv, D 4 VJWJiJS -i 3til -J - j

dividing the calibration dependence and the subsequent measurement of the analog signal for the monitored material, followed by determining its mass surface density or thickness using the calibration dependence, characterized in that, in order to increase accuracy, the constant reference signal IL is subtracted from the analog signals, the value of which is determined from solutions of the equation

25

thirty

35

40

45

-

50

55

i2l2i-Uo) + in (d, :: d

1 ln (C, -Uo) -ln (CA-Uo) | BUT

 1--5;: a; - - j, where is a constant coefficient7, then the signal is measured in the absence of an absorber, the value of the maximum mass surface density or thickness is determined

d

Moinc i

And the sample is irradiated with a mass surface density or thickness (, the signal Cj, -Uj is recorded, it is converted to the frequency of the "Satisfying ® usM condition the specified measurement time, the Cd-Id signal is converted to the frequency f, at which the specified condition is fulfilled provide static error value of the number of pulses, convert the signal C / -U into frequency

f fo-fc (M «w / p II d SG-cT bf

° "(" "KS

determine the number of pulses during the time tti mass surface density or thickness is determined from the ratio

d - 1- InK / N ,,

in the process of measurement, the adjustment

and woo.

1IPI

XJllilL,

i

w

1п {С У,} in (CiU,)

%

ifffc-i) - - tn (

Claims (1)

Claim A method for measuring mass surface density or thickness, including the preliminary irradiation of at least three samples with known values of mass surface density or thickness dj, dj, dj, recording transmitted radiation and converting it into analog signals C _f , C _g , C _e, respectively determination of the calibration dependence and subsequent measurement of the analog signal for the controlled material with subsequent determination of its mass surface density or thickness using the calibration dependence w, characterized in that, in order to improve accuracy, a constant reference signal, the value of which is determined from the solution of the equation, is subtracted from the analog signals G _ I ln (C _a -Uo) -ln (C _s -U _e ) - (where yj is a constant coefficient, then measure the signal Cg-U ^ in the absence of an absorber, determine the value of the maximum mass surface density or thickness d = Max ~ ~ p> ₀ th irradiate a sample with mass surface density or thickness d _{Me (Ke} , record the signal Cj _Mejt -U _e , convert it to a frequency satisfying CONDITION ^f o (M0 | Ke * ^ M3M ^{7 /} ^ » ^g D ^e t 9M is the specified measurement time, the signal C ₀ -U _a is converted to the frequency f, at which the value ^ _О ⁼ 6 _(44m 1 'in the number of pulses), which is set from the condition for providing a static error, is converted, the signal C _{ ^ -U _o I = A determine the number of pulses in time t No. ^{= f} oT4 »M ' ^{and the} mass surface density or thickness is determined from the relation _d = - 1-1ηΝ / Ν _ο , In this case, during the measurement process, And and ₀ . '! - 1408213