JPH0348124A - Method and apparatus for measuring volume - Google Patents

Abstract

PURPOSE:To enhance measuring accuracy by volumetrically changing the internal pressures of main and auxiliary tanks communicating each other at predetermined frequency and measuring the volume of the object to be measured in the main tank on the basis of the correlation value of the detection value of the detection output of a pressure sensor and volume change driving frequency. CONSTITUTION:An oscillator 50 drives a speaker 33 under voltage V0sinomegat and the phase difference phi with the output A1sin(omega+phi) of a microphone 34a is detected by a phase difference detection circuit 51 to output voltage V0sin(omega+phi). When this output is multiplied by A1sin(omega+phi) by a multiplier 53, an integrator 55 starts integration by the first zero cross detection circuit 54 and gammaP0V0 is obtained after a time (t); while -V0sin(wt+phi) is obtained by a reversal circuit 56 and multiplied by the detection value -A2sin(wt+theta) of a microphone 34b by a multiplier 57 and the obtained value is operated on the basis of the output of the second zero cross detection circuit 58 by an integrating circuit 59 to obtain gammaP0V0/V2. Subsequently, V2/V1 is outputted from a divider 40. By this constitution, digital signal processing can be performed and an S/N ratio can be enhanced and measuring accuracy can be also enhanced.

