RU2007730C1 - Spark energy meter - Google Patents

Abstract

FIELD: electric measurement technology. SUBSTANCE: meter has current measuring converter 1, squarer 2, integrator 3, calibration unit 4, analog-to-digital converter 5, indicator 6, discriminator 7, pulse formers 8 and 9, rejection unit 10. EFFECT: simplified design. 2 dwg

Description

 The invention relates to electrical engineering, in particular to devices for measuring the energy of fast-flowing pulse processes, and can be used to determine the ratio of the energy of discharge pulses that occur, for example, in spark plugs, to the energy of a capacitive storage device that causes discharge pulses.

 Known energy meters based on the method of multiplying the instantaneous values of current and voltage with subsequent integration.

 The disadvantages of these meters are the limited application and low measurement accuracy due to the use of two measuring transducers - current and voltage. In terms of functionality, these meters are not suitable for measuring the energy of pulsed discharges, for example, in candles during the discharge of a pre-charged capacitor through a switching spark gap.

 The closest in technical essence to the claimed one, selected for the prototype, is a spark energy meter containing a signal multiplier, the inputs of which are connected to the outputs of the voltage and current transducers, and the outputs are connected to an indicator through an integrator.

 The disadvantage of this meter is the low accuracy of the measurement, as well as the relatively narrow functionality. Low measurement accuracy is caused, firstly, by the presence of a voltage measuring transducer, which, when registering a voltage drop in the spark, voltage dividers are used, which have a significant error, and secondly, that the measurement circuit does not turn off during the absence of a spark discharge, and As a result, the energy released in the spark gap before the start of the spark discharge is measured. This is the case, for example, in semiconductor spark plugs, in which currents of the so-called preparatory stage of the discharge flow through the spark plug prior to the formation of a spark discharge and significant energy is released. The reason for the limited functionality is also the presence of a voltage measuring transducer - a voltage divider having a narrower operating frequency range compared to a current measuring transducer, for example a current transformer. Moreover, the measuring transducer - voltage divider when measuring the energy of the spark should be connected to the electrodes of the candle directly at the working end of the candle, i.e., in the immediate vicinity of the spark discharge. When the voltage divider is connected to the high-voltage input of the plug, the voltage drop is measured not only in the spark, but also on the electrodes, while due to the distribution of the inductance and capacitance of the electrodes, the shape of the voltage drop curve is distorted and large measurement errors are introduced. This circumstance does not allow the use of an energy meter to record the energy of a spark discharge in a candle mounted on an aircraft engine, since, firstly, it is practically impossible to connect the input cable of the voltage divider to the working end of the candle without violating the integrity of individual engine components, second, even if this can be done, the input cable of the divider, when connected to the working end of the candle, distorts the aerodynamic processes in the combustion chamber at the location of the candle.

 The purpose of the invention is the expansion of the functionality of the meter and improving the accuracy of conversion of input signals.

 This is achieved by the fact that a signal quadrator, a meter calibration unit, an analog-to-digital converter (ADC), a level discriminator, two pulse shapers, a zeroing unit, and a measurement output are introduced into the spark energy meter containing a current transducer, a quadrator, an integrator and an indicator. the current transducer is connected to the inputs of the signal quadrator, the output of which is connected to the integrator input, the integrator output is connected to the meter calibration unit, which is connected by its output to the ADC input, the output The ADC is connected to an indicator made in the form of a digital indication unit, the input of the level discriminator is connected to the output of the current measuring transducer, and the output of the level discriminator is connected to the corresponding inputs of the first and second pulse shapers, the output of the first pulse shaper is connected to the control input of the zeroing unit included in integrator reset circuit, the output of the second pulse shaper is connected to the control input of the ADC.

 In FIG. 1 presents a structural diagram of the proposed meter; in FIG. 2 - time diagrams explaining the principle of operation of the meter.

 The spark energy meter contains a current measuring transducer 1, a 2-signal quadrator, an integrator 3, a calibration unit 4, an ADC 5, an indicator 6, a level 7 discriminator, the first 8 and second 9 pulse shapers, a zeroing unit 10.

= R_н·i²dt= R

i $\genfrac{}{}{0ex}{}{\text{2}}{\text{н}}$ dt где R_Н - эквивалентное искровое сопротивление;
i_Н - мгновенное значение разрядного тока;
t_Н - длительность искры.The principle of operation of the meter is based on the method of determining the energy of a spark by a discharge current. In this case, the spark energy is calculated by the formula
W _n =

= R _n · i ² dt = R

i $\genfrac{}{}{0ex}{}{\text{2}}{\text{n}}$ dt where R _N is the equivalent spark resistance;
i _N is the instantaneous value of the discharge current;
t _N - the duration of the spark.

