JP2006138840A - Current meter and flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exclude effects of pulsation in measurements of the flow velocity and flow quantity of a fluid. <P>SOLUTION: The current meter measures the flow velocity of gas flowing through a channel on the basis of a phase difference signal output by a phase difference signal output circuit 11 according to a phase difference between a sine-wave driving signal output to a microheater 33 by a drive circuit 5 for energizing and driving the microheater 33 arranged on the gas channel and a flow velocity signal output according to the temperature of heat emitted from the microheater 33 and detected by a thermopile 35 arranged at an interval from the microheater 33 in the direction of the gas flow in the channel. The flow velocity signal output from the thermopile 35 and amplified by an amplifier 7 is passed through a band pass filter 9 for passing only the same component of frequency as that of the driving signal of the drive circuit 5 and input to the phase difference signal output circuit 11. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a velocimeter and a flow meter that measure the flow velocity or flow rate of a fluid such as a gas on the flow path.

For example, when measuring the flow rate of a fluid such as gas on the flow path, it is placed on the flow path as a technique for detecting the velocity of the fluid flowing in the flow path, which is necessary to obtain the flow rate by multiplying the known cross-sectional area of the flow path. The heater is energized and driven by an AC signal, and an AC signal output from the heater in accordance with the propagation speed of the heat released from the heater by a temperature sensor disposed at intervals in the fluid flow direction in the flow path, and the heater There is known a method for obtaining a phase difference from an AC signal used for current-carrying driving (for example, Patent Document 1).
JP-A-5-264567

  However, in the conventional method for obtaining the flow velocity of the fluid from the phase difference between the output signal of the temperature sensor and the AC signal used for energization driving of the heater, for example, the gas connected to the upstream side of the flow path through which the fluid flows If a pulsation occurs in the fluid flowing through the flow path due to frequent repetition of combustion and combustion stop by a consumption source such as a heat pump, the frequency component corresponding to the original flow rate in the output signal of the temperature sensor is A different frequency component corresponding to the frequency of pulsation is superimposed, and there is a problem that the flow velocity of the fluid cannot be accurately obtained from the phase difference from the AC signal used for energization driving of the heater.

  The problem that the fluid flow velocity cannot be obtained accurately due to the influence of pulsation generated in the fluid is that the fluid flow velocity is obtained from the phase difference between the AC signal used for the heater energization drive and the temperature sensor output signal. The present invention is not limited to this, and is generally applicable when the flow velocity of the fluid is obtained based on the waveform of the output signal of the temperature sensor.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to use the heat source and the temperature sensor arranged at intervals in the flow direction of the fluid in the flow path, and use the AC signal described above or a signal obtained by linearly shifting the AC signal. Based on the waveform of the flow velocity signal output by the temperature sensor that detects the heat propagated from the heat source that is energized and driven by the signal of the periodic voltage waveform that changes in voltage at a constant cycle output by the driving means, such as To provide a velocity meter and a flow meter capable of measuring the flow velocity or flow rate of a fluid with high accuracy without being affected even when pulsation occurs in the fluid when measuring the flow velocity or flow rate of the fluid flowing through the passage. is there.

  The present invention according to claims 1 to 3 that achieves the above object relates to a flow meter, and the present invention according to claim 4 relates to a flow meter.

  According to the first aspect of the present invention, the current source arranged on the flow path of the fluid to be measured is output by the drive means, and the drive signal having a periodic voltage waveform in which the voltage changes at a constant period. A flow rate signal corresponding to the detected heat temperature is detected by detecting the heat released or absorbed by the heat source by a temperature sensor that is energized and is disposed at a distance from the heat source in the fluid flow direction in the flow path. Output from the temperature sensor, and based on the waveform of the flow velocity signal, a flowmeter that measures the flow velocity of the fluid flowing through the flow path, or the same frequency band as the frequency of the drive signal, or the frequency of the drive signal The frequency signal output from the temperature sensor is passed through a band-pass filter that passes a signal in the double frequency band and cuts the signal in the other frequency band. Based on the waveform of the flow rate signal after passage of data, and measuring the flow rate of the fluid flowing through the flow channel.

  According to a second aspect of the present invention, there is provided the anemometer of the present invention, wherein the heat source is a heater, and the driving means DC-shifts the signal of the periodic voltage waveform. The heater is energized and driven by the drive signal having a positive potential or a negative potential.

  Furthermore, the flowmeter of the present invention described in claim 3 is the flowmeter according to claim 1 or 2, wherein the drive signal is a square wave and has the same frequency as the drive signal after passing through the band-pass filter. The flow velocity of the fluid flowing through the flow path is measured based on the waveform of the flow velocity signal after waveform shaping into a sine wave.

  Further, the flowmeter of the present invention described in claim 4 is configured such that the heat released or absorbed on the flow path of the fluid to be measured is transferred from the heat release position or absorption position to the fluid flow direction in the flow path. A flow meter that detects a flow rate of a fluid that flows through the flow path based on a flow velocity signal that is detected by a temperature sensor disposed at an interval and that is output according to the temperature of heat detected by the temperature sensor, The flow velocity of the fluid flowing in the flow path using the flow velocity of the fluid flowing through the flow path measured by the current meter and the known cross-sectional area of the flow path is measured. It is characterized by measuring the flow rate.

  According to the velocimeter of the present invention as set forth in claim 1, when the drive means drives the heat source to be energized by the drive signal of the periodic voltage waveform signal, the energization amount or the discharge (or absorption) heat amount of the heat source continuously increases or decreases. Following this, the level of the flow rate signal output from the temperature sensor increases or decreases, so that the flow rate signal has a signal component having the same frequency as the drive signal or an AC waveform containing a frequency component that is twice the frequency of the drive signal. Become.

  By the way, the signal component having the same frequency as the drive signal or the frequency component twice the frequency of the drive signal included in the flow velocity signal of the periodic voltage waveform output from the temperature sensor has its amplitude and the drive means is driven by energization of the heat source. Since the phase difference with the drive signal used for the flow changes according to the flow velocity of the fluid flowing in the flow path, the signal component of the same frequency as the drive signal or the drive signal from the flow velocity signal of the periodic voltage waveform output from the temperature sensor The frequency component that is twice the frequency of the frequency is extracted, and the fluctuation of the waveform element that changes according to the flow velocity of the fluid flowing in the flow path, such as the amplitude and the phase difference from the drive signal that the drive means uses to drive the heat source, is monitored Then, the flow velocity of the fluid flowing through the flow path is measured.

  For this reason, even if pulsation occurs in the fluid flowing through the flow path and the frequency component of pulsation is superimposed on the flow velocity signal of the periodic voltage waveform output from the temperature sensor, the same frequency band as the frequency of the drive signal or the drive A bandpass filter that passes a signal in a frequency band that is twice the frequency of the signal and cuts a signal in the other frequency band, or other than the same frequency band as the drive signal used to measure the flow velocity of the fluid, or the frequency of the drive signal The signal component of the frequency other than the frequency band of twice is removed from the flow rate signal, and the signal component of the same frequency as the drive signal included in the flow rate signal or the frequency component of the frequency of the drive signal is taken out. From the amplitude, phase difference, etc., the flow velocity of the fluid flowing through the flow path can be measured with high accuracy without being affected by pulsation.

  Further, according to the flowmeter of the present invention described in claim 2, in the flowmeter of the present invention described in claim 1, driven by a positive or negative potential drive signal obtained by direct-shifting the periodic voltage waveform signal. When the means drives the heater energized, the polarity of the drive signal does not reverse between positive and negative, and the heater energization amount changes to a periodic voltage waveform, so the amount of heat released from the heater increases or decreases to the periodic voltage waveform, The waveform of the flow velocity signal output from the temperature sensor that detects the heat released from the heater is a periodic voltage waveform having the same frequency as the drive signal.

