RU207674U1 - Liquid volume meter with capacitive rotation sensor - Google Patents

Abstract

The utility model relates to measuring the volume of liquid, in particular fuel, and is designed to measure the volumetric quantity of pumped oil products and other liquids with a viscosity of 0.55 to 300 mm2 / s passing through the hydraulic system of stationary dispensing installations, as well as ground mobile refueling facilities and pumping. The technical result of the claimed utility model is to minimize the energy consumption of the volume meter during autonomous operation from a battery while maintaining high measurement accuracy of the volume of liquid (fuel) passing through the device. The specified technical result is achieved due to the fact that the liquid volume meter includes mechanical and electronic parts, and the mechanical part is a measuring chamber, inside which there are two interlocked oval gears, one of which is mounted on a drive shaft, which is connected to a magnetic coupling, on the axis of the output shaft of which, outside the measuring chamber, a mark is installed, and the electronic part includes interconnected capacitive rotation sensor coupled to the mark, a control unit, an indication unit and an autonomous power source.

Description

The utility model relates to measuring the volume of liquid, in particular fuel, and is designed to measure the volumetric amount of pumped oil and other liquids with a viscosity of 0.55 to 300 mm ² / s passing through the hydraulic system of dispensing stationary installations, as well as ground mobile refueling facilities and pumping.

Known liquid meters with oval gears (Kremlin P.P. rotating in opposite directions. The tail shaft of one of the gears is connected to the counting device through a magnetic coupling.

Also known are the measuring devices (counters) of the volume of liquid, developed by OOO Prompribor [Electronic resource. Access to the resource: https://www.promizmeritel.ru/images/prod/schet/re_schet.pdf - free]. The liquid meter consists of two main parts: a mechanical part (flow meter) and an electronic meter, which includes a shaft rotation angle converter and counting pulses and an indicator. Induction speed sensors (for example, "LUCH" or DI-O-5 meters) are used as flow converters and electronic meters. The principle of operation of the DI-O-5 sensor is based on the registration of the change in the magnetic field vector by the sensitive element of the sensor when a metal with magnetic properties (turbine blade, obturator disc protrusion) enters the working area of the sensor.

Also known are volume meters with optical sensors [Electronic resource. Access mode to the resource: http://inno-tech.ru/datchiki-rashodomera/ - free], which are widely used in flow meters to measure the amount of liquid. The principle of their operation is based on receiving information from electromagnetic radiation in various ranges (visible, infrared, ultraviolet). Accordingly, the sensor transmits this information to the control system of the flow meter, where, based on the analysis of optical effects, the volume of the substance used is calculated. To be able to work with low power consumption when using an optical encoder, such sensors use a method of supplying a light-emitting diode with a pulsed power supply, which, on the one hand, leads to a decrease in the average consumption current, but on the other hand, it becomes possible to skip a slot / petal of a rotating disk when operating at high speeds. ... To preserve the metrological properties of this type of measurement, it is necessary either to increase the frequency of the optocoupler interrogation flashes, or to reduce the number of slots / blades of the rotating disk, which leads to a loss of resolution.

Thus, the main disadvantages of the known volume meters with inductive and optical readout devices are either the high power consumption required to ensure the required measurement accuracy during autonomous operation, since a large amount of energy is required to operate the illumination in optical devices and to create a magnetic field in inductive readouts, therefore, the resource of their operation from the battery is significantly reduced, or the measurement resolution is low, due to which it is possible to save the battery charge.

The technical result of the claimed utility model is to minimize the energy consumption of the volume meter during autonomous operation from a battery while maintaining high measurement accuracy of the volume of liquid (fuel) passing through the device.

The specified technical result is achieved due to the fact that the liquid volume meter includes

mechanical and electronic parts,

moreover, the mechanical part is a measuring chamber, inside of which there are two interconnected oval gears, one of which is mounted on a drive shaft, which is connected to a magnetic coupling, on the axis of the output shaft of which, brought out of the measuring chamber, a mark is installed,

and the electronic part includes interconnected capacitive rotation sensor coupled with a tag, a control unit, an indication unit and an autonomous power source.

Thus, due to the specified set of essential features, it was possible to significantly reduce power consumption, simplify the design and maintain the measurement accuracy, thanks to the presence of a capacitive rotation sensor. Since the entire sensor of the rotation sensor is interrogated at the same time, this makes it possible to fix the position of the mark in space. If, in the case of an optical or electromagnetic type of sensors, the absence of a sensor polling during the passage of a counting element (slit / lobe) leads to a skip of the counting pulse, and the sampling frequency must be at least the product of twice the number of counting elements and the maximum rotation speed, then in the case of using a ring capacitive sensor , it is enough for the polling rate to be no less than the mark passing time a little less than half a revolution of the sensor rotation. Those. the polling speed drops significantly, and with it the consumption of the sensor from the battery drops. Plus, the sensor itself operates on such a physical principle that it does not need large currents for operation.

The essence of the claimed utility model is illustrated by the following figures and description.

