JP4889233B2 - Ultrasonic flow meter - Google Patents

Description

  The present invention relates to an ultrasonic flowmeter that measures the flow rate of a fluid using ultrasonic waves, and more particularly to a technique for reducing power consumption.

  Conventionally, a pair of ultrasonic transducers are provided at a certain distance on the upstream side and downstream side of the fluid flow path, and ultrasonic signals are repeatedly transmitted and received between them, and the ultrasonic signal from the upstream side to the downstream side There is known an ultrasonic flowmeter that obtains a flow rate based on the difference between the accumulated propagation time of 1 and the accumulated propagation time from the downstream side to the upstream side. In this ultrasonic flow meter, a battery is often used as a power source for driving an internal circuit.

  In an ultrasonic flowmeter that operates using such a battery as a power source, power is consumed for repeated ultrasonic transmission / reception and signal processing performed along with ultrasonic transmission / reception, and even in a standby state where no transmission / reception is performed. Consume power. Therefore, the life of the battery is shortened, and the battery needs to be replaced in a short period of time.

Therefore, a switch that detects the presence or absence of the gas flow in the gas flow path is provided, and the supply or cut-off of power to the ultrasonic sensor and its drive circuit is controlled based on the detection result of the switch, thereby reducing power consumption. A technique is known (see, for example, Patent Document 1).
JP 2000-111041 A

  However, in the technique disclosed in Patent Document 1 described above, it is necessary to provide a switch for detecting the presence or absence of a gas flow in the gas flow path. Depending on the size of the switch, the size of the ultrasonic flowmeter is required. Increases and costs increase. Moreover, due to the provision of the switch in the gas flow path, there is a problem that the gas flow in the gas flow path is disturbed and accurate measurement cannot be performed.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a small and inexpensive ultrasonic flow meter capable of measuring a flow rate stably and accurately over a long period of time.

In order to achieve the above object, an ultrasonic flowmeter according to the present invention is provided with a first ultrasonic transducer disposed in a gas flow path and a flow path facing the first ultrasonic vibrator. The second ultrasonic transducer, the propagation time measured by intermittently transmitting ultrasonic waves from the first ultrasonic transducer to the second ultrasonic transducer, and the first ultrasonic transducer from the second ultrasonic transducer Between the first ultrasonic transducer and the second ultrasonic transducer, and a control circuit that measures the flow rate of the gas flowing through the flow path based on the difference from the propagation time measured by intermittently transmitting ultrasonic waves to Power supply control means for supplying power to the control circuit only during a period in which the ultrasonic wave is transmitted and the propagation time is measured , and the control circuit counts the number of times the ultrasonic waves are repeatedly transmitted, and the repetition circuit counts A transmission circuit that generates a drive pulse signal each time the number of times counted The driving pulse signal from the transmission circuit is sent to the first ultrasonic transducer and the signal from the second ultrasonic transducer is received, or the signal is sent to the second ultrasonic transducer and the signal from the first ultrasonic transducer is received. A transmission / reception switching circuit for switching between, a reception circuit for receiving a signal from the transmission / reception switching circuit, a filter circuit for removing noise of the signal from the reception circuit, a comparator for converting the signal from the filter circuit into a digital signal, and repetition And a flow rate measuring circuit for calculating the flow rate of the gas flowing through the flow path based on the digital signal sequentially received from the comparator when the predetermined number of times is counted by the circuit, and the power supply control means includes a repetition circuit, a transmission circuit, and a transmission / reception switching circuit , Receiving circuit, filter circuit, comparator, and flow measurement circuit, supply power in the order in which operation starts, power in order in which operation stops And wherein the stopping the supply.

  According to the ultrasonic flowmeter of the present invention, the power is supplied to the control circuit only during the period in which the ultrasonic wave is transmitted between the first ultrasonic transducer and the second ultrasonic transducer and the propagation time is measured, In other periods, the power supply to the control circuit is stopped, so that power consumption can be reduced.

