JPH0392725A - Method and apparatus for measuring volume - Google Patents

Abstract

PURPOSE:To reduce overlapped noises by changing the internal pressures of a main tank and a correcting tank which communicate with each other by a volume changing means which is driven by a signal at a specified frequency whose phase is inverted at every specified section, detecting the pressures with a pressure sensor, obtaining correlation between the obtained signal and the preceding driving signal, and measuring the volume based on the correlation. CONSTITUTION:A volume measuring tank is composed of a main tank 30 and a correcting tank 31 which communicate with each other. Liquid is contained in the tank 30. The inside of the tank 31 is filled with gas which is evaporated from the liquid. When the volume of the tank is measured, a signal VoSin omegat is outputted from a first oscillator 50, and a signal Sin Nomegat (n is an even number) which is transmitted at 1/2 period is outputted from a second oscillator 51. The outputs are multiplied in a first multiplier 52. A speaker 33 which is a volume changing means is operated by the output of the multiplier. The sound is received with a microphone 34a. Then, the output of the multiplier 52 is aligned with the output of the microphone 34a in a first phase aligning circuit 54. Integration is performed in a zero-cross detection circuit 57, and the intended measured value is outputted.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a volume measuring method and apparatus for measuring the volume of a liquid or the like as an object to be measured stored in a tank.

[Conventional technology]

