JPH01267422A - Pulsation detector for vortex flowmeter - Google Patents

Abstract

PURPOSE:To enable detection of a pulsation of a vortex signal properly, by generating a one-shot pulse at the rising of the vortex signal to count the cycle thereof. CONSTITUTION:A vortex signal with a waveform thereof shaped from a vortex signal detection means is inputted into a one-shot circuit 14a to generate a one-shot pulse at the rising thereof. A first counter 14b counts the cycle of the one-shot pulse by a reference clock. A decoder 14e judges whether an output of the first counter 14b is higher or lower than a decoder criterion frequency and a latch circuit 14c latches the results of the judgement. A second counter 14d judges the presence of a pulsation using on an output of the one-shot circuit 14a as clock and an output of the latch circuit 14c as clear signal and a signal indicating the presence of a pulsation is outputted from a flip flop 14f according to the results of judgement.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides information for appropriately switching a filter group for removing transient noise of an air flow sensor.
The present invention relates to a pulsation detection device for a vortex flowmeter that detects the presence or absence of pulsation by detecting the density of an output signal.

[Conventional technology]

Conventionally, as a vortex flowmeter used in an engine, for example, Japanese Patent Publication No. 58-5641 is known.

FIG. 1 is a block diagram of a pulsation detection device for a vortex flowmeter according to the present invention, which will be described later. In this FIG. When explaining the technology, FIG. 1 will be referred to.

In FIG. 1, an ultrasonic transmitter 4 and an ultrasonic receiver 5 are arranged facing each other via a flowmeter 1 having a vortex generator 2, and a Karman vortex is generated downstream of the vortex generator 2. The ultrasonic transmitter 4 is excited by the ultrasonic oscillation circuit 6 so that the ultrasonic wave propagates across the flow in the row 3.

The ultrasonic wave that crosses the flow of the Karman vortex street 3 is phase-modulated by the Karman vortex street, and is received by the ultrasound receiver 5. This received signal is waveform-shaped by a waveform shaping circuit 8 and then output to a phase comparator 9.

On the other hand, the output of the ultrasonic oscillation circuit 6 that excites the ultrasonic transmitter 4 is applied to the voltage controlled phase shift circuit 7.

This voltage-controlled phase shift circuit 7 maintains the high frequency stability of the ultrasonic oscillation frequency signal and controls only the phase shift angle. This voltage-controlled phase shift circuit shifts the phase of the output of the ultrasonic oscillation circuit 6 and applies it to the phase comparator 9.

The phase comparator 9, the ultrasonic oscillation circuit 6, the voltage controlled phase shift circuit 7, and the loop filter 10 constitute a phase locked loop. 11 is a low pass filter.

A phase comparator 9 compares the phases of the output of the waveform shaping circuit 8 and the output of the voltage-controlled phase shift circuit 7, and adds the comparison result to the loop filter 10. The loop filter 10 removes unnecessary frequency components of the comparison result. Remove.

Depending on the output voltage of the loop filter 10, the voltage controlled phase shift circuit 7 controls the phase shift angle of the output signal of the ultrasonic oscillation circuit 6 and outputs it to the phase comparator 9.

Thereby, the output of the voltage controlled phase shift circuit 7 is synchronized with the ultrasonic reception signal, and as a result, the output of the loop filter 10 directly becomes the phase demodulated output.

In this way, the parts indicated by reference numerals 1 to 11 constitute an eddy signal detection means 100 for detecting eddy signals.

[Problem to be solved by the invention]

Since the conventional vortex flow meter is configured as described above, there is a problem that the vortex frequency is disturbed by noise other than the signal received by the ultrasonic receiver 5 and low-frequency undulations caused by the flow direction of the fluid. there were.

This invention was made to solve the above problems, and it is possible to appropriately remove the noise and pulsation superimposed on the vortex signal, and also to appropriately switch the filters in the filter group, which in turn makes it possible to control the pulsation. The purpose of this study is to obtain a pulsation detection circuit for a vortex flowmeter that can be used.