  As a result, the flow rate can be measured stably and accurately without changing the battery over a long period of time. Further, unlike the gas flow meter described in Patent Document 1, it is not necessary to provide a switch in the flow path, so that the size of the ultrasonic flow meter can be reduced and the cost can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram illustrating the configuration of the ultrasonic flowmeter according to the first embodiment of the present invention. The ultrasonic flowmeter includes a first ultrasonic transducer 101, a second ultrasonic transducer 102, a transmission / reception switching circuit 103, a transmission circuit 104, a repetition circuit 105, a reception circuit 106, a filter circuit 107, a comparator 108, and a flow measurement circuit. 109, an oscillation circuit 110, a timing generation circuit 111, a power supply circuit 112, and a voltage monitoring circuit 113.

  The control circuit of the present invention includes a transmission / reception switching circuit 103, a transmission circuit 104, a repetition circuit 105, a reception circuit 106, a filter circuit 107, a comparator 108, and a flow rate measurement circuit 109. The power supply control means of the present invention includes an oscillation circuit 110, a timing generation circuit 111, a power supply circuit 112, and a voltage monitoring circuit 113. The power supply of each circuit constituting the control circuit is controlled by power supply control means. The power source of the power control means is always turned on.

  The first ultrasonic transducer 101 is arranged on the upstream side of the flow path 100 through which a fluid such as gas or air flows. The second ultrasonic transducer 102 is disposed on the downstream side in the flow channel 100 and at a distance L from the first ultrasonic transducer 101 so as to face the first ultrasonic transducer 101. The Further, the first ultrasonic transducer 101 and the second ultrasonic transducer 102 are arranged coaxially in the flow channel 100.

  The first ultrasonic transducer 101 generates an ultrasonic wave according to the drive pulse signal sent from the transmission / reception switching circuit 103 and transmits the ultrasonic wave toward the second ultrasonic transducer 102. The first ultrasonic transducer 101 receives the ultrasonic wave from the second ultrasonic transducer 102, converts it into an electrical signal, and sends it to the transmission / reception switching circuit 103.

  The second ultrasonic transducer 102 generates an ultrasonic wave according to the drive pulse signal from the transmission / reception switching circuit 103 and transmits the ultrasonic wave toward the first ultrasonic transducer 101. The second ultrasonic transducer 102 receives the ultrasonic wave from the first ultrasonic transducer 101, converts it into an electrical signal, and sends it to the transmission / reception switching circuit 103.

  The transmission / reception switching circuit 103 sends the drive pulse signal sent from the transmission circuit 104 to the first ultrasonic transducer 101 to generate an ultrasonic wave, and obtains it from the second ultrasonic transducer 102 that has received this ultrasonic wave. Signal to the receiving circuit 106, or conversely, the driving pulse sent from the transmitting circuit 104 is sent to the second ultrasonic transducer 102 to generate an ultrasonic wave, and the first ultrasonic wave that has received this ultrasonic wave Whether to send a signal obtained from the sound wave oscillator 101 to the receiving circuit 106 is switched.

  The transmission circuit 104 generates a drive pulse signal for driving the first ultrasonic transducer 101 or the second ultrasonic transducer 102 every time a transmission signal is transmitted from the repetition circuit 105. The drive pulse signal generated by the transmission circuit 104 is sent to the transmission / reception switching circuit 103.

  The repetition circuit 105 counts the number of times that ultrasonic waves should be repeatedly transmitted from the first ultrasonic transducer 101 or the second ultrasonic transducer 102. Specifically, the number of repetitions is counted up every time a clock signal is received from the oscillation circuit 110, and a transmission signal is sent to the transmission circuit 104 and the flow rate measurement circuit 109 every time the clock signal is counted up.

  The receiving circuit 106 receives a signal transmitted from the first ultrasonic transducer 101 or the second ultrasonic transducer 102 via the transmission / reception switching circuit 103 and amplifies the signal with a certain gain. The reception signal amplified by the reception circuit 106 is sent to the filter circuit 107.

