RU132206U1 - DEVELOPMENT OF EXPRESS CONTROL OF OCTAN NUMBER OF GASOLINE - Google Patents

Abstract

A device for express control of the octane number of gasoline, comprising an autonomous power supply integrated in a common housing, a cylindrical capacitive sensor connected to the input of the first generator, and a temperature sensor connected to the input of the second generator, the output of which is connected to the first input of the data processing unit, the first output the first generator is connected to the second input of the data processing unit through an analog-to-digital converter, the control input of which is connected to the first output of the data processing unit, the second the output of which is connected to the interface unit and a digital indicator, a crystal oscillator and a frequency subtraction unit are additionally introduced, and a dielectric coating is applied to the central rod of the cylindrical capacitive sensor, while the second output of the first generator is connected to the first input of the frequency subtraction unit, the output of the crystal oscillator is connected to the second the input of the frequency subtraction unit, the output of which is connected to the third input of the data processing unit.

Description

The utility model relates to means of measuring the parameters of the physical environment and can be used for rapid measurement of the octane number of gasolines of various brands.

A device for express quality control of automobile gasoline is known, which contains a generator, a cylindrical capacitive sensor, a voltage source and a digital display unit based on an analog-to-digital converter and a liquid crystal indicator [RF Patent No. 2287811, IPC G01N 27/22].

In this device, to obtain a measurement result proportional to the octane number, a piecewise linear approximation of the conversion characteristic is applied using analog detector circuits, an adder and threshold amplifiers, the instability of the parameters of which leads to a decrease in the control accuracy. The temperature of controlled gasoline also has a significant effect on the error of the device, an increase in which leads to a directly proportional increase in the results obtained, since the octane number depends not only on the dielectric constant of gasoline, but also on the temperature and density of gasoline. Despite the fact that this device implements the simultaneous measurement of the dielectric constant and electrical conductivity of gasoline, the presence of analog functional signal converters leads to a limitation of the control range. In particular, the measurement of an additional parameter - specific electrical conductivity - is carried out in the nanoscale / meter range, which is equivalent to measuring the resistance of gasoline in the range from hundreds of megaohms to tens of gigaohms. However, the presence of even a small percentage of water, acetone or other impurities in gasoline leads to a decrease in its electrical resistance to tens - hundreds of kilo-ohms, which limits the possibility of practical use of this device.

The closest in technical essence of the proposed device is a device for measuring the octane number of gasoline, containing a cylindrical capacitive sensor and a temperature sensor integrated in the common housing, connected to the inputs of the first and second generators, the outputs of which are connected to the first and second inputs of the data processing unit, the first output of which connected to interface and indication units. In this case, the second output of the first generator through an analog-to-digital converter is connected to the third input of the data processing unit, the second output of which is connected to the control input of the analog-to-digital converter. [Patent No. 2460065, IPC G01N 27/22].

The disadvantage of this device is the limited measurement range of the active resistance of controlled gasoline, the value of which for high-quality fuel is tens of gigaohms, and in the presence of water or conductive additives it decreases to units of kilo-ohms, which leads to a breakdown of the oscillations of the first generator and, as a result, does not allow to determine the octane number low quality fuel.

The objective of the utility model is to create a device for express control of the octane number of gasoline, which allows to expand the control range and increase the sensitivity of the device to controlled parameters.

This problem is solved in that in a device containing an autonomous power supply integrated in a common housing, a cylindrical capacitive sensor connected to the input of the first generator, and a temperature sensor connected to the input of the second generator, the output of which is connected to the first input of the data processing unit, the first the output of the first generator is connected to the second input of the data processing unit through an analog-to-digital converter, the control input of which is connected to the first output of the data processing unit, the second output of which is connected a crystal oscillator and a frequency subtraction unit are additionally introduced to the interface unit and a digital indicator, and a dielectric coating is applied to the central rod of the cylindrical capacitive sensor, while the second output of the first generator is connected to the first input of the frequency subtraction unit, the output of the crystal oscillator is connected to the second input of the block subtracting frequencies whose output is connected to the third input of the data processing unit.

Structurally, all functional blocks are placed in the device body, on the end of the handle of which is located a digital indicator.

Figure 1 shows a functional diagram of the proposed device for measuring the octane number of gasolines, figure 2 shows a diagram of a first generator with a capacitive sensor connected to it, and figure 3 shows a diagram of a frequency subtraction unit with a crystal oscillator.