As a conventional method and apparatus for measuring volume of this type, there is a prior art technique shown in Japanese Patent Application No. 1-27808, for example, which will be explained based on FIGS. 3 to 7. First, in FIG. 3, to explain the principle, 3o is an irregularly shaped main tank that stores fixed objects such as liquid, powder, granules, irregularly shaped objects, etc., and this main tank 30 A correction tank 31 having a smaller volume than the main tank 30 is connected to the main tank 30 via a connecting vibrator 32 . Further, a small-diameter ventilation hole 35 is provided in the upper part of the irregularly shaped main tank 30 (note that the ventilation hole 35 may not be provided). For example, there is a piston in the upper part of the correction knob 31. A volume changing means (mechanism) 33 such as a speaker shape (hereinafter referred to as a speaker) is provided, and the operation of this volume changing means 33 causes the correction tank 3 to
The volume within 1 can be changed. The structure of this embodiment has been described above, and the measurement principle based on this structure will be explained next. Measurement principle (1) First, a correction tank 31 with a small volume V1 and a large volume v
Consider a connected tank system as shown in FIG. 3 in which two main tanks 30 are connected. This is main tank 3
0 and the correction tank 31 are connected by a pipe 32 having a flow resistance rl, and the vent hole 35 of the tank 30 has a flow resistance r2. Let γ be the specific heat ratio of the gases in both tanks 30 and 31, R be the gas constant, and τ be the thermal time constant of the kunk 31. 3 Attach a volume change stage 33 using a piston, diaphragm, head, beaker shape, etc. to the tank 31, and calculate the amount of volume change actually generated by this volume change means 33 by V(0. Tank 30 .3] is a rigid body, the tank 30.31 will not be distorted when the internal pressure of the tank 3031 is increased or decreased, so
Volume change due to piston, diaphragm, helices, etc. ■. (1) and the amount of volume change ν(1) that actually occurs are equal. If tank 30 is flexible, tank 30
．． 31. Since the tank 30 is distorted when the internal pressure is increased or decreased, the actual volume change v(t) changes by an amount corresponding to the volume change due to expansion or contraction. When v(t) is 10, the absolute pressure, temperature, and number of moles of the gas in the tank 31 are P, respectively. , T. , n also the absolute pressure of the gas in the tank 30. P the temperature and number of moles, respectively. , T2, n. shall be. If the measurement environment does not change significantly, gas flows into and out of the tank 30.31 through the vent hole 35, so the tank 31. ; Absolute pressure P within 30
. Is P equal to the external pressure 4? , its change is very slow and changes equally with the outside pressure. When v(t)≠0, pressure. i degrees and the number of moles also change depending on the situation of the volume changing means 33, and in the tank 31, the pressure is P0-1-ΔP+(t), the temperature is T, 1ΔTl(t), and the number of moles is n1-Δn1■( 1). In tank 30, the pressure is P. 1Δpz(t). The temperature changes as T2+ΔTz(t) and the number of moles changes as n2+Δn+z(t)−Δnz(t). Δn+z(t) is the number of moles of air flowing from the tank 31 to the tank 30, and Δnz(t) is the number of moles of air flowing from the tank 30 to the vent hole 3.
This is the number of moles of air that leaked to the outside through 5. We now make the following assumptions about this system. I) The gas in tanks 30 and 31 is an ideal gas. 2) V0) (f■+, V2) 3) The heat capacity of the tank 30 is large, and the pressure change ΔP25
The temperature change inside the tank due to the change in volume v(t) is very slow compared to the speed of change in the volume change amount v(t) and can be ignored. 4) The rate of change of the volume change amount v(t) is such that the pressure that changes accordingly is the same throughout the tank 30, 31. 5) Even if an object to be measured is placed in the tank 30, the object does not create two or more closed gas spaces, that is, cavities within the tank 30. The above assumptions are not a major constraint. 8P+(t), 8Pz(t
)ΔT I(t), ΔT2(t), Δn+z(t)
, Δn2(t) is originally expressed by a nonlinear equation, but according to assumption 2), its magnitude is P. , Tl, T
2 + rl+ + nz, very small;
Therefore, it can be approximated by a linear equation. In a static state, the relationship between the pressure, temperature, and number of moles of gas in the tank 30.31 is expressed by the following algebraic equation. PoV+ 1n lRTl+ PoVz=nJT2
(la) Also assumptions 1), 3), 4). 5)
Therefore, in a dynamic state, the relationship between the pressure, temperature, and number of moles of the gas in the tank 30.31 is expressed by the following linear ordinary differential equation. ΔT+(0) 10(1f) Flow resistance r, in the above equation, r r2 is determined from the length l and diameter d of the pipe 32 as shown in the following experimental equation. This formula shows that the length l is 50 to 650 [mmL diameter d
is 2.0 to 9. This was experimentally determined using an aluminum pipe with a diameter of 0 [mm]. Further, the volume change amount v(t) is expressed as follows. V(t) = v. (t)−Δv(t)
(lh) Δ■ is a constant specific to the tank determined from the material, shape, volume, etc. of the tank, and Δv(t) is the volume change amount V of the 1,000-stage volume change 33. Tank 3 due to change in (t)
This is the amount of volume change due to expansion or contraction of 0. Applying Laplace transform to equations (1a) to (li), human power v(
The transfer function from t) to the output ΔP l(t) is as follows. (2a) 8 9 Coefficient 1-2V2/RT2 +r+Vz/RT2. r. V
1/RT1+r+Vz/RT+ is the time constant of pressure change. For example, r2V2/RT2 means that the gas at the absolute temperature T2 in the hollow part of the kunk 30 will flow through the vent hole 3 with the flow resistance r2.
5 is the time constant of pressure decay when flowing out of the tank 30 through 5. Correction coefficient k2 (Szrl+r2+VI+V2
) changes depending on the volume v2 of the main tank 30,
In the frequency characteristic of kz (s+r++rz+L+Vz) shown in FIG.
By selecting a frequency between XlO-' and 10-'H2, it can be approximately regarded as a constant. r+ <<< rz (rz is the flow resistance of the air vent 35), and the thermal time constant τ and rz (ν+ +Min Vd
