RU2286554C2 - Weight-measuring device - Google Patents

Abstract

FIELD: strain measurement equipment, applicable in balances for measurement of packaged free-flowing materials.

SUBSTANCE: the device has a strain gauge whose output is connected to the input of an analog-to-digital converter, main averager and a weight indicator with a signal input. The device has also an averaging buffer, selector switch with control and signal inputs and a signal output, at least one additional averager, OR element, on-line storage, expectation meter, dispersion meter, derivative computer, null detector and a multi-threshold comparator whose number of thresholds equals the number of additional averagers, each threshold of the multi-threshold comparator is made for adjustment of the level of operation, the weight indicator is additionally provided with an authorized input, the output of the analog-to-digital converter is connected to the input of the averaging buffer, whose output is connected to the selector switch signal input installed in the device circuit for connection of the device signal output to the input of one of the averagers, whose outputs are connected to the inputs of the OR element, whose output is connected to the input of the on-line storage, the inputs of the expectation meter and the dispersion meter are combined and connected to the output of the on-line storage, the output of the dispersion meter is connected to the input of the multi-threshold comparator, whose output is connected to the control input of the selector switch, the output of the expectation meter is connected to the input of the derivative computer and the signal input of the weight indicator, the output of the derivative computer is connected to the null detector, whose output is connected to the authorizing input of the weight indicator.

EFFECT: provided effective suppression of sinusoidal and asymmetric vibrations and interference within a wide spectrum of frequencies.

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Description

The invention relates to a measurement technique, in particular to a strain gauge technique, and can be used, for example, in scales for measuring packaged bulk materials. A device is known for scales containing a load cell, the output of which is connected via an analog-to-digital converter to a digital indicator (see, for example, Pat. RF No. 2105270, Mcl. G 01 G 3/142, 10/19/94).

The disadvantage of this device is the low noise immunity to external disturbances such as vibrations, which dramatically reduces the accuracy of measuring the weight of the packaged portion of the product. To eliminate this drawback, various hardware processing of the strain gauge signal is used, in particular, filtering the signal with a low-pass filter (see, for example, Pat. RF No. 2186347, Mcl. G 01 G 3/142 of 01.12.00). Other signal processing methods are also possible: to increase accuracy due to more complete suppression of dynamic noise, a non-recursive digital filter with a Dolph-Chebyshev window is used (see US Pat. RF No. 1183839, Ml G 01 G 19/03, as well as Auth. USSR No. 1566226, Ml G 01 G 19/04). However, the use of all these technical solutions to increase the accuracy of measurements reduces the reaction rate of the dosing system, since the time of reliable weight measurement increases along with an increase in accuracy.

The aim of the invention is to eliminate this drawback, i.e. ensuring the adaptability of the device to the level of external influences. This device allows you to effectively suppress sinusoidal and asymmetric vibrations and interference in a wide range of frequencies, which significantly improves the dynamic properties of the measuring system.

To this end, in the device for measuring weight, containing a strain gauge force sensor, the output of which is connected to the input of the analog-to-digital converter, an averager and a weight indicator, an averaging buffer, a switch with control and signal inputs and a signal output, at least one additional averager, "OR" element, random access memory, mathematical expectation meter, variance meter, derivative calculator, null-organ and multi-threshold comparator, the number of thresholds of which is equal to for additional averagers, each threshold of the multi-threshold comparator is configured to adjust the response level, the weight indicator is additionally equipped with an enable input, the output of the analog-to-digital converter is connected to the input of the averaging buffer, the output of which is connected to the signal input of the switch installed in the circuit of the device for measuring weight connecting its signal output to the input of one of the homogenizers, the outputs of which are connected to the inputs of the element "OR", the output of which is connected but to the input of random access memory, the inputs of the math and dispersion meters are combined and connected to the output of the random access memory, the output of the dispersion meter is connected to the input of a multi-threshold comparator, the output of which is connected to the control input of the switch, the output of the mathematical expectation meter is connected to the input of the derivative calculator and the signal input of the weight indicator, the output of the derivative calculator is connected to the input of the zero-organ, the output of which is connected to permissive input of the weight indicator.

The invention is illustrated in the drawing, which shows a functional diagram of the device. The device contains a strain gauge force sensor 1, an analog-to-digital converter (ADC) 2, an averaging buffer 3, a switch 4 with control and signal inputs and a signal output, the main averager 5 and an additional averager 6. The number of additional averagers 6 can be large, which increases flexibility of the device.