- 1

, где R_з - эквивалентное сопротивление разрядного контура при закороченной свече;
i_з - мгновенное значение разрядного тока при закороченной свече;
t_з - длительность разряда при закороченной свече.The value of the spark resistance of the candle R _H can be determined by the expression resulting from the equality of the energies released when the candles are not shorted and shorted (according to the law of conservation of energy)
R _n = R

- 1

where R _z is the equivalent resistance of the discharge circuit with a shorted candle;
i _s is the instantaneous value of the discharge current with a shorted candle;
t _s - discharge duration with a shorted candle.

 The spark resistance obtained in this way is taken into account using the converter calibration unit, which allows you to convert the input signal of the discharge current to a value proportional to the energy of the spark.

 The meter works as follows.

i $\genfrac{}{}{0ex}{}{\text{2}}{\text{н}}$ dt.A measuring current transducer 1, for example a current transformer, is connected in series with the spark gap under study. In the spark gap with a certain frequency, spark discharges are formed (Fig. 2a). At the time of the appearance of a spark discharge from the converter 1, a signal proportional to the discharge current is fed to the input of the square 2 and to the input of the discriminator 7. At the output of the square 2, a signal is generated proportional to the square of the discharge current (Fig. 2b), which is fed to the input of the integrator 3. B the moment of the appearance of the spark discharge, the discriminator of level 7 is triggered, which generates negative logical impulses at its output (Fig. 2c). On the decline of the first pulse, the shapers 8 and 9 are triggered. The duration of the pulse generated at the output of the first shaper 8 (Fig. 2d) is chosen equal to the time of the maximum possible duration of the spark and the conversion time of the ADC 5. The pulse duration of the second shaper 9 is equal to the time of the maximum possible duration of the spark ( Fig. 2e). From the output of the first driver 8, the pulse goes to the control input of block 10, which stops the integrator 3 from zeroing. From the output of the second driver 9, the pulse goes to the control input of the ADC 5, and the ADC is reset on the leading edge of this pulse, and the ADC is launched on the falling edge. During the development of the discharge process in the spark gap at the output of the integrator 3, the signal X is formed (Fig. 2e), equal to
X =

i $\genfrac{}{}{0ex}{}{\text{2}}{\text{n}}$ dt.

This value is fed to the input of the meter calibration block 4, which generates, taking into account the spark resistance R _Н (for a particular type of candle), a signal proportional to the energy of the spark at its output. This signal is fed to the input of the ADC 5, where it is converted to a digital code. The converted amount of spark energy in a digital code is supplied for visual observation in indicator 6.

 At the end of the discharge process and the expiration of the time specified by the first driver 8, the zeroing unit 10 switches to the zeroing mode of the integrator 3. The meter is ready to convert the information of the next discharge pulse.

 Thus, in comparison with the prototype, the claimed technical solution allows to expand the functionality and accuracy of the conversion of input signals by using one measuring current transducer and eliminating the voltage measuring transducer, which has a significant error and has a narrower operating frequency range compared to the current transducer. In addition, to reduce the conversion error, the voltage measuring transducer during the conversion and measurement of spark energy should be connected to the electrode electrodes directly along the working end of the candle close to the spark discharge. This circumstance does not allow the use of known spark energy converters for detecting the energy of a spark discharge in a candle mounted on an aircraft engine. The proposed technical solution is devoid of this drawback and can be used to convert and record the energy of the spark discharge in the spark plug located directly in the combustion chamber of the engine. (56) Bolotin I.B. and Eidel L.Z. Measurements in short circuit modes. M.: Energy, 1988, p. 149.

Claims (1)

 SPARK ENERGY METER, comprising a current measuring transducer, an integrator and an indicator, characterized in that the meter calibration unit and an analog-to-digital converter are connected in series, a level discriminator, a first pulse shaper and a zeroing unit connected in series, a signal quadrator, a second pulse shaper, moreover, the output of the measuring current transducer is connected to the input of the level discriminator directly and through the signal quadrator to the first input of the integrator, the second input of which is connected to the output of the zeroing unit, the output of the level discriminator is connected through a second pulse shaper to the second input of the analog-to-digital converter, the output of which is connected to the indicator input, which is made in the form of a digital indication unit, and the integrator output is connected to the input of the meter calibration block.

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