  Therefore, the frequency signal different from the drive signal is not included in the flow velocity signal so that the phase difference between both signals changes only depending on the flow velocity of the fluid flowing through the flow path. Based on the phase difference from the flow velocity signal, the flow velocity of the fluid flowing through the flow path can be measured with high accuracy.

  Further, in the velocimeter of the present invention described in claim 1 or 2, when the drive signal is a square wave, the temperature sensor outputs according to the amount of heat released from the heat source that increases or decreases in a periodic voltage wave shape following the drive signal. A flow rate signal with a periodic voltage waveform that has undergone deformation due to a slight delay at the rise and fall is waveformd into a sine wave of the same frequency as the drive signal using a bandpass filter that selectively passes only the frequency of the drive signal The flow velocity signal after shaping and shaping the waveform into a sine wave can be used as a base signal for measuring the flow velocity of the fluid flowing through the flow path.

  According to the flowmeter of the present invention described in claim 4, the flow velocity of the fluid flowing through the flow path measured with high accuracy by the flowmeter of the present invention described in claim 1, 2, or 3 is used. The flow rate of the fluid flowing through the flow path can be measured with high accuracy.

  Hereinafter, an embodiment of a flow meter according to the present invention will be described together with an embodiment of a current meter with reference to the drawings.

  First, it is used in the gas flowmeter according to the first to third embodiments of the present invention to which the current meter according to the present invention is applied and the gas flowmeter according to the seventh to ninth embodiments of the present invention described later. A schematic configuration of the flow sensor will be described with reference to an explanatory diagram of FIG.

  A flow sensor denoted by reference numeral 3 in FIG. 1 is a micro heater 33 (corresponding to the heater in the claims) as described in, for example, Japanese Patent Laid-Open No. 9-257721 with reference to FIG. ) And a thermopile 35 (corresponding to the temperature sensor in the claims), and the micro heater 33 is disposed on the flow path S of gas (corresponding to the fluid to be measured in the claims). The thermopile 35 is disposed on the upstream side in the fluid flow direction so as to be located on the downstream side.

  In this flow sensor 3, the microheater 33 emits heat by energizing and driving the microheater 33 with a drive signal, and an electromotive force corresponding to the temperature of the heat transmitted from the microheater 33 is generated in the thermopile 35. The electromotive force is configured to be output from the thermopile 35 as a flow velocity signal corresponding to the flow rate of the gas flowing through the flow path S.

  Next, a schematic configuration of the gas flow meter according to the first embodiment of the present invention that measures the flow rate of the gas flowing through the flow path S using the flow sensor 3 described above will be described with reference to the block diagram of FIG. To do.

  The gas flow meter of the first embodiment indicated by reference numeral 1 in FIG. 2 is a drive circuit 5 (corresponding to drive means in claims) for energizing and driving the flow sensor 3 and the microheater 33 with a sinusoidal drive signal. ), An amplifier 7 that amplifies the flow velocity signal output from the thermopile 35, a bandpass filter 9 that passes only the same frequency component as the drive signal of the drive circuit 5 from the flow velocity signal amplified by the amplifier 7, and a drive circuit A phase difference detection circuit 11 for detecting a phase difference of the flow velocity signal that has passed through the band pass filter 9 with respect to the phase of the drive signal 5 and outputting a phase difference detection signal (corresponding to the phase difference signal in the claims). Equivalent to the phase difference signal output means).

  Further, the gas flow meter 1 of the first embodiment includes a calculation device 13 such as a microcomputer that calculates the flow rate or flow rate of the gas flowing through the flow path S from the phase difference detection signal from the phase difference detection circuit 11.

  As shown in the circuit diagram of FIG. 3, the drive circuit 5 is configured so that a sine wave signal corresponding to the oscillation frequency of the crystal oscillator 51 becomes a positive potential or a negative potential over the entire width of the amplitude. A direct current shift is performed by an amplifier 53 at a subsequent stage, and a signal based on a positive or negative sine wave is output to the micro heater 33 of the flow sensor 3 as the drive signal.

  Further, as shown in the circuit diagram of FIG. 4, the phase difference detection circuit 11 couples the drive signal of the drive circuit 5 with a capacitor C1, and uses a power supply Vcc (DC 5V in the present embodiment) and a pull-up resistor R1. After pulling up to a potential determined by the voltage dividing ratio between the resistor R2 and the pull-up resistor R1, a DC voltage having an intermediate potential (2.5 V in this embodiment) of the amplitude of the drive signal generated at the midpoint of the resistors R3 and R4. And the comparator A1, the comparison output of the comparator A1 is input to the input S of the RS flip-flop F / F, and the flow rate signal that has passed through the band-pass filter 9 is coupled by the capacitor C2, and the power supply Vcc and the pull-up resistor After being pulled up to a potential determined by the voltage dividing ratio between the resistor R6 and the pull-up resistor R5 by R5, it is generated at the middle point of the resistors R3 and R4. The comparator A2 compares the DC voltage of the intermediate potential of the dynamic signal with the comparator A2, inputs the comparison output of the comparator A2 to the input R of the RS flip-flop F / F, and performs bandpass with respect to the phase of the drive signal of the drive circuit 5 An H-level phase difference detection signal is output from the RS flip-flop F / F while the phase of the flow velocity signal that has passed through the filter 9 is out of phase.

  In the present embodiment, the resistors R1, R2, R3, R4, R5, and R6 have the same resistance value.

  Further, the arithmetic unit 13 uses the data relating to the conversion formula for converting the phase difference detection signal output from the phase difference detection circuit 11 into the flow velocity of the gas flowing through the flow path S, and the flow path from the converted flow velocity of the gas. Data of the cross-sectional area of the flow path S necessary for calculating the flow rate of the gas flowing through S is stored in an internal memory.

  In the gas flow meter 1 according to the first embodiment having the above-described configuration, the drive signal 5 used for the drive circuit 5 to drive the energization of the microheater 33 is a positive or negative drive signal obtained by direct-shifting the sine wave. The electric potential of the microheater 33 is simply changed in a sine wave form without being inverted between them, and the energization amount of the microheater 33 is also increased or decreased in a sine wave form. The waveform of the flow velocity signal is the same frequency as the drive signal.

  Although the waveform has the same frequency as that of the drive signal, the flow velocity signal output from the thermopile 35 is superimposed with other frequency components in addition to the same basic frequency component as that of the drive signal. Since the change in the phase difference of the flow velocity signal is determined depending on the frequency of the flow velocity signal, if the flow velocity signal from the thermopile 35 containing frequency components other than the fundamental frequency is used as it is, the phase difference detection circuit 11 In this case, it is impossible to accurately detect the phase difference from the drive signal.

  However, since the frequency components other than the fundamental frequency included in the flow velocity signal are removed by the bandpass filter 9, what is input to the phase difference detection circuit 11 is a sine wave based on the fundamental frequency of the drive signal.

  The waveform of the flow velocity signal output from the thermopile 35 is deformed so that the higher the flow velocity of the gas flowing in the flow path S, the higher the phase, the smaller the phase delay with respect to the drive signal, and the larger the amplitude. Therefore, the duty ratio of the phase difference detection signal from the phase difference detection circuit 11 having an H level period corresponding to the phase difference of the flow velocity signal that has passed through the band pass filter 9 with respect to the phase of the drive signal of the drive circuit 5 is The value reflects the flow velocity of the gas flowing through the flow path S.