FIG. 1 is a sectional view of a liquid volume meter.

FIG. 2 shows a section b-b from fig. 1.

FIG. 3 shows a diagram of the arrangement of the electrodes of the capacitive sensor sensor.

The liquid volume meter (Fig. 1-3) includes mechanical and electronic parts.

The mechanical part is a measuring chamber, including a metal case 1 (for example, from an aluminum alloy), closed by a front cover 2 and a back cover 3, with two screwed-in nozzles (not shown in the figure) for connection to the pipeline of the measured medium.

Inside the body 1, between the covers 2 and 3, there are restrictive plates 4, as well as the front guide plate 5, the rear guide plate 6 and the O-rings 7, which ensure the tightness of the connection of the body parts to each other.

Guide plates 5, 6 are designed to install the shaft 10 and the drive shaft 11, with fixed oval gears 8 and 9, respectively, fixed to them, which are in constant mesh with each other. Plates 4 limit parasitic gaps between the plates and the ends of the oval gears 8, 9 to limit parasitic fluid leaks. The body 1, the plates 4 and the oval gears 8, 9 on the shafts 10, 11, together form a measuring chamber, the volume of which is used in the future when calculating the amount of liquid passing through the meter per shaft revolution.

To transfer rotation from the drive shaft 11 to the output shaft 12 of the meter, a magnetic coupling is used. It consists of an outer coupling half 13 and an inner coupling half 14. The outer coupling half 13 includes a half-coupling housing with an external magnet fixed in it and a gear that meshes with the drive shaft 11. The inner coupling half 14 includes a housing with a fixed internal magnet and an output shaft 12, on which the bronze petal is attached - mark 15, the position of which is read by a capacitive sensor. The transfer of the torque from the outer coupling half 13 to the inner coupling half 14 occurs due to the interaction of the magnetic fields of the outer and inner magnets. At the same time, the half-couplings 13, 14 (and the magnets) themselves are separated by a glass 16 made of aluminum alloy, which, with the help of an O-ring 17, forms a fixed tight connection with the front cover 2, while providing increased reliability against leaks. That is, the glass 16, together with the body parts 1, 2, and 3, form a sealed cavity where the measured liquid is located and the outer half of the coupling 13 rotates, and the inner half of the coupling 14 with the output shaft 12 is located outside, in the "dry" zone.

The electronic part is located under the front cover 18 of the meter and includes a sensor board 19 and an indication board 20. On board 19, a capacitive rotation sensor is installed, coupled with a metal mark 15, and a control unit (processor). An indication unit and an autonomous power supply 21 are installed on the board 20 (Fig. 2).

The power supply 21 can be placed in an additional housing 22 and sealed with an insulating compound 23. This simplifies the process of replacing the power supply 21, since its fasteners are not filled with compound.

The sensor of the rotation sensor has a variable area depending on the position of the mark 15 and consists of measuring electrodes 24 rolled into a ring and divided into groups, each of the groups being interrogated alternately (Fig. 3).

Inside the housing 1, under the pressure of the fuel flow, gears 8, 9 rotate, the magnetic coupling transmits rotation from the driving oval gear 9 to the mark 15. The sensor pad on the rotation sensor board 19 reads the position angle of the mark 15 with high accuracy tens of times per second, determining the increment of the angle, direction and speed of rotation of gears 8, 9.

Further, these parameters, mathematically processed and corrected by the calibration coefficients using a specially developed algorithm, are converted into the actual volume of liquid (fuel) passed through the measuring chamber and displayed on indicators or transmitted to the control system via one of the interfaces: CAN, RS-485.

The operation of the rotation sensor is based on the principle of measuring the capacitance between the rotating mark 15 (flag) and the sensor pad on the sensor board 19.

Mark 15 with a sensor pad form a classic flat air-dielectric capacitor. One of the electrodes (mark 15) has a constant area, and the sensor sensor on the board 19 has a variable depending on the position of mark 15. By moving mark 15 along the sensor sensor and measuring the capacity, you can find the overlap area, and from it determine the location of mark 15 from any from the sensor ends of the sensor.

To increase the accuracy of determining the position of the mark 15, an improved sensor design is used: at least two electrodes 24 are used, the capacitance of which is measured alternately (so that the measurements do not interfere with each other). By increasing the number of electrodes 24, thus dividing the entire range of capacities into subranges, we obtain greater linearity and measurement accuracy. To obtain the position of the mark 15 during circular movement, for example, eight measuring electrodes 24 are combined into two groups (even and odd) and rolled into a ring (Fig. 3). Each group of electrodes 24 is interrogated alternately to exclude the mutual influence of the electric fields of the electrodes 24 on each other. The measurement takes place in parallel for the entire group. First, a measurement is made for all odd electrodes, grounding the even ones, then a measurement for even ones, grounding the odd ones.

The measurement results are converted into signals that are transmitted to the control unit.

