WO1982002591A1

WO1982002591A1 - Heat-pulse type flow meter

Info

Publication number: WO1982002591A1
Application number: PCT/JP1982/000017
Authority: WO
Inventors: Corp Anima
Original assignee: Togawa Tatsuo; Nemoto Tetsu; Tsubakimoto Hirohisa
Priority date: 1981-01-19
Filing date: 1982-01-18
Publication date: 1982-08-05
Also published as: DE3231663T1; DE3231663C2

Abstract

A heat-pulse type flow meter, in which a heating line is heated in pulses, fluid to be measured passes over the heating line and is then detected downstream, the heating line is heated with a period corresponding to the flow rate of the fluid to be measured, and the heating period is measured to obtain the amount of flow. This meter has a wider measuring range than the conventional one.

Description

Description Title of invention

Thermal pulse flow meter

Eleven

Technical field

This invention is suitable, for example, for determining the flow rate of air or intake air, heats the fluid to be measured in pulses, and heats the heated fluid below the heating position. This article relates to a hot-wire pulse flowmeter that measures the flow velocity of a fluid by Technique: A fluid to be measured is heated by a heat pulse on the upstream side in a flow tube through which the flow to be measured flows, and the heated fluid to be measured is separated from the heated volume by a predetermined distance. By measuring the time from the time of heating of the fluid to be measured to the time of detection by detecting it on the downstream side of the vine flow tube circle, the flow velocity of the fluid to be measured is measured, and based on that, the flow velocity of the fluid to be measured is measured. Measurement of the flow rate of ryoton is being carried out. In this case, if the flow rate of the fluid to be measured is L^Zsec and the new area of the flow tube for measurement is , then the average flow of the fluid to be measured^V is given by the following equation. '

A ¾ constant-flow heat-up is installed upstream in the flow tube, and an il section WG s ½ d installed downstream of the flow tube. (cm) and T is the time required for heating the measured fluid in the heating section until the warmed measured flow in the heating section is detected, then the following equation is established.

T = - S d ( sec ) (2)

As is clear from the equation (2), when the flow rate of the fluid to be measured increases by L ¾ W, the time T decreases in inverse proportion to this. In the conventional hot spring pulse flow meter, the force Π heat for the measured flow was periodically measured. Therefore, in a measurement system in which the flow rate of the fluid to be measured varies greatly, it is difficult to set the heating cycle of the fluid to be measured in the heating unit. In other words, if the heating period is set too long, the measurement time will be delayed, and if the flow rate of the flow to be measured changes rapidly, the measurement can accurately follow the change. ¾ less. On the other hand, if the heating period is shortened, the fluid detected at the downstream side of the flow tube per unit time will be affected by heating in the next time period, resulting in inaccurate detection. to

For example, fluids with various compositions are used as measuring fluids, and their flow rates vary over a wide range. It is placed under a sump and the flow rate is determined. Under these various conditions, the heating conditions of ¾J ylL, during heating, change, and ¾a constant temperature with respect to the measured flow. It is strange to let the heating be done. For example, if the flow velocity of the fluid to be measured increases, the amount of heat lost from the ripening cavity will increase, the resistance value of the ripening hole will decrease, and the strength of heating to the fluid to be measured will weaken. If the temperature of the part heated by the fluid to be measured in the temperature sensing part is large, it is difficult to reliably detect the heat content of the fluid to be measured.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pulse-type flowmeter with a wide measurement range.

Another object of the present invention is to provide a heat pulse type flow rate that can accurately measure even a fluid to be measured whose flow rate changes rapidly and greatly, such as exhalation and inhalation. The purpose is to provide an estimate.

Invention disclosure

According to this invention, a heating element is provided in the flow tube through which the fluid to be measured flows, and a heating circuit applies a heat pulse to the heating element to heat the fluid to be measured pulsewise, A temperature-sensitive extractor is provided in the flow tube downstream of the heating element, and the detector detects the temperature of the heated portion of the flow to be measured. By this detection, a motion timing signal is generated, and the heating cycle is reactivated by the motion timing signal to heat the projectile. The phase of return heat for this heat source is determined, and the measured flow is measured according to this phase. is displayed on the display.

In this way, when the passage of the heating flow is detected, the heating element is heated again, so the flow velocity of the fluid to be measured increases during the heating phase of the heat generation. voluntarily short

3) Heating during the S-cutting stage is applied to the developing body according to the flow velocity of the measured stream. For heat generation, it is preferable to allow twice the time for the heated measurement fluid to reach the detection body as the ripening stage. Furthermore, when the flow rate of the fluid to be measured becomes smaller than the constant minimum value, the heating element is heated at a constant cycle for preheating. To be able to measure the flow rate correctly. A heating circuit is constructed so that the heating of the fluid to be measured by the heating element remains constant regardless of its flow rate, ensuring reliable detection by the test body. made to be In addition, in order to properly detect the object to be detected, the lowest level of the output of the object to be detected is detected, and the maximum level plus a constant value is taken as the reference value. When the force of the detected object exceeds the basic value, it is made to detect the movement of the mature flow. In addition, as it is affected by changes in local temperature and the temperature of the fluid itself to be regulated, it is sensitive to these temperatures, but the heat flow is compensated for in tight positions. ^: is provided so that the excess of the heating flow ^: can be detected in fact. Brief description of the drawing ¾