The drawing shows only two additional averager 6 to simplify the explanation of the operation of the device, the element "OR" 7, random access memory 8, meter 9 mathematical expectation, meter 10 dispersion, multi-threshold comparator 11, calculator 12 derivative, zero-organ 13 and weight indicator 14 .

The device operates as follows.

In the initial state, the signal output of the switch 4 is installed on the main averager 5 having the smallest number of samples, i.e. the smallest averaging coefficient, which is due to the fact that the signal from the strain gauge 1 does not arrive, respectively, there is no signal from the output of the dispersion meter 10, and the multi-threshold comparator 11 is in the corresponding state. When the signal from the output of the strain gauge 1, corresponding to the applied load, is fed to the input of the ADC 2, from its output the data Xi is written to the averaging buffer 3. When each i-th value arrives, the average value of the ADC code in the main averager 5 is calculated with the least number of samples, for example, with two samples. Then, in the main averager 5, an average value is calculated from each of the first and second samples. The averaged signal through the element "OR" 7 enters the random access memory 8, consisting, for example, of 30 cells, which are filled with incoming codes. In this case, 60 ADC codes (30 × 2) are collected in random access memory 8, the accumulated signal is fed to meters 9 and 10. The signal from dispersion meter 10 is fed to a multi-threshold comparator 11, where it is compared with predetermined thresholds. Depending on the comparison result — if the dispersion value is less than the threshold — switch 4 is switched to an additional averager 6, which has a correspondingly higher averaging coefficient, i.e. provides averaging over a larger number of samples, for example, over 8 samples. This additional averager 6, respectively, calculates the average of 8 samples, and collects (30 × 8) 240 samples in the random access memory 8. In all cases, the mean and variance are calculated by filling in random access memory (RAM) 8. Upon receipt of a new value in (RAM) 8, the mean and variance are recalculated in blocks 9 and 10, respectively.

The value of the mathematical expectation from the output of the meter 9 mathematical expectation is supplied to the indicator 14 of the weight and the calculator 12 of the derivative. The moment when the value of the derivative vanishes corresponds to the moment of the end of the determination of weight. At this point, the zero-organ 13, in which the moment of stabilization of the weight indications is determined, gives a signal to the enable input of the weight indicator 14 to fix the result of static weighing.

With the stabilization of the balance, the value of the resulting dispersion will decrease, switching to the next additional averager will allow a better filtering of the signal. With a large dispersion of the input signal, the weight filtering is less qualitative, but at a higher speed, which allows you to more accurately determine the moment of issuing the control signal during dosing. With a small dispersion, the filtration occurs more efficiently, while the measurement time can be longer, which positively affects the accuracy of weighing.

Thus, with a rapid change in the input signal and large dispersion, the device increases the reaction rate of the dosing system, and with slowly changing weight and small dispersion, it provides high weighing accuracy. Therefore, this device allows you to effectively suppress sinusoidal and asymmetric vibrations and noise in a wide range of frequencies and significantly improve the dynamic properties of the measuring system, i.e. reduce the response time to external influences while maintaining measurement accuracy.

Claims (1)

A device for measuring weight, containing a strain gauge force sensor, the output of which is connected to the input of an analog-to-digital converter, a main averager and a weight indicator with a signal input, characterized in that an averaging buffer, a switch with control and signal inputs are included in the device for measuring weight signal output, at least one additional averager, OR element, random access memory, mathematical expectation meter, dispersion meter, derivative calculator th, zero-organ and multi-threshold comparator, the number of thresholds of which is equal to the number of additional averagers; each threshold of the multi-threshold comparator is made with the possibility of adjusting the response level, the weight indicator is additionally equipped with an enable input, the output of the analog-to-digital converter is connected to the input of the averaging buffer, the output of which is connected to the signal the input of the switch installed in the circuit of the device for measuring weight with the ability to connect its signal output to the input of one of the averagers, you the moves of which are connected to the inputs of the OR element, the output of which is connected to the input of random access memory, the inputs of the math and dispersion meters are combined and connected to the output of random access memory, the output of the dispersion meter is connected to the input of a multi-threshold comparator, the output of which is connected to the control input of the switch, the output of the mathematical expectation meter is connected to the input of the derivative calculator and the signal input of the weight indicator, the output of the calculator is derivative connected to the input zero-body, whose output is connected to the enabling input weight indicator.