  The filter circuit 107 removes a noise component included in the signal sent from the receiving circuit 106. The signal from which noise has been removed by the filter circuit 107 is sent to the comparator 108.

  The comparator 108 converts the analog signal sent from the filter circuit 107 into a digital signal by slicing it with a predetermined threshold voltage. A digital reception signal obtained by the conversion in the comparator 108 is sent to the flow rate measurement circuit 109.

  The flow measurement circuit 109 receives and stores a digital reception signal sent from the comparator 108 in response to the clock signal from the oscillation circuit 110. Then, when the transmission signal sent from the repetition circuit 105 indicates a predetermined number of times, the flow of the fluid flowing in the flow path 100 is determined using a known algorithm based on the stored digital reception signal. Calculate the flow rate.

  The oscillation circuit 110 generates a clock signal. The oscillation circuit 110 is always supplied with power from the power supply circuit 112. The clock signal generated by the oscillation circuit 110 is sent to the repetition circuit 105, the flow rate measurement circuit 109, and the timing generation circuit 111.

  The timing generation circuit 111 counts the clock signal from the oscillation circuit 110 and generates a timing signal. The timing generation circuit 111 is always supplied with power from the power supply circuit 112. The timing signal is not a timing for supplying power to the control circuit, that is, inactive in a standby state in which flow rate measurement is not performed by transmission / reception of ultrasonic waves, and is a timing for supplying power to the control circuit, that is, ultrasonic waves This signal becomes active in the operation state in which the flow rate is measured by transmission and reception. The timing signal generated by the timing generation circuit 111 is fed back to the oscillation circuit 110 and sent to the power supply circuit 112.

  When the timing signal fed back from the timing generation circuit 111 is inactive, the oscillation circuit 110 generates a clock signal having a smaller amplitude than when the timing signal is active. As a result, power consumption can be reduced in a standby state where the flow rate is not measured by transmission and reception of ultrasonic waves.

  The power supply circuit 112 includes a battery (not shown), and according to a timing signal from the timing generation circuit 111, a transmission / reception switching circuit 103, a transmission circuit 104, a repetition circuit 105, a reception circuit 106, a filter circuit 107, a comparator 108, and Electric power is supplied to the flow rate measuring circuit 109.

  The voltage monitoring circuit 113 corresponds to the notification means of the present invention, and monitors the power supply voltage of the power supply circuit 112. The voltage monitoring circuit 113 is always supplied with power from the power supply circuit 112. When the voltage monitoring circuit 113 detects that the power supply voltage of the power supply circuit 112 has become a predetermined value or less, the voltage monitoring circuit 113 notifies the outside to that effect. As a means for notifying outside, a display, a communication device, or the like can be used.

  Next, the operation of the ultrasonic flowmeter according to the first embodiment of the present invention configured as described above will be described. In the following, a case where the first ultrasonic transducer 101 on the upstream side is set to the ultrasonic wave transmission side and the second ultrasonic transducer 102 on the downstream side is set to the ultrasonic wave reception side will be described as an example.

  When the drive pulse signal generated by the transmission circuit 104 is applied to the first ultrasonic transducer 101 via the transmission / reception switching circuit 103, the first ultrasonic transducer 101 has the magnitude of the applied drive pulse signal. A corresponding ultrasonic wave is generated and transmitted toward the second ultrasonic transducer 102 on the downstream side. The ultrasonic wave reaches the second ultrasonic transducer 102 on the downstream side with a propagation time t multiplied by the sound velocity V and the distance L. The second ultrasonic transducer 102 converts the received ultrasonic wave into an electrical signal and outputs it.

  The signal output from the second ultrasonic transducer 102 is input to the reception circuit 106 via the transmission / reception switching circuit 103, amplified by the reception circuit 106 with a constant gain, and transmitted to the filter circuit 107. Then, the noise component is removed by the filter circuit 107 and sent to the comparator 108.

  The comparator 108 converts the analog reception signal sent from the filter circuit 107 into a digital reception signal by slicing the analog reception signal with a predetermined threshold voltage. The output of the comparator 108 is sent to the flow rate measurement circuit 109.