Fig. 1 is a block diagram showing an example of a pulse-type flowmeter made by this research, and Fig. 2 ^shows another specific example of the temperature control circuit part 15 in Fig. 1. FIG. 3 is a logic circuit diagram showing a specific example of the drive timing signal generation circuit 16 in FIG. 1; FIG. A graph showing the M coefficient of the initial heating period for

Fig. 5 shows the relational arrangement of the developing body and the detecting body when the flowmeter of the present invention is designed to be able to measure the flow in both forward and reverse directions; Fig. 7 is a perspective view showing another example of the heating circuit 18, Fig. 8 is a plan view of Fig. 7, Fig. 9 shows the measurement range. FIG. 10 is a further expanded block diagram showing another embodiment of the present invention, and FIG.

Best Mode for Carrying Out Clarity

FIG. 1 is a diagram showing the configuration of the present invention, in which a flow tube 101 to be measured is introduced into a flow tube 1:1, and an upstream portion of the flow tube 11' is supplied as required. A turbulence generator 12 is provided. This turbulent flow septum 12 is, for example, formed on a mesh wall with a metal wire, on an angle set against a steady flow of 101 for example. Constant flow i¾ introduced into flow tube 1 1

0 1 is a reverberating current and In the angle ¾ plane, a certain 1? A state in which the average velocity is uniform in the plane perpendicular to the flow.

In the flow tube 11 downstream of the turbulent flow 12, a heat generator 13 is stretched in the diameter direction of the flow tube 11. This heating element 13 is formed of, for example, a tundus steel with a diameter of 5, and a ripening pulse for heating the subject 1 is given to the fluid 101 to be measured from this ripening body 13 . That is, a heating circuit section 14 is provided, and in this heating circuit section 14, a heating current pulse with a predetermined pulse width generated from a heating panless width setting circuit 10 is applied to a heating circuit 18. The heat circuit 18 is excited by the force, and the heat generation circuit 13 connected to the excited heating circuit 18 develops and the fluid to be measured 101 is heated by this heat pulse. .

A temperature-sensing circuit portion 15 is provided downstream of the ripening circuit portion 14 in the flow tube 11 . In the temperature sensing circuit section 15, a detector 19 that responds to the temperature of the fluid 101 to be measured is arranged in the flow tube 11, and a temperature detector 20 is connected between the output terminals of the detector 19. Amplifying circuit 21 is connected to the output terminal of this sensing circuit 20, and filter 9 is read out to the output terminal of this amplifying circuit 21 _. The constant current flow heated by the thermal pulse is detected as an electrical pulse by the detector 19 and the shunt circuit 20. The DC component of this signal is blocked by the filter 9, and the output signal of the filter 9 is passed through the multiplication filter 21. A pulse input of a predetermined value or more is applied to the output terminal of the Schmitt circuit 7 to obtain the output signal SD.

The drive timing generation circuit 16 is driven by this actuation signal SD, and the circuit 16 generates a body timing at a timing corresponding to the flow velocity of the fluid 101 to be measured. A mining signal S τ is emitted. The fluid to be measured 101 is heated based on the timing signal S τ between and .

Therefore, the fluid to be measured 10 1 is heated by the heat pulse of the heating element 13, and the heated fluid to be measured reaches the flow velocity after a time corresponding to the flow velocity of the fluid. If the speed is fast, it will reach the ejected body 19 in a short time, and if it is slow, it will reach the ejected body 19 in a long time. Since it is repeated, the heating period for the heating element 13, that is, the period of the D drive timing signal Sτ, is shorter if the velocity of the flow 01 to be measured is faster, and longer if it is slower. By determining this phase, the flow velocity or flow rate of the fluid 101 to be measured is determined. In the state in which the flow velocity of the constant tidal current in the flow tube 11: 101 drops below a predetermined level, this ΙΪto timing signal Sτ has a constant return Station ^ ¾ steady flow ^ 1

0 1 is aged and the flow in tube 1 1 is non-constant. The heating element 13 is constructed so that it is maintained at a minimum of a predetermined degree of rotation even when it is in a boiling state or the flow rate is zero. For example, when measuring the flow rate of air or inhalation, the amount changes rapidly and widely over the life span, so it is necessary to deal with this sudden change in the constant flow rate. Even so, heating by heat 13 is enough to apply a sufficient ¾ heat pulse to the constant fluid to enable reliable and accurate measurement. wife

]5 Heating chamber 13 is provided with a means of preheating.