[Means to solve the problem]

The pulsation detection device for an eddy flowmeter according to the present invention includes a one-shot circuit that receives the output of a waveform shaping circuit and generates a one-shot pulse at the rising edge of the output, and a first counter that counts the period of this one-shot pulse using a reference clock. a decoder that decodes the output of this first counter, a latch circuit that latches the output of this decoder,
A second counter that uses the output of the one-shot circuit as a clock and the output of the latch circuit as a clear signal, and a flip-flop that uses the output of the second counter as a clock and uses the output of the latch circuit as a set signal. It is something that

[For production]

The one-shot circuit in this invention generates a one-shot pulse at the rising edge of the output of the waveform shaping circuit, counts the period of this one-shot pulse using a reference clock in a first counter, and uses the output of the first counter as the decoder judgment frequency. The launch circuit latches the judgment result, and when the output is higher than the judgment frequency, the flip-flop outputs an output indicating that there is pulsation, and when it is lower than the judgment frequency, the second counter outputs the reference signal. Counts the clock and outputs it to the flip-flop, producing an output that eliminates flip-flop pulsation.

[Example] Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 is a block diagram showing the overall configuration, and in this FIG.
The 0 part has already been described in the [Prior Art] column, and a repeated explanation of that part will be avoided.

In FIG. 1, the parts starting from the reference numeral 12 will be mainly described. The output of the phase comparator 9 is input to a loop differential filter 10, and is also input to a filter group 12 via a low-pass filter 11. The output of this filter group 12 is input to a waveform shaping circuit 13.

A Karman vortex frequency signal corresponding to the flow rate of the flowmeter 1 is outputted from the waveform shaping circuit 13, and
It is also input to the pulsation determination circuit 14.

The switching circuit 15 is switched based on the output of the pulsation determination circuit 14. This switching circuit 15 has a fixed terminal 15 leading to the output of each filter of the filter group 12.
ax15n is switched by the output of the pulsation determination circuit 14, and has a movable terminal 150 that leads the output of one of the filters to the waveform shaping circuit 13. This switching circuit 15 switches the filter group 12.

With this configuration, as described above, the vortex signal, that is, the phase demodulated signal, generated in accordance with the flow rate of the fluid to be measured flowing through the flowmeter 1 is input to the filter group 12 via the low-pass filter 11.

By the way, in an engine, for example, in a low flow region such as when idling, there is no ultrasonic noise or undulation, and a stable vortex frequency can be measured. Therefore, the vortex frequency can be detected based on this correct value.

Normally, when the engine is idling, the air valve angle is extremely small, so the air that has passed through the flow meter is once throttled by the valve (not shown) before being sent to the engine, so the throttle effect causes air to be generated in the engine. Pulsating flow and ultrasonic noise downstream of the air valve do not propagate upstream, so the flow meter provides a stable output.

If the pass band of the filter group 12 is determined based on the obtained frequency output, as the engine rotation speed increases and the output frequency increases, the filter group 12 will switch accordingly, so that it will always be outside the signal output frequency. The noise cannot pass through the filter group 12.

Therefore, in the embodiment shown in FIG. 1, the waveform shaping circuit 13 shapes the output of the filter group to obtain a vortex frequency output, and this vortex frequency output is applied to the pulsation determination circuit 14 to determine filter switching. This filter switching determination result is input to the switching circuit 15.

By controlling the pass band by switching the filter group 12 using the switching circuit 15, noise other than the signal output frequency always does not pass through the filter group 12, as described above.

FIG. 2 is a block diagram showing the internal configuration of the pulsation determination circuit 14 of FIG. 1, and 14a in FIG. 2 is a one-shot circuit. A vortex signal output from the waveform shaping circuit 13 of FIG. 1 is input to this one-shot circuit 14a.

The one-shot circuit 14a generates a one-shot pulse at the rising edge of this vortex signal to clear the first counter 14b. A reference clock is input to the first counter 14b, and this reference clock is counted until it is cleared.

The output of the one-shot circuit 14a is the latch circuit 14c.
The clock signal is input to the clock input terminal of the second counter 14d.

The output of the first counter 14b is sent to a decoder 14e, and the output of the decoder 14e is sent to a latch circuit 14c.

The output of the latch circuit 14c clears the second counter 14d, and also clears the flip front 14f (hereinafter referred to as
(referred to as FF). FF14
The output of the second counter 14d is input to f as a clock. The first output is from FF14f.
The switching circuit 15 shown in the figure is switched.

Next, the operation of the pulsation determination circuit 14 shown in FIG. 2 will be explained using the time chart shown in FIG. 3.