  For this reason, in the arithmetic unit 13 which has taken in the phase difference detection signal from the phase difference detection circuit 11, the flow velocity or flow rate of the gas flowing through the flow path S is measured with high accuracy based on the data stored in the internal memory. Will be.

  By the way, for example, when a consumption source such as a gas heat pump connected to the upstream side of the flow path S repeats combustion and combustion stop frequently, pulsation occurs in the gas flowing through the flow path S. In the flow velocity signal output from the thermopile 35, a frequency component corresponding to the pulsation frequency, which is different from the frequency component corresponding to the original gas flow velocity, is superimposed.

  However, in the gas flow meter 1 of the first embodiment, the band-pass filter 9 that passes only the same frequency component as the drive signal of the drive circuit 5 from the flow velocity signal amplified by the amplifier 7 is provided in the previous stage of the phase difference detection circuit 11. Therefore, the frequency component corresponding to the pulsation frequency is removed from the flow velocity signal when passing through the bandpass filter 9, and the flow velocity signal having only the same frequency component as the drive signal is supplied to the phase difference detection circuit 11. Is done.

  Therefore, the phase difference detection signal corresponding to the phase difference with respect to the drive signal of the drive circuit 5 that depends only on the flow velocity of the gas flowing through the flow path S is output from the phase difference detection circuit 11 and the phase difference detection signal is taken in. In the device 13, based on the data stored in the internal memory, the flow velocity or flow rate of the gas flowing through the flow path S can be measured with high accuracy without being affected even if pulsation occurs in the gas. it can.

  The phase difference detection signal having an H level period corresponding to the phase difference of the flow velocity signal that has passed through the band pass filter 9 with respect to the phase of the drive signal of the drive circuit 5 used in the gas flow meter 1 of the first embodiment. Instead of the phase difference detection circuit 11 that outputs the peak value of the flow velocity signal from the thermopile 35 that has passed through the bandpass filter 9 as in the gas flow meter 1A of the second embodiment shown in the block diagram of FIG. A band detected periodically by the peak hold circuit 15 using a peak hold circuit 15 (equivalent to the peak hold means in the claims) that is periodically detected while being reset for each cycle of the drive signal of the drive circuit 5. The peak value of the flow velocity signal that has passed through the pass filter 9 is A / D converted by the A / D converter 17, and the digital value after A / D conversion by the A / D converter 17 Calculation unit 13 captures, the digital value from the arithmetic unit 13 may be configured to calculate the flow velocity or flow rate of gas flowing through the flow channel S.

  In the case of such a configuration, as a matter of course, the data relating to the conversion formula for converting into the flow velocity of the gas flowing through the flow path S, which is stored in the internal memory of the arithmetic unit 13, is output from the thermopile 35. A gas flowing through the flow path S is converted into a digital value taken in through the A / D converter 17 of a peak value periodically detected by the peak hold circuit 15 of the flow velocity signal amplified by the amplifier 7 and passed through the band pass filter 9. It becomes the data regarding the conversion formula for converting to the flow velocity of.

  Also in the gas flowmeter 1A of the second embodiment configured as described above, the flow velocity signal output from the thermopile 35 has the same frequency as that of the drive signal, and the waveform of this flow velocity signal indicates that the flow velocity of the gas flowing through the flow path S is high. The faster the phase is, the smaller the phase delay with respect to the drive signal is reduced and the amplitude is increased. Therefore, the peak hold circuit 15 detects the cycle of the drive signal, in other words, the drive signal. The peak value of the flow velocity signal after passing through the band-pass filter 9, which is detected every cycle of the flow velocity signal having the same frequency, is a value reflecting the flow velocity of the gas flowing through the flow path S.

  For this reason, in the arithmetic unit 13 which has captured the digital value of the peak value of the flow velocity signal periodically detected by the peak hold circuit 15 and A / D converted by the A / D converter 17, it is stored in the internal memory. Based on the data, the flow rate or flow rate of the gas flowing through the flow path S is measured with high accuracy.

  Also in the gas flow meter 1A of the second embodiment, only the same frequency component as that of the drive signal is peaked out of the flow velocity signal output from the thermopile 35 by the bandpass filter 9 provided in the previous stage of the peak hold circuit 15. Even if a frequency component corresponding to the pulsation frequency supplied to the hold circuit 15 is superimposed on the flow velocity signal, it is removed when passing through the band-pass filter 9, so that only the flow velocity of the gas flowing through the flow path S is reduced. The peak value of the amplitude of the dependent flow velocity signal is output from the peak hold circuit 15, and the data stored in the internal memory in the arithmetic unit 13 that captures the digital value after A / D conversion by the A / D converter 17. Based on the above, even if pulsation occurs in the gas, the flow rate or flow rate of the gas flowing through the flow path S is measured with high accuracy without being affected by the pulsation. Rukoto can.

  Further, in place of the phase difference detection circuit 11 used in the gas flow meter 1 of the first embodiment and the peak hold circuit 15 used in the gas flow meter 1A of the second embodiment, the third embodiment shown in the block diagram of FIG. Like the gas flow meter 1B of the embodiment, the integration circuit 19 that integrates the flow velocity signal from the thermopile 35 amplified by the amplifier 7 for each period of the drive signal of the drive circuit 5 (corresponding to the integration means in the claims) , The integration value of the flow velocity signal after passing through the band-pass filter 9 integrated by the integration circuit 19 every cycle is A / D converted by the A / D converter 17, and the A / D converter 17. The digital value after A / D conversion by the calculation device 13 may be taken in, and the calculation device 13 may calculate the flow rate or flow rate of the gas flowing through the flow path S from the digital value.

  In the case of such a configuration, as a matter of course, the data relating to the conversion formula for converting into the flow velocity of the gas flowing through the flow path S, which is stored in the internal memory of the arithmetic unit 13, is output from the thermopile 35. The flow rate signal amplified by the amplifier 7 and passed through the band-pass filter 9 is integrated with the digital value taken through the A / D converter 17 of the integral value integrated for each cycle of the drive signal by the integration circuit 19. It becomes the data regarding the conversion formula for converting into the flow velocity of the gas which flows.

  Also in the gas flow meter 1B of the third embodiment configured as described above, the flow velocity signal output from the thermopile 35 has the same frequency as that of the drive signal, and the waveform of this flow velocity signal indicates that the flow velocity of the gas flowing through the flow path S is high. The faster the phase, the smaller the phase lag with respect to the drive signal and the larger the amplitude, so that the integration circuit 19 integrates the drive signal every cycle. In other words, the drive signal and The integrated value of the flow velocity signal after passing through the band pass filter 9 integrated for each cycle of the flow velocity signal having the same frequency is a value reflecting the flow velocity of the gas flowing through the flow path S.

  For this reason, in the arithmetic unit 13 that takes in the digital value A / D converted by the A / D converter 17 of the integral value of the flow velocity signal amplified by the amplifier 7, the flow is calculated based on the data stored in the internal memory. The flow rate or flow rate of the gas flowing through the path S is measured with high accuracy.

  Also in the gas flow meter 1B of the third embodiment, only the same frequency component as the drive signal among the flow velocity signals output from the thermopile 35 is integrated by the bandpass filter 9 provided in the previous stage of the integration circuit 19. 19, even if a frequency component corresponding to the pulsation frequency is superimposed on the flow velocity signal, it is removed when it passes through the bandpass filter 9, and therefore depends only on the flow velocity of the gas flowing through the flow path S. Based on the data stored in the internal memory in the arithmetic unit 13 which outputs the peak value of the amplitude of the flow velocity signal from the integration circuit 19 and takes in the digital value after A / D conversion by the A / D converter 17. Even if pulsation occurs in the gas, the flow velocity or flow rate of the gas flowing through the flow path S can be measured with high accuracy without being affected by the pulsation.