This preheating means is achieved, for example, as follows. Measurement of the measured flow of the drive timing misog signal Sτ A timer 4 is provided with a period slightly longer than that corresponding to the minimum flow rate. This timer 4 is triggered by a timing signal ST 3 , generates a prohibit gate signal S during the set time of the timer 4 , and outputs a prohibit gate signal S 9 to the prohibit gate signal S 9 . yo]? Close the gate of switch circuit 6. When the driving timing signal ST is applied to the timer 1 within the set time of the timer 4, the gate of the switch circuit 6 remains closed. However, after timer 4 has finished, even if the timer setting time has elapsed, if the next desired timing signal Sτ is not given to timer 4, the timer 4 stops generation of the gate signal S and opens the switch ¾ 6 G gate. In this state, the O pulse is sent from the pulse generator 5 through the switch circuit 6 to the power Π heat recovery 18 _. Counting is started by a heating pulse SH from the pulse width setting circuit 10 when the heating circuit 18 is recognized by the timing signal Sτ. For example, an up-down counter 24 that counts the oscillation signal of the oscillator 25 whose wave number is 20 KHz is provided in the timing generator circuit 16. It is done. This up/down counter 24 counts up during the time that the heated fluid to be measured flows between the developing body 13 and the detecting body 19. , down-counting is performed by the production signal SD from the temperature sensing circuit section 15 . When this down-count number matches the final value of the up-count, this is detected by the match circuit 26, and this match detection output is used as timing. signal ST and ¾.

In this way, while the detection period by the detection object 19 is smaller than the set time of the timer 4, the object is heated by the motion timing signal Sτ. A pulse width setting circuit 10 is operated at a period twice the time from heating of the fluid to be measured to detection by the detector 19, and a heating pulse SH is issued. However, when the detected object 19 causes the detection cycle to become larger than the set time of timer 4, the supply of the prohibition gate signal from timer 4 is stopped. The gate of switch circuit 6 is opened. Therefore, in this state, a 10 Hz O pulse signal ifi switch circuit 6 is supplied from the pulse generator 5 to the pulse setting circuit 10, for example. Re No Nores! A thermal panoreth SH is emitted from the setting circuit 10. The aging pulse SH is inhibited.

A period measurement signal is connected to the output terminal of the pulse width setting circuit 10.

3 is connected, and a display 2 is connected to the output end of the local measuring circuit 3, and the measurement cycle or measurement frequency is displayed on the display 2 as a value calibrated to the flow velocity or flow rate of the fluid to be measured.

Next, specific examples of each part will be described. 2. During measurement, as shown in Fig. 2, a starting signal is applied to the base of transistor 30 through terminal 17a, and the output of transistor 30 ]3 pulse ^ 'Width setting circuit 10 is driven. The pulse width setting circuit 10 is formed by, for example, a monostable multi-pibrator, and adjusts the time constant of its time constant circuit 10a to adjust the pulse width of the output calothermal pulse SH. width is set. This heating pulse SH is applied to the heating circuit 18, and a heating current ΣΛΪ is applied to the heating element 13 during heating.

This force II heat circuit 18 is constructed, for example, as shown in FIG. A series connection circuit of ¾ resistances 81 and 82 is connected between the power terminal 102 and the contact. The connection point of S-resistances 81 and 82 is connected to the base of transistor 83, and its emitter is connected. Transistor 8 3 An S resistor 84 is connected between the collector of the power supply terminal 103 and the power supply terminal 103, and a predetermined voltage is applied to the power supply terminal 103.

30 V is applied. The collector of transistor 83 is connected to the anode side of diode 85, and its negative side is connected to the base of transistor 86. . A resistor 87 is connected between the base of this transistor 86 and the emitter. The collector of transistor 86 is connected to the output terminal of amplifier 89 . A resistor 90 is connected between the inverting input terminal of this amplifier 89 and ground, and a capacitor 88 is connected between its inverting input terminal and the output terminal of amplifier S9. . The output terminal of amplifier 89 is connected to the base of transistor 91, the emitter of which is connected to the base of transistor 92. connected to The emitter of transistor 92 is connected to the emitter of transistor 86 through resistor 93 . Further, the emitter of transistor 92 is connected to the base of transistor 94, and the emitter of transistor 94 is connected to the transistor It is read directly by the emitter of data 86. The collector of transistor 94 is connected to the negative terminal of booster 89 and to the collector of transistor 86 .

A bridge circuit ¾ 104 is ripened ^ 1 3 with the connection point between the resistor 9 δ and the developing body 1 3 and the connection point between the ¾ resistor 9 7 and the variable resistor 9 8 as output sources. , ¾g resistance 9 5 , 9 7 , variable Resistance to 9 8! ) It is composed by ΌO ~ Heat 13 and 98 1). The connection point between the immature body 13 and the ram resistor 98 is grounded, and the terminals of the ram resistors 95 and 97 are connected to the emitter of the transistor 86. The connection point of heat generation & 13 and resistor 95 is increased through resistor 99: connected to the inverting input terminal of ϋ device 89, and the connection point of resistors 97 and 98 is the non-inverting input of amplifier 89. O connected to terminal

In the state in which a voltage is applied to input terminal 102, transistor 83 is in a continuous state, and diode 85 is therefore in a conducting state. Therefore, the transistor 86 is in a conductive state, and the base of the transistor 91 is short-circuited by this transistor 86. Since transistors 91- and 92 are in a cut-off state, power supply terminal 103, diode 85, the base of transistor 86, and the emitter are connected. A slight current flows through each arm of the bridge circuit 104 through the heat generating element 18, but the heating element 18 does not substantially generate heat.

