JPS58214813A - Measuring device for flow rate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION In order to measure the flow rate of a fluid, the present invention includes two ultrasonic transducers arranged apart from each other by a measuring section in the axial direction of a flow path, and these ultrasonic transducers. The output signals of one ultrasonic oscillator to be energized and one ultrasonic transducer acting as an ultrasonic receiver are applied to one comparison input.
The present invention relates to a flow rate measuring device having a phase comparator, an additional oscillator and an evaluation device for converting the output signal of the phase comparator into a form suitable as an input signal for a downstream integral indicating device.

Furthermore, the invention provides at least one heat exchanger inlet and
The present invention relates to a flow rate measuring device which is applied as a calorimeter by using a signal source configured as a means for measuring an outflow temperature difference.

Such a flow measuring device is known from German Patent Application No. 2724661. In that case, two ultrasound transducers arranged at a distance from each other in the axial direction of the flow path are each used simultaneously as ultrasound transmitters over a first time span. During this first time cycle, both ultrasound transducers are provided with identical sinusoids to each other. The duration of this first time span is chosen to be shorter than the propagation time of the sinusoids between the two ultrasound transducers.
Subsequently, both ultrasonic transducers are used as ultrasonic receivers for the incoming sinusoidal signal. In this case, over a second time span, the phase difference between the centers of the sinusoids arriving at the ultrasound transducer after passing through the measurement section is evaluated. This phase difference is proportional to the flow velocity because the propagation time of the sine waves traveling in the flow direction is shorter than the propagation time of the sine waves traveling in the opposite direction to the flow direction. This phase difference is converted by a phase comparator into a pulse having a width proportional to the propagation time difference. An additional oscillator repeatedly controls the transmission and reception cycles described above. The pulses occurring at the output of the phase comparator are a signal which can be configured as a constant current source or a constant voltage source, as shown in FIG. 6 of German Patent Application No. 2724661. It is used to control one switch connected between the output of the source and the input of one quantizer. A quantizer, acting as an analog frequency converter, converts its input signal into a train of pulses with a frequency proportional to its magnitude. This pulse train is applied to an integral indicator configured as a pulse counter, the rate of which is proportional to the propagation time difference of the two sinusoidal groups traveling in opposite directions and thus also to the flow velocity. The signal source, controllable switch and quantizer form an evaluation device which converts the output signal of the phase comparator into a form suitable for feeding to a downstream indicating device. If the signal source is configured to produce an output signal proportional to the inlet/outlet temperature difference of the at least one heat exchanger, the controllable switch produces a signal proportional to the flow rate and the inlet/outlet temperature difference t/C. Since it acts as a kind of time-sharing multiplier that forms a product with a proportional signal, the integral type indicating device configured as a pulse counter in this case reduces the amount of heat energy consumed by at least one heat exchanger. instruct. This flow rate measuring device requires expensive and very precise time control to form a phase comparator output signal that is proportional to the flow rate.

Additionally, German Patent Application No. 282893
From specification No. 7, particularly claim 2 thereof, it is clear that two ultrasonic transducers arranged apart from each other in the axial direction of the flow path are used alternately as an ultrasonic transmitter or an ultrasonic receiver, respectively. Flow rate measuring devices are known. in this case,
Alternately, both ultrasound transducers are provided with a first ultrasound frequency and a different second ultrasound frequency as transmitters.

To generate both these frequencies, a phase-locked loop (P
LL), and its frequency is set to 1(, In other words, it is adjusted so that the flow velocity of the fluid in the flow path can be determined from the difference between the two frequencies.Since both different ultrasonic frequencies are sent one after another, two signals proportional to these frequencies are prepared at the moment of evaluation. Therefore, it is necessary for f to memorize the Ryosogo.This requires considerable technical expense.

The aim is to improve the fixed equipment in such a way that it can be realized with little technical outlay.

a) the additional oscillator is configured as a square wave generator with a duty factor of 1/2 and a lower frequency compared to the frequency K of the ultrasonic oscillator; b) a switching device controlled by the additional oscillator; is provided, in whose first switching position one ultrasonic transducer is connected to an ultrasonic oscillator and acts as an ultrasonic transmitter, and the other ultrasonic transducer is connected to one comparison input of a phase comparator. c) the output signal of the additional oscillator is provided to the evaluation device for time control; d) The second input of the phase comparator is achieved by a flow measuring device, characterized in that it is fed with the output signal of an ultrasonic oscillator.

As a result, sinusoids are transmitted between the two ultrasonic transducers in a circular direction and during the following half-cycle in a direction counter to the flow direction.