  Next, the gas flowmeter according to the fourth to sixth embodiments of the present invention to which the current meter according to the present invention is applied and the gas flowmeter according to the tenth to twelfth embodiments of the present invention described later are used. A schematic configuration of the flow sensor will be described with reference to an explanatory diagram of FIG.

  The flow sensor denoted by reference numeral 3A in FIG. 7 is configured by using a Peltier element 37 instead of the micro heater 33 of the flow sensor 3 described with reference to FIG. Further, the Peltier element 37 is disposed on the upstream side in the fluid flow direction, and the thermopile 35 is disposed on the downstream side.

  In this flow sensor 3A, the Peltier element 37 is energized and driven by a drive signal, whereby the Peltier element 37 releases or absorbs heat according to the direction of current flow, and according to the temperature of the heat transmitted from the Peltier element 37. An electromotive force is generated in the thermopile 35, and the electromotive force is output from the thermopile 35 as a flow velocity signal corresponding to the flow rate of the gas flowing through the flow path S.

  Next, a schematic configuration of the gas flowmeter according to the fourth embodiment of the present invention that measures the flow rate of the gas flowing through the flow path S using the flow sensor 3A described above will be described with reference to the block diagram of FIG. To do.

  In the gas flow meter of the fourth embodiment indicated by reference numeral 1C in FIG. 8, the flow sensor 3 is replaced with the flow sensor 3A, and the positive and negative potentials are omitted from the drive circuit 5 by omitting the DC shift amplifier 53. In the same manner as the gas flow meter 1 of the first embodiment, except that the drive circuit 5A is used to output an alternating current signal of a sine wave having a potential across the Peltier element 37 of the flow sensor 3A as the drive signal. It is configured.

  In the gas flowmeter 1C according to the fourth embodiment having the above-described configuration, even if the drive circuit 5A causes the Peltier element 37 to be energized and driven by an alternating drive signal using a sine wave having a potential straddling a positive potential and a negative potential, Is reversed between positive and negative, the direction of the current flowing through the Peltier element 37 is reversed, and the opposite Peltier effect (warm → cold or cold → warm) that occurred in the Peltier element 37 before the inversion. ), And the tendency of increase / decrease in the amount of heat released or absorbed by the Peltier element 37 with respect to the increase / decrease of the energization amount of the Peltier element 37 does not cause a reverse phenomenon before and after the reversal of the direction of the current flowing through the Peltier element 37 The waveform of the flow velocity signal output from the thermopile 35 that detects the heat released or absorbed by the Peltier element 37 is the AC signal in which the drive signal is inverted between the positive and negative polarities. Both, the polarity regardless of whether the non inverting DC (shift) signal between positive and negative mutual, a sinusoidal with the same frequency as the drive signal.

  The waveform of the flow velocity signal output from the thermopile 35 is deformed so that the higher the flow velocity of the gas flowing in the flow path S, the higher the phase, the smaller the phase delay with respect to the drive signal, and the larger the amplitude. Therefore, the duty ratio of the phase difference detection signal from the phase difference detection circuit 11 having an H level period corresponding to the phase difference of the flow velocity signal that has passed through the band pass filter 9 with respect to the phase of the drive signal of the drive circuit 5 is The value reflects the flow velocity of the gas flowing through the flow path S.

  For this reason, in the arithmetic unit 13 which has taken in the phase difference detection signal from the phase difference detection circuit 11, the flow velocity or flow rate of the gas flowing through the flow path S is measured with high accuracy based on the data stored in the internal memory. Will be.

  Also in the gas flow meter 1C of the fourth embodiment, only the same frequency component as the drive signal among the flow velocity signals output from the thermopile 35 by the band pass filter 9 provided in the previous stage of the phase difference detection circuit 11 is obtained. Even if a frequency component corresponding to the pulsation frequency supplied to the phase difference detection circuit 11 is superimposed on the flow velocity signal, it is removed when passing through the bandpass filter 9, so that the flow velocity of the gas flowing through the flow path S The phase difference signal corresponding to the phase difference with respect to the drive signal of the drive circuit 5 depending only on the output is output from the phase difference detection circuit 11 and is stored in the internal memory in the arithmetic unit 13 that has captured the phase difference detection signal. Based on the data, even if pulsation occurs in the gas, the flow velocity or flow rate of the gas flowing through the flow path S can be measured with high accuracy without being affected by the pulsation.

  Since the flow sensor 3A using the Peltier element 37 instead of the micro heater 33 brings the above-described action to the output of the thermopile 35, the gas flow rate of the first embodiment of the gas flow meter 1C of the fourth embodiment. Even if the same configuration change as the configuration change for the meter 1 is applied to the gas flow meter 1A of the second embodiment to configure the gas flow meter 1D of the fifth embodiment as shown in the block diagram of FIG. The same effect as that exhibited by the gas flow meter 1A of the second embodiment can be obtained.

  Moreover, the change of the structure with respect to the gas flowmeter 1 of 1st Embodiment of the gas flowmeter 1C of 4th Embodiment, or the change of the structure with respect to 1A of gas flowmeters 1A of 2nd Embodiment of the gas flowmeter 1D of 5th Embodiment. Even if the same configuration change is applied to the gas flow meter 1B of the third embodiment to configure the gas flow meter 1E of the sixth embodiment as shown in the block diagram of FIG. The same effect as that exhibited by the gas flow meter 1B can be obtained.

  In the gas flowmeters 1, 1 </ b> A, 1 </ b> B of the first to third embodiments described above, the microheater 33 is driven by a positive potential or negative potential drive signal obtained by direct-shifting the sine wave. Also, the present invention can be applied to the case where the microheater 33 is driven by a positive potential or negative potential drive signal obtained by direct-shifting a signal having a periodic voltage waveform in which the voltage changes at a constant cycle such as a square wave.

  Accordingly, the seventh embodiment of the present invention corresponds to a modification of the gas flow meter 1 of the first embodiment described above, and the microheater 33 is driven by a positive potential or negative potential drive signal obtained by direct-shifting a square wave. A schematic configuration of the gas flowmeter according to the present invention will be described with reference to the block diagram of FIG.

  The gas flow meter of the seventh embodiment indicated by reference numeral 1F in FIG. 11 is a positive or negative potential drive signal obtained by shifting the square wave to a direct current instead of the drive circuit 5 of the gas flow meter 1 of the first embodiment. Except for the point of using the drive circuit 5F (corresponding to the drive means in the claims) for driving the microheater 33, the rest is configured in the same manner as the gas flow meter 1 of the first embodiment.

  As the drive circuit 5F, a well-known astable multivibrator can be used, for example, although the illustration and illustration are omitted.

  In the gas flow meter 1F of the seventh embodiment having the above-described configuration, the drive circuit 5F is used to drive the microheater 33 to be energized. Therefore, the potential of the microheater 33 is increased or decreased in a square wave shape, so that the amount of heat released from the microheater 33 rises and falls. The waveform of the flow velocity signal output from the thermopile 35 that detects the heat released from the micro heater 33 is also caused by a slight delay at the rise and fall of the same frequency as the drive signal. It becomes a square wave shape with deformation.