When a voltage is applied to the input terminal 102, the transistor 83 in the new state is turned on, and the voltage on the anode side of the diode 85 drops. When the transistor 86 is in the normal state, the output of the bridge circuit 104 is amplified by the amplifier 89. , the force causes transistor 91 to conduct, and transistor 91 conducts; When transistor 92 is in a conducting state. When transistor 92 is in a conductive state, power supply terminal 103 ?? current flows. When this current starts to flow, the heating element 13 is in a cold state and its resistance is low, so the non-reverse input side of the booster 89 is also affected by the pressure on the non-reverse input side. , is high, and the output voltage of amplifier 89 causes a large current to flow through transistors 91 and 92 . This current increases the current flowing through the heating element 13, heating the heating element 13, increasing its resistance, and balancing the bridge circuit 104. The current of the heating element 13. increases until . In this manner, the heat generator 13 can be heated to a predetermined temperature. In other words, the cooling of the heating element 13 differs depending on the velocity of the flow to be measured. can be heated at a constant intensity.

¾ When an overcurrent flows through transistor 92, transistor 94 conducts, reconnects transistor 91, and cuts off transistor 92. new. .,

When the temperature rise 1 3 is heated, then the measured fluid flowing through the ignited 1 3 part is heated. As this heated ^constant flow^ passes through 19 ¾ of a body,

?19 is heated, and when it is heated: 19 and ϋ times ₂₀ are second; The body 19 is an iTL body in which the resistance value changes _by 1 degrees]), and a bridge 34 is formed with this detection point 19 as one side, and the block A ί¾'!-3 device 35 is connected to the detection terminal i¾1 of the ridge 34. When the fluid to be measured which is heated by the heating body 13 pulls the discharge body 19, the body 19 is heated and the bridge 34 becomes unbalanced m. , the output signal S c is emitted from the amplifier 35 .

In the embodiment shown in FIG. 1, the detection body 19 consists of two detection bodies 19-1 and 19-2]), which, as shown in FIG. Arrayed in the direction perpendicular to the flow direction, one of the detection angles 19-1 is supplied with the measurement flow heated by the heating element 13. The detected part is allowed to pass through the 19-2- part. For example, in the case of air measurement, the amount of heat given by the salary to the exhaled air is given equally to both the detection bodies 19-1 and 19-2, -1, 19-2 are used for the opposite arms of the bridge 34. Therefore, it is possible to remove the influence of the amount of heat given by the human body following the flow to be measured, and to correctly discharge the passage of the heated fluid by the heating element 13.

When the air and intake air are separated from each other by ¾ Μζ. ~ 3 Ό, as shown in Fig. 5, two sets of bodies 19, 19 ' should be placed.

¾ of output fe l 9': 1 9 - 1 1 and 1 9 - 1 2 are Corresponding to 19-1 and 19-2. Returning to the description of FIG. 2, the detection signal Sc detected by the ϋ circuit 20 is applied to an integration circuit 36, which is composed of a resistor 37 and a capacitor 38, and the high-frequency noise component is removed. be done. The output of the integration circuit 36 is applied to a capacitor 39 to block the DC component in the detection signal Sc. The detection signal _Sc with the DC component blocked is amplified by amplifiers 40 and 41. This amplified detection pulse S c is applied to the non-inverting input terminal of the comparator 4 2 of the temperature sensitive circuit section 1 5 .

On the other hand, the output terminal of amplifier 41 is connected to the non-inverting input terminal of comparison amplifier 43, and the cathode side of diode 44 is connected to the output terminal of comparison amplifier 43. The positive side of the diode 44 is connected to one end of a capacitor 45, the other end of which is grounded. The anode side of diode 44 is connected to the non-inverting input terminal of buffer circuit 46, and the non-inverting terminals of comparison amplifier 43 and buffer circuit 46 are connected to each other. be. The output terminal of the buffer circuit 46 is connected through a resistor 47 to the counter input terminal of the comparator 42, and the variable terminal of the variable resistor 49 is connected to this counter input terminal. Shot through 48. Although not shown in the figure, both ends of the variable resistor H49 are connected to an electric field. The positive of diode 44 is connected to the negative ¾ ¾ of diode 50, and this diode The positive electrode side of the first electrode 50 is connected to the positive end of the Wuxing multivibrator 51 . An inverse circuit 52 is connected to the output terminal of the comparator 42. A heating pulse SH is applied to the input terminal of the monostable multivibrator 51. Therefore, the capacitor 45 is charged to a predetermined value through the diode 50 by the power of the multivibrator 51 for each heating pulse SH. The voltage of this capacitor 45 is applied through a buffer circuit 46 to the opposite input side of the comparator 43. The output of multiplier 41: the low level of detected pulse S c force not obtained is compared with the output of buffer circuit 46 by comparison amplification H43, and both The charge in capacitor 45 is discharged through diode 44 until . In this way a minimum level of increase mm4:1 is obtained at the output of the buffer circuit 46 in the absence of the detection pulse Sc. A predetermined value is added to this lowest level by the mover of the variable resistor 49 and given to the comparator 42 as this reference value. When the detection pulse S c exceeds this reference value, the output of the hysteresis amplifier 4.2 reverts to a logic high "1", which acts as the signal SD through the buffer circuit 52. is applied to terminal 105. In Fig. 2, ϋ 4 2 is used instead of the Schmitt times ¾ .7 in Fig. 1.

