RU2071039C1 - Electronic scales - Google Patents

Abstract

FIELD: weighing automobiles and various goods. SUBSTANCE: scales have microcomputer 1, input/output port 2, analog-to-digital converter 3, leadings platform 4, loading device 5, strain gage 6, strain-gage bridge 7, sine-wave signal generator 8, instrument transformer 9, instrument amplifier 10, phase detector 11, voltage repeater 12, voltage divider 13, high-frequency filter 14, differential amplifier 15, integrator 16, comparator 17, register 18, input/output ports 19,20, digital-to-analog converter 21, crystal oscillator 22, low-frequency filter 23, power amplifier 24, central processor unit 25, read-only memory 26, main memory 27, control panel 28, display unit 29, timer 30, printing unit 31, control bus 32, data bus 33, and address bus 34. EFFECT: improved design. 2 dwg

Description

 The invention relates to a weight measuring technique, in particular to automobile and commercial scales.

 Known scales (ed. St. USSR 1559255 class G 01 G 9/00) containing a processing unit, which includes an analog-to-digital converter ADC, load platform, a sensor and a loading device that transmits force from the load platform to the sensor, the correction circuit and processing unit.

 Scales work as follows.

 When setting a test load corresponding to the largest weighing limit, the ADC sets the exact value (scale), then another control weight corresponding to the smallest weighing limit sets the ADC to zero, and then the load receiving platform is unloaded, and the readings will be more than zero. The zero value of the readings is set by the correction scheme using the processing unit due to a change in power. Subsequently, the cargo is weighed taking into account the adjusted zero and scale.

 The disadvantage of these scales is the use of schemes for adjusting the weight values through the control load, which reduces their speed.

 Known electronic scales (US patent 4782904 CL G 01 G 19/40 88.11.08) containing a microcomputer, the inputs and outputs of which are connected through the input input ports to the outputs of the analog-to-digital Converter, low-pass filter, load platform, strain gauge the bridge of the strain gauge, the first and second inputs of which are connected to the first and second outputs of the sinusoidal signal generator, and the measuring diagonal is connected through the measuring transformer to the inputs of the measuring amplifier, the output of which is connected to the first input m of the phase detector and a second input connected to the third output of the generator sinusoidal signal.

 Electronic scales work as follows.

 When loading the loading platform, the weight value is transmitted through the loading device to the strain gauge, the supply voltage of which is supplied from the first and second outputs of the sinusoidal signal generator to the first and second inputs of the strain gauge bridge, and a signal proportional to the weight value is generated in the measuring diagonal and transmitted through the measuring a transformer to the inputs of the measuring amplifier and further to the input of the phase detector.

 After detection by a low-frequency filter (digital filter), the value of the carrier frequency is allocated, which is fed to the input of the analog-to-digital converter.

 An analog-to-digital converter transmits the received carrier frequency values to the micro-computer (storage device) through the input-output ports.

 During processing, samples are used to obtain a signal proportional to the average value of the processed values.

 The disadvantage of these electronic scales is the processing (averaging) of a large number of weight values (samples), which significantly reduces the performance of electronic scales.

 Closest to the technical nature of the invention is US patent 4,804,052 G 01 G 19/40, claimed. 11.30.87 publ. 02/14/89.

 Electronic scales containing a microcomputer, the outputs and inputs of which are connected via input and output ports to the outputs of an analog-to-digital converter, a load receiving platform, strain gauges, a loading device that transmits force from the load receiving platform to strain sensors, the strain gauge bridge, the first and the second inputs of which are connected to the first and second outputs of the sine wave generator, and the measuring diagonal is connected through the measuring transformer to the inputs of the measuring amplifier, the output of which is connected to the first input of the phase detector, the second input of which is connected to the third output of the sine wave generator, while the output of the phase detector is connected to the input of the repeater and the second input of the differential amplifier, and the output of the repeater is connected in series with a voltage divider, high-pass filter differential amplifier and integrator, the output of the integrator is connected to the first input of the analog-to-digital converter.

 Electronic scales work as follows.

 When loading the load receiving platform (truck scales), through the loading device, the force is transmitted to the strain gauge sensors, each of which has its own autonomous processing channel, containing the first and second inputs of the bridge of the strain gauge connected respectively to the first and second outputs of the sinusoidal signal generator, while measuring the diagonal of the strain gauge bridge is connected through the measuring transformer to the inputs of the measuring amplifier and then to the input of the phase detector. The converted signal, adequate to the force, is transmitted through a repeater, a voltage divider, differential amplifiers and an integrator to the input of an analog-to-digital converter.

 An analog-to-digital converter transmits the obtained signal values through the input-output port to the microcomputer, where further processing takes place.

The disadvantages of these scales are:
low speed due to the need for channel multiplexing;
low accuracy due to limitations associated with the capacity of the analog-to-digital converter.

 The purpose of the invention is the increase in speed and accuracy of the balance.