During each half-period, a phase comparator detects an ultrasound propagation time relative to the output signal of the ultrasound oscillator, which increases or decreases depending on the flow velocity compared to the propagation time in a stationary fluid. In the evaluation device, under time control by the output signal of an additional oscillator, a propagation time difference proportional to the flow velocity of the ultrasound waves traveling in the flow direction and in the opposite direction is determined relative to the output signal of the ultrasound oscillator. can be evaluated.

In this way, a propagation time difference proportional to the flow velocity of the ultrasound waves in the flow direction and in the opposite direction is determined by a relatively inexpensive circuit.

It is advantageous that the ultrasonic oscillator produces a square wave-shaped output signal, in that the phase comparison in the phase comparator and the evaluation in the evaluation device can be significantly simplified. In this case, it is not necessary to detect the zero crossing of the output i of the ultrasound oscillator and the output signal of the ultrasound transducer acting as ultrasound receiver;
A very accurate temporal line detection of the square wave signal is achieved.

One advantageous embodiment of the invention provides that the evaluation device has a signal source which produces a constant output signal and the output of the phase comparator, as described in German Patent Application No. 27 24 662 mentioned above. at least one controllable switch means controlled by the signal, the output signal of the signal source being applied to a quantizer via the controllable switch means, and integrating at the output of the quantizer. In a flow measuring device to which a pulse counter with an accumulating function is connected as a shape indicating device, a) the evaluation device includes a logic circuit consisting of two exclusive-OR gates with negated output signals, and b) a second C) The first exclusive OR gate performs a logical operation on the output signal of the phase comparator and the output signal i of the quantizer; C) The second exclusive OR gate performs a logical operation on the output signal of the first exclusive OR gate and the output signal of the additional oscillator. Output signal and ms extra mmcy
d) In one output state of the second exclusive OR gate, the non-inverted output signal of the signal source is applied to the quantizer, and in the other output state, the inverted output signal of the signal source is applied to the quantizer. It is characterized in that it is connected to the input end of.

By applying the non-inverted or inverted output signal of the signal source to the input of the quantizer under the control of such a logic circuit, the rectangular alternating voltage signal generated at the input of the quantizer is applied over one period of the additional generator. The integrated value corresponds to the product of the value of the signal of the signal source and the difference in propagation time of the ultrasonic waves in the flow direction and the opposite direction, that is, a value proportional to the flow velocity.

In one advantageous embodiment of the invention, the signal source has a non-inverting output and an inverting output, the non-inverting output via the first controllable switch means and the inverting output via the second controllable switching means. The output signal of the second exclusive-OR gate is connected to the input of the quantizer via controllable switch means, and the output signal of the second exclusive-OR gate is connected to the input of the quantizer for controlling the first controllable switch means. For control, a signal obtained by inverting the output signal of the second exclusive OR gate using an inverter is used. More than that,
The input signal of the quantizer is obtained in a particularly inexpensive manner.

It is advantageous if an exclusive-OR gate with negative output is used as the phase comparator. A particularly good and economical phase comparator is thereby realized.

Advantageously, the quantizer is an integrator followed by a limit value circuit with two voltage limit values. In this case, whenever the output signal of the integrator exceeds one of the voltage limits of the limit value circuit, the output signal jumps from one of the two possible states to the other.

A square-wave pulse train is thus obtained at the output of the quantizer, the state of the zero counter whose parnus are accumulated in integral kakuntas, being a measure of the amount of fluid flowing into the channel.

As described in the specification, when the flow measuring device is applied as a calorimeter with a signal source configured as a means for measuring the inflow/outflow temperature difference of at least one heat exchanger, the inflow One temperature-dependent resistor is provided for sensing the temperature and the outflow temperature, each of which is powered by a constant current source, and the voltage drop across both resistors is respectively applied to the input of one differential amplifier. It is an advantage to be given. In this case, the output signal of the signal source applied to the input terminal of the quantizer under the control of the logic circuit is not constant, but changes depending on the temperature difference between the inflow and outflow of the heat exchanger, so quantization is not possible. Add the input signal of the oscillator to one of the oscillators
The value integrated over the period is the product of the ultrasonic propagation time difference in the flow direction and the opposite direction, that is, the value proportional to the flow velocity, and the value proportional to the temperature difference between the inflow and outflow of the heat exchanger. The invention will be explained in more detail by the examples shown in .

FIG. 1 shows a block connection diagram of a flow rate measuring device applied as a calorific value integrator.

