RU2687506C1 - Electronic unit of vane water meter - Google Patents

Abstract

FIELD: measuring equipment.SUBSTANCE: invention relates to volumetric flow rate measuring devices, in particular, to electronic units of vane water meter. Invention consists in that electronic unit of vane water meter additionally comprises second Hall sensor located above path of impeller magnets diametrically opposite to first Hall sensor, wherein Hall sensors along power circuit are in-series connected to output of microcontroller and current-limiting resistor, first outputs of Hall sensors are connected to each other, second outputs are to inputs of instrument amplifier, feedback resistor of hysteresis circuit of comparator is connected to output of microcontroller, power circuits of Hall sensors and circuit elements are connected to outputs of microcontroller.EFFECT: possibility to compensate for influence of external magnetic field on meter readings, reduction of current consumption of electronic unit.1 cl, 1 dwg

Description

The invention relates to instruments for measuring volumetric flow rate, in particular to electronic units of a vane water meter, and can be used to account for the flow rate of cold or hot water using vane or turbine water meters with compensation of the external magnetic field.

A device is known for protecting a water meter from an external magnetic field [1], in which a water meter is placed in an iron cylindrical body with two cutouts for access to the water meter nozzles and a rotary upper iron lid with a rectangular window to observe the meter readings. The iron case with a cover serves as a magnetic screen and protects the water meter from the effects of an external magnetic field. The disadvantage of this device is a large consumption of materials and the complexity of the design.

Known water meter wing type [2], comprising a housing with inlet and outlet nozzles, mounted inside the impeller housing with magnets, the rotation of which is transmitted through a separating lid made of plastic driven magnetic coupling mechanical counting device containing a gearbox and a drum counter. To protect the magnetic coupling of the meter from the effects of an external magnetic field, a magnetic screen is used, made in the form of a steel washer reinforced in a separation cover. The disadvantage of the counter is the difficulty of changing the transmission coefficient due to the mechanical change of the gear ratio of the gearbox and the counter, as well as the large static and dynamic resistance of the mechanical counting device, which reduces the sensitivity threshold of the counter and its accuracy in the area of low flow rates.

A known method of measuring fluid flow and a device for its implementation [3], consisting in the fact that the fluid flow is directed to the impeller of the counter with a magnet attached to it, the electronic counting device contains a reed switch and a microcircuit connected with a liquid crystal indicator that records the closure of the reed switch and recalculates them in fluid flow. The disadvantage of analogue is the limited service life of the reed switch, as well as its susceptibility to the influence of an external magnetic field.

Known counter for water accounting [4], selected as a prototype. The counter contains an impeller installed in the cavity of the housing with two magnets diametrically arranged on it, a Hall sensor installed on the outer part of the housing, a pulsed power generating unit for the Hall sensor, a microcontroller-based control and calculation unit, a conversion factor optimization unit, a timer, a liquid-crystal indicator, power supply, computer communication unit. The disadvantage of the prototype is the exposure of the Hall sensor to an external magnetic field, which leads to a distortion of the counting results.

The present invention is the achievement of the technical result, which consists in compensating for the influence of an external magnetic field on the results of water flow metering, as well as minimizing the current consumption by the electronic unit.

This result is achieved due to the fact that in the electronic unit of the vane water meter containing the Hall sensor located above the path of the impeller magnets, the current limiting resistor, the instrument amplifier of the output signal of the Hall sensor, a comparator with a feedback resistor in the hysteresis circuit, a microcontroller with a liquid crystal indicator which is connected to the comparator output, the following differences are provided; a second Hall sensor is additionally introduced, located above the path the passage of the impeller magnets diametrically opposite the first Hall sensor, while the Hall sensors along the power circuit are connected in series with the microcontroller output and current limiting resistor, the first outputs of the Hall sensors are connected to each other, the second - with the inputs of the instrumentation amplifier, the feedback resistor of the comparator hysteresis circuit is connected to the output the microcontroller, the power supply circuit of the Hall sensors, the circuit elements and the liquid crystal indicator are connected to the outputs of the microcontroller.

There is a causal relationship between the set of essential features of the claimed invention and the technical result achieved. Namely, the output voltage from series-connected Hall sensors located diametrically opposite to the impeller magnets depends on the external magnetic field only on the magnetic field of the impeller magnets. Hall sensors and circuit elements from the conclusions of the microcontroller allows minimizing consumption due to their pulse power supply from eroded duty cycle.

The technical solution makes it possible to compensate for the effect on the meter reading of an external magnetic field and to reduce the current consumption of the electronic unit.