  The flow rate measurement circuit 109 measures the time from when the drive pulse signal is output from the transmission circuit 104 to when the reception circuit 106 obtains the reception signal, so that the ultrasonic wave transmitted from the first ultrasonic transducer 101 is the first. 2 The propagation time to reach the ultrasonic transducer 102 is obtained and stored in a memory (not shown). The above operation is repeated until the transmission signal transmitted from the repetition circuit 105 indicates a predetermined number of times.

  Then, when the transmission signal sent from the repetition circuit 105 indicates a predetermined number of times, the integrated propagation time is obtained based on the digital reception signal stored in the memory. FIG. 2A shows the accumulated propagation time of the ultrasonic wave propagated from the first ultrasonic transducer 101 to the second ultrasonic transducer 102 in the period Ta in which the operation state is set at a constant cycle (Ta + Tb + Tu). It shows a state. In FIG. 2, a period Tu indicates a standby state.

  Subsequently, the flow measurement circuit 109 obtains the propagation time until the ultrasonic wave transmitted from the second ultrasonic transducer 102 reaches the first ultrasonic transducer 101 in the same manner as described above, and stores it in a memory (not shown). Remember.

  Then, when the transmission signal sent from the repetition circuit 105 indicates a predetermined number of times, the integrated propagation time is obtained based on the digital reception signal stored in the memory. FIG. 2B shows the accumulated propagation time of the ultrasonic wave propagated from the second ultrasonic transducer 102 to the first ultrasonic transducer 101 in the period Tb in which the operation state is maintained at a constant cycle (Ta + Tb + Tu). It shows a state.

  When the two accumulated propagation times are obtained as described above, the flow rate measurement circuit 109 calculates the flow rate of the fluid flowing in the flow path 100 from the difference between the two accumulated propagation times using a known algorithm.

  As described above, according to the ultrasonic flowmeter according to the first embodiment of the present invention, the ultrasonic wave is transmitted between the first ultrasonic transducer 101 and the second ultrasonic transducer 102 to reduce the propagation time. Power is supplied to the control circuit (transmission / reception switching circuit 103, transmission circuit 104, repetition circuit 105, reception circuit 106, filter circuit 107, comparator 108, and flow rate measurement circuit 109) only in the operation state indicated by the measurement period Ta and the period Tb. However, since the power supply to the control circuit is stopped in the atmospheric state indicated by the other period Tu, the power consumption can be reduced.

  As a result, the flow rate can be measured stably and accurately without changing the battery over a long period of time. Further, unlike the gas flow meter described in Patent Document 1, it is not necessary to provide a switch in the flow path, so that the size of the ultrasonic flow meter can be reduced and the cost can be reduced.

  Further, as described above, in the standby state indicated by the period Tu, the oscillation circuit 110 makes the amplitude of the clock signal smaller than that in the operation state indicated by the period Ta and the period Tb, as shown in FIG. Therefore, power consumption can be suppressed.

  Note that the oscillation circuit 110 and the timing generation circuit 111 can be formed in an integrated circuit housed in the same package. According to this configuration, the path length of a signal transmitted and received between the oscillation circuit 110 and the timing generation circuit 111 is shortened and is less susceptible to disturbance, so that noise can be reduced. As a result, since the SN ratio is improved, the amplitude of a signal transmitted and received between the oscillation circuit 110 and the timing generation circuit 111 can be reduced, so that power consumption can be reduced.

  Further, the power generation circuit 112 is configured to individually supply power to the repetition circuit 105, the transmission circuit 104, the transmission / reception switching circuit 103, the reception circuit 106, the filter circuit 107, the comparator 108, and the flow rate measurement circuit 109, and the timing generation circuit 111. As shown conceptually in FIG. 3, among the repetition circuit 105, the transmission circuit 104, the transmission / reception switching circuit 103, the reception circuit 106, the filter circuit 107, the comparator 108, and the flow rate measurement circuit 109, as shown in FIG. The power can be supplied in the order in which the operation is started, and the supply of power is stopped in the order in which the operation is stopped. According to this configuration, the power of each circuit is turned on only when necessary, so that the power consumption can be suppressed as a whole.