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 device for measuring volume of this type, there is one shown in Japanese Patent Application No. 1-278'l)8 as a prior art, which will be explained based on FIGS. 5 to 9. do. First, in FIG. 5, to explain the principle, 3° is an irregularly shaped main tank that stores, for example, liquid, nine particles of powder, irregularly shaped objects, etc., and a connecting pipe 32 is connected to this main tank 30. A correction tank 31 having a smaller volume than the main tank 30 is connected via the main tank 30. 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), and a small diameter ventilation hole 35 is provided in the upper part of the correction tank 31, for example. A volume changing means (mechanism) 33 such as a piston, a speaker shape (hereinafter referred to as a speaker), etc. is provided, and the volume inside the correction tank 31 can be changed by the operation of this volume changing mechanism 33. 0 or more is the configuration of this embodiment, and the measurement principle using this configuration will be explained next. Measurement principle (1) Consider a connected tank system as shown in Figure 5. This is constructed by connecting a correction tank 31 with a small volume (1) and a main tank 30 with a large volume (2). The tanks 31, 30 are connected by pipes 32 with a flow resistance r, and the vents 35 of the tanks 30 have a flow resistance r□. Let T 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 tank 31. Piston, diaphragm, bellows in tank 31. Attaching a volume change mechanism 33 using a speaker shape, etc.
Let v(t) be the amount of volume change actually generated by this volume change mechanism 33. When the tank 30.31 is a rigid body, when the internal pressure of the tank 30.31 is increased or decreased, the tank 30.31 is a rigid body. Since 31 is not distorted, volume change due to piston, diaphragm, bellows, etc.■. (1) and the amount of volume change v(L) that actually occurs are equal. If the tank 30 is flexible, the tank 30 will be distorted when the internal pressure of the tank 30.31 is increased or decreased, and therefore v(t) will change by an amount corresponding to the volume change due to expansion or contraction. When v(t)-0, the absolute pressure and temperature of the gas in the tank 31 are Pg and Tt+nl+, respectively.
Further, the absolute pressure and temperature of the gas in the tank 30 are expressed as Por Tt and nz, respectively. If the measurement environment does not change significantly, the tank 30 is
．． Since gas flows inside and outside the tank 31, the absolute pressure P0 inside the tank 31.30 is equal to the outside pressure, and its change is very slow and equal to the outside pressure. When v(t)≠0, the pressure and temperature also change according to the situation of the volume change means 33, and in the tank 31, the pressure is P, +ΔP+(t). The temperature changes as T, +ΔT+(t), and the number of moles changes as n, −Δn+z(t). In the tank 30, the pressure is P0+ΔPg(t). The temperature changes as T2+ΔT t (t) and the number of moles changes as n2+Δn+z(t)−Δnz(t). Δn+g(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 35.
is the number of moles of air that leaks to the outside through the We now make the following assumptions about this system. 1) The gas in tanks 30 and 31 is an ideal gas. 2) v(t) < (V+, V!) 3) The heat capacity of the tank 30 is large, and the pressure change ΔP is (1
) The change in temperature inside the tank due to this change is very slow compared to the speed of change in volume change v(t) and can be ignored. 4) The rate of change of the volume change amount v(L) 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, a hollow portion, in the tank 30. The above assumptions are not a major constraint. ΔP+(t), ΔPg(t
). ΔT I(t), ΔT2(t), Δn+z(
t), Δnz(t) is originally expressed by a nonlinear equation, but based on assumption 2), the magnitude is P(1, TI, TI
, n+ , are very small with respect to nz and can therefore be approximated by a linear equation. Tank 30.31 in static condition
The relationship between the pressure, temperature, and number of moles of the gas inside is expressed by the following algebraic equation. PoVl = 11RT++ PoVz=nzRT
z (la) Also assumptions 1), 3), 4), 5
), the pressure of the gas in the tank 30.31 in the dynamic state. The relationship between temperature and number of moles is expressed by the following linear ordinary differential equation. (1b) ΔP! (t) = RT. v2 Δn+z(t) - Anal Δnz(t) Vz (lc) dΔnz(t) = t 1hdan' Δnt(0) =O 2 (le) ΔT, (0)=0 (1f) Flow resistance r, above formula In , r 1 r rz is the length of the pipe 32! and the diameter d, it can be obtained from the following empirical formula. ΔV is a tank-specific constant determined from the material, shape, volume, etc. of the tank, and Δv(t) is the volume change amount due to expansion or contraction of the tank 3° due to a change in the volume change means 330 volume change 1ye(t). be. Applying Laplace transform to equations (1a) to (11), input v(
The transfer function from t) to the output ΔF+(t) is determined as follows. ΔPI(s) P. v(s) V++Vt+ΔV ””””’ν+
゛Vz)=T (2a) This formula is calculated when length 2 is 50 to 650 [mml, diameter d is 2
．． It was experimentally determined using an aluminum pipe of 0 to 9.0 mml. Also, the volume change amount v(t) is expressed as follows: v (t) = vo(t )−Δv(t)
(lh) ΔV ΔV (t) =v, + v2+Δv V・(t)
(li) Coefficient rtVt/RTz +r+Vz/R
Tz, r+V+/RT++r+Vz/RT+ is the time constant of pressure change. For example, rzVz/RTz is a time constant of pressure attenuation when gas at the absolute temperature T2 in the hollow portion of the tank 30 flows out of the tank 30 through the vent hole 35 having a flow resistance r2. To the correction factor! (S+r, rl
+Vl+V varies depending on the volume v2 of the main tank 30, but kz(S+r++rt+V
In the frequency characteristic of ++Vz), by selecting an appropriate frequency, for example, the frequency of 4XlO-' to 10-')lz in section A, it can be approximately regarded as a constant. ri <<< rz (rz is the flow resistance of the air vent 35) and the thermal time constant τ and rz (Si, +Min Vz)
