JPS59147271A - Correlation type speed measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a simple and compact equipment by providing a heating element outside a pipeline and thermosensitive elements for detecting a fluid temperature at two points downstream to determine the fluid velocity continuously using the maximum value of a cross-correlation function of a detection signal. CONSTITUTION:A heating element 52 is provided outside a pipeline close to the inner surface thereof and a pulselike current is applied thereto from a power surface 59 to heat an internal fluid. The fluid temperature is detected with thermosensitive elements 54A and 54B provided on the downstream of a passage and the maximum value of the cross-correlation function of these detection signals is determined with an arithmetic unit 60 to determine the fluid speed continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to an analyzer or a similar device. The present invention relates to a device that continuously measures the velocity of a relatively small amount of fluid used in equipment or various plant equipment, particularly a relatively small amount of fluid flowing in a narrow pipe. Since the flow rate can be calculated by multiplying the speed by the cross-sectional area of the pipe constituting the flow path, the present invention also belongs to the technical field of flow measurement devices.

(Prior art and its problems) As an example of this type of device, a relatively small flow rate (several ml/
The conventional technology and its problems will be specifically explained regarding a flow rate or flow rate measuring device in a liquid chromatograph device that is required to accurately measure the liquid velocity of the culm.

FIG. 1 shows the basic configuration of a liquid chromatograph apparatus. As can be seen from the figure, the liquid chromatograph apparatus basically includes a liquid sending pump 11, a measurement liquid injection valve 2, a separation column 3, a detector 4, and a carrier liquid reservoir 5. Usually, a plunger-type metering pump is used as the liquid pump 1, and the flow t is adjusted and set by the stroke length of the plunger and the frequency of reciprocating motion.

In such a configuration, a fixed amount of the liquid to be measured (normally 50-100 μl) is injected through the liquid to be measured injection valve 2, which is separated into each component while passing through the separation column 3, and each component reaches the detector 4 with a time delay specific to the component substance. , detected. In other words, in liquid chromatography devices, substances are identified by taking advantage of the fact that the time delay between when the liquid to be measured is injected into the carrier flow and when it is separated and detected differs depending on the component, so the flow rate of the liquid to be measured is It is important to accurately understand the flow rate (or flow rate, hereinafter not specified) accurately.

However, as will be explained later, there is currently no suitable flow rate measuring device, so the flow rate adjusted and set by the liquid feed pump 1 during some form of flow rate calibration prior to actual measurement does not change during actual measurement. In reality, component analysis of the liquid to be measured is performed based on this assumption. However, in reality, it is quite possible that the flow rate adjusted and set in advance is different from that at the time of actual measurement, resulting in an inaccurate analysis. A flow rate measuring device is needed. The reason why it is thought that the flow velocity at the time of actual measurement may be different from that at the time of calibration is as follows.

In general, if the plunger-type metering pump used in the liquid transfer pump 1 is operating normally, it is possible to transfer liquid with a flow rate error of 1 to 2% or less. However, inside the pipe 100
Since the pressure is as high as ~200 kg/cm2, if there are incomplete seals in the plunger part of the liquid pump 1, piping connections, etc., air bubbles or coatings may occur when the carrier liquid is insufficiently degassed. Due to reasons such as the force of the gas mixed in when injecting the measurement liquid, and the inability to separate from the separation column A3 (which is filled with fine particles of about 10 μm),
In many cases, the quantitative performance of the liquid transfer pump 1 is impaired. In FIG. 1, the flow rate measuring device 6 is shown in parentheses, but
This shows a desirable installation location for the flow rate measuring device, which is not actually installed.

Figure 2 is an example of a reactive liquid chromatography device that attempts to identify the original components by combining separated component substances with specific reagents and detecting the resulting substance.The same symbols as in Figure 1 are the same. The parts are shown. This is a separate reaction liquid pump 7 for the component substances separated in the separation column 3.
, a reagent that causes a chemical reaction with a specific component is sucked from the reaction liquid reservoir 8 and pressure-injected through the three-way valve 9 .While passing through the reaction coil 10 , the two react and turn into an easily detectable substance, which is detected by the detector 4 . It is something to do. If necessary to accelerate the reaction, heating is performed in the reactor 11. Examples of devices that perform chemical reactions within a liquid chromatograph include those used to analyze amino acids, amines, and the like. In such cases, conventionally, there was no suitable small flow rate measuring device 6 that could be connected directly to the middle of the pipe, so it was easy to overfill the reagent, which was not only uneconomical but also caused the liquid to be measured to Detection sensitivity was adversely affected due to dilution.

As mentioned above, there is no flow rate measuring device that is considered the most desirable in this field, so here we will give an example of a currently used flow rate measuring device despite its drawbacks and explain the problems that need to be solved.