The device includes a cylindrical capacitive sensor 1, one of the electrodes of which is made in the form of a short rod coated with a dielectric protective film and located inside the cylinder with the edges bent inward. A small semiconductor temperature sensor 2 is fixed on one of the inner walls of this cylinder. The internal electrode of the capacitive sensor 1 is connected to the resonant circuit of the first generator 3, and the output of the temperature sensor 2 is connected to the input of the second generator 4. The output of the crystal oscillator 5 and the first output of the first generator 3 and connected to the frequency subtraction unit 6, and the second output of the first generator 3 through an analog-to-digital converter 7 is connected to one of the inputs of the data processing unit 8, the other two inputs of which are connected enes respectively to the outputs of the frequency generator 4, and the subtracting unit 6. These functional units are housed in the casing 9 of the device.

An interface unit 10 with a personal computer and a digital indicator 11 are connected to the output of the data processing unit 8. To obtain the supply voltage of the device’s functional units, an autonomous power supply unit 12 is located in the handle of the device 13, and the common terminal of the power supply unit is connected to the device case.

Schematic diagram of a capacitive sensor 1 contains the measured sensor capacitance 1.1, the equivalent resistance of gasoline 1.2, inversely proportional to its electrical conductivity, and the equivalent insulation capacity of the dielectric coating 1.3 of the Central rod (figure 2).

The circuit of the first generator 3 is assembled according to the inductive three-point circuit on the field-effect transistor 3.1, the source of which through the first inductance 3.2 is connected to the capacitive sensor 1 and the output of the device, and through the second inductance 3.3 it is connected to the second output of the first generator 3 and through the resistive-capacitive filter 3.4, 3.5 connected to the housing 8 of the device. In this case, the gate of the field-effect transistor 3.1 is connected through a feedback capacitor 3.6 to the first output of the generator 3, and also through a parallel-connected resistor 3.7 and a diode 3.8 connected to the device case (Fig. 2).

A quartz oscillator 5 is assembled on a logic element 5.1. Schmidt trigger with a quartz resonator 5.2 at the input and a resistor 5.3 in feedback (figure 3). The frequency subtraction unit 6 includes a pulse shaper 6.1 connected to the first input of the D-flip-flop 6.2, the second input of which is connected to the output of the crystal oscillator 5.

A device for measuring the octane number of gasoline works as follows.

When performing measurements, the capacitive sensor 1 together with the temperature sensor is immersed in gasoline, depending on the octane number of which the relative permittivity between the plates of the capacitive sensor 1 changes. This leads to a change in the equivalent capacitance C _{1.1 of the} capacitive sensor 1, which changes the oscillation frequency f _{3 of the} first generator 3, which are fed to the first input of the frequency subtraction unit 6. The pulses of the reference frequency f ₅ from the crystal oscillator 5 are fed to the second input of the frequency subtraction unit 6, at the output of of which pulses of difference frequency f ₆ = f ₅ -f ₃ are generated, which are fed to the first input of data processing unit 8.

A change in the temperature of gasoline leads to a change in the resistance of the temperature sensor 2 and a proportional change in the oscillation frequency f _{4 of the} second generator 4, which are fed to the second input of the data processing unit 8. Digital measurement of the frequency of the oscillations coming from the generator 4 and the frequency subtraction unit 6 is performed in the processing unit data 8 during an interval of fixed duration T _ISM = const, at the end of which two codes are written into the memory of data processing unit 8: N ₄ = f ₄ · T _ISM and N ₆ = f ₆ · T _ISM .

Digital code N ₆ depends on the difference frequency at the output of frequency subtraction unit 6 and corresponds to the dielectric constant of controlled gasoline, and code N ₄ is determined by the frequency f _{4 of the} second generator 4 and is proportional to the temperature of the gasoline. In addition, the third input of the data processing unit 8 receives the code N ₇ from the analog-to-digital Converter 7, the value of which is proportional to the electrical conductivity of gasoline.

To obtain the conversion result corresponding to the octane number of gasoline, a calibration characteristic is pre-recorded in the programmed memory of the data processing unit 8, i.e. the dependence of the octane number on the code N ₆ proportional to the difference frequency, as well as two tables of correction factors. The coefficients recorded in the first table depend on the code N ₄ proportional to the frequency f _{4 of the} second generator 4, and when processing the data, they are used to automatically introduce corrections for the temperature of gasoline. The coefficients recorded in the second table depend on the value of the code N ₇ proportional to the electrical conductivity of gasoline, and during the processing of the data obtained, they are used to correct the result of N ₆ digital measurement of the differential frequency. After joint processing of the codes in the microprocessor data processing unit 8, a conversion result is obtained corresponding to the octane number of gasoline, which is displayed on the digital indicator 11.