/ I? If T2 has a similar value, the following angular frequency ω exists. (2c) Under this condition, the correction coefficient kz(S+r++r'z+V
++Vz) is approximated as follows. Kg (1”l rl+ r2+ V++ Vz)
# IZKg(iω+ r++ r2+ ν.ν2)
10 (2d) Therefore, when the condition of equation (2c) is satisfied, the transfer function from the input v (t)10 to the output ΔP+(t) is 7 Po/(
V+10ν20ΔV). Note that when the volume changing means 33 is driven in a sinusoidal manner at an angular frequency ω0, it is considered to be equivalent to a state in which the volume changing means 32 is closed. In other words, it is sufficient if . (2) Next, consider a single tank system as shown in Figure 5. This is tank 31 in Figure 3. ．． This corresponds to a case in which the cross-sectional area of the pipe 32 connecting the pipes 30 is made very large, and the value of the flow resistance rl of the pipe 32 is thereby made very small. From this, from v(t) in Fig. 5, ΔP
The transfer function up to 2(t) is rl −
0, Tz =TI ΔP2−ΔPV 2' 1V
+ + V Z and is as follows. becomes. Consider the following angular frequency ω. For example, 10-1H shown in 8 in the frequency characteristics of Figure 6
The frequency is higher than z. By setting such a frequency, the correction coefficient L(iω, rz, V3') can be approximated as follows. k, (tω, r2+V3')l';1k, (
iω, r2, 'L+')'. 0
(2i) At this time, the transfer function is TPO/(V2'+△V
). Next, the above principle will be explained based on FIG. In FIG. 7, numeral 33 is a speaker (volume changing means). 30 and a correction tank 31 are arranged so as to be partitioned. Furthermore, a condenser microphone (first pressure detection means) 34b is provided on the main tank 30 side, and a correction tank 31
On the side, there is a Dynaξ microphone (second pressure detection means) 34 which has a 3/Ib sensitivity lower than that of the first microphone.
A is provided. Further, the speaker 33 has a predetermined angular frequency ω. Drive with. In this case, the single tank system theory shown in FIG. 5 applies. Here, the volume of the correction tank 31 is 1, the main tank 30
The volume of the gas in the main tank 30 is v2, the volume of the liquid in the main tank 30 is 2, and the sum of the volumes of the correction tank 31 and the main tank 30 is 2a. The pressure change ΔP+(t) in the correction tank 31 is calculated as follows using the angular frequency ω■ that satisfies equation (2h): ΔP+(t) = r-! -Ll k+ IVoSin
(ωo t + φ1) ν1 + ΔV Po = 7 − v. sin ω}lt (
3a) V, +ΔV. In addition, the main tank 30 is a rigid body, that is, Δ■
= 0, and when the angular frequency ωH satisfies formula (2h) 1 3 , ΔP (0 is as follows. ΔP (L) k ν.sin (ωI1 L +φ2) ΔPI' on the positive tank 31 side ( 1) When the amplitude of ΔP1' (t) - r PO v2 + ΔV k, vosin (ωH1 +φ2) is measured, the amplitude of the correction tank 31 when the volume change means 33 is driven so that the pressure change becomes a sine wave Assuming that the amplitude value of the pressure change is AI and the amplitude value of the pressure change of the main tank 30 is A2, the ratio of these amplitude values is expressed by formulas (3a) and (3b
) from this v 2-1 1! + (v1 -△■, k2 The volume of liquid stored in the tank 30, VI, May, is 1 4 -VL=V.-V2=y, what 1i1V+-ΔV]. Next, the above principle A specific prior art based on this will be explained. Fig. 7 shows a case in which a subica (volume change means) 33 is placed between a correction tank 31 and a main tank 30, and
In order to equalize the static pressure in the main tank 30 and the correction tank 3l, both tanks 30 and 31 are connected by a thin pipe 47 having an orifice 47a, so that the main tank 30 and the correction tank 31 are not affected by atmospheric pressure. Since the system is almost completely closed, the driving angular frequency ω of the speaker 33 is ω. This is very large compared to the slow change in atmospheric pressure, and the fluid resistance r2 in the vent hole 35 is very large.
5 acts as if it is blocked, so tank 30.3
The air pressure inside the tank 30 is not affected by the difference in air pressure between the inside and outside of the tank 31. Here, the time constant of the pressure transmission through the pipe 47 is sufficiently larger than the time constant of the pressure change in the correction tank 31 due to the subveaker 33, and the time constant of the pressure change in the atmospheric pressure outside the tank 30, 3], that is, the absolute pressure. It is assumed that the v. When a volume change as represented by a function of sin ωot is given to the correction tank 31 and the main tank 30, the principle of a single tank system is applied to both the main tank 30 and the correction tank 31. Therefore, V(t) 1v. sin ωat (4
a), the pressure change ΔPIO) of the correction kunk 31 becomes (4b), and the angular frequency ω in the above equation. If (2b) is satisfied, then in the above equation, the main tank 30 is a rigid body and the angular frequency ω is the same as the correction tank 31. When satisfies formula (2h), it becomes. That is, the volume of each of the main tank 30 and the correction tank 31 is ν due to the suveka 33. sjnω. L is the angular frequency ω. When the pressure inside the main tank 30 and the correction tank 31 are varied regularly, the pressure fluctuations in the main tank 30 and the correction tank 31 are caused by the dynax microphone 34a and the condenser microphone 34b attached to the respective tanks 30 and 31.
The output of the condenser microphone 34b that has detected the pressure fluctuation in the main tank 30 has a gain l and a center angular frequency ω. The angular frequency ω is set by the bandpass filter 37b. A certain portion of the signal is extracted, and then the second
The dynamic microphone 3 is supplied to the amplitude detector 39b and detects the pressure fluctuation of 17 31.
The output of 4a has a gain of ■, and a center angular frequency ω. The angular frequency ω is determined by the bandpass filter 37a. Only the signal intensity is multiplied by 1 and extracted, and then the first amplitude detector 3
9a, γP0v0 is detected and output. After that, the output γP0ν from the first amplitude detector 39a. is divided by the second amplitude detection, the volume V2 of the hollow part of the main tank 30 is calculated, and the calculation result is sent to the subtracter 4.
The total volume of the main tank 30 supplied and set to 1■
7, and as a result, the volume VL of the liquid stored in the main tank 30 is calculated.