FIG. 3 is a diagram showing the principle of a siphon counter.

In this case, a droplet 32 dripping from the end 31 of the flow path is received by a siphon 33 with a known volume, and when the liquid level 34 reaches a certain level, the liquid in the container flows out to the outside due to the principle of the siphon. The signal is output by means that do not. The advantage of this device is that since it directly integrates the volume of the outflowing liquid, it can be measured regardless of the type of liquid, and cumulative errors are less likely to occur. However, the disadvantages are that it can only output signals intermittently, and it is not possible to connect it before the separation column 3 because it requires high pressure to be applied to the pipe line. When the flow returns to a continuous flow, the separated components are remixed and there is no point in passing it through the separation column, so in the end it can only be connected to the end of the flow path.If you want to improve accuracy, you have to suppress the evaporation of the liquid. In addition, the detection unit including the body becomes larger.

FIG. 4 is a diagram showing the principle of a drop counter.

This measures the droplet 42 dripping from the end 41 of the flow path using an optical means such as a combination of a light emitting element 43 and a light receiving element 44. This drop counter can output a flow rate signal almost continuously, but the drawback is that the droplet size changes depending on the physical characteristics of the liquid used, such as viscosity, and the influence of temperature, so it can be used for various types of liquids. It is difficult to correct this in an analyzer that uses a light source, and using a liquid that absorbs the wavelength of the light source causes errors, which limits the type of liquid that can be used. , and that it can only be installed at the end of the flow path.

In addition to the above, in a bubble flow meter (not shown), bubbles are introduced into a flow path, and the flow velocity is calculated by measuring the time it takes for the bubbles to flow through a certain section. This is because if connected in front of the separation column, air bubbles will accumulate in the separation column and inhibit its function, and if connected in front of the detector, most current detectors that use optical principles will not function properly. Generally, it can only be installed at the end of the flow path. To measure the flow rate in the middle of the flow path, a branch path must be installed to avoid affecting the measurement.
This method not only does not directly measure the flow rate, but also has the drawback of complicating the device.

In addition, as a correlation type flow rate measuring device, for example, one of the applicants has applied
514 and published in Japanese Unexamined Patent Publication No. 57-125319 are known, but both of these assume a liquid mixed with powder, that is, two phases of solid and liquid, and collision with the pipe wall or powder The detection signal is the electric charge of the powder that is charged due to the collision between bodies, or the change in capacitance based on fluctuations in the powder concentration is used as the detection signal.

However, injecting powder into the flow rate in order to obtain fluctuation signals is not allowed in liquid chromatography devices, and it is often difficult to apply conventionally devised correlation type flow rate measurement devices. It is.

Furthermore, even in a device (not shown) that measures flow velocity using the Doppler effect of ultrasound, it is necessary to mix fine particles to give fluctuations, making it difficult to use in liquid chromatography devices and the like.

Furthermore, there is also a known method of determining the flow velocity from the difference in the round-trip propagation time of the ultrasonic waves that pass between a transmitter and a receiver that are placed oppositely around the pipe constituting the flow path. In addition to being dependent on humidity, there are disadvantages in that the measurement error is theoretically large for small-diameter flow channels, making it difficult to apply, and the detection results fluctuate due to mechanical vibrations in the conduit.

(Objective of the Invention) The present invention eliminates the above-mentioned drawbacks of conventional devices and makes it possible to remove the liquid to be measured from the flow path and to remove special structures that cause pressure loss and turbulence that interfere with analysis. A smaller, lighter flow velocity measurement device that can be directly connected anywhere in the flow path without having to be installed inside the flow path, the measurement results are not affected by the type of fluid, can transmit continuous signals, is easy to correct, and is The purpose is to provide.

(Summary of the Invention) In the present invention, a correlation type speed measuring device calculates the speed of a measured object using the maximum point of correlation between two signals from the measured object detected at two locations separated by a predetermined distance. In this paper, we focused on obtaining these signals as a result of artificially applied pulse-like thermal fluctuations, and specifically,
One of the signals is a pulsed current waveform of a heating means provided in a tube forming a flow path of the object to be measured, or a detection signal of the temperature of the object to be measured downstream of the heating means, which is heated by the heating means. , and the other one is a signal from a temperature detection means of the object to be measured downstream of the detection means, and these heating means and detection means are not provided inside the valve pipe body, but are placed on the outer surface of the pipe body, for example, respectively. Since it was constructed by winding resistance wires for heating and temperature measurement, the object of the present invention was achieved without interfering with the functions that the object to be measured should originally perform.

(Embodiment of the invention) FIG. 5 shows an embodiment of the invention. A circular tube body 51 made of a metal material such as stainless steel or copper is connected to a conduit 57 through which the object to be measured flows through a backing 56 by joints 55 provided at both ends to prevent liquid leakage. It has been concluded.

