RU2399154C1 - Device for generating pulses from signals of rotational frequency inductance pickup - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: device has two comparators, one connected directly and the other through an inverter to an input signal source. The device also has a reference signal source whose outputs are connected to inputs of the comparators, a frequency metre whose input is connected to the output of the second comparator, a device for measuring rate of change of frequency whose input is connected to the output of the frequency metre, the control input of the reference signal source, and a timer whose start input is connected to the output of the first comparator, the first control input is connected to the output of the second comparator, the second control input is connected to the output of the device for measuring rate of change of frequency, the third control input is connected to the output of the frequency metre and the outputs are connected to control inputs of the comparators respectively.

EFFECT: increased noise immunity.

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Description

The present invention relates to measuring equipment and can be used in automatic measurement, control and emergency protection systems, which include sensors that generate bipolar signals, in particular induction sensors of speed and flow.

A device for generating pulses from the signals of induction speed sensors [1], based on the principle of selection of the input signal by area. Its disadvantage is the lack of reliability due to the fact that only one signal polarity is used to generate pulses from the signals of the induction speed sensors.

Of the known closest in technical essence is a device that implements a method of generating pulses from signals of induction speed sensors [2]. Its structural diagram is shown in figure 1, figure 2 presents the waveform of the output signal of the induction speed sensor.

The device comprises a volt-second area measurement unit S _{1 of the} first half-wave of a bipolar signal e _{c of} induction rotation sensors 1, a memory unit 2, a comparison unit 3, an inverter 4, a volt-second area measurement unit S _{2 of a} second half-wave of a second half-wave of a bipolar signal e _{c of} induction speed sensors 5 and control unit 6. The output signal e _{c of the} induction speed sensors is supplied to the inputs of the volt-second area measurement unit S _{1 of the} first half wave of the bipolar signal e _{c of the} induction rotation sensors 1, 6 and through the inverter 4 to the input of the volt-second area measurement unit S _{2 of the} second half-wave of the bipolar signal e _{c of the} induction speed sensors 5. The outputs of the memory unit 2 and the volt-second area measurement unit S _{2 of the} second half-wave of the bipolar signal e _{c of the} induction speed sensors 5 are connected to the comparison input inputs of the storage unit 2. The second output of the storage unit 2 is connected to the input of the threshold setting Spor1 of the comparison unit 3 and the input of the control unit 6. The outputs of the control unit 6 are connected, respectively, to the control inputs eniya comparison memory blocks 3 and 2, and inputs the measurement control units volt-second area S ₁ of the first half-cycle of the bipolar signal e _with inductive rotation sensor 1 and S ₂ of the second half-cycle of the bipolar signal ec inductive speed sensors 5.

The work of induction speed sensors is based on the Faraday law, according to which the induced EMF e _s is determined by the rate of change of the magnetic field Ф, coupled to a coil of W turns [3]:

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In the case under consideration, a change in the magnetic field is caused by the intersection of the field lines of the sensor magnet field with the protrusions of a rotating pathogen [4]. When the pathogen enters the magnetic field in the coil, the first half-wave of the signal is induced, and when it exits, the second half-wave is of opposite polarity (Fig. 2).

The volt-second area S _{1k of the} first half-wave of such a signal is approximately equal to the same area S _{2k of the} second (opposite polarity) half-wave, and the ratio of these areas R = S _1k / S _{2k is} close to 1, does not depend on the error in setting the gap between the sensor and the exciter, characteristics the pathogen itself and remains constant over a wide range of speeds. The amplitude of the signal e _c increases linearly with increasing speed, and the duration decreases.

The device operates as follows. The control unit 6 contains threshold elements (comparators) and logic circuits. When the input signal exceeds _a predetermined e to the comparators 6, the detection threshold control unit produces enable signal measurement S ₁ and fed to the measurement unit volt-second area of the block 1. The measurement volt-second area of the input signal 1 is carried out _with e integration as long as the input signal e _c does not become less than the detection threshold set in the control unit 6. In this case, the output signal of the volt-second area measurement unit 1 reaches the value S _1k . If the value of S _1k exceeds the threshold value Spr.min, which is equal to the maximum minimum permissible value of the volt-second area of the studied signal half-waves S ₁ к> Sr.min, and the control unit 6 detects the second half-wave of the signal e _s , then a signal appears on the output of the control unit 6 resolution measurements S ₂ in the volt-second area measurement unit 5 during the action of the second half-wave of signal e _s , as well as a resolution signal comparing the current measurement result Sxк with the threshold value Sпор1 = Sпор ₁ = Q · S ₁ к (Q is slightly less than unity), formations nnym in the memory unit 2 from S ₁ to the signal.

The comparator 3 compares the area with Sxk Spor Sxk with ₁ or S ₁ in. In the cases S _2> Spop Sxk≈S ₁ or ₁ to the desired pulse is generated.

The disadvantage of this device is its low noise immunity. In the case of actions during the entire signal e _with unipolar noise pulse interference or force coincident in sign and time of occurrence of the first half-wave signal e _with or opposite in sign to the second half-wave, none of the terms S _2> Spor ₁ or Sxk≈S ₁ not executed, and no signal is detected. In addition, low-frequency bipolar noise, for example from an AC mains, even of small amplitude, can have the same value of the volt-second area of each of the half-waves as the signals of the induction rotation sensors. The appearance of such interference will lead to false detection of the signal.