When the volume meter operates in an autonomous mode from its own power source 21 (battery), to further minimize power consumption, the microcontroller of the control unit in the intervals between measurements goes into a reduced power consumption mode, stopping its main functions, except for the most necessary ones, reducing consumption to units of microamperes. At the signal of a micro-consuming (microampere) timer operating during sleep, the microcontroller exits sleep mode to measure the position of mark 15. If there is no change in the position of mark 15 or speed below 260 degrees per second, the microcontroller polls the sensor 10 times per second. As the speed increases, the polling rate of the sensor increases. This speed is necessary for a possible abrupt start of the measurement, for example, during a water hammer. With an increase in the rotation speed, the sampling rate of the sensor dynamically increases, maintaining a margin in the measurement speed for possible acceleration of counting from the processes occurring in the hydraulics.

Algorithm for determining the position of the mark 15:

1. Searches for the strongest signal strength of all. Upon finding, it remembers the number of the electrode where this signal was. Thus, we find the position of marker 15 in the + - 45 degree sector, and we cut off the weak signal from the counterweight tail of marker 15.

2. Checks if the signal level exceeds the threshold level specified in the settings. This is necessary to cut off false alarms of the sensor with small changes in capacitance arising from external interference.

3. We memorize the numbers of the electrodes to the left and to the right of the electrode with the strongest signal.

4. We make vector transformations, which are described in more detail below.

5. We calculate the angle of the vector, and in fact we determine the angle at which the label 15 is currently located.

Each electrode 24 is clearly fixed on the board 19 at an angle of 45 degrees to the adjacent electrodes 24. Thus, the electrodes 24 cover 360 degrees in 45 degree increments, and as the initial data there is a fixed angle for each electrode and the signal level from it. All this forms pairs of polar coordinates of the vector (in classical geometry this is a pair: angle + length, where the length of the vector is the measured signal power).

In order to determine the angle of the mark 15, you need to find its vector, which is defined as the sum of the vectors of the electrode with the strongest signal and two adjacent electrodes.

The main problem with measuring the speed from the sensor is that the speed changes during the whole revolution. At an average speed of 350 rpm, the instantaneous speed per revolution ranges from 50 to 650 rpm. Such speed jumps occur due to the design of the mechanical part of the meter, which is a chamber with gears 8, 9, where the resistance of engagement of gears 8, 9 depends on many parameters, for example, such as the purity of the passing liquid from mechanical impurities, the presence of gas bubbles, viscosity, and the degree of wear and tear on the camera itself.

In addition, at different flow rates, the shape of the instantaneous speed curve per revolution varies greatly, which does not allow using most of the classical methods for calculating the instantaneous speed.

Therefore, the speed measurement is as follows:

1. With each new measurement of the position of the mark 15, the value of the RTC clock timer, set at 32786 counting pulses per second, is fixed and added to the measurement array, which stores the last 3 seconds of measurements. 65Hz · 3 = 195 measurements at 65Hz.

2. Also, for each measurement, the current angle of the position of the mark 15 is fixed.

3. When measuring new data, they are added to this array of measurements, while the oldest measurements are discarded from the array.

4. For the array of angles, find the total angle of rotation of the label 15 for the last three seconds.

5. For an array of time - we find the exact time up to 1/32768 of a second, during which the angle from item 4 was passed.

6. Dividing the angle by time, we get the average angular velocity in 3 seconds.

This method of calculation from the results of measurements turned out to be optimal for obtaining the average speed of rotation of the sensor, taking into account all real fluctuations in speed.

To save power in stand-alone mode, a special algorithm of button operation can additionally be used. The master button is always powered, and pressing it is transmitted to the processor immediately. By pressing this button, power is turned on for the remaining two buttons and a 10-minute countdown timer is started. While the user is working with the buttons, the countdown timer is reset to the original 10 minutes after pressing any of the buttons. If there are no more pressing and 10 minutes have elapsed, two of the three buttons are de-energized and stop responding to pressing, before pressing the main function button.

The device can contain two micro-consuming timers, capable of operating while the processor is sleeping, consuming current in units of microamperes. These are LPTIM (low power timer), and RTC (real time clock) timer. Both timers use as a clock signal, the output from the RTC oscillator on a thermostable crystal resonator with a frequency of 32768 Hz 10 ppm. The LPTIM timer has two configurations: interrupt generation with a frequency of 10 Hz and 65 Hz. Interrupts of this timer are used both to wake up the microcontroller from sleep in battery mode, and to start measuring the position of tag 15, both in battery mode and in external power mode. The RTC timer is non-standard configured. The prescaler is 1 and the divisor is 32768. This is not a very economical mode of operation of the timer, but it allows maximum use of the counting register of the timer to measure the time required to calculate the speed.

Claims (1)

Liquid volume meter, including mechanical and electronic parts, and the mechanical part is a measuring chamber, inside which there are two interlocked oval gears, one of which is mounted on a drive shaft, which is connected to a magnetic coupling, on the axis of the output shaft of which limits of the measuring chamber, a mark is set, and the electronic part includes an annular capacitive rotation sensor connected to each other, coupled to the mark, a control unit, an indication unit and an autonomous power supply.

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