 This goal is achieved by the fact that the electronic balance contains a microcomputer, the inputs and outputs of which are connected via input and output ports to the outputs of the analog-to-digital converter, a load receiving platform, a strain gauge, a loading device that transmits force from the load receiving platform to the strain gauge. The first and second inputs of the strain gauge bridge are connected to the first and second outputs of the sinusoidal signal generator, and the measuring diagonal of the strain gauge bridge is connected through the measuring transformer to the inputs of the measuring amplifier, the output of which is connected to the first input of the phase detector, the second input of which is connected to the third output of the sinusoidal generator signal, while the output of the phase detector is connected to the input of the repeater and the second input of the differential amplifier, and repeat the output I am connected in series with a voltage divider, a high-pass filter, a differential amplifier and an integrator, the output of the integrator is connected to the first input of an analog-to-digital converter, and the first and second inputs and outputs of the register through the input-output port are connected to a microcomputer, while the outputs register connected to the inputs of the digital-to-analog converter DAC, the output of which is connected to the second input of the analog-to-digital converter and the first input of the comparator, the output of the latter is connected to the third input of the register, and the first input of the analog-to-digital converter is connected to the second input of the comparator, while the analog-to-digital converter operates in the processing mode of the difference in the values of the signals supplied to the first and second inputs of the analog-to-digital converter.

 Distinctive features of the proposed electronic scales are the register, digital-to-analog converter and comparator.

 The listed devices are widely used in technical solutions for their intended purpose (V. Gutnikov. Integrated electronics in measuring devices. L. Energy. 1980).

 The connection of the register outputs to the inputs of the digital-to-analog converter, the output of which is connected to the first input of the comparator, and the output of the latter is connected to the third input of the register, allows you to get an additional analog-to-digital converter (Jansen, J. Digital Electronics Course, T.Z. Complex IPs for data transmission devices. M. Mir, 1987, p. 221).

 Connecting the first and second inputs and outputs of the register through the input-output port to the microcomputer allows the exchange of digital processed information.

 The operation of the analog-to-digital converter in the processing mode of the difference of the signals arriving at the first and second inputs, when the signal from the output of the digital-analog converter is supplied to the second input, allows the corresponding information exchanges to be made through the input-output ports.

 The above relationships allow using a microcomputer to isolate the signal by mathematical processing of the measurement results from two essentially analog-to-digital converters, which allows us to conclude that the proposed technical solution has significant differences.

 The register is made on a K155IR17 chip, a comparator on a K554SAZ chip, a digital-to-analog converter on a K1108PA chip, and an analog-to-digital converter on a KP572PV2 chip. The remaining elements of the circuit are made on well-known microcircuits and components.

 FIG. 1 block diagram of electronic scales; figure 2 algorithm of electronic scales.

 Electronic scales contain: micro-computer, input-output port 2, analog-to-digital converter 3, load platform 4, load device 5, transmitting force from the load platform 4 to strain gauge 6, which has strain gauges included in the strain gauge bridge 7, which connected to the first and second outputs of the sinusoidal signal generator 8, and the measuring diagonal of the bridge of the strain gauge 7 is connected through the measuring transformer 9 to the inputs of the measuring amplifier 10, the output of which is inen with the first input of the phase detector 11, the second input of which is connected to the third output of the sinusoidal signal generator 8, a voltage follower 12, a voltage divider 13, a high-pass filter 14, a differential amplifier 15 and an integrator 16 are connected in series, and to the second (inverse) input of the differential the amplifier 15 is connected to the output of the phase detector 11, and the output of the integrator 16 is connected to the first input of the analog-to-digital converter 3 and the second input of the comparator 17, register 18, the first, second inputs and outputs of which through the input-output ports 19 and 20, they are connected to a microcomputer, the digital-to-analog converter 21 whose inputs are connected respectively to the outputs of the register 18, and the output to the first input of the comparator 17 and the second input of the analog-to-digital converter 3.

 The sinusoidal signal generator 8 contains a crystal oscillator 22, the output of which is connected to a low-pass filter 23, the output of the low-pass filter 23 is connected to the third output of the sinusoidal signal generator 8 and the input of the power amplifier 24, the outputs of which are connected to the first and second outputs of the sinusoidal signal generator 8 .

 The microcomputer 1 contains a central processor 25, ROM 26, RAM 27, a control panel 28, an indication unit 29, a timer 30, a print unit 31 connected via an internal interface including a control bus 32, data bus 33, address bus 34 and corresponding ports input-output

 Electronic scales work as follows.

 In the initial state, the load receiving platform 4 through the load device 5 loads the strain gauge 6. This load value of the strain gauge 6 must correspond to a zero weight value.

 After turning on the power (Fig. 2), all variables and constant I / O ports are initialized and the RAM 27 and ROM 26 are tested. Upon completion of initialization, the print unit 31 is printed, which imprints (header) the heading "Electronic scales".

