A method of measuring the level of grain or fodder in silos

 

(57) Abstract:

Usage: in the temperature control systems and products stored in insulated tanks. The inventive exercise disposable pre-calibration readings of temperature-sensitive elements. Use these readings to adjust subsequent current values of the difference. This takes into account the scatter of the readings of temperature-sensitive elements. Preliminary measurement of temperature differences between the top, in the air column over the product, point and lower, are in the product, point. This difference is compared with the selected threshold for the test conditions to obtain reliable measurements. 1 Il.

The invention relates to measuring technique and can be used for designing control systems level and temperature of grain or fodder stored in silos silos.

Known methods and devices for measuring the level of solids stored in insulated tanks, based on the accommodation of pressure sensors, floats, temperature-sensitive elements, etc., and non-contact methods and devices based on subsequent measurements reflected from a surface of the waves.

In particular, the known contactless radio-frequency method for measuring the surface environments, details of which are given in the description.with. N 1642250, CL G 01 F 23/28, 1980, in accordance with which directional sensing surface frequency-modulated waves of the microwave range, the reception of the reflected waves, their mixing with the probing waves and determining the frequency of beating of the resulting signal, when the signal delay of the beating and in each cycle of frequency modulation calculate the autocorrelation function of the signal beating on the time interval, the increase in the frequency of the probe and reflected signals in time delay varying from the specified minimum value until a zero value of the autocorrelation function. Time delay calculates the level of occurrence of the product to the source dimension.

The disadvantages of the considered method are the complexity and limited application, because it is, first of all, ineffective for measurements in tanks large (25 to 30 m) high with large quantity of air layer, secondly, it is not possible simultaneously with the measurement to measure the temperature.

the p on the determination of the resonant frequency of the generated oscillations, depending on the level of occurrence of the measured environment.

The second analog inherent in the same technical shortcomings as the first.

The closest entity and the technical result of the proposed method is a method performed by a device to control the level of high-temperature granular media, described ed. St. N 794384, CL G 01 F 23/22, 1978.

The essence of this technical solution is that for level measurement in high-temperature granular media in a controlled point-of-tank product accommodate sensing elements with which they measure the temperature on the horizons of the reservoir, sequentially compare the temperature values at the two adjacent points and the results determine the level of occurrence of the substance in the tank.

The method solves the problem of simultaneous measurement of level and temperature of high-temperature granular matter in the tank on the testimony installed thermosensitive elements, however, as it follows from the title, it is applicable only for level measurement in high-temperature granular media, giving a significant temperature drop at the boundary of the medium (air).

In this case, the known technical solution or do not provide the solution for level measurement or solves it, but with significant errors.

In addition, the variation in the readings of temperature-sensitive elements causes an error in determining the temperature difference between adjacent points, which degrades the accuracy of the level measurement at small temperature differences.

These drawbacks are substantially reduced in the proposed method of level measurement.

The essence of the proposed solution lies in the fact that in the method of level measurement based on the measurement using a temperature-sensitive element of the temperature in the n control points of the bins are evenly distributed vertically, and determining the temperature difference between adjacent points in i = ti-ti+1,, i 1-(n-1), pre-produced disposable determining and memorizing the differences in the readings of the adjacent heat-sensitive ele is UB>i-tTi+1,

and before each measurement level is determined by the temperature difference between the first, located directly under the roof of the silo, and the last points1,n= t1-tnand the temperature difference between the outside air and the last point0,n= to-tncompare the modules of the obtained values with the threshold value of1and continue the measurement process, and when and in the air space of the silo pump outside air, adjust the value of each temperature difference

Ki=i-Ti,

compare the values of the modules sequentially from top to bottom with a threshold value of2fix the value ofKjthe first time exceeded its threshold, and then the value of Kj+1compare them with each other according to the rule "more", "less" and determine the level of products according to the formula

,

where Dh is the distance between adjacent control points.

Thanks disposable pre-calibration readings of temperature-sensitive elements and use them to adjust subsequent current values of the difference takes into account the scatter of readings thermosensitive the temperature between the upper, in the air column over the product of the point and the bottom, in the product, point and comparing this difference with the selected threshold checks the conditions to obtain reliable measurements.

When this condition is not fulfilled it is created artificially by forced injection of outside air in the upper cavity of the silo.

The transition to the absolute values of the differences provides the ability to determine the level not only in cases, when the product temperature above the temperature of the air column in the silo, but in cases where it is lower. All this together provides increase as the reliability and accuracy of the level measurement.

Theoretically, the maximum measurement error level of the proposed method is estimated as half the distance between adjacent control points.

For example, when using Thermopolis Voronezh VCCB "pole" with a total length of 28 meters twelve thermosensitive elements, measurement error does not exceed one meter.

The accounting ratios of the first two temperature differences exceeding the threshold allows you to specify the location of the boundary of two media regarding contrariwise drawing, where indicated:

1-1nthe sensing elements placed in the silo (TCE1-n);

the outer sensing element (NTCA);

3 block switching and signal transformation temperature-sensitive elements;

4, the computing unit;

Thermosensitive elements 11-1n(TCE) uniformly with constant step h is placed vertically in the silo. The sensing element 2 is installed outside of the silo and is designed to measure the outside temperature.

As thermosensitive element 11-1n2 can be used commercially available temperature sensors. To obtain more reliable and accurate measurements it is desirable to use sensors with higher sensitivity.

Unit 3 switching to the transform is used to alternately survey thermosensitive elements 11-1nand 2 in accordance with the program stored in the block 4, the conversion of input analog signals into digital form and issue codes in block 4.

Unit 4 performs in accordance with the selected algorithm processing determining current differences i, the correction values according to the results predescu expression. Block 4 also under appropriate conditions generates a command to turn on the fan for blowing outside air into the silo.

The block 4 may be implemented on the basis of commercially available microprocessors.

The technical result from the implementation of the method is to achieve higher accuracy and reliability of measurement.

In addition, one of the advantages of this method is that its implementation does not require specially set in silos additional sensors, because they can be used temperature sensors, which are already equipped with silo.

A method of measuring the level of grain or fodder in silos, based on the measurement using a temperature-sensitive element of the temperature in the n control points of the silo, which are evenly distributed vertically, and determining the temperature difference between adjacent points in i = ti- ti+1, i 1oC (n 1), characterized in that the pre-produced disposable determining and memorizing the differences in the readings of the adjacent heat-sensitive items at a temperature T, the same for all temperature-sensitive elements Ti= tTi- tTi+1and before each and>- tnand the first point come directly under the roof of the silo, as well as the temperature difference between the outside air and the last point0,n= to- tncompare the modules of the obtained values with the threshold value of1and continue the measurement process, and when in the air space of the silo pump outside air, adjust the value of each difference of the readings ofKi=i-Ticompare the value of the modules sequentially from top to bottom with a threshold value of 2fix the value ofKjthe first time exceeded its threshold, and then the value ofKj+1compare them with each other on the module by the rule of "more", "less" and determine the level of product according to the formula

< / BR>
where Dh is the distance between adjacent control points.

 

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