  By the way, since the drive signal of the positive or negative potential microheater 33 obtained by DC-shifting the square wave includes a harmonic component in addition to the fundamental frequency component, the square wave flow velocity signal output from the thermopile 35 is also included. The drive circuit 5F includes harmonic components other than the fundamental frequency in the same manner as the drive signal used to energize and drive the microheater 33, but the amount of change in the phase difference of the flow rate signal relative to the change in flow rate is the flow rate signal. Therefore, if the flow velocity signal from the thermopile 35 containing harmonic components other than the fundamental frequency is used as it is, the phase difference detection circuit 11 detects the phase difference from the drive signal. It cannot be done accurately.

  However, since the harmonic component contained in this flow velocity signal is removed by the band-pass filter 9, what is input to the phase difference detection circuit 11 is a sine wave based on the fundamental frequency of the drive signal.

  The sine wave flow rate signal output from the thermopile 35 and passed through the band-pass filter 9 increases in phase as the flow rate of the gas flowing through the flow path S increases, and the phase lag with respect to the drive signal decreases. In addition, since the amplitude is increased so as to increase, the phase difference detection circuit 11 has an H level period corresponding to the phase difference of the flow velocity signal that has passed through the bandpass filter 9 with respect to the phase of the drive signal of the drive circuit 5F. The duty ratio of the phase difference detection signal is a value reflecting the flow velocity of the gas flowing through the flow path S.

  For this reason, in the arithmetic unit 13 which has taken in the phase difference detection signal from the phase difference detection circuit 11, the flow velocity or flow rate of the gas flowing through the flow path S is measured with high accuracy based on the data stored in the internal memory. be able to.

  A phase difference detection signal having an H level period corresponding to the phase difference of the flow velocity signal that has passed through the bandpass filter 9 with respect to the phase of the drive signal of the drive circuit 5F used in the gas flow meter 1F of the seventh embodiment. Instead of the phase difference detection circuit 11 that outputs the peak value of the flow velocity signal from the thermopile 35 that has passed through the bandpass filter 9, as in the gas flow meter 1G of the eighth embodiment shown in the block diagram of FIG. The band detected periodically by the peak hold circuit 15 using the peak hold circuit 15 (corresponding to the peak hold means in the claims) that is periodically detected while being reset every cycle of the drive signal of the drive circuit 5F. The peak value of the flow velocity signal that has passed through the pass filter 9 is A / D converted by the A / D converter 17, and the data after the A / D conversion by the A / D converter 17 is converted. Tal value calculation unit 13 captures, the digital value from the arithmetic unit 13 may be configured to calculate the flow velocity or flow rate of gas flowing through the flow channel S.

  In the case of such a configuration, as a matter of course, the data relating to the conversion formula for converting into the flow velocity of the gas flowing through the flow path S, which is stored in the internal memory of the arithmetic unit 13, is output from the thermopile 35. A gas flowing through the flow path S is converted into a digital value taken in through the A / D converter 17 of a peak value periodically detected by the peak hold circuit 15 of the flow velocity signal amplified by the amplifier 7 and passed through the band pass filter 9. It becomes the data regarding the conversion formula for converting to the flow velocity of.

  Also in the gas flow meter 1G of the eighth embodiment configured as described above, the flow velocity signal output from the thermopile 35 and passed through the bandpass filter 9 has the same frequency as the drive signal, and the waveform of the flow velocity signal is the flow path As the flow velocity of the gas flowing through S increases, the phase advances and the phase lag with respect to the drive signal decreases, and the amplitude increases, so that the peak hold circuit 15 causes the drive signal to change every cycle. Detected, in other words, the peak value of the flow velocity signal after passing through the bandpass filter 9 that is detected every cycle of the flow velocity signal having the same frequency as the drive signal reflects the flow velocity of the gas flowing through the flow path S. It becomes the value.

  For this reason, in the arithmetic unit 13 which has captured the digital value of the peak value of the flow velocity signal periodically detected by the peak hold circuit 15 and A / D converted by the A / D converter 17, it is stored in the internal memory. Based on the data, the flow rate or flow rate of the gas flowing through the flow path S is measured with high accuracy.

  In the gas flow meter 1G of the eighth embodiment, only the same frequency component as that of the drive signal is peaked out of the flow velocity signal output from the thermopile 35 by the bandpass filter 9 provided in the previous stage of the peak hold circuit 15. Even if a frequency component corresponding to the pulsation frequency supplied to the hold circuit 15 is superimposed on the flow velocity signal, it is removed when passing through the band-pass filter 9, so that only the flow velocity of the gas flowing through the flow path S is reduced. The peak value of the amplitude of the dependent flow velocity signal is output from the peak hold circuit 15, and the data stored in the internal memory in the arithmetic unit 13 that captures the digital value after A / D conversion by the A / D converter 17. Based on the above, even if pulsation occurs in the gas, the flow rate or flow rate of the gas flowing through the flow path S is measured with high accuracy without being affected by the pulsation. Rukoto can.

  Further, in place of the phase difference detection circuit 11 used in the gas flow meter 1F of the seventh embodiment and the peak hold circuit 15 used in the gas flow meter 1G of the eighth embodiment, the ninth embodiment shown in the block diagram of FIG. Like the gas flow meter 1H of the embodiment, the integrating circuit 19 for integrating the flow velocity signal from the thermopile 35 amplified by the amplifier 7 for each period of the driving signal of the driving circuit 5 (corresponding to the integrating means in the claims) , The integration value of the flow velocity signal after passing through the band-pass filter 9 integrated by the integration circuit 19 every cycle is A / D converted by the A / D converter 17, and the A / D converter 17. The arithmetic device 13 may take in the digital value after A / D conversion by the calculation device 13 so that the arithmetic device 13 calculates the flow rate or flow rate of the gas flowing through the flow path S from the digital value.

  In the case of such a configuration, as a matter of course, the data relating to the conversion formula for converting into the flow velocity of the gas flowing through the flow path S, which is stored in the internal memory of the arithmetic unit 13, is output from the thermopile 35. The flow rate signal amplified by the amplifier 7 and passed through the band-pass filter 9 is integrated with the digital value taken through the A / D converter 17 of the integral value integrated for each cycle of the drive signal by the integration circuit 19. It becomes the data regarding the conversion formula for converting into the flow velocity of the gas which flows.

  Also in the gas flow meter 1H of the ninth embodiment configured as described above, the flow velocity signal output from the thermopile 35 and passed through the bandpass filter 9 becomes a sine wave having the same frequency as the drive signal, and the waveform of the flow velocity signal is As the flow velocity of the gas flowing through the flow path S increases, the phase advances and the phase delay with respect to the drive signal is reduced and the amplitude is increased. In other words, the integrated value of the flow rate signal after passing through the band-pass filter 9, which is integrated every cycle of the flow rate signal having the same frequency as the drive signal, is the flow rate of the gas flowing through the flow path S. It reflects the value.

  For this reason, in the arithmetic unit 13 that takes in the digital value A / D converted by the A / D converter 17 of the integral value of the flow velocity signal amplified by the amplifier 7, the flow is calculated based on the data stored in the internal memory. The flow rate or flow rate of the gas flowing through the path S is measured with high accuracy.

  Also in the gas flow meter 1H of the ninth embodiment, only the frequency component same as the drive signal among the flow velocity signals output from the thermopile 35 is integrated by the band-pass filter 9 provided in the previous stage of the integration circuit 19. 19, even if a frequency component corresponding to the pulsation frequency is superimposed on the flow velocity signal, it is removed when it passes through the bandpass filter 9, and therefore depends only on the flow velocity of the gas flowing through the flow path S. Based on the data stored in the internal memory in the arithmetic unit 13 which outputs the peak value of the amplitude of the flow velocity signal from the integration circuit 19 and takes in the digital value after A / D conversion by the A / D converter 17. Even if pulsation occurs in the gas, the flow velocity or flow rate of the gas flowing through the flow path S can be measured with high accuracy without being affected by the pulsation.