The present invention is aimed at improving noise immunity. This is achieved by the fact that in the pulse shaper from the signals of induction speed sensors, containing two comparators connected directly and the second through an inverter with an input signal source, according to the invention, a reference signal source is introduced, the outputs of which are connected to the inputs of the comparators, a frequency meter, connected at the input to the output of the second comparator, a frequency change rate meter, connected at the input to the output of the frequency meter, controlling the input of the source a reference signal, and a timer, the start input of which is connected to the output of the first comparator, the first control input is connected to the output of the second comparator, the second control input is connected to the output of the frequency change rate meter, the third control input is connected to the output of the frequency meter, and the outputs are connected, respectively , with the control inputs of the comparators.

Figure 3 shows the structural diagram of the proposed device pulse shaper from the signals of induction speed sensors.

The device consists of a reference signal source 1, an inverter 2, comparators 3 and 4, a timer 5, a frequency meter 6, and a frequency change rate meter 7.

The bipolar signal of the induction speed sensor e _s is supplied to the input of the comparator 3 and through the inverter 2 to the input of the comparator 4. The second inputs of the comparators 3 and 4 are connected, respectively, to the outputs of the reference signal source 1, connected through the control circuit to the output of the frequency meter 6. Output the comparator 3 is connected to the start input of the timer 5, and the output of the comparator 4 is connected to the first control input of the timer 5 directly, through a frequency meter 6 to the third control input. The second control input of the timer 5 is connected to the output of the frequency change rate meter 7. The outputs of the timer 5 are connected, respectively, to the control inputs of the comparators 3 and 4. The output of the comparator 3 is the output of the required pulse 8, the output of the frequency meter 6 is connected to the input of the frequency change rate meter 7 and serves as a conclusion of the measurement result of the rotational speed 8, and the output of the frequency change rate meter 7 is a conclusion of the value of the rate of change of the frequency 10.

All elements that make up the device can be implemented as separate functional units or programmatically using a microcontroller equipped with comparators, a timer and a digital-to-analog converter.

The device operates as follows. At the beginning of the operation, the response threshold of the comparators 3 and 4 is set by the reference signal source 1 equal to half the minimum possible amplitude of the signal of the induction speed sensor e _s , the choice of the thresholds of the comparators 3 and 4 equal to half the minimum possible signal amplitude of the induction speed sensor e _s . This ensures the stable operation of the device in the event that during the entire signal e _with unipolar interference, not exceeding the threshold of operation of the comparators 3 and 4, with alternating interference, antiphase signal e _with and satisfying the same condition. That is, the device provides stable operation with a ratio of signal amplitudes and interference of more than two. Powerful unipolar pulsed interference, having the same sign and the time of occurrence of one of the half waves signal e _s, also did not affect the operation of the device as a condition of excess signal e _with half its minimum possible amplitude is not disturbed.

When the input signal of the device becomes greater than the threshold, the output of the comparator 3 appears the start pulse of the timer 5. The timer 5 generates a pulse whose duration is equal to the expected duration of the second half-wave of bipolar pulses of the induction speed sensor. This pulse is supplied to the control input of the comparator 4, allowing it to work. If during the action of this pulse the second inverted half-wave of the input signal e _c exceeds half of its minimum possible amplitude, the comparator 4 will work, and the required pulse will appear at its output 8. After receiving at least three pulses at the output 9 of the device, the result of measuring the rotational speed appears, and at the input 10, the result of measuring the rate of change of frequency. In this case, timer 5 begins to generate control pulses for comparators 3 and 4, the appearance and duration of which depend on the extrapolated time, based on the known time of the last required pulse at output 8, the results of measuring the frequency and rate of change, respectively, at outputs 9 and 10. At the same time in accordance with the results of measuring the frequency, the value of the reference signal of the comparators at the output of the source of reference signals 1 is increased. At the beginning of work, I always There is a work permit signal. If during the opening of the comparators 3 and 4 their operation does not occur, that is, the signal of the induction speed sensor is not detected at the expected time, then the device returns to its original state until three new pulses appear at the output 8.

The generation of control signals for comparators 3 and 4 (gating) adaptively to the value of the measured frequency and the rate of its change eliminates false alarms of the device in case of alternating interference of any amplitude in the pauses between the signals of the induction speed sensor. Furthermore, with increasing signal frequency f increases _with the value of a reference signal source 1 output signal, which also increases the noise immunity of the device in signal e _with a high frequency.

Thus, the introduction of new units into the device and the connections between them provides increased noise immunity of the device.

Claims (1)

A pulse generator from the signals of induction speed sensors, containing two comparators connected directly and the second through an inverter with an input signal source, characterized in that a reference signal source is inserted into it, the outputs of which are connected to the inputs of the comparators, a frequency meter connected by the input with the output of the second comparator, a frequency change rate meter connected at the input to the output of the frequency meter, controlling the input of the reference signal source, and a timer, the trigger input which is connected to the output of the first comparator, the first control input is connected to the output of the second comparator, the second control input is connected to the output of the frequency meter, the third control input is connected to the output of the frequency meter, and the outputs are connected respectively to the control inputs of the comparators.

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