  The ultrasonic flowmeter of the present invention can be applied to an ultrasonic gas meter or the like.

It is a block diagram which shows the structure of the ultrasonic flowmeter which concerns on Example 1 of this invention. It is a timing chart for demonstrating operation | movement of the ultrasonic flowmeter which concerns on Example 1 of this invention. It is a figure for demonstrating the modification of the ultrasonic flowmeter which concerns on Example 1 of this invention.

Explanation of symbols

100 Flow path 101 First ultrasonic transducer 102 Second ultrasonic transducer 103 Transmission / reception switching circuit 104 Transmission circuit 105 Repetition circuit 106 Reception circuit 107 Filter circuit 108 Comparator 109 Flow measurement circuit 110 Oscillation circuit 111 Timing generation circuit 112 Power supply circuit 113 Voltage monitoring circuit

Claims (5)

A first ultrasonic transducer disposed in a gas flow path;
A second ultrasonic transducer disposed in the flow path so as to face the first ultrasonic transducer;
Propagation time measured by intermittently transmitting ultrasonic waves from the first ultrasonic transducer to the second ultrasonic transducer and intermittent ultrasonic waves from the second ultrasonic transducer to the first ultrasonic transducer A control circuit for measuring the flow rate of the gas flowing through the flow path based on the difference between the propagation time measured and transmitted automatically,
Power control means for supplying power to the control circuit only during a period in which propagation time is measured by transmitting ultrasonic waves between the first ultrasonic transducer and the second ultrasonic transducer;
Equipped with a,
The control circuit includes:
A repeating circuit that counts the number of times ultrasonic waves are transmitted repeatedly;
A transmission circuit for generating a drive pulse signal each time the number of times counted by the repetition circuit is counted up,
A drive pulse signal from the transmission circuit is sent to the first ultrasonic transducer to receive a signal from the second ultrasonic transducer, or is sent to the second ultrasonic transducer and sent to the first ultrasonic transducer. A transmission / reception switching circuit for switching whether to receive a signal from,
A receiving circuit for receiving a signal from the transmission / reception switching circuit;
A filter circuit for removing noise of the signal from the receiving circuit;
A comparator that converts a signal from the filter circuit into a digital signal;
A flow rate measuring circuit for calculating a flow rate of the gas flowing through the flow path based on digital signals sequentially received from the comparator when a predetermined number of times is counted in the repetition circuit;
With
The power control means includes
Among the repetitive circuit, transmission circuit, transmission / reception switching circuit, reception circuit, filter circuit, comparator, and flow rate measurement circuit, power is supplied in the order in which the operation is started, and power supply is stopped in the order in which the operation is stopped. An ultrasonic flowmeter characterized by that. The power control means includes
  An oscillation circuit for generating a clock signal for operating the control circuit;
  A timing generation circuit that generates a timing signal that defines a timing for supplying power to the control circuit based on a clock signal generated by the oscillation circuit;
  A power supply circuit that supplies power to the control circuit according to a timing signal generated by the timing generation circuit;
The ultrasonic flowmeter according to claim 1, further comprising: When the timing signal generated by the timing generation circuit indicates that it is not the timing to supply power to the control circuit, the oscillation circuit indicates that it is time to supply power to the control circuit. 3. The ultrasonic flowmeter according to claim 2, wherein a clock signal having a smaller amplitude than that of the case is generated. 4. The ultrasonic flowmeter according to claim 2, wherein the oscillation circuit and the timing generation circuit are formed in an integrated circuit housed in the same package. The power supply control means further comprises notification means for notifying the outside when it is detected that the output voltage of the power supply circuit has become a predetermined value or less. Item 5. The ultrasonic flowmeter according to any one of Items 4 to 5.

Images