CN1071753A

CN1071753A - The periodic sampling penalty method of level gauging vibration interference

Info

Publication number: CN1071753A
Application number: CN 91109535
Authority: CN
Inventors: 田志恒
Original assignee: HENGYANG POLYTECHNIC COLLEGE
Current assignee: HENGYANG POLYTECHNIC COLLEGE
Priority date: 1991-10-16
Filing date: 1991-10-16
Publication date: 1993-05-05
Anticipated expiration: 2006-10-16
Also published as: CN1025693C

Abstract

The invention discloses a kind of periodic sampling penalty method of level gauging vibration interference.Material its shipment, needs continuous shaking in process of production when handling or being processed with, bond to prevent the equipment and the material of being adorned, and vibration equipment will produce larger interference to level gauging.The periodic sampling penalty method that the present invention proposes is decided to be the integral multiple in vibration equipment cycle with sampling period of level-sensing device, can eliminate the vibration interference in the level gauging fully.

Description

The periodic sampling penalty method of level gauging vibration interference

The present invention relates to a kind of method of measuring material level, especially utilize the method for radioactive source actinometry material level.

In process of production, the shipment of some material, processing or process equipment need continuous shaking, in case this equipment bonds with the institute material of adorn, for example steel mill to make steel the conticaster crystallizer of usefulness be to make the steel ingot demoulding of wherein condensing, need be with the amplitude up-down vibration of 12-24 millimeter.And when utilizing gamma ray radiator to carry out level gauging, usually can run into the problem of vibration interference.If adopt γ radiation detection molten steel in mold surface location, gamma emitter and sensor probe are installed on the crystallizer water jacket, at this moment measurement mechanism certainly will vibrate with crystallizer.Under the constant situation of molten steel surface, the fluctuation up and down of 12-24 millimeter will appear in the level-sensing device indicated value.In order to reduce above-mentioned vibration interference, two kinds of methods are arranged at present basically, a kind of as described in the document " LB300-2Mould Level Gauge Operating Lnstruct-ion ", be to utilize the output signal of level-sensing device band fluctuation that the input pulse amplitude of detector is carried out anti-phase modulation, though this method has certain effect, but the liquid level indicated value still has the fluctuation of 5-10 millimeter, and the time constant of filtering is longer, has reduced the response speed of level-sensing device; Another kind method is, γ source and sensor probe are installed in away from the conticaster position component method that is adopted as Kay-Ray 4720CC Contineous Caster Level System in the document " Kay-Ray Inc.Instruction Manual ".Though this method can be eliminated vibration interference fully, but because the distance between γ source and the probe is far away, must adopt bigger γ source, this has just brought the radiation protection problem, and need bigger installing space and special-purpose supporting construction, the difficulty that increase equipment is installed.

The purpose of this invention is to provide a kind of periodic sampling penalty method, can be under the γ source and the condition that off line is not installed of popping one's head in, the interference of abatement apparatus periodic vibration fully.

The objective of the invention is to realize by following method.

A kind of periodic sampling penalty method of level gauging vibration interference, it comprises the following steps:

1. gamma emitter and sensor probe are installed on the vibratory equipment, make the γ source be the wire special distribution, and make probe output counting rate with the material level linear change;

2. make number system that probe output is carried out periodicity collection, sampling period Ts is decided to be the integral multiple of vibration equipment period T v, i.e. Ts=nTv(1), n is a positive integer in the formula, the sampling period is imported number system by keyboard;

3. the counting rate that records of number system is handled by single-chip microcomputer.

When γ source and probe along with equipment together with respect to equilibrium point (being controlling level) when making up-down vibration, if material level remains unchanged, the counting rate of probe output will change (as shown in Figure 1) by generating period synchronously.In the response that guarantees grain position meter is under the condition of linearity, controlling level H and probe output counting rate

Get in touch by following formula:

H＝a-b

（2）

A and b are constant in the formula, determine by the measurement to two material levels.At this moment, the up-down vibration of equipment is equivalent to material level motion in the opposite direction, and counting rate is symmetrical in equilibrium value vibration up and down, so the equipment minimizing value that upwards probe output is counted in the half period of the added value of probe output counting and equipment vibration downwards in the half period of vibration can be offset mutually fully.So, as long as being the integral multiple (not requiring phase-locking) of vibration period, the sampling period can begin sampling (shown in the shadow zone of Fig. 2) in arbitrary phase place of vibration, and the response of probe is linear, then the indication of level-sensing device will be not can be because of vibration equipment changes, thereby eliminated vibration interference fully.