/ If RTz has a similar value, the following angular frequencies exist. (2c) Under this condition, the correction coefficient kg(S+r++rz+V+
+Vz) is approximated as follows. z(iω, rl+ rz+ Vt+ Vz)
w 1/ to z(iω+ r++ rz+ VI+ Vz
)=O(2d) Therefore, when the condition of equation (2c) is satisfied, the transfer function from the input v(t) to the output Δp+(t) is rPoV,+V. +ΔV). Note that the volume change mechanism 33 has an angular frequency ω. When driven sinusoidally by RT, (if − is satisfied, the pipe r+V,
This is considered to be equivalent to a state in which 2 π 32 is occluded. In other words, it becomes. 111L-"L-1, (s, r,, v,'
) (2gv(s) ” ν2′+ΔV. Consider the following angular frequency ω. It is sufficient. (2) Next, consider a single tank system as shown in Figure 7. This is the fifth This corresponds to a case in which the cross-sectional area of the pipe 32 connecting the tanks 31 and 30 in the figure is made very large, and the value of the flow resistance r of the pipe 32 becomes very small. From v(t) in the figure to ΔPg(
The transfer function up to t) is based on the formula %v,' =v, +v, and is as follows, for example, 1O-3Hz shown in A in the frequency characteristics of Fig. 7.
This is the frequency above. By setting such a frequency, the correction coefficient +(iω, r2.V,') can be approximated as follows. k, (iω, rz, Vl')l'=1°k+ (
iω, rt, V3') ”;0 (
2i) At this time, the transfer function is T P 6/(V2'+Δ
V). Next, a specific example to which the above principle is applied will be explained based on FIG. 6. In FIG. 6, 33 is a speaker (volume changing means), and the main tank 30 and the correction tank 31 are partitioned by this body HI changing means. Further, a condenser microphone 34b is provided on the main tank 30 side, and a dynamic microphone 34a having lower sensitivity than the first microphone is provided on the correction tank 31 side. Further, the speaker 33 has a predetermined angular frequency ω. Drive with. In this case, the single tank system theory shown in FIG. 7 applies. Here, the volume of the correction tank 31 is ■3, and the volume of the main tank 30 is
The volume of the gas in the tank is 2, 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 2. The pressure change ΔP r (t) in the correction tank 31 is expressed by the formula (2h
), then ΔP+ (t) −7” l kl l vostn
(ωHt+φl)V, 1ΔV O = 1− v+sfn ω11t (3a
)vI+ΔV, and the main tank 30 is a rigid body, that is, ΔV
−Q, and when the angular frequency ω8 satisfies equation (2h), Δ
P r (t) is as follows. ΔP+(t) = r' l k, l vo
sin(ω, 1φ2)V. When measuring the amplitude of ΔP+'(t) for 31 positive tanks,
Here, when the volume change means 33 is driven so that the pressure change becomes a sine wave, the amplitude value of the pressure change in the correction tank 31 is defined as AI, and the amplitude value of the pressure change in the main tank 30 is defined as A2. The ratio of values is expressed by equations (3a) and (3b
) From this, v, = lkLlv, -Δ■, and the volume ■, of the liquid stored in the main tank 30 is VL
-Vt Vz =Vt [1*, I V+-Δ■
] To be a spider. Next, specific prior art based on the above principle will be explained. In FIG. 9, a speaker (volume changing means) 33 is placed between the correction tank 31 and the main tank 30, and
In order to equalize the static pressure in the main tank 30 and correction tank 31, both tanks 30 and 31 are connected by a thin pipe 47 having an orifice 47a, so that the main tank 30 and 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. is very large compared to the slow change in atmospheric pressure, and the fluid resistance in the vent hole 35 is very large, so that the vent hole 35 acts as if it were blocked while the speaker 33 is being driven. The atmospheric pressure inside tank 30.31 is equal to tank 30.31. 31 It is completely unaffected by the difference in air pressure inside and outside. 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 compensation tank 31 due to the speaker 33, and the time constant of the pressure change in the atmospheric pressure outside the tank 30, 31, that is, the absolute pressure. This is based on the assumption that the speaker 33 is sufficiently smaller than v6sinω. When a volume change as shown by a function of L is given to the correction tank 31 and the main tank 30, that is, the principle of a single tank system is applied to both the main tank 30 and the correction tank 31. Therefore, V(t)=vosinωot (4a
), the pressure change ΔP+(t) of the correction tank 31 is (4b), and the angular frequency ω in the above equation. If satisfies (2h), then ΔPg(t) is as follows. Here, in the above equation, the main tank 30 is a rigid body and, like the correction tank 31, has an angular frequency ω. If satisfies formula (2h), ΔP2(t) = 7 fl-v, sin ωet
(4c) '2. That is, the volume of each of the main tank 30 and the correction tank 31 is set to V, sinω by the speaker 33. L is the angular frequency ω. When the pressure is varied regularly in the main tank 30 and the correction tank 31, the pressure fluctuations in the main tank 30 and the correction tank 31 are compensated by the dynamic microphone 34a1 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 of 1 and a center angular frequency ω. The angular frequency ω is set by the bandpass filter 37b. signal components are extracted, and then the second
is supplied to the amplitude detector 39b, where TPovo- is detected and output. In addition, the dynamic microphone 3 that detected the pressure fluctuation of the correction tank 2 31
The output of 4a has a gain ■1 and a center angular frequency ω. The angular frequency ω is set by the bandpass filter 37a. Only the signal component of is extracted by multiplying by 70, and then the amplitude detector 3
9a and γP. ν0 is detected and output. Thereafter, the output rPoVo from the first amplitude detector 39a is transmitted to the second amplitude detector 39a.
The output from b is divided by Povo by 2 by the divider 40 to calculate the volume 2 of the hollow part of the main tank 30, and the calculation result is supplied to the subtracter 41 and the set main tank subtracted from the total volume vT of 30,
As a result, the volume of the liquid contained in the main tank 30 is calculated.