  Similarly, in the gas flowmeters 1C, 1D, and 1E of the fourth to sixth embodiments described above, the microheater 33 is driven by an alternating drive signal using a sine wave of a potential across a positive potential and a negative potential. However, the present invention is also applicable to the case where the Peltier element 37 is driven by an AC drive signal having a potential that straddles a positive potential and a negative potential in a periodic voltage waveform in which the voltage changes at a constant cycle such as a square wave. Applicable.

  Therefore, it corresponds to a modification of the gas flow meter 1C of the fourth embodiment described above, and the Peltier element 37 is driven by an AC drive signal with a square wave of a potential across a positive potential and a negative potential. A schematic configuration of the gas flowmeter according to the seventh embodiment will be described with reference to the block diagram of FIG.

  The gas flow meter of the tenth embodiment indicated by reference numeral 1J in FIG. 14 is replaced with a direct current from the drive circuit 5F of the gas flow meter 1F of the seventh embodiment, instead of the drive circuit 5A of the gas flow meter 1C of the fourth embodiment. A drive circuit 5J that outputs a square wave having a potential ranging between a positive potential and a negative potential to the Peltier element 37 of the flow sensor 3A as a drive signal without a shift configuration. Except for the point using the equivalent), the rest is configured in the same manner as the gas flow meter 1C of the fourth embodiment.

  As the drive circuit 5J, although not shown and described again, for example, a known astable multivibrator can be used.

  In the gas flow meter 1J according to the tenth embodiment having the above-described configuration, even if the drive circuit 5J drives the Peltier element 37 to be energized with an AC drive signal using a square wave having a potential straddling a positive potential and a negative potential, Is reversed between positive and negative, the direction of the current flowing through the Peltier element 37 is reversed, and the opposite Peltier effect (warm → cold or cold → warm) that occurred in the Peltier element 37 before the inversion. ), And the tendency of increase / decrease in the amount of heat released or absorbed by the Peltier element 37 with respect to the increase / decrease of the energization amount of the Peltier element 37 does not cause a reverse phenomenon before and after the reversal of the direction of the current flowing through the Peltier element 37 The waveform of the flow velocity signal output from the thermopile 35 that detects the heat released or absorbed by the Peltier device 37 is an AC signal in which the drive signal is inverted between positive and negative polarities. Is even, regardless of whether the polarity is not inverted DC (shift) signal between positive and negative mutual deformation by a slight delay rise and fall of the same frequency as the drive signal becomes a square wave generated.

  By the way, since the drive signal of the Peltier element 37 by the square wave of the potential straddling the positive potential and the negative potential includes the harmonic component in addition to the fundamental frequency component, the square wave-shaped flow velocity signal output from the thermopile 35 is included. Similarly, the drive circuit 5F includes harmonic components other than the fundamental frequency in the same manner as the drive signal used to energize and drive the Peltier element 37, but the amount of change in the phase difference of the flow velocity signal with respect to the change in flow velocity is the flow velocity. Since it is determined depending on the frequency of the signal, the phase difference detection circuit 11 detects the phase difference from the drive signal in the phase difference detection circuit 11 when the flow velocity signal from the thermopile 35 containing harmonic components other than the fundamental frequency is used as it is. Cannot be done accurately.

  However, since the harmonic component contained in this flow velocity signal is removed by the band-pass filter 9, what is input to the phase difference detection circuit 11 is a sine wave based on the fundamental frequency of the drive signal.

  The sine wave flow rate signal output from the thermopile 35 and passed through the band-pass filter 9 increases in phase as the flow rate of the gas flowing through the flow path S increases, and the phase lag with respect to the drive signal decreases. Further, since the amplitude is changed so as to increase, the phase difference detection circuit 11 has an H level period corresponding to the phase difference of the flow velocity signal that has passed through the band pass filter 9 with respect to the phase of the drive signal of the drive circuit 5J. The duty ratio of the phase difference detection signal is a value reflecting the flow velocity of the gas flowing through the flow path S.

  For this reason, in the arithmetic unit 13 which has taken in the phase difference detection signal from the phase difference detection circuit 11, the flow velocity or flow rate of the gas flowing through the flow path S is measured with high accuracy based on the data stored in the internal memory. Will be.

  The phase difference detection signal having an H level period corresponding to the phase difference of the flow velocity signal that has passed through the bandpass filter 9 with respect to the phase of the drive signal of the drive circuit 5J used in the gas flow meter 1J of the tenth embodiment. Instead of the phase difference detection circuit 11 that outputs the peak value of the flow velocity signal from the Peltier element 37 that has passed through the bandpass filter 9 as in the gas flow meter 1K of the eleventh embodiment shown in the block diagram of FIG. The peak hold circuit 15 (corresponding to the peak hold means in the claims) that detects periodically while resetting the drive signal of the drive circuit 5J is periodically detected by the peak hold circuit 15. The peak value of the flow velocity signal that has passed through the band pass filter 9 is A / D converted by the A / D converter 17 and after A / D conversion by the A / D converter 17 A digital value calculating unit 13 captures, the digital value from the arithmetic unit 13 may be configured to calculate the flow velocity or flow rate of gas flowing through the flow channel S.

  In the case of such a configuration, as a matter of course, the data relating to the conversion formula for converting into the flow velocity of the gas flowing through the flow path S, which is stored in the internal memory of the arithmetic unit 13, is output from the thermopile 35. A gas flowing through the flow path S is converted into a digital value taken in through the A / D converter 17 of a peak value periodically detected by the peak hold circuit 15 of the flow velocity signal amplified by the amplifier 7 and passed through the band pass filter 9. It becomes the data regarding the conversion formula for converting to the flow velocity of.

  Also in the gas flow meter 1K of the eleventh embodiment configured as above, the flow velocity signal output from the thermopile 35 and passed through the bandpass filter 9 has the same frequency as the drive signal, and the waveform of the flow velocity signal is the flow path As the flow velocity of the gas flowing through S increases, the phase advances and the phase lag with respect to the drive signal decreases, and the amplitude increases, so that the peak hold circuit 15 causes the drive signal to change every cycle. Detected, in other words, the peak value of the flow velocity signal after passing through the bandpass filter 9 that is detected every cycle of the flow velocity signal having the same frequency as the drive signal reflects the flow velocity of the gas flowing through the flow path S. It becomes the value.

  For this reason, in the arithmetic unit 13 which has captured the digital value of the peak value of the flow velocity signal periodically detected by the peak hold circuit 15 and A / D converted by the A / D converter 17, it is stored in the internal memory. Based on the data, the flow rate or flow rate of the gas flowing through the flow path S is measured with high accuracy.

  In the gas flow meter 1K of the eleventh embodiment, only the same frequency component as that of the drive signal is peaked out of the flow velocity signal output from the thermopile 35 by the bandpass filter 9 provided in the previous stage of the peak hold circuit 15. Even if a frequency component corresponding to the pulsation frequency supplied to the hold circuit 15 is superimposed on the flow velocity signal, it is removed when passing through the band-pass filter 9, so that only the flow velocity of the gas flowing through the flow path S is reduced. The peak value of the amplitude of the dependent flow velocity signal is output from the peak hold circuit 15, and the data stored in the internal memory in the arithmetic unit 13 that captures the digital value after A / D conversion by the A / D converter 17. Therefore, even if pulsation occurs in the gas, the flow velocity or flow rate of the gas flowing through the flow path S is measured with high accuracy without being affected by the pulsation. It can be.