Fig. 3 shows U? — Give an example. The output activation signal SD of comparator 42 in FIG. there is The output terminal of the NOR circuit 61 is connected to one input terminal of the N0R circuit 62 and forms a flip-flop. The input terminal of the NOR circuit 63 is connected to the output terminal of a NANI circuit 64, and one input terminal of this NAND circuit 64 is grounded through a capacitor 65 and connected to a resistor. It is connected to the power supply terminal 103 via 66. A start switch 67 is connected between the two poles of the capacitor 65 . The output end of the NOR circuit 62 is connected to one input terminal of the NAND circuit 69 and the inversion circuit 70 through the buffer circuit 68 . The other input terminal of the NAND circuit 69 is supplied with the reference signal from the terminal 25a of the generator 25. The output side of the inversion circuit 7 0 is connected to one input terminal of the NAND circuit 7 1 . A reference signal is applied from a terminal 25b of the oscillator 25 to another input terminal of the NAND circuit 71. Each output terminal of the NAND circuits 69 and 71 is connected to each input terminal of the NOR circuit 72G. In this NOR circuit 72, Yasuko Shiniki connected up-down counters 73, 74 and 7 directly to the up-down counter 24. Two or more cowls are connected to each of the five clicks . The output terminal of the impulse circuit 68 is connected to the up-count and down-count control terminals tc of the counters 73, 74 and 75, respectively.

The counter terminals t (3i, _t02 , t03 and control) of the counters 73, 74 and 75 in the count-zero state are connected to the input of the N0R circuit 76. The output terminal of this NOR circuit 76 is connected to the input terminal of the NAND circuit 64 through the NOR circuit 77. The NOR circuit 76 is connected to the input terminal of the NAND circuit 64 through the NOR circuit 77. It constitutes the matching circuit 26 inside.

At the beginning, Switch 67 was put in, and NAN

The output of D circuit 64 is applied to the base of transistor 30 in FIG. 2 through impulse circuit 107, OR circuit 108 and terminal 17a. A message "f ^e 1" is given and a mature pulse SH is generated from the pulse width setting circuit 10. Since this carothermal pulse SH is also applied to the input terminal 106 of the N0R circuit 61, when the NOR circuit 63 is given a logical value of 1" from the NAND circuit 64, N0 The I value of the signal at the output terminal of the R circuit 6 2 is ^β 1 " and ¾ j? , which is applied to the control terminal _tc of each of the counters 73, 74, 75 via the buffer circuit 68 as a logic gate <<1", these counters being up-counters. Each counter 73, 74, 75 is connected to terminal 25a of support H25] NAND circuit 69, N0R [¾72 Start counting a reference signal of, for example, 20 K ¾ given via .

¾ When a heat pulse given to the fluid to be measured is detected by the detection body 19 and an actuation signal SD is issued from the buffer circuit 52, this actuation signal SD is sent through the terminal 105 to the NOR circuit Given to 60. At that time, the output of the NOR circuit 61 is "*1" and this is applied to the NOR circuit 62, and the logic value of the signal at its output terminal is "0". 0 " and ]3 Each counter 73 , 74 , 75 is in a down counting state ] , these counters are connected to terminal 25 b of oscillator 25 ] 5 NAND circuit 71 and NOR circuit 72 to down-count the reference signal provided.

During this down-counting, the count values that have already been incremented are exhausted, and the signals at the output terminals _tQ1 , _t02 , and t03 all become the logic value ^β 0", the signal at the control terminal tc also becomes a logic value "0" during the turn count, so this is detected by the NOR circuit 76 and the output of the NOR circuit 76 A drive timing signal ST appears at the end of the drive timing signal ST.This drive timing signal Sτ is applied to the NAND circuit 64 through the N0R circuit 77, and thus again The heating of heat 3 and the up-count operation of counter 24 are started, and the above-mentioned operations are performed. Corresponds to flow speed If the number of stations of the reference signal at terminals 25a and 25b is 1 =J-D-, the time taken for the flow heated in 13 to reach the detection object 19 is 2 doubled. In this case, the circuits 69, 70, 71 and 72 can be omitted and the reference signal of one terminal 25a can be supplied directly to the counter 24. ΙΪft? The timing signal Sτ, or the phase of the heating pulse SH, is measured by the regulator circuit 3 (Fig. 1)', ^which indicates the flow rate or force of the constant flow. displayed in instrument 2.