[Problem to be solved by the invention]

However, in such conventional volume measurement methods and devices, the output amplitude value of the bandpass filters 36, 37 and 36, 37, which remove noise from the electrical signal from the speaker 33, is Amplitude detector 38 to detect. Microphone 34a by 39 etc.
, 34b was configured to perform analog processing on the detected signal, so there was a problem that it was difficult to integrate the circuit, and since a large amount of noise was superimposed on the signal in the low frequency range,
The capacitance of the capacitors constituting the bandpass filters 36 and 37 increases, and the circuit scale increases. Therefore, there was a problem that if the circuit was kept compact, it could not follow noise. The present invention has been made to solve the above-mentioned problems, and aims to provide a volume measuring method and device that facilitates circuit integration and can track noise. .

[Means to solve the problem]

The volume measuring method according to the first claim is characterized in that the volume changing means is driven by a detection output obtained by changing the internal pressures of a main tank and a correction tank that are connected to each other at a predetermined frequency using a volume changing means. Take the autocorrelation with the signal
The volume of the object to be measured stored in the main tank is measured based on the correlation value. The volume measuring device according to the second aspect includes a volume changing means for changing the internal pressure of each of a main tank and a correction tank which are provided in communication with each other at a predetermined frequency, and a detection output for detecting a pressure change by the volume changing means. an autocorrelation means for calculating a correlation between a drive signal of a predetermined frequency that drives the volume change means, and an object to be measured stored in the main tank based on the correlation value obtained by the autocorrelation means. It is composed of a measuring object calculating means for measuring the volume.

[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 with the drive signal is calculated. The volume measuring device according to the second aspect changes the internal pressures of the main tank and the correction tank, which are provided in communication with each other, and detects pressure changes in both tanks. 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
FIG. 1 is a circuit diagram showing a first embodiment of the present invention. In FIG. 1, the same or equivalent components as in FIG. 9 are given the same reference numerals and redundant explanation will be omitted. In the figure, 50 is a signal V. An oscillator that outputs sinωt drives a speaker 33, which is a volume changing means. 51 is a phase difference detection circuit, which receives the output signal V from the oscillator 50.
, sinωt and the detection signal A, sin (ωt+φ) output from the first microphone 34a.
Detect. A phase matching circuit 52 matches the output signal V, sin ωt of the oscillator 50 to the phase difference φ of the detection output from the phase difference detection circuit 51, and the phase of the output of the first microphone 34a. 53 is a first multiplier that multiplies the detection output ^, sin (ωt+φ) of the first microphone 34a and the output Vos4n (ωt+φ) of the phase difference matching circuit 52. Reference numeral 54 denotes a first zero cross detection circuit, which outputs an integration start signal at a certain zero cross of the output Al5in (ωL+φ) of the first microphone 34a, and outputs an integration end signal at a zero cross after the nth predetermined time (1). Output. 55 integrates the output from the first multiplier 53 based on the integration start signal and integration end signal from the first zero cross detection circuit 54 to obtain rPoν. The first integrator 55 outputs no integral output until an integral end signal is received. 56 is an inversion circuit that inverts the output from the phase matching circuit 52, and 57 is a second multiplier, which has the same function as the first multiplier 53. Reference numeral 58 denotes a second zero-cross detection circuit, which has the same function as the first zero-cross detection circuit 54. 59 is the second
This integrator has the same function as the first integrator 55, and the second integrator 55 has the same function as the first integrator 55.
The operation of integrating when the integration end signal is supplied from the zero cross detection circuit 54 will be described next. The oscillator 50 supplies an output signal represented by V6sinωt to the speaker power 33 to drive the speaker 33. Output V of oscillator 50. The detection output from the first microphone 34a is A+sin (ωt+
The phase difference φ between the output V and
t+φ). This modified signal ν. 5in(
ωt+φ) is the first multiplier 53 and the first microphone 3
The detection signal Al5in (ωt+φ) from 4a is combined with ^1sin (ωt+φ)・vosin(ω