  Further, in place of the phase difference detection circuit 11 used in the gas flow meter 1J of the tenth embodiment and the peak hold circuit 15 used in the gas flow meter 1K of the eleventh embodiment, a twelfth embodiment shown in the block diagram of FIG. Like the gas flow meter 1L of the embodiment, the integration circuit 19 that integrates the flow velocity signal from the thermopile 35 amplified by the amplifier 7 for each cycle of the drive signal of the drive circuit 5J (corresponding to the integration means in the claims) , The integration value of the flow velocity signal after passing through the band-pass filter 9 integrated by the integration circuit 19 every cycle is A / D converted by the A / D converter 17, and the A / D converter 17. The arithmetic device 13 takes in the digital value after A / D conversion by the calculation device 13 so that the arithmetic device 13 calculates the flow rate or flow rate of the gas flowing through the flow path S from the digital value. It may be.

  In the case of such a configuration, as a matter of course, the data relating to the conversion formula for converting into the flow velocity of the gas flowing through the flow path S, which is stored in the internal memory of the arithmetic unit 13, is output from the thermopile 35. The flow rate signal amplified by the amplifier 7 and passed through the band-pass filter 9 is integrated with the digital value taken through the A / D converter 17 of the integral value integrated for each cycle of the drive signal by the integration circuit 19. It becomes the data regarding the conversion formula for converting into the flow velocity of the gas which flows.

  Also in the gas flow meter 1L of the twelfth embodiment configured as described above, the flow velocity signal output from the thermopile 35 and passed through the bandpass filter 9 has the same frequency as the drive signal, and the waveform of the flow velocity signal is the flow path The higher the flow velocity of the gas flowing through S, the more the phase is advanced and the phase delay with respect to the drive signal is reduced and the amplitude is increased. Therefore, the integration circuit 19 integrates each cycle of the drive signal. In other words, the integrated value of the flow velocity signal after passing through the band-pass filter 9 in which the drive signal and the frequency are integrated for each period of the same flow velocity signal reflects the flow velocity of the gas flowing through the flow path S. Value.

  For this reason, in the arithmetic unit 13 that takes in the digital value A / D converted by the A / D converter 17 of the integral value of the flow velocity signal amplified by the amplifier 7, the flow is calculated based on the data stored in the internal memory. The flow rate or flow rate of the gas flowing through the path S is measured with high accuracy.

  Also in the gas flow meter 1L of the twelfth embodiment, only the same frequency component as the drive signal among the flow velocity signals output from the thermopile 35 is integrated by the bandpass filter 9 provided in the previous stage of the integration circuit 19. 19, even if a frequency component corresponding to the pulsation frequency is superimposed on the flow velocity signal, it is removed when it passes through the bandpass filter 9, and therefore depends only on the flow velocity of the gas flowing through the flow path S. Based on the data stored in the internal memory in the arithmetic unit 13 which outputs the peak value of the amplitude of the flow velocity signal from the integration circuit 19 and takes in the digital value after A / D conversion by the A / D converter 17. Even if pulsation occurs in the gas, the flow velocity or flow rate of the gas flowing through the flow path S can be measured with high accuracy without being affected by the pulsation.

  Incidentally, the drive circuit 5 used in the gas flowmeters 1, 1A, 1B of the first to third embodiments is different from the drive circuit 5 used in the gas flowmeters 1C, 1D, 1E of the fourth to sixth embodiments. The DC shift amplifier 53 may be omitted, and the drive circuit 5A that outputs a signal of a sine wave of a potential straddling a positive potential and a negative potential as a drive signal may be used.

  In that case, the drive signal of the sine wave used by the drive circuit 5A to drive the micro heater 33 energized is inverted between the positive and negative polarities, and the energization amount of the micro heater 33 becomes a so-called half-wave rectified wave shape. Therefore, the heat radiation amount of the microheater 33 proportional to the electric power that is the product of the current and the voltage becomes a sine wave having a frequency twice that of the drive signal used for energization driving of the microheater 33, and is thus released from the microheater 33. The waveform of the flow velocity signal output from the thermopile 35 that has detected the heat that follows is a sine wave having a frequency double that of the drive signal, following the amount of heat released from the microheater 33.

  Therefore, in the gas flowmeters 1, 1 </ b> A, 1 </ b> B according to the first to third embodiments, when the drive circuit 5 </ b> A is used instead of the drive circuit 5, the waveform of the flow velocity signal output from the thermopile 35 is the drive signal. In accordance with the sine wave having a frequency double that of the frequency, the band pass filter 9 is replaced with a filter that passes only a frequency component that is twice the frequency of the drive signal output from the drive circuit 5A. By extracting a frequency component that is twice the frequency of the drive signal from the flow velocity signal and supplying it to the phase difference detection circuit 11, the phase difference detection circuit 11 can accurately detect the phase difference from the drive signal, The flow rate or flow rate of the gas flowing through the flow path S can be measured with high accuracy.

  Further, the gas flowmeters 1 and 1F of the first and seventh embodiments that use the flow velocity signal that has passed through the bandpass filter 9 as it is in detecting the phase difference with respect to the drive signal necessary for measuring the flow velocity or flow rate of the gas. In the gas flowmeters 1A and 1B of the second and third embodiments and the gas flowmeters 1G and 1H of the eighth and ninth embodiments, the peak hold circuit used for measurement of the gas flow velocity or flow rate is different. The peak value and integrated value of the flow velocity signal detected and calculated by 15 and the integration circuit 19 are the elements obtained by processing the flow velocity signal. During the processing, the influence of the deformation of the flow velocity signal waveform on the waveform of the drive signal is almost the same. Therefore, the waveform of the flow velocity signal output from the thermopile 35 is not a sine wave or square wave having the same frequency as that of the drive signal, but is close to a sine wave or square wave having a frequency twice that of the drive signal. Even if the flow waveform, it is possible to measure the flow velocity or flow rate of the gas flowing in the flow path S with high accuracy.

  Nevertheless, a positive or negative potential sine wave, such as the gas flowmeters 1, 1A, 1B of the first to third embodiments and the gas flowmeters 1F, 1G, 1H of the seventh to ninth embodiments. In particular, the driving circuit 5 or 5F that energizes and drives the microheater 33 with a driving signal using a square wave or the like is configured so that the waveform of the flow velocity signal output from the thermopile 35 has the same frequency as the driving signal. Measurement of the flow rate or flow rate of the gas flowing through the flow path S in the gas flowmeters 1 and 1F of the first and seventh embodiments using the flow velocity signal that has passed through the bandpass filter 9 as it is in detecting the phase difference with respect to the signal. The accuracy can be further improved, which is advantageous.

  Further, the drive circuit 5A used in the gas flow meters 1C, 1D, and 1E of the fourth to sixth embodiments and the drive circuit 5J used in the gas flow meters 1J, 1K, and 1L of the tenth to twelfth embodiments are as follows. The drive circuit 5 used in the gas flowmeters 1, 1A, 1B of the first to third embodiments and the drive circuit 5F used in the gas flowmeters 1F, 1G, 1H of the seventh to ninth embodiments may be used. Good.

  In this case, the drive signals 5 and 5F used to drive the Peltier element 37 to be energized are inverted between the positive and negative polarities of the positive or negative drive signal obtained by direct-shifting a sine wave or square wave. However, the potential simply changes to a sine wave shape or a square wave shape, and the direction of the current flowing through the Peltier element 37 is the same direction. Therefore, the Peltier element 37 always releases or absorbs heat, and the amount of heat released or absorbed. The amount of heat is increased or decreased in a sine wave shape or a square wave shape.