[Problem to be solved by the invention]

However, in such a conventional volume measurement method and device, band-pass filters 37a and 37 are used to remove noise from the electric signal from the speaker 33.
A microphone 34 is detected by amplitude detectors 39a, 39b, etc.
a. 34b performs analog processing on the detected signal, and since large noise is superimposed on the signal in a low frequency range, there is a problem in that there is a high probability that a measurement error will occur. The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a volume measuring method and an apparatus therefor, which can significantly reduce superimposed noise and improve measurement accuracy.

[Means to solve the problem]

The volume measuring method according to the first claim is a detection output and a volume change obtained by changing the internal pressures of a main tank and a correction tank which are provided in communication with each other using a signal of a predetermined frequency whose phase is inverted every certain interval. An autocorrelation is taken with the signal that drives the means, and the volume of the object to be measured stored in the main tank is measured based on the correlation value. Second! i * Term C This volume measuring device has a first oscillator that oscillates at a predetermined frequency, a second oscillator that oscillates in synchronization with 1/n of the oscillation frequency of this first oscillator,
n A multiplier that multiplies the oscillation outputs of these first and second oscillators, a main tank that houses the object to be measured, a correction tank that is provided in communication with this main tank, and the internal pressure of each of these tanks. a volume changing means for changing the volume by a multiplication signal of the multiplier; an autocorrelation means for calculating a correlation between a detection output of the pressure change detected by the volume changing means and a multiplication signal for driving the volume changing means; and object calculation means for measuring the volume of the object housed in the main tank based on the correlation value obtained by the autocorrelation means.

[Effect]

The volume measuring method in the first claim changes the internal pressure of each of a main tank and a correction tank that are provided in communication with each other by a volume changing means, and drives the volume changing means with a detection output that detects the accompanying pressure change. The correlation is calculated with a drive signal of a predetermined frequency whose phase is inverted every fixed interval. 20 The volume measuring device according to the second claim changes the internal pressure of each of the main tank and the correction tank that are provided in communication with each other, detects the pressure change in both tanks, and uses this detection output and a drive signal to drive the volume changing means. The correlation between the two is determined by autocorrelation means.