A fluid used as a heating medium in the heating system flows in the flow path l in the flow direction indicated by the arrow r. Two ultrasonic transducers w1 and W2 are arranged in this flow path axially spaced apart from each other. The section between these ultrasonic transducers Wl and W2 is a measurement section, in which ultrasonic waves travel alternately in the flow direction and in the opposite direction. To alternately energize both ultrasonic transducers W1 and W2, an ultrasonic oscillator G1 is used which generates square wave signals of frequency f1 and period T. These square wave signals have a duty ratio of 1/2. It is preferable to have. The output signal ul of this ultrasonic oscillator G1 is shown in FIG. .

This alternating supply takes place via a switching device U controlled by an additional oscillator G2. The additional oscillator 02 is configured as a square wave oscillator with a duty ratio of 1/2 and produces a square wave signal u4 of frequency f2 and period T2. The frequency f2 of the additional oscillator G2 is selected lower than the frequency fl of the ultrasonic oscillator G1,
1 is preferably an integral multiple of the frequency f2 of the ultrasonic oscillator G2. Output signal u of additional oscillator G2
4 is shown in FIG. In the example of FIGS. 2 and 5, the period T of the output signal u4f emitted from the additional oscillator G2 is the output signal u1 emitted from the ultrasonic oscillator G1.
It is six times the period T of .

The switching devices controlled by the additional oscillator G2 each have a first half period T. /2, the output signal u1 of the ultrasonic oscillator amplified by the amplifier v1 is transmitted to the ultrasonic transducer WIK.
Pass. During this time span, ultrasound transducer W2 acts as an ultrasound receiver for the ultrasound signals emitted from ultrasound transducer W1.

During this first half-cycle, the output signal of the ultrasound receiver W2 is transferred to the switching device U and the amplifier V in the switching position shown.
2 to the input end e1 of 1 to the phase comparator. The signal u2 applied to this input terminal e1 is shown in FIG. The following half-cycle (T marked in Figure 5./
2 to T. ), the switching device U is in the second switching position and the performance of the ultrasonic transducers w1 and W2 is exchanged. In this case, the ultrasonic transducer W2 is energized by the output signal LIIK of the ultrasonic oscillator G1 amplified by the amplifier v1,
On the other hand, the ultrasonic transducer Wl acts as an ultrasonic receiver, the output signal of which is fed via a switching device U and an amplifier v2 to a first comparison input e1 of a phase comparator. An ultrasonic oscillator G is connected to the second comparison input terminal e2 of the phase comparator.
1 output signal u1 is given. In a particularly simple and economical embodiment, this phase comparator Kl is an exclusive-OR gate with an anti-i capability signal. The output signal u3 of phase comparator 1 is shown in FIG. The first half period T of the output voltage u4 of the additional oscillator G2. /2, ultrasonic transducer W
A group of ultrasonic waves emitted from 1 travels in a direction opposite to the flow direction. In this case, at the output of the phase comparator 1, a pulse train consisting of six pulses with a width tg as shown in FIG. 4 is generated. In the second half cycle (To/2 or even To) in which the ultrasonic wave group advances in the flow direction, the width t in FIG.
A pulse train of 6 pulses of i results. here,
The flow rate is the duration T. It is assumed that it does not change during the Q period. Furthermore, for the sake of understanding the waveform diagram shown in FIG. 4, it should be mentioned that when the fluid is stationary, that is, when the flow velocity is There exists a phase difference of , and the output signal u3 of the phase comparator has a duty ratio of 1/2. This duty ratio of 1/2 in the signal u3 changes to larger or smaller values depending on the flow direction and flow velocity, with the difference t 1-1 g being proportional to the flow velocity V.

The output signal u3 of the phase comparator 1 and the output signal u4 of the additional oscillator G2 are fed to an evaluation device A, which is shown within the dashed line in FIG. The evaluation device includes a signal source S1 logic circuit L1 controllable switches y-81 and S2 (operating inversely to each other) and a quantizer Q. The square-wave output signal u8 of the evaluation device A is fed to an integral indicator Z, which is configured as an accumulation counter. This indicating device Z is
Depending on the configuration of the signal source S, it corresponds to the flow rate of the fluid flowed through the channel or the amount of heat dissipated by the at least one heat exchanger.

The logic circuit of the evaluation device A includes two exclusive OR gates El and R2 with negated outputs, the first exclusive OR gate (El) has an output signal u3 of 1 to the phase comparator and an output signal of 1 to the quantizer Q. An output signal u8 is provided. 1st
The output signal of the exclusive OR gate E1 and the additional oscillator G
2's output signal u4 is processed in a second exclusive onergame) R2. The output signal u5 of the second exclusive or game R2 shown in FIG.
It is also used to control the second controllable switch S2 after being inverted by the inverter N. In this way, S
1 and 82 perform a push-pull operation.