  Therefore, when the Peltier element 37 is energized and driven by the drive circuits 5 and 5F, the waveform of the flow velocity signal output from the thermopile 35 that detects the heat released or absorbed by the Peltier element 37 is determined by the drive circuits 5A and 5J. Similarly to the case of energizing and driving 37, it becomes a sine wave shape or a square wave shape having the same frequency as the drive signal. Therefore, the gas flowmeters 1C, 1D, 1E of the fourth to sixth embodiments and the tenth to twelfth embodiments are used. In the gas flowmeters 1J, 1K, and 1L, the Peltier element 37 is energized and driven by the drive circuits 5 and 5F, but the gas flowmeters 1C, 1D, and 1E of the fourth to sixth embodiments, The same effect as that of the drive circuit 5J used in the gas flow meter 1F of the tenth to twelfth embodiments can be obtained.

  In each of the above embodiments, the case where the thermopile 35 is located downstream of the microheater 33 and the Peltier element 37 in the fluid flow direction has been described. However, in the present invention, the thermopile 35 is the microheater 33 and the Peltier element. The present invention can also be applied to a case where it is located upstream of 37 in the fluid flow direction.

  In this case, the sine wave or square wave flow velocity signal output from the thermopile 35 is the gas flowing through the flow path S as in the case where the thermopile 35 is located downstream of the micro heater 33 and the Peltier element 37 in the fluid flow direction. The higher the flow velocity of the is, the more the phase is advanced and the phase delay with respect to the drive signal is reduced.

  For this reason, the first, fourth, seventh, and tenth embodiments for measuring the flow velocity or flow rate of the gas flowing through the flow path S in the arithmetic unit 13 that has captured the phase difference detection signal from the phase difference detection circuit 11. For the gas flowmeters 1, 1C, 1F, and 1J, the thermopile 35 may be disposed in the flow path S so as to be positioned upstream of the micro heater 33 and the Peltier element 37 in the fluid flow direction. It is possible to measure the flow rate or flow rate of the gas flowing through the chamber with high accuracy.

  On the other hand, when the thermopile 35 is arranged in the flow path S so as to be located upstream of the micro heater 33 and the Peltier element 37 in the fluid flow direction, the amplitude of the flow velocity signal output from the thermopile 35 is determined by the thermopile 35. Contrary to the case where it is located downstream of the micro heater 33 and the Peltier element 37 in the fluid flow direction, the higher the flow velocity of the gas flowing through the flow path S, the lower the flow rate.

  For this reason, the peak value of the flow velocity signal periodically detected by the peak hold circuit 15, the digital value A / D converted by the A / D converter 17, and the integrated value A of the flow velocity signal amplified by the amplifier 7. The second, third, fifth, sixth, eighth, and eighth measuring the flow rate or flow rate of the gas flowing through the flow path S in the arithmetic unit 13 that has captured the digital value A / D converted by the / D converter 17. For the gas flow meters 1A, 1B, 1D, 1E, 1G, 1H, 1K, and 1L of the ninth, eleventh and twelfth embodiments, the peak of the flow rate signal stored in the memory inside the arithmetic unit 13 The thermopile 35 is positioned upstream of the microheater 33 and the Peltier element 37 in the fluid flow direction with respect to a conversion formula for converting the digital value of the value and the integral value into the flow velocity of the gas flowing through the flow path S. By substituting the contents corresponding to when placed in the flow path S so, it is possible to measure the flow velocity or flow rate of the gas flowing in the flow path S with high accuracy.

  In each of the above embodiments, the gas flowmeter for measuring the gas flow rate has been described as an example. However, the present invention is applicable to the measurement of the flow rate or flow rate of various fluids such as gases and liquids other than gas. In addition, it goes without saying that the present invention can be widely applied to the case where only the flow velocity at the previous stage is measured without measuring the flow rate.

It is explanatory drawing which shows schematic structure of the flow sensor used in the gas flowmeter which concerns on the 1st thru | or 4th embodiment of this invention. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 1st Embodiment of this invention to which the current meter by this invention is applied. FIG. 3 is a circuit diagram showing an internal configuration of the drive circuit of FIG. 2. FIG. 3 is a circuit diagram showing an internal configuration of a phase difference detection circuit of FIG. 2. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 2nd Embodiment of this invention to which the current meter by this invention is applied. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 3rd Embodiment of this invention to which the current meter by this invention is applied. It is explanatory drawing which shows schematic structure of the flow sensor used in the gas flowmeter which concerns on 4th thru | or 6th embodiment of this invention. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 4th Embodiment of this invention to which the current meter by this invention is applied. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 5th Embodiment of this invention to which the current meter by this invention is applied. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 6th Embodiment of this invention to which the current meter by this invention is applied. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 7th Embodiment of this invention to which the current meter by this invention is applied. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 8th Embodiment of this invention to which the current meter by this invention is applied. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 9th Embodiment of this invention to which the current meter by this invention is applied. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 10th Embodiment of this invention to which the velocity meter by this invention is applied. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 11th Embodiment of this invention to which the current meter by this invention is applied. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 12th Embodiment of this invention to which the current meter by this invention is applied.

Explanation of symbols

1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1J, 1K, 1L Gas flow meter 5, 5A, 5F, 5J Drive circuit (drive means)
11 Phase difference detection circuit (phase difference signal output means)
15 Peak hold circuit (peak hold means)
19 Integration circuit (integration means)
33 Micro heater (heat source, heater)
35 Thermopile (temperature sensor)
37 Peltier element (heat source)
S channel

Claims (4)

A heat source disposed on the flow path of the fluid to be measured is energized and driven by a drive signal output by the drive means and having a periodic voltage waveform whose voltage changes at a constant cycle, and the heat source is arranged in the flow direction of the fluid in the flow path. Based on the waveform of the flow rate signal, the flow rate signal corresponding to the temperature of the detected heat is output from the temperature sensor by detecting the heat released or absorbed by the heat source by the temperature sensor arranged at an interval from In the anemometer for measuring the flow velocity of the fluid flowing through the flow path,
A signal in the same frequency band as the frequency of the drive signal or a frequency band twice the frequency of the drive signal is allowed to pass, and a band-pass filter that cuts signals in other frequency bands is output from the temperature sensor. Passing the flow velocity signal, and measuring the flow velocity of the fluid flowing through the flow path based on the waveform of the flow velocity signal after passing through the band-pass filter;
An anemometer characterized by that.   The current meter according to claim 1, wherein the heat source is a heater, and the driving unit drives the heater to be energized by the positive potential or negative potential drive signal obtained by direct-shifting a signal having a periodic voltage waveform.   The drive signal is a square wave, and the flow velocity of the fluid flowing through the flow path based on the waveform of the flow velocity signal after being shaped into a sine wave having the same frequency as the drive signal after passing through the band-pass filter The anemometer according to claim 1 or 2, wherein Heat that is released or absorbed on the flow path of the fluid to be measured is detected by a temperature sensor arranged at an interval in the flow direction of the fluid in the flow path from the heat release location or absorption location, and the temperature sensor A flowmeter that measures the flow rate of the fluid flowing through the flow path based on a flow velocity signal that is output according to the detected temperature of the heat,
The anemometer according to claim 1, 2, or 3,
Using the flow velocity of the fluid flowing through the flow path measured by the anemometer and the known cross-sectional area of the flow path, the flow rate of the fluid flowing through the flow path is measured.
A flow meter characterized by that.

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