The technical essence of the proposed technical solution is illustrated by the drawing, where FIG. contains a block diagram of the proposed electronic unit, which includes:

1, 2 - Hall elements;

3 - current limiting resistor;

4 - instrumental amplifier;

5 - comparator;

6 - feedback resistor;

7 - microcontroller;

8 - LCD.

Hall elements 1 and 2 are connected in series with each other and the current-limiting resistor 3 and are powered from the output of the microcontroller 7, which also supplies power to the instrumentation amplifier 4 and the comparator 5. From the other output of the microcontroller 7, LCD 8 is powered.

Note. FIG. the power supply circuit elements from the outputs of the microcontroller 7 are not shown.

According to [5], the output voltage of the Hall element, in addition to the Hall voltage Ux, contains the residual voltage Un and the thermopower of the contacts Ut. At the same time, the residual voltage of the Hall element is large and significantly depends on the temperature, which introduces a significant error in the measured output voltage of the Hall element.

The output voltage on the Hall elements 1 and 2 contains two components of the magnetic field - the unidirectional influence of the external magnetic field F - Ux and the opposite direction of the magnetic field of the impeller magnets Fs and Fn - ΔUx.

In accordance with [5], the output voltage of Hall elements 1 and 2 are determined by the formulas

The output voltage of oppositely connected Hall elements 1 and 2 is determined by the formula

Thus, the output voltage of the Hall elements 1 and 2 depends only on the Hall voltage of the Hall elements when exposed to the magnetic field of the impeller magnets, and doubled, in which the influence of the external magnetic field voltage, thermoelectric power and the residual voltage of the Hall elements with its temperature dependence is excluded.

The comparator 5 is built according to a typical comparator circuit with hysteresis with the only difference - the feedback resistor 6 of the hysteresis circuit is connected to the output of the microcontroller 7, which, when energized to the comparator, sets a voltage on the resistor 6 depending on the previous state of the comparator 5.

The microcontroller 7 by changing the signals of the comparator 5, which occurs at each half-turn of the impeller magnets, considers the volume of water passed in accordance with the established coefficient of recalculation of the price of the impeller revolutions and displays the accumulated volume in calibrated units to the liquid-crystal indicator 8. impeller characteristics due to the correction of the conversion factor.

In order to reduce the current consumption by the electronic unit, the Hall sensors and output signal processing circuits are powered from the microcontroller's output by the interrupt signals from the built-in timer, while the microcontroller is in sleep mode, the minimum consumption mode, before the timer triggers. Power is supplied to the circuits for a time sufficient to establish the output signals of the circuit and interrogate them by the microcontroller. In the absence of rotation of the impeller is set the minimum frequency of the survey sensors. Upon detecting the rotation of the impeller, the maximum sampling frequency of the sensors is set, which then adaptively adjusts to the frequency of rotation of the impeller. In addition, the indication of the meter readings on the LCD is carried out only on request for a time sufficient to read the meter readings.

The use of two Hall sensors provides an output signal with doubled sensitivity and half the current consumption, which compensates for the influence of an external magnetic field and the residual voltage of the Hall elements with their temperature dependence.

Compared with mechanical counting devices, the proposed device has higher accuracy in the area of minimum costs due to the elimination of resistance to rotation of the impeller due to the resistance of the mechanical calculating device, as well as compensation for the decline of the transfer characteristic of the impeller due to the correction of the conversion factor in the area of minimum water consumption.

Information sources:

1. Patent RU 2380713,

2. Patent RU 2347194,

3. Patent RU 2152128,

4. Patent RU 2337320 - prototype

5. A.A. Golubev, V.K. Ignatiev, Digital nanoteslometer, Izv. Universities. Instrument making. 2010. T. 53, No. 1, p. 49-54

Claims (1)

The wing water meter electronic unit containing the Hall sensor located above the path of the impeller magnets, the current-limiting resistor, the instrument amplifier of the output signal of the Hall sensor, a comparator with a feedback resistor in the hysteresis circuit, a microcontroller with a liquid crystal indicator, whose input is connected to the output of the comparator the fact that the second Hall sensor, located above the path of the magnets of the impeller, is diametrically opposed to The first Hall sensor, while the Hall sensors along the power circuit are serially connected to the microcontroller output and current limiting resistor, the first Hall sensor outputs are connected to each other, the second to the instrumentation amplifier inputs, the comparator hysteresis feedback resistor is connected to the microcontroller output, and the sensor power supply Hall and circuit elements are connected to the outputs of the microcontroller.

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