A heating element ratio 51A1, a first heat-sensitive element seat 51B, and a second heat-sensitive element dust 510 separated from this by a certain distance t are formed in the tube body 51 in order from the upstream left side in the drawing, and are heated. The element 52, the first heat sensitive element 54A, and the second heat sensitive element 54B are seated. The heating element 52 can be constructed by, for example, winding a nichrome wire around the heating element dust 51A via a heat-resistant insulator, or two heat-sensitive elements 54A,
54B can be constructed by winding insulated wires of nickel, copper, etc. around the first heat-sensitive element dust 51B and the second heat-sensitive element dust 510, respectively. The first heat insulating phase 53A and the second heat insulating material 53B are made of, for example, foamed plastic to avoid unnecessary heat radiation from the pipes.

In such a configuration, when the heating element 52 is made to generate heat by a pulsed current such as a rectangular wave from the power supply 59 through the wiring 58, the temperature of the liquid passing under the heating element dust 51A increases due to the conduction heat. Heating element 52 and heating element dust 51
Thermal properties of A, liquid flow rate, double-seated thermal elements 54A and 54
After a time delay determined by the distance between B and the thermal characteristics of both heat-sensitive element seats 51A and 51B, the two heat-sensitive elements 54A and 5
4B successively detects the temperature change and sends it to the arithmetic unit 60 through the first signal line 61A and second signal line 61B, respectively. Now, when the pipe line is sufficiently thin and the flow can be regarded as a plug flow (also called a piston flow), and the heat radiation from the pipe body 51 can be ignored, the flow shown in Fig. 6 ('Z
), (b), the temperature φA (t) detected by the first heat sensitive element 54A and the humidity φe (t) detected by the second heat sensitive element 54B are separated by a time τ. Since the waveforms have almost the same delay, they can be related by equation (1).

φB(t) = φA (−τ.) (1) On the other hand, the delay time τ. and the flow velocity ■ is v=l/τ.

The relationship holds true. Next, the cross-correlation function of φA(1) and φe (t) is by definition, where T is the time width in which the temperature signal exists. Substituting equation (1) into equation (2), φA (−
τ0+τ) dt (3), but the right-hand side of equation (3) is in the form of an autocorrelation function of φA (t), which is τ2τ. The function has a maximum at , and has the form shown in Figure 7. Therefore, if we find τ0 where the cross-correlation function φAS(τ) is maximum, the flow velocity is v=Z/τ. It can be found by

Stainless steel pipes used in liquid chromatography equipment have an inner diameter of 0.5 mm or less and a thickness of 0.5 mm. , 5 mm, which can be said to satisfy the above-mentioned conditions for plug flow, and it is also possible to insulate the pipe body.

However, even if this ideal condition is not met, ■ and τ
. has a relatively simple functional relationship and can often be easily calibrated. In addition, in this invention, since signal processing is performed through integral calculation, thermal fluctuations inherent in the fluid,
Even when there are disturbances such as changes in ambient temperature or waveform distortion due to heat dissipation, the flow velocity can be calculated accurately and stably. In this embodiment, if the heat-sensitive elements 54A and 54B having the same thermal characteristics and humidity characteristics are used, the error factors are canceled out, which is more advantageous in terms of accuracy.

According to the inventor's experiments at room temperature, it is possible to calculate the flow rate with sufficient practicality simply by setting the maximum detected temperature to around 600C. In addition, the pulsed current applied to the heating element may generally have any waveform, and it is sufficient to select one that makes it easy to calculate the correlation function in a short time under given conditions.

FIG. 8 shows another embodiment, in which the same reference numerals as in FIG. 5 represent the same members. In this embodiment, there is only one heat-sensitive element 54, and the structure is smaller and simpler than that in FIG. 5. In this case, the cross-correlation function between the signal detected by the current pro-pro 2 of the pulsed current applied to the heating element 52 and the temperature signal detected by the heat-sensitive element 54 is calculated,
The flow velocity is calculated in the same way as described above. but,
Unlike the embodiment shown in FIG. 5, in which the fluid temperature is detected by two heat-sensitive elements 54A and 54B, and φA(t) and φS (t) are respectively detected, in this embodiment, the heating element 5 is
The detection signal of the current waveform itself added to 2 is φA (t)
, the temperature detection signal from the thermosensitive element 54 is φs (t), so a larger time delay and waveform difference occur between the two waveforms than in the embodiment shown in FIG.