When a vortex signal as shown in FIG. 2(a) is input to the waveform shaping circuit 13, the waveform is shaped by the waveform shaping circuit 13, and the output of the waveform shaping circuit 13 is as shown in FIG. 3(b). The signal is input to one-shot circuit 14a in FIG.

This output signal of the waveform shaping circuit 13] As is clear from FIG. Circuit '14a outputs a one-shot pulse as shown in FIG. 3(C).

This one-shot pulse is input as a clear signal to the first counter 14b, and a reference clock is input to this first counter 14b. The clock starts counting and is cleared again when the next one-shot pulse is input.

That is, the first counter 14b counts the period of the one-shot pulse. The output of this first counter 12b is sent to a decoder 14e.

The decoder 14e is a first counter 1 shown in FIG. 3(d).
4b is decoded to determine whether this output is higher or lower than the determination frequency.

The determination result by this decoder 14e is the latch time Q 14
c, and is latched by the latch circuit 14c at the falling edge of the one-shot pulse. This circuit 14c
As shown in FIG. 3(e), the output is sent to the second counter 14d as a clear signal, and is also sent to the FF 14f as a set signal.

When the output of the latch circuit 14c is higher than the determination frequency, the rH signal is unconditionally output from the FF 14f (FIG. 3(g)). When this rH signal is output, the switching circuit 15 of FIG. is switched.

When this rH signal is being output, the second counter 14d is in a reset state by the output of the latch circuit 14c.

On the other hand, the one-shot pulse (FIG. 3(C)) generated by the one-shot circuit 14a is inputted to the second counter 14d as a clock signal.

Here, when the output of the latch circuit 14c becomes lower than the determination frequency, the second counter 14d starts counting the number of one-shot pulses, and after counting a certain number of pulses,
As shown in FIG. 3(f), the output is output as a clock for the FF 14f, and the FF 14f outputs an "L" signal as shown in FIG. 3(9).

Table 1 below shows the logic for determining the presence or absence of pulsation.

<Table 1> [Effects of the Invention] As described above, according to the present invention, a one-shot pulse is generated from the one-shot circuit at the rising edge of the vortex signal to clear the first counter, and the first counter is cleared. The period of one-shot pulse is counted by counting the reference clock, the decoder judges whether the count output is higher than the judgment frequency, the judgment result is latched by the latch circuit, and when the output is higher than the judgment frequency, pulsation occurs. Assuming that there is no pulsation, the output of the flip-flop drives a switching circuit that switches the filter group unconditionally, and when the output of the latch circuit is lower than the determination frequency, it is assumed that there is no pulsation, and the flip-flop outputs an rLJ times signal. , it is possible to appropriately switch the filter group inserted for removing noise superimposed on the vortex signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of a pulsation detection device for a vortex flow meter according to an embodiment of the present invention, FIG. 2 is a block diagram showing the internal configuration of a pulsation determination circuit in the same embodiment, and FIG. 3 2 is a waveform diagram for explaining the operation of the pulsation determination circuit of FIG. 2. FIG. DESCRIPTION OF SYMBOLS 1... Flowmeter, 12... Filter group, 13... Waveform shaping circuit, 14... Pulsation determination circuit, 14a... One-shot circuit, 14b... First counter, 14c
...Launch circuit, 14d...Second counter, 14
e...decoding, 14f...flip flop. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] an eddy signal detection means for detecting an eddy signal generated in response to the flow rate of the fluid to be measured; a group of filters for removing noise upon receiving the output of the eddy signal detection means; a waveform shaping circuit that outputs a vortex frequency output in response to the waveform shaping circuit; a one-shot circuit that receives the output of the waveform shaping circuit and generates a one-shot pulse at its rising edge; and a first circuit that counts the period of the one-shot pulse using a reference clock. a counter, a decoder that determines whether the output of this first counter is higher or lower than the determination frequency, a latch circuit that latches the determination result of this decoder, and when the output of this latch circuit is higher than the determination frequency, there is pulsation. is set by this output to switch the switching circuit to switch the filter group, and when the output of the latch circuit is lower than the determination frequency, there is no pulsation and the flip-flop does not switch the switching circuit, and the output of the latch circuit is A pulsation detection device for a vortex flowmeter, comprising a second counter that is cleared when the frequency is higher than the determination frequency and counts the reference clock and outputs the result to the flip-flop when the frequency is lower than the determination frequency.