The signal source S is used in the embodiment shown in FIG. 1 to obtain a signal "jd" which is proportional to the inflow/outflow temperature difference in at least one heat exchanger.
a temperature-sensitive resistor R1 on the inlet side of at least one heat exchanger;
Further, a temperature-sensitive resistor R2 is arranged on the outflow side. Both temperature sensitive resistors R1 and R2 are connected to constant current source II or I, respectively.
Power is supplied from 2. Both these resistors R1 and R2
The voltage drop that occurs is applied to the differential input terminal of one differential amplifier v3, and an output signal uA proportional to the inflow/outflow temperature difference Δθ=19V−19FL is obtained at its output ial. At the output terminal i of the differential amplifier -3, a signal -u J , F, which has the polarity of this signal inverted, is obtained. In this embodiment, the flow measuring device shown in FIG. 1 is used as a calorific value integrator. That is, the measurement result given by the integral indicator B corresponds to the amount of heat consumed by at least one heat exchanger.

For use as a pure flow measuring device, the signal source S is modified in such a way that it provides at its output a DC voltage or current of constant amplitude in non-inverting and inverting form.

The output signal 'J11' appearing at the non-inverting output terminal al of the differential amplifier V3 is passed through the first controllable switch y-8l, and the output signal -uJd appearing at the inverting output terminal 〒 of the differential amplifier V3 is It is applied to the input of the quantizer Q via two controllable switches S2.

The signal u6 applied to the input of the quantizer Q by the switch S1 and 82, which operates as a psono-pull, is shown in FIG. is applied to an integrator constructed using operational amplifier v4. For this purpose, the output signal of the operational amplifier V4 is fed back via the capacitor C to the inverting input, which is also connected to the resistor R3, while
The non-inverting input terminal of No. 4 is connected to a reference potential. The output signal u7 of the integral failure shown in FIG. 8 is applied to the input terminal 2 of a limit value circuit having a voltage limit value gl as an upper limit value and a voltage limit value g2 as a lower limit value. Therefore, the output signal u7 varies between these two voltage limit values g1 and g2, and each time one of these voltage limit values C is reached, the output signal u8 of two in the limit value circuit changes into two possible signal states. jump from one side to the other. This is illustrated in FIG.

Each pulse of the output signal ug causes a stepping operation of the integral indicating device Z, which is configured as an accumulation counter.

Integral break works by the capacitor charging/discharging method.

This will be explained below using formulas. For the purpose of ren, reference is made to Figure 7. Now, the upper integration phase of the integrator ■ (FIG. 8) during the first period ending at T of the square wave output signal u4 of the additional oscillator G2 (FIG. 5) is considered. This first time span T . The integration of the input signal u6 of the integrator I in the integrator I is expressed as the sum of the voltage and time area of this signal by the following equation.

Δ−)−n+((T/z−ti)−Δd+ti−(−Δ
*)) -n)2・kan=-ΔI9(t g t t ) T.

=ko·Δσ·V where, k: the current/outflow temperature difference Δθ, the output voltage u i of the differential amplifier v3 proportional to it, and −uA.

The proportional coefficient To2 between the period T/2 of the output voltage u4 of the additional oscillator G2: the half period t of the output voltage u1 of the ultrasonic oscillator Gl: the first half period of the output voltage u4 of the additional oscillator q2 (
T in Figure 5. The pulse width t of the output signal u3 of 1 to the phase comparator between (up to /2): the second half period of the output voltage u4 of the additional oscillator G2 (
T in Figure 5. /2 and T. pulse width n of the output signal u3: one half period T. /2 phase comparator Kl
Thus, in the case of the embodiment shown in FIG. The signal u7 shown in the figure is obtained. If the signal source S is configured as a constant voltage source or constant current source for pure flow measurement, the signal corresponding to the quantity Δ- is also constant, so that the output signal u7 corresponds to the flow rate of the fluid in the flow path. V
is only proportional to

This output signal u7 is converted by a limit value circuit into a square wave pulse train u8 having a frequency proportional to the integral value and used as the output signal of the quantizer Q.