迦The timing signal S τ is also given to the timer 4 as described above, and the driving timing signal S τ is shorter than the reference period corresponding to the flow rate. The pulse width setting circuit 10 is driven by the driving timing signal Sτ, and the period of the driving timing signal S.T becomes slightly larger than the reference period. Then, the timer 4 stops supplying the gate signal S as described above. In this state, the output signal Sn of the switch circuit 6 is applied to the 0R circuit 108 as described above, and the output of the noise setting circuit 10 changes to m be moved. Therefore, even if the starting switch 67 is not provided in this example, if the power switch is turned on, the flow rate of the flow to be measured is zero, but the switch circuit 6 The heating element 13 is locally heated by the output. s66, capacitor 65, switch 67, circuit 64 It suffices to omit the buffer circuit 107 and connect the output side of the NOR circuit 76 directly to each input side of the N0I circuit 63 and the 0R circuit 10S. Also, it is clear that the NOR circuits 60 and 61 may be omitted in FIG. be.

Fig. 4 shows the relationship between the flow rate obtained by the hot-wire pulse flowmeter of this invention and the time from heating to detection. It is shown that In the past, the heat source 13 was periodically heated and the time from the heating to the detection by the detection body 19 was measured. In this case, it is necessary to lengthen the heating period for the heating element in order to be able to measure whether the flow velocity of the fluid to be measured is fast or slow. If so, is the measurement time longer than necessary]? Moreover, when the flow velocity changes rapidly, it is impossible to follow the change and measure it correctly. If the heating cycle is shortened, it is not possible to measure slow flow velocities.

However, in this invention, the heat generator 13 is heated based on the detection output of the test body 19! ), when the flow velocity is fast, the heating period is automatically shortened, and when the flow velocity is slow, the heating period is automatically lengthened. For this reason, as shown in Fig. 4, the flow velocity (flow *)

^ can be measured, and a measured output that follows the change in flow velocity can be obtained.

In the above description, instead of the motor timing signal Sτ, the pulse width setting circuit 10 may be changed by detecting the S pulse Sc of the output 19. In this case, if the flow velocity is high, the force ϋ of the body 13 [I becomes significantly more mature]9, so that the heating 3 is heated before it cools down sufficiently. , it is difficult to correct the detection pulse S c in the detection object 19 . In order to prevent such a phenomenon from occurring, it is necessary to delay the time from obtaining the detection pulse S c to reheating the heating element 13. . It is possible to measure the flow rate using the delay as a constant time. Calculation of flow rate (flow velocity) is easy. This delay is equal to the time T0 required for the fluid heated by the heating element 13 to reach the detection element 19 in ifli. The output reference signal of 25b is multiplied by 2, 3, or 4 times the reference signal of terminal 25a. It can also be doubled, tripled, or quadrupled.

In addition, as explained in Fig. 6, this generation can provide constant heating regardless of the velocity of the flow to be measured. ^ in 9 can be performed reliably. Due to these points, according to the present invention, it is possible to accurately determine the expiratory or inspiratory flow rate even if the air or inspiratory flow rate changes significantly during measurement. In addition, the timer 4, the pulse generator 5, and the switch circuit 6 are cycled, the flow rate is below the predetermined 1' straight line, and the heating element 13 is preheated. It is possible to accurately measure the flow rate of the fluid to be measured, which is input to the , including its start-up resistance. In this respect as well, the flowmeter of this invention is suitable for measuring expiration and inspiration. Similarly, by using the detection bodies 19-1 and 19-2, it is possible to ensure detection by the detection body 19-1 regardless of changes in the ambient temperature and the temperature of the fluid to be measured. I can do and

When the fluid to be measured 101 flowing in the whirl tube 11 vibrates due to external vibrations, etc., it becomes difficult to detect the heated portion of the fluid to be measured 101 with the detection body 19. sometimes In order to alleviate such a problem, it would be better to use the example shown in FIGS. 7 and 8. FIG. That is, turbulence occurs in, for example, acrylic flow tube 11 having an inner diameter of 33 and a total length of 12, in which fluid 101 is flowed; Heating collars 13a and 13b are stretched parallel to each other and substantially perpendicular to the axis. The heating chambers 13a and 13b are, for example, followed by tungsten chambers with a diameter of 5^ and a length of 30 mm. Both ¾ ¾ of § 1 3 a, 1 .. 3 b are respectively holders - 1, f - 2

¾υ丄 and - 3 , ? - 4 ]) Fixed to the tube wall of the flow tube 11 o The distance between the rain calorie hot pots 13 a and 13 b The salary 101 or the heated part 111b is brought as close as possible. On this side, the maturing circuit section 14 (Fig. 1) is commonly connected to the heating wires 13a and 13b.

Power. It is on the lower side of the fluid 101 with respect to the hot wire 13a, 13b, for example, from the heating wire 13a, 13b to 4 ~

1 4 ⅰ ⋅ 'JUL ^r¾ i 1 9 a , 1 9 ¾ are stretched parallel to each other o -t^ i¾ ¾. ¾ "T" 1 9 a , 1 For 9b, for example, a 5mm diameter and 30mm length tundus steel is used, and each end is fitted with a retainer ^-5, ^-6 and -7, ^-8]? The temperature sensing circuits 20 described with reference to FIG. When the heating irons 13a and 1'3b are heated by the α carothermal node S H which can be logically summed with S c , at this time, the caro ripening 13a and 13b are heated. A fluid to be measured passing through the portion is heated. That is, as shown in FIG. 8, the fluid portions 111a and 111 shown in dotted green are heated by the heating plates 13a and 1.3b, respectively, and this heated The flow segment llla, 111 moves downstream in the flow tube 11 along its tube axis.