【Example】

Hereinafter, the present invention will be explained in detail based on the drawings. 1st
The figure is a circuit diagram showing a first embodiment of the present invention. In FIG. 1, the same or equivalent parts as in FIG. 7 are given the same reference numerals, and redundant explanation will be omitted. In the figure, 50 is a signal ν. The first oscillator 51 outputs the signal sinωt, and the second oscillator 51 outputs the signal sin nωt.
The oscillation frequency of the second oscillator 51 oscillates in synchronization with the oscillation frequency of the first oscillator 50 (where n is an even number). 52 is the first and second
The first multiplier multiplies the oscillation signals of the oscillators 50 and 51, and the speaker 33, which is the volume changing means, is driven by this multiplied signal. 53 is a phase difference detection circuit which receives the output signal 21V from the first multiplier 52. sinωisinnωt and the first microphone 34
Detection signal Alsin (ωt + φ) output from a
detect the phase difference φ between sin(nωt+φ). 5
4 is a first phase matching circuit, and output signal ν of the first multiplier 52; sinωisin n Q)t is matched to the phase of the output of the first microphone 34a by the phase difference φ of the detection output from the phase difference detection circuit 53. 55 is a second multiplier, which outputs the detection output of the first microphone 34a, 8Isin(ω
t+φLsin n ωL and the output V of the first phase combiner circuit 54. sin(ωt] one φ)・sin(nωt ten φ
). 56 is a second phase matching circuit having the same function as the first phase matching circuit 54;
1 output signal sin n ωt as signal sin(nωtφ
) is output as 6 57 is a zero cross detection circuit, which outputs an integration start signal at a zero cross at a certain point in time of the output sin(nωLφ) of the second phase matching circuit 56, and then outputs an integration start signal after a predetermined time (L) of the mth time. An integration end signal is output at the ``ZI'' cross. 58 divides the output from the second multiplier 55 into r r'ov based on the integration start signal and integration end signal from the zero cross detection circuit 57. This first integrator 58 outputs no integration until an integration end signal is received. 59 is an inversion circuit that inverts the output from the first phase matching circuit 54; 60 is a third multiplier, which has the same function as the second multiplier 55; A second integrator 61 has the same function as the first integrator 58, and when an integration end signal is supplied from the zero-cross detection circuit 57, it stops integration and outputs TPovo at V2. Next, the operation will be explained. The first oscillator 50 has a voltage of V as shown in FIG. 2(a). sin
The output signal of ωt is also output from the second oscillator 51 in FIG.
) are outputted to the first multiplier 52, respectively, to produce a multiplication signal ν shown in FIG. 2(C). The speaker 33 is driven by supplying sinωt-sinnωt to the speaker 33. Output of first multiplier 52
V. Based on sinωisinnωt, the detection output from the first microphone 34a ^Isin(ωt+φ)(
For example, the phase difference φ between FIG. sin ω les sin
Correcting the phase of nωt, νosjn(ωL+φ) ・s
in (n ωt+φ) (FIG. 2(e)). This modified signal V. sin(ωt+φ) sin(n
ωt +φ) is the second multiplier 55 and the first microphone 3
It is multiplied by the detection signal A, sin (ωL + φ) from 4a. On the other hand, the output signal sin of the second oscillator 51
nωL is determined by the second phase matching circuit 56 as shown in FIG. 2(f).
It is converted into sin (nωL + φ) as shown in FIG. Then, the second multiplier 55
The first integrator 58 starts integrating the supplied multiplication signal based on the integration start signal from the zero-cross detection circuit 57, and then integrates the supplied multiplication signal based on the integration end signal from the zero-cross detection circuit 57 after a predetermined time (1). Terminate the integration based on Let S be the signal component that should be obtained in the interval from the start of integration to the end of integration, and if stationary noise N is superimposed on it, then in the positive interval shown in Fig. 2(f), S + N
SN is . In the negative interval, 1 is calculated, 1·-2 zN is canted, and only the signal component S is calculated. That is, TPoVo is obtained. On the other hand, the output V(1 sin(ω
L0φ)·sin(nωt+φ) is inverted by an inverting circuit 59 and its output is 1V. sin・(ωttenφ)・sin(
nωt +φ) is the detection signal 1A. from the second microphone 34b. sin(ωt+θ) ・sin(n ωL+φ
) is multiplied by the third multiplier 60, and based on the integral signal from the zero-cross detection circuit 57, the second integrator 61 obtains a γ-ramus LV2 having the same function as the first integrator 58. Thereafter, the divider 40 converts the first integrator 58
The integral value γP0ν0 of the second integrator 61 is the integral 4ar''
"-" to obtain the gas volume v2 of the main tank 30, and then use the subtractor 41 to subtract the gas volume 2 from the total volume Vr of the main tank 30 to calculate the air volume in the main tank 30. The volume VI of the measurement object can be determined.