Determined after the sampling period that when vibration period during offrating, the beat-type fluctuation will appear in the level-sensing device indication by (1) formula, its amplitude △ H can be expressed as:

△H＝ (△f)/(nf) Hv（3）

Hv is the vibration equipment amplitude in the formula, and f is specified vibration frequency, and △ f is the absolute value of actual vibration frequency departure rated frequency.By (3) formula as can be known, when the amplitude Hv=12 of vibration equipment millimeter, the departing from less than 1% o'clock of vibration frequency, the fluctuation of the level-sensing device indicated value that is caused by vibration is less than 0.12/n millimeter (n is a positive integer).

The periodic sampling penalty method that in level gauging, adopts the present invention to propose, have following advantage and good effect compared with the prior art: 1. owing to guarantee that sampling period Ts equals the integral multiple of vibration period Tv, and the response of probe is linear, the indication of level-sensing device will not change because of vibration equipment, and when actual vibration frequency departure rated frequency, the fluctuation that the fluctuation of the level-sensing device indicated value that vibration causes will cause much smaller than statistic fluctuation, thereby do not observe this fluctuation, that is vibration interference in fact is eliminated; 2. the periodic sampling penalty method of the present invention's proposition is simple and easy to do, and the space and the special support structures that neither need to increase erecting equipment needn't adopt bigger gamma emitter again, do not need to consider the radiation protection problem.

The invention will be further described below in conjunction with drawings and Examples.

Fig. 1 is the mold oscillation curve map of the embodiment of the invention, and 1 is the oscillating curve of crystallizer among the figure; The 2nd, constant liquid level line.

Fig. 2 is the graph of relation of sampling period and vibration period.

Embodiment:

Conticaster crystallizer is with the frequency of 135 cycle per minutes (being Tv=4/9 second) and the amplitude up-down vibration of Hv=24 millimeter, and frequency shift is less than 1 cycle per minute.The molten steel surface meter ¹³⁷Cs γ source and sensor probe all are contained on the crystallizer. ¹³⁷The Cs source strength is 6.4 millicuries, is the wire special distribution, and probe output counting rate is changed with molten steel surface is linear.Record counting rate and handled by 8098 single-chip microcomputers, the sampling period is imported by keyboard.The level-sensing device random fluctuation that the ionising radiation statistic fluctuation causes is 1 millimeter.Utilize (1) formula to select the sampling period, make n=2, i.e. Ts=8/9 second, crystallizer is during with the rated frequency vibration of 135 cycle per minutes, and vibration interference just can be eliminated fully.When vibration frequency changed 1 cycle per minute, the fluctuation amplitude of the level-sensing device indication that vibration causes only was 0.04 millimeter, and the fluctuation that causes much smaller than statistic fluctuation does not observe so be actually, that is observable vibration interference can not occur.If do not utilize (1) formula, but arbitrarily determine the sampling period, for example get Ts=1 second.Although should be worth very near 8/9 second.But vibration equipment this moment caused level-sensing device indication fluctuation amplitude reaches 3 millimeters, the random fluctuation value that causes much larger than statistic fluctuation.

Because it is of the present invention ¹³⁷Cs γ source and sensor probe all are contained on the crystallizer, and its spacing is from ¹³⁷The Cs source strength only needs 6.4 millicuries just much of that.Under the contrast, off line is installed ¹³⁷Cs γ wants 500 millicuries in the source, and is bigger 78 times than the radioactivity in the used γ of the present invention source.

Claims

1, a kind of periodic sampling penalty method of level gauging vibration interference is characterized in that comprising the following steps:

(1) gamma emitter and sensor probe are installed on the vibratory equipment, make the γ source be the wire special distribution, and probe output counting rate is changed with the material level surface linear;

(2) make number system carry out periodicity to the sensor probe output signal and gather, sampling period Ts is decided to be the integral multiple of vibration equipment period T v, i.e. Ts=nTv, and wherein n is a positive integer, the sampling period is imported number system by keyboard;

(3) counting rate that records of number system is handled by single-chip microcomputer.