Is the flow of ιτπ: normal and the flow is turbulent ¾? Since the portions 111a and 111b occupy the positions of the tiles 19a and 19b respectively, the flow portion 111a is the linear thermosensitive element 19a, Further, the flow portions 111b are detected by the iron-shaped temperature sensing elements 19b, respectively. Fluid turbulence caused by external factors, such as external vibration applied to the flow tube 11, or turbulent flow caused by temperature changes in the fluid itself. The flow path in the flow tube 11 of 11a may be disturbed as indicated by the dotted arrow Φ in FIG. Due to this turbulence in the flow path, the heated flow passage portion 111a did not reach the position of the linear heating element 19a correctly, and was stuck in the pipe axis of the flow tube 11. It is assumed that it is shifted in the right angle direction and cannot be detected by the raven-shaped temperature sensing element 19a or that the detection output is extremely small. Even in such a case, in the examples of FIGS. 7 and 8, the heated fluid portion 111a is detected by the linear thermosensitive element 19b as shown in FIG. It depends on what is being done. Therefore, even if the fluid to be measured, which is heated by the turbulence of the flow path in the flow tube 11, is positioned at the position of the tiger-shaped temperature sensing element and is displaced in the direction perpendicular to the flow tube 11, High-sensitivity detection is possible without reducing detection sensitivity. In this example, two heating elements and two worm-like heating elements were stretched in parallel with each other. A battery, for example, a single heater and three heating elements. ^ Even as a set rule

As mentioned above, according to the flow meter of the present invention, it is possible to measure a large change in flow rate in comparison with the medium pulse type flow meter. However, in order to further widen the measurement range, it is necessary to divide it into low-voltage flow rate and i i s: . The parts corresponding to those in FIG. 1 are denoted by the same reference numerals in FIG. A high-speed detector 19-2 is provided further downstream of the detector 19-1. 21, these correspond to the detection bodies 19-9-2 in FIG. 9-1, an amplifier 21-1 and a shumit circuit 7-1 are provided, and a high-speed output 19-2 is provided with a temperature control circuit 20-2 and a filter 9-1. 2, an amplifier 21-1 and a Schmitt circuit 7-2 are provided.

Each output of the Schmitt circuits 7-2 of the low-speed temperature sensing circuit section 15-1, the Schmitt circuit section 7-1, and the high-speed temperature sensing circuit section 1-5-2 is connected to the switch. input to switch circuit 30.

The switch circuit 30 is created by the output of the static circuit 3. This town times ¾ 3 O—one input 5¾ A drive timing signal S τ of a matching circuit 26 is applied to the terminal, and the output of a reference signal ϋ 32 is applied to the other input terminals. In the control circuit 3 1 , the period of the timing signal S τ is compared with the switching period T m preset by the reference signal generator 3 2 . The cut-off period Tm is used as a reference when switching between the high speed detector 19-1 and the high speed detector 19-2 according to the flow rate in the flow tube 11. . 1: Low speed while the period of the timing signal Sτ emitted from the circuit 26 is larger than the switching period Tm ^Signal detected by the detector 19-1 The output activation signal SDI of the Schmitt circuit 7-1 is taken out from the switch circuit 30 to be taken out and supplied to the Rao timing signal generator circuit 16.

As the flow rate of the fluid in the flow tube 11 increases, the phase of the three-moving timing signal Sτ emitted from the coincidence circuit 26 changes to the switching period Tm! ), the switch circuit 30 is turned off by the control circuit 31, and the switch circuit 30 outputs the signal detected by the high-speed detector 19-2. The output of the Beschmitt circuit _7-2 , which is taken out, is supplied to the operation timing signal generating circuit 1'6.

As the control circuit 31, for example, a digital comparator is bent, and the count value immediately before the up/down counter 24 turns is counted. is given as an input to the control circuit 31, and given as a digital signal from the reference signal generator 32. It should be compared with the switching period T m obtained, and the switch circuit 30 should be switched according to the result.