【Effect of the invention】

As explained, according to the first claim, the internal pressures of the main tank and the correction tank 25, which are provided for transporting the structure, are reversed at a predetermined frequency at regular intervals. This pressure change is detected by a pressure sensor, the detection output of this pressure sensor is correlated with the signal that drives the volume change means, and then the correlation is The volume measurement method measures the volume of the object stored in the main tank based on the value, which greatly reduces superimposed noise.
Effects such as being able to improve measurement accuracy can be obtained. Further, according to the second claim, there is provided a first oscillator that oscillates the structure at a predetermined frequency;
A second oscillator n that oscillates in synchronization with /n, a multiplier that multiplies the oscillation outputs of these first and second oscillators, a main tank that houses the object to be measured, and a main tank that communicates with the main tank. A correction tank provided, a volume change means for changing the internal pressure of each of these tanks by the multiplication signal of the multiplier, a detection output obtained by detecting the pressure change by the volume change means, and the above volume change. an autocorrelation means that calculates a correlation between the multiplication signal that drives the means; Since the volume measuring device is equipped with means for calculating the volume of the measured object, it is possible to improve the S/N for stationary noise without reducing the S/N for random noise, which has the effect of increasing measurement accuracy. can get.

[Brief explanation of drawings]

FIG. 1 is an explanatory circuit diagram showing a first embodiment of the volume measuring method and device according to the present invention, FIG. 2 is a time chart diagram for explaining FIG. 1, and FIG. 3 is the principle of the prior art. An explanatory diagram, FIG. 4 is a characteristic diagram showing how the coefficient K2 of the transfer function changes when the drive frequency of the volume changing means and the volume of the object to be measured in the tank are changed in FIG. 3, and FIG. Principle explanatory diagram for explaining the technology, Figure 6 is the 5th
In the figure, the coefficient K of the transfer function when the driving frequency of the volume changing means and the volume of the object to be measured in the main tank are changed.
, and FIG. 7 is a diagram illustrating a specific system of the prior art. : Correction tank 30: Main tank 31 33: Sveaker (volume change means) 50, 51: Oscillator 52 53; Phase difference detection circuit 54, 56: Phase matching circuit 55: Second multiplier 57:
Zero cross detection circuit 582 First integrator 60: Third multiplier 61: Second integrator: First multiplier (Fig. 5 Voct) Fig. 6

Claims (2)

[Claims] (1) The internal pressure of each of the main tank and correction tank, which are provided in communication with each other, is changed using a volume changing means driven by a signal of a predetermined frequency whose phase is reversed at regular intervals, and this pressure change is converted into pressure. A volume that is detected by a sensor, correlates the detected output of the pressure sensor with a signal that drives the volume changing means, and then measures the volume of the object to be measured stored in the main tank based on the correlation value. Measuring method. (2) a first oscillator that oscillates at a predetermined frequency;
The second oscillator oscillates in synchronization with 1/n of the oscillation frequency of the oscillator.
oscillator, a multiplier that multiplies the oscillation outputs of these first and second oscillators, a main tank that houses the object to be measured, a correction tank that is provided in communication with this main tank, and a A correlation is calculated between a volume changing means that changes each internal pressure by a multiplied signal of the multiplier, a detection output obtained by detecting a pressure change by this volume changing means, and a multiplied signal that drives the volume changing means. and an object volume calculation means for measuring the volume of the object stored in the main tank based on the correlation value obtained by the autocorrelation means. .