 Then there is a prompt through the display unit 29 "Number?". The current number is set, followed by a hint through the display unit 29 "Month?". The current month is set, and the display unit displays the following prompt “Year?”. The operator sets the current year and then the current time, counted by the timer 30.

 Each transition is carried out through the key "VK", control panel 28.

 After the introduction of the necessary details, Micro-computer 1 proceeds to the "Warm-up" subroutine, which lasts for 10 minutes.

 After 10 minutes, the display unit 29 issues a prompt "Mode?". To compensate for the load (tare) of the strain gauge 6 by the weight of the load receiving platform 4, it is necessary to enable the "Correction" (K?) Mode. In this case, the variable frequency signal from the generator of the sinusoidal signal 8 feeds the bridge of the strain gauge 7.

 Strain gauge 6 receives the initial load and the imbalance signal of the strain gauge bridge 7 in the form of an amplitude-modulated signal fed to the input of the measuring transformer 9 and then to the input of the measuring amplifier 10. After amplification by the measuring amplifier 10, the amplitude-modulated signal is fed to the input of the phase detector 11, the demodulated signal is fed to the input of the voltage follower 12, which is connected to the voltage divider 13 and the output of the phase detector 11, as well as to the inverse input of the differential ntsialnogo amplifier 15, the other input thereof receiving a signal with a high pass filter 14. The filter cutoff frequency is selected based on the upper frequency of claims obstruction operating range for low-frequency envelope of the operating signal.

 After passing the signals, the noise signals are subtracted, and in this way we obtain a low-frequency envelope with minimal ripple. Further, from the output of the differential amplifier 15, the signal is fed to the input of the integrator 16, which integrates the ripple and supplies the initial signal to the first input of the analog-to-digital converter 3 and to the second input of the comparator 17. Micro-computer 1, through the input-output ports 19 and 20 , by the signal of readiness (the first input of the register 18), starts the operation of the register 18 and the input 2 (start of the register 18).

 Thus, a sequential approximation (coarse) of the signal value occurs through the corresponding inputs of the digital-to-analog converter 21. As a result, at the outputs of the register 18, a code is set that is close to the corresponding input signal, and at the output of the digital-to-analog converter 21, the analog signal value, the comparator 17 closes the register 18. The analog value of the signal from the output of the DAC 2 is fed to the second input of the analog-to-digital converter 3. Thus, to the differential inputs (first and second) analog-to-digital Converter 3, operating in the mode of subtraction (difference) of the input signals, the input signal and its "rough" approximate value, i.e. the difference between these signals is measured, which is in addition to a certain "coarse" value, respectively, with a + or - sign.

 The obtained values of the "coarse" reference and additions to the "coarse" value through the input-output ports 2,19 and 20 are received in the microcomputer 1 and processed accordingly.

The estimated number of divisions thus obtained on specific microcircuits in which the reference voltage U _op is 5.12 V for the “coarse” value and 51200 divisions for the “additional” 0.1 V.

 The display unit 29 provides information about the loading of the strain gauge sensor 6 in the initial state. This value of the microcomputer 1 is stored in RAM27 and with subsequent weighings this value is zero, i.e. source.

 After the end of the "Correction" mode, the display unit 29 indicates the initial zero.

 Electronic scales are ready for weighing. The mode "Scales" is set. When loading electronic scales with a certain weight, the processes described above in the "Correction" mode occur. The microcomputer 1 processes the incoming information values taking into account the initial zero, provides information corresponding to this weight value and displays the weight value by the display unit 29.

 Compared with the prototype, electronic scales have increased speed and accuracy due to sequential processing of the “coarse” and then the “additional” signal values.

Claims (1)

 Electronic scales containing a microcomputer, the outputs and inputs of which are connected through the input and output ports to the outputs of the analog-to-digital converter, a load receiving platform, a strain gauge, a loading device that transmits force from the load receiving platform to the strain gauge, the first and second inputs of the bridge of the strain gauge are connected with the first and second outputs of the sinusoidal signal generator, and the measuring diagonal of the strain gauge bridge is connected via a measuring transformer to the inputs of the measuring amplifier, the output of which is connected to the first input of the phase detector, the second input of which is connected to the third output of the sinusoidal signal generator, while the output of the phase detector is connected to the input of the repeater and the second input of the differential amplifier, and the output of the repeater is connected in series with a voltage divider, filter high frequencies, differential amplifier and integrator, the output of the integrator is connected to the first input of an analog-to-digital converter, characterized in that they are introduced the register, digital-to-analog converter and comparator, the first, second inputs and outputs of the register through the input / output ports are connected to the microcomputer, while the outputs of the register are connected to the inputs of the digital-to-analog converter, the output of which is connected to the second input of the analog-to-digital converter and the first input of the comparator, the output the latter is connected to the third input of the register, the first input of the analog-to-digital converter is connected to the second input of the comparator, while the analog-to-digital converter is configured to work in the processing mode of the difference in the magnitude of the signals received at the first and second inputs of the analog-to-digital Converter.

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