As described above, by providing the low-speed temperature sensing circuit section 15-1 and the high-speed temperature sensing circuit section 15-2, the measurement range can be increased to that shown in Fig. 1. It is easy to see that g can be expanded. In order to match the detection sensitivities of the low-sequence detection angle 19-1 and the high-speed detection angle 19-2, the high-speed detection object 19-2 is designed as shown in Fig. 10. Provided in parallel with the ripening body 13 , the low-speed detecting body 19 - 1 is slightly rotated in a plane perpendicular to the tube axis of the flow tube 11 to slightly shift parallel to the ripening body 13 . and

Claims

The scope of the claims

1. A flow tube through which the fluid to be measured flows, a heating element provided in the flow tube for heating the fluid to be measured, a heating circuit for pulsatingly heating the heating element, and the inside of the flow tube. A detection body provided downstream of the heating element in the flow of the constant flow iron to respond to temperature changes, and detecting passage of the heated portion of the fluid to be measured through the detection body A temperature sensing circuit, a driving timing signal generating circuit that generates a timing signal for the heating circuit by the detection output of the sensing circuit, and a heating period for the heating element is measured. and a measuring circuit for obtaining the _flow rate or flow velocity of the fluid to be measured by

2. The above-mentioned Luo-sheng timing signal generation circuit has a counter, which heats up the above-mentioned heating element, measures a reference signal, and obtains a detection output from the above-mentioned temperature-sensing circuit. The thermal pulse flowmeter according to claim 1, further comprising a circuit for generating the cumulative timing signal at the time when the same value as the count value up to the time is further counted.

o 3. The upper counter is an up-counter, which starts up-counting due to the above heating and detects the above temperature circuit. Then put the other counter into the down count state, and indicate the point where the count ίί of the counter reached zero in the previous down count. Ι above

C?I The mature Hals formula in the second term of the special rr that generates the dynamic timing signal

4. Measure return flow rate and ^! A panoreth generator that generates a pulse with a period longer than the local period of the corresponding driving timing signal and a detection that the above-mentioned percussive timing signal is obtained for a predetermined period. The pulse of the self-less generator is controlled by the means for slowing down and the detection output of the failure to be obtained for a predetermined period of time, and the pulse of the self-less generator is sent to the above-mentioned aging circuit as a timing signal. 2. The thermal panorless flow meter of claim 1, wherein the range of allowable Iff comprises a switch circuit supplied as a

5. According to the claim, the means for indicating that the driving timing signal is obtained for the predetermined period is a timer controlled by the driving timing signal. Thermal panoreth formula ΪΤΕ篁5† in the fourth term of the range §匚 ¾¾.

6. The heating circuit is provided with constant heating means for heating the fluid to be measured at a constant strength regardless of the conditions of the fluid to be measured. σ i o

7. Above = 3 The resistance value of the body increases depending on the temperature. to control the current flowing through the above heat wave

T ST Wm equation of the 6th term of the formula ^ : ! o

8. The above constant heating means includes the above-mentioned anti-bridging? , A. A bridge circuit, a differential amplifier circuit that amplifies the output of the resistance bridge circuit, and the output of the differential amplifier circuit creates a current to the resistor bridge circuit. by a variable impedance element inserted in series

5 Thermal pulse type flow pIo described in claim 7

9. a compensating detector mounted in said flow tube in contact with said heated portion of said flow to be measured, responsive to temperature changes, and having a change characteristic similar to said detector; , and a compensating means for adjusting the temperature fluctuation of the detected iron by means of the compensating detection body. ·

10. Both the detection body and the compensating detection body are temperature sensitive antibodies, and the compensation means is a resistance bridge circuit having the detection body and the compensation detection body on opposite arms. The thermal pulse flowmeter according to claim 9, which is

1 1. The temperature sensing circuit is the detection body]) means for detecting the lowest level of the obtained electrical signal, and adding a constant level to the detected lowest level to obtain the reference level. By means of the means for controlling and the increase of the latter in comparison with the electrical signal o of the reference level and the above detection, the heated portion of the above-mentioned tidal constant fluid becomes A pulse-type flowmeter as recited in claim 1, comprising a rhinostat that is verified to have passed inspection.

4 12. Further below the test object in the flow tube A second temperature sensing circuit is provided on the side and detects a reduction in the heated portion of the measured flow, the second sensing element of which is responsive to changes in temperature. and a switching circuit for supplying the detection force of either the second temperature sensing circuit or the temperature sensing circuit to the driving timing signal generating circuit. The thermal pulse flowmeter according to paragraph 1 of paragraph 1.

13. Comparing the period of the drive timing signal and the set period, the former is shorter than the latter by D. c_t nCt

2. The device according to claim 12, further comprising a control circuit for controlling the cut-off circuit so as to supply the detection output of the temperature control circuit (2) to the drive timing signal generation circuit. Pulse flow meter.

14. The thermal pulse flowmeter of claim i2 or claim 13, wherein the detector has a reduced detection sensitivity (than the second detector).

15. The heating element and the detecting element are parallel bodies, respectively, and the heating elements are arranged substantially parallel, and the heating element is a plurality of substantially parallel lines. The heat pulse type ft according to any one of Claims 1 to 11, wherein the states are arranged in a direction substantially perpendicular to the direction of the fluid to be measured.

1 6. The heating element and the detection angle are arranged in parallel with each other.

C:.:FI The pulse according to any one of Claims ¹ to ¹¹ , in which a plurality of troughs are arranged substantially perpendicular to the flow direction of the measured flow: δ.

17. Claims 1 to 11 including a ^second sensing element provided in the flow tube on the side opposite to the sensing element with respect to the developing angle and responsive to temperature changes. A thermal pulse dc meter according to any one of the preceding paragraphs.

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