Since the output signal u8 is also given to one input terminal of the first exclusive OR game) El, the signal u5 which connects and connects the switches S1 and G2 via the logic circuit each time the signal L'8 changes. The duty ratio of is changed accordingly, thereby effecting a switching of the direction of integration for the output signal u7 of the integrator I. In the embodiment of the heat quantity integrator shown in FIG. 1, the frequency of the output signal u8 of the limit value circuit 2, which is a pulse train, is proportional to the instantaneous quantity of heat. Therefore,
By integrating the pulses of the pulse train within the integral indicator 2, the amount of heat consumed during the integration time, which coincides with the activation time, is determined. If the signal source S is configured as a constant voltage or constant current source, the frequency of the output signal u8 configured as a pulse train is proportional to the flow velocity V, so that the fluid consumed during the operating time by the integral indicating device Z The cumulative flow rate is calculated.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a flow rate measuring device according to the invention applied as a calorific value integrator, and FIGS. G1, which is a diagram showing flow path, A...
Evaluation device, C... Capacitor, El, E2... Exclusive OR gate, G1... Ultrasonic oscillator, G2.
...Additional oscillator, ■...Integrator, II, I2...
Constant current source, 'Kl... Phase comparator, R2... Limit value circuit, L... Logic circuit, N... Inverter,
Q...Quantizer, R1 (I9v), R2 (Shio R)
...Temperature-sensitive resistor, R3...Resistor, S...Signal source, Sl. S2...controllable switch, U...switching device, V
l. V2. V3...Amplifier, wl, w2...Ultrasonic transducer, Z...Instruction device.

Claims (1)

[Claims] 1) A device for measuring the flow rate of a fluid, two ultrasonic transducers arranged apart from each other by a measuring section in the axial direction of the flow path, and a device for energizing these ultrasonic transducers. one ultrasonic oscillator, one phase comparator to which the output signal of the ultrasonic transducer acting as an ultrasonic receiver is applied to one comparison input, one additional oscillator, one phase comparator, and one additional oscillator; and an evaluation device for converting the output signal into a form suitable as an input signal for a downstream integral indicating device, characterized in that: a) the additional oscillator has a duty ratio of 1/2 and is ultrasonic; configured as a square wave generator with a low frequency compared to the frequency of the oscillator; b) a switching device controlled by an additional oscillator is provided, in a first switching position of which one ultrasonic transducer is switched off; The ultrasonic transducer is connected to the ultrasonic oscillator and acts as an ultrasonic transmitter, and the other ultrasonic transducer is connected to one comparison input of the phase comparator, and in its second switching position both ultrasonic transducers c) the output signal of the additional oscillator is fed to the evaluation device for time and control purposes, and d) the second input of the phase comparator is fed the output signal of the ultrasonic oscillator. A flow rate measuring device characterized by: 2. The flow rate measuring device according to claim 1, wherein the ultrasonic oscillator generates a square wave shaped output signal. 3) Claim 1 provides a flow rate measuring device according to claim 2, wherein the evaluation device produces a constant output signal.
one signal source and at least one controllable switch means controlled by the output signal of the phase comparator, the output signal of the signal source being applied to one quantizer via the controllable switch means. a pulse counter with an accumulative effect as an integral indicating device is connected to the output of the quantizer; a) the evaluation device includes a logic circuit consisting of two exclusive-OR gates with negated output signals; b) The first exclusive OR gate performs a logical operation on the output signal of the phase comparator and the output signal of the quantizer, and C) The second exclusive OR gate performs a logical operation on the output signal of the first exclusive OR gate. a logical operation is performed between the signal and the output signal of the additional oscillator, d) in one output state of the second exclusive-OR gate the non-inverted output signal of the signal source and in the other output state the inverted output signal of the signal source; A flow rate measuring device 0 characterized in that the signal is connected to an input end of a quantizer 4) A flow rate measuring device according to claim 3, wherein the signal source has a non-inverting output end and an inverting output end. The non-inverting output terminal is connected to the input terminal of the quantizer via the first controllable switch means, and the inverting output terminal is connected to the input terminal of the quantizer via the second controllable switch means. An output signal of the second exclusive OR gate is used to control the switch means, and a signal obtained by inverting the output signal of the second exclusive OR gate using an inverter is used to control the second controllable switch means. Flow rate measuring device. 5) The flow rate measuring device according to any one of claims 2 to 4, characterized in that an exclusive OR gate having a negative output is used as the phase comparator &Xz#. measuring device. . 6) In the flow rate measuring device according to any one of claims 1 to 5, the quantizer includes an integrator and a limit value circuit connected after the integrator and having two voltage limit values. A flow rate measuring device characterized in that it is used. 7) In the flow measuring device according to any one of claims 1 to 6, using a signal source configured as a means for measuring an inflow/outflow temperature difference of at least one heat exchanger, In order to use the flow measuring device as a calorimeter and detect the inlet and outlet temperatures, one temperature-dependent resistor is provided, each of which is powered by a constant current source, and the voltage across both resistors is A flow measuring device characterized in that a drop is applied to each input end of one differential amplifier.