[
+φ) is obtained. Then, it is supplied to the first integrator 55 to start integration based on the integration start signal from the first zero cross detection circuit 54, and after a predetermined time (1), an integration end signal is sent from the first zero cross detection circuit 54. The integration is finished based on 2, and the integral value during that time is S double, 5in (ωt
+φ)・ν. 5in(ωt+φ) dt, that is, T
Obtain P6V6. On the other hand, the output V of the phase matching circuit 52 is 5 inches (ωt1φ)
is inverted by the inverting circuit 56 and its output −v6sin(ω
t+φ) is the detection signal from the second microphone 34b -
A+5in(ωt+-θ) is multiplied by the second multiplier 57 to give Azsin (ωt+θ) V6Sln(
OJt 1φ) is obtained. Then, it is supplied to the second integrator 59 and starts integration based on the integration start signal from the second zero cross detection circuit 58, and then ends the integration based on the integration end signal after a predetermined time (1), 5',, A2
5in ((+) t+θ)・ν, sir*(ωt
+φ)dt Next, a second embodiment shown in FIG. 2 will be described. In the first embodiment described above, the case where conditions such as the shape and size of the tank are arbitrarily given is explained. 1. The second embodiment shows a case where conditions such as the shape and size of the tank are known in advance. Once the shape and size of the tank are determined, the phase difference can be determined experimentally, and by setting the determined value in the phase difference setting circuit 60, it can be used in place of the phase difference detection circuit. Next, a third embodiment shown in FIG. 3 will be described. In the figure, 61 is a signal ν. sjnω,t, this first oscillator 61 outputs an output signal V 6
The speaker 33 is driven by S inωLt, and the overall pressure of the main tank 30 and the correction tank 31 is varied. 62 is a second oscillator that outputs the signal V6sinωHt, and this second oscillator 62 outputs the output signal Vosinω
The speaker 33 is driven with Ht to vary the pressure in the correction tank 31. 63 is a first changeover switch that supplies either the output from the first oscillator 6I or the output from the second oscillator 62 to the speaker 33, and this first changeover switch 63 is connected at predetermined time intervals by a timer 64. Switch. 65 is a microphone, the first oscillator 61 and the second oscillator
The pressure fluctuation inside the tank when the speaker 33 is driven by the output of each oscillator 62 is detected. 66 is a signal A+5in(ωi+φ
) and a signal V based on the oscillation output of the second oscillator 62 from the phase matching circuit 52. A correction tank multiplier 67 outputs the product of Al5in(ω, L+φ) and the phase matching circuit 5 which outputs Al5in(ωi+φ) from the microphone 65 when the changeover switch 63 is in the state shown by the dotted line in FIG.
The signal v based on the oscillation output of the first oscillator 61 from 2
A multiplier for the entire tank outputs the product of 0sin(ω, t+φ), a second switch 69 switches the output from the phase matching circuit 52 in conjunction with the first switch 63, and outputs the output, and a correction switch 69 Output A+5 from tank multiplier 66
in(ωHt+φ) This is a correction tank integrator that integrates XVosin(ωHt+φ) based on the integration start signal and integration end signal from the first zero cross detection circuit 54. Then the output will stop. Furthermore, both integrators 69 and 70 have a latch circuit that latches the integrated value until the next integration start signal arrives. Reference numeral 70 denotes an integrator for the whole tank which has almost the same function as the integrator 69 for the correction tank. FIG. 4 shows a fourth embodiment of the present invention.
In this embodiment, the oscillator 50 of the first embodiment is replaced with an M-series signal generation circuit 71, and a fourth embodiment equipped with this M-series signal ordering circuit will be described below. The M-series signal generation circuit 71 has a three-stage shift register and an exclusive OR circuit driven by, for example, a 10 Hz clock signal, and generates a signal (FIG. 5(a)) for driving the speaker 33 ON and OFF. Output. 72 is a first phase matching circuit that adjusts the phase of the M-sequence signal outputted from the M-sequence signal generation circuit 71 so that the output of the first integrating circuit 77, which will be described later, is maximized and outputs it (the fifth Figure ■)). A second phase matching circuit 73 has the same function as the first phase matching circuit 72, and adjusts and outputs the phase of the M-sequence signal so that the output of a second integrating circuit 78, which will be described later, is maximized. A first multiplier 74 multiplies the detection signal from the first microphone 34a and the output signal from the first phase matching circuit 72 and outputs the result (FIG. 5(d)). That is, when the output of the first phase matching circuit 72 is at H level, the output of the first microphone 34a is multiplied by +1, and when it is at L level, it is multiplied by -1. 75 is a second multiplier, which outputs the detection signal from the second microphone 34b and the first phase matching circuit 7 via an inversion circuit 76.
The first multiplier 74 multiplies the output signal from the second multiplier 2 with the output signal from the first multiplier 74 and outputs the result. 77 is a first integrating circuit having a capacitor C and a resistor R, which integrates the output from the first multiplier 74 and outputs it (FIG. 5(e)). 78 is also the same as the first integrating circuit 77. 79 is an amplifier with a gain of 1. Next, the operation of the above configuration will be explained. Now, if the frequency of the signal output from the M-sequence signal generation circuit 71 (FIG. 5(a)) is set to a low frequency, the signal detected by the first microphone 34a is shown in FIG. 5(C). The waveform has a predetermined amount of phase shift with respect to the waveform of (a), and the waveform is in a differential form and is output. In addition, the signal output from the M-sequence signal generation circuit 71 (see FIG.
In a)), the phase shift amount is adjusted by the first phase matching circuit 72 so that the output of the first integrating circuit 77 is maximized (FIG. 5(b)) and is supplied to the L first multiplier 74, Figure 5(d)
The waveform shown in is output. The output of the first multiplier 74 is integrated and averaged by the first integration circuit 77, and is output as an integrated signal γm without noise (FIG. 5(e)). On the other hand, the detection output of the second microphone 74b is also subjected to signal processing as described above, and as a result is sent to the second integrating circuit. Therefore, when the signal is amplified by the amplifier 79 with a gain of 1, the output becomes equal to the volume of the cavity of the main tank 30. In each of the above-mentioned embodiments, the same components are given the same reference numerals and the explanation thereof will be omitted. [Effects of the Invention] As explained above, according to the present invention, the internal pressures of the main tank and the correction tank, which are provided in communication with each other, are changed using volume changing means driven at a predetermined frequency. , 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, based on the correlation value, the measurement target stored in the main tank is Since the volume measurement method measures the volume of the sample, it is possible to perform digital signal processing, which makes it possible to handle it with software, as well as to reduce the circuit size and improve the S/N, thereby increasing measurement accuracy. You can get effects such as:

[Brief explanation of drawings]

FIG. 1 is a circuit block explanatory diagram showing a first embodiment of the volume measuring method and device according to the present invention, FIG. 2 is a circuit block explanatory diagram showing a second embodiment of the present invention, and FIG. FIG. 4 is a circuit block explanatory diagram showing a third embodiment of the invention, FIG. 4 is a circuit block explanatory diagram showing a fourth embodiment of the invention, FIG. 5 is a time chart diagram for explaining FIG.
The figure is an explanatory diagram of the principle of the prior art, and Figure 7 is a characteristic showing a change state of 2 in the coefficient of the transfer function when the driving frequency of the volume changing means and the volume of the object to be measured in the tank are changed in Figure 6. Figure 8 is a principle explanatory diagram for explaining the prior art, and Figure 9 shows the transfer function when the drive frequency of the volume changing means and the volume of the object to be measured in the main tank are changed in Figure 8. FIG. 10 is a characteristic diagram showing a state where the coefficient changes by 1, and is a diagram illustrating a specific system of the prior art. 30: Main tank 31: Correction tank 33: Speaker (volume change means) 50: Oscillator 51: Phase difference detection circuit 52: Phase matching circuit 53: First multiplier 54: First zero cross detection circuit 55: First integration Multiplier 57: Second multiplier 58:
Second zero cross detector 59: second integrator

Claims (2)

[Claims] (1) Change the internal pressure of each of the main tank and correction tank, which are provided in communication, using volume change means driven at a predetermined frequency, detect this pressure change with a pressure sensor, and A volume measuring method in which a correlation is established between a detection output and a signal for driving the volume changing means, and then the volume of an object to be measured stored in the main tank is measured based on the correlation value. (2) A main tank for storing the object to be measured, a correction tank provided in communication with the main tank, a volume changing means for changing the internal pressure of each of these tanks at a predetermined frequency, and this volume changing means autocorrelation means for calculating a correlation between a detection output obtained by detecting a pressure change by and a drive signal of a predetermined frequency for driving the volume change means;
A volume measuring device comprising: object volume calculation means for measuring the volume of the object housed in the main tank based on the correlation value obtained by the autocorrelation means.