FIG. 9 shows an example of a circuit configuration for calculating a cross-correlation function. Two heat sensitive elements 54A, 54 in the embodiment of FIG.
The signals from B (in the embodiment of FIG. 8, the signals from the lightning probe 62 and the heat sensitive element 54) are alternately A/D converted by an A/D converter 93 via a preamplifier 91 and a multiplexer 92. , 0PU94 and stored in the memory 95. After sampling for a certain period of time, 0P
U94 has two digital signal strings φA (tj) and φB
(tj), considering the time difference of τ, Sτ=ΣφA (tj) ・φB(tj+τ)(4
) and store it in memory 95. While performing this for different τ, compare the size of Sτ,
τ that gives its maximum value. seek. The flow velocity is v=77τ
. The result is displayed on the display 96.

FIG.]-o shows another example of the circuit configuration for calculating the cross-correlation function, and the same reference numerals as in FIG. 9 indicate the same members.

In this, the signal is digitized by an A/D converter 93 via a preamplifier 91 and then sent to a buffer memory 9
7, but the memory contents are updated without going through 0PU94.
MA (Direct Memory Access
s) The controller 98 directly communicates with the main memory 99, and the 0PU 94 is used only for calculating the correlation function, so that the flow velocity measurement value can be updated promptly. Furthermore, if high speed is required, it is better to configure the entire circuit with dedicated hardware without using a CPU.

(Effects of the Invention) In this invention, a heating element is provided on the outside of the pipe as close as possible to the inner surface of the pipe, the internal fluid is heated by passing a pulsed current from an external power source through this, and the heating current is detected. Continuous detection using the maximum value of the cross-correlation function between the signal or the fluid temperature detection signal from the heat-sensitive element provided downstream of this and the fluid temperature detection signal from the heat-sensitive element provided further downstream. We adopted a method that allows the fluid velocity to be determined visually, and connected the heating section and detection section to an external heating power source and calculation device via wiring and signal lines, respectively. A flow rate measuring device has been completed that can be constructed in an extremely small size, can be connected to any part of the pipe to be measured using ordinary connection means, and can be easily calibrated if necessary. Since this device does not require any special structure to be installed inside the pipe, there is no pressure loss or turbulence that would interfere with the original function of the internal fluid, and the part through which the fluid flows can easily withstand pressure. Since it can be shaped, for example, circular, it can be applied even when high pressure is applied to the flow path, such as in a liquid chromatography device. Furthermore, there is no requirement that measurements be made without branching the flow path or taking out the fluid, and the measurement principle is strong against disturbances, and it is not affected by the characteristics of the fluid or by the presence or absence of liquid color. Nor.

In general, even when measuring changes in temperature of a fluid due to changes in ambient temperature, it is possible in principle to measure flow velocity in the same manner as in the present invention. However, the natural thermal fluctuations of fluids are small and change extremely slowly, making accurate detection difficult with a heat-sensitive element that can normally be done manually, making this a practical measurement method. As disclosed in this invention, it is only by providing a special heating means and artificially applying a practically detectable temperature change to the fluid that a practical flow rate measurement can be performed.

In addition to the liquid chromatograph apparatus described in the examples, the present invention is also applicable to various analytical apparatuses or similar apparatuses that need to accurately measure the velocity of a relatively small amount of liquid, or to flow rate or flow rate control in various plants. Its general applicability to devices is clear from the above description.

[Brief explanation of the drawing]

Figure 1 is a basic configuration diagram of a liquid chromatograph device, Figure 2
The figure is a block diagram of a reactive liquid chromatography device, Figure 3 is a diagram of the principle of a siphon counter, Figure 4 is a diagram of the principle of a drop counter, Figure 5 is an explanatory diagram of an embodiment of the present invention, and Figure 6 is a diagram of the principle of a drop counter. is a diagram illustrating detection signals of two heat-sensitive elements, and FIG. 17 is a circuit configuration diagram of a two-detection Shinmei arithmetic unit. 51: Pipe body, 52: Heating element as heating means, 54: Heating element as means for detecting heating output, 54A
: A first heat sensitive element as a temperature detection means, 54B: A second heat sensitive element as a temperature detection means, 62: A current probe as a heating input detection means. Imo Rijin Iθ Riju Yama am Figure 71 Figure d 72 6

Claims (1)

[Scope of Claims] 1) In a correlation speed measuring device that calculates the speed of the object to be measured based on the maximum point of correlation between two signals from the object to be measured detected at two locations separated by a predetermined distance, One of the two signals is a signal from the heating pulse input or output detection means of the heating means provided in the tube forming the flow path of the object to be measured, and the other is a signal from the detection means downstream of the detection means. A correlation type speed measuring device characterized in that the signal is a signal from a temperature detecting means of the object to be measured. 2. Correlation type speed measuring bag Fi' in the apparatus according to claim 1, characterized in that the heating pulse input to the heating means is an electric current. 3) A correlation type velocity measuring device according to claim 1, characterized in that the output of the heating means is the temperature of the object to be measured downstream of the heating means.