The interface unit 10 with the PC is used to record the calibration characteristics and correction coefficients in the reprogrammable memory of the data processing unit 8 during the calibration of the device when using gasoline of different grades with a known value of the octane number. Calibration of the device is practically carried out at different temperatures and at different percentages of water or additives in gasoline.

During operation of the device, a table of correspondence of octane numbers of gasoline to the measured frequency, electrical conductivity and temperature is stored in the memory of data processing unit 8, and intermediate values of octane numbers are calculated in data processing unit 8 by interpolation.

The extension of the control range of electrical conductivity is ensured by the use of an insulating coating of the central rod of the capacitive sensor 1, which ensures the stable operation of the first generator 3 even with high electrical conductivity of the studied fuel. Moreover, also in the proposed device, an increase in sensitivity to the dielectric properties of the fuel is achieved by measuring the frequency difference f _{5 of the} crystal oscillator 5 and f _{3 of the} first generator 3.

For example, the dependence of the oscillation frequency of the first generator 3 on the equivalent capacitance C _{1.1 of the} sensor 1 in the prototype circuit is determined by the expression

,

,

according to which a relative change in the sensor capacitance by 100 · ΔC _1.1 / C _1.1 = 1% leads to a change in the oscillation frequency by 100 · Δf _3.P / f _3.P ≈0.5%.

In the proposed device, the oscillation frequency is affected by the equivalent capacitance C _{1.3 of the} dielectric coating of the sensor rod, taking into account which the oscillation frequency is determined by the formula

,

,

and at the same values of the capacitances of the sensor and the dielectric coating С _1.1 ≈С _{1.3, a} relative increase in the capacitance of the sensor by 100 · ΔС _1.1 / С _1.1 = 1% leads to a decrease in the oscillation frequency by only 100 · Δf ₃ / f ₃ ≈ 0.25%, which is two times less than that of the prototype. However, when the pulse frequency of the quartz oscillator 5 is set 10% higher than the initial oscillation frequency of the first oscillator 3 with an empty sensor 1 under the condition f ₅ ≥1,1f ₃ , the difference frequency at the output of the frequency subtraction unit 6 will be f ₆ = f ₅ -f ₃ ≈0.1f ₃ , therefore, a similar increase in the sensor capacity by 100 · ΔС _1.1 / C _1.1 = 1% will lead to a relative change in the frequency at the output of the frequency subtraction unit by 100 · Δf ₃ / f ₆ ≈ 2.5%, t. e. five times more than the prototype, which is equivalent to a five-fold increase in the sensitivity of the device.

At the outputs of the generator 3 circuit (Fig. 2), two parameters are formed: by the frequency of oscillations f _3, we can judge the dielectric constant and the octane number, and by the voltage U ₃ on the resistive-capacitive filter 3.4, 3.5 - the conductivity of gasoline, which increases with increasing the content of conductive impurities in gasoline. This allows you to use the voltage U ₃ together with the frequency f _{4 of the} generator 4, proportional to the temperature, to correct the measurement results of the octane number of gasolines.

In addition, the low power consumption of the device is ensured by the use of a field-effect transistor in the generator 3 (for example, type KP303E), which for most of each oscillation period operates in the cutoff mode, so its maximum supply current does not exceed tens of microamps. Low power consumption is also achieved through the use of CMOS microprocessor and LCD digital indicator. The use of microcircuits with a high input resistance (Schmidt trigger 5.1 in generator 5 and a pulse shaper 6.1 on a single chip of type K561TL1, a D-trigger on chip K561TM2 in a quartz oscillator 4 and a block for subtracting CMOS frequencies) allows us to exclude their influence on the frequency stability f ₃ at low power consumption. As a result, the battery life of the device increases without replacing the galvanic power elements in a wide range of electrical conductivity and with high sensitivity to the octane number of fuel.

Claims (1)

A device for express control of the octane number of gasoline, comprising an autonomous power supply integrated in a common housing, a cylindrical capacitive sensor connected to the input of the first generator, and a temperature sensor connected to the input of the second generator, the output of which is connected to the first input of the data processing unit, the first output the first generator is connected to the second input of the data processing unit through an analog-to-digital converter, the control input of which is connected to the first output of the data processing unit, the second the output of which is connected to the interface unit and a digital indicator, a crystal oscillator and a frequency subtraction unit are additionally introduced, and a dielectric coating is applied to the central rod of the cylindrical capacitive sensor, while the second output of the first generator is connected to the first input of the frequency subtraction unit, the output of the crystal oscillator is connected to the second the input of the frequency subtraction unit, the output of which is connected to the third input of the data processing unit.

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