JP2010181389A - Liquid level measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressurized gas supply type liquid level measuring device capable of reducing the frequency of supply of pressurized gas. <P>SOLUTION: The liquid level measuring device of pressurized gas supply type is composed of: a sensing tube 3 for immersing a front end thereof into the liquid to be subjected to liquid level measurement; a pressurized gas supply source 2 for supplying pressurized gas; a pressure sensor 5 for measuring gas in the sensing tube; a display unit 8 for displaying a depth from the end of the sensing tube to a liquid surface as a liquid level; a temperature sensor 10 for performing pressure compensation; and a control unit 7 having a microcomputer for performing arithmetic processing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a detection tube in which a tip is immersed in a liquid whose liquid level is to be measured, a pressurized gas supply source connected to the detection tube to leak pressurized gas from the tip of the detection tube, and a detection The present invention relates to a liquid level measuring apparatus that includes a pressure sensor connected to a detection pipe so as to detect the pressure in the pipe, and performs measurement processing, control, alarm generation, etc. by calculating the detection value of the pressure sensor. Is.

In the atmospheric pressure type liquid level detection device disclosed in Japanese Patent Application Laid-Open No. 2007-78413 (Patent Document 1), a pressurized gas supply source is driven for a predetermined time every predetermined period in order to supply pressurized gas. After a lapse of a certain time from the stop of the pressurized gas supply source until the influence of the pressure fluctuation disappears, the pressure value in the detection tube is stored as a reference value, and the reference value fluctuates beyond a predetermined width. Even in this case, it is described that the pressurized gas supply source is provided with a control means for driving.

Japanese Unexamined Patent Publication No. 2007-78413

In a pressurized gas supply type liquid level measurement device, in the scene where the liquid level rises or falls while the supply of pressurized gas is stopped, a control or alarm signal corresponding to the pressure change rate is issued, or an automobile Like kerosene, it is convenient if additional information such as the remaining time until the fuel runs out can be obtained.

When the pressure value in the detection tube is detected and stored as a reference value after a certain period of time until the pressurized gas supply source stops driving and there is no effect of pressure fluctuation, the depth of the liquid to be measured Since the time until the influence of the pressure fluctuation disappears changes depending on the length of the detection tube, it is necessary to change each time even if it is a fixed time.
Even if the depth of the liquid to be measured, the length of the detection tube, and the like differ depending on the installation location, a method is required in which the time does not need to be changed each time.

In the case of theft such as kerosene, the pressure change at the time of a sudden drop in the liquid level, and at the time of a sudden rise in the level of the river or the sea level, it is the time of the day to detect the pressure change rate of the liquid level and issue an alarm It is a request.

The distance to the water surface of a deep well is generally measured by actually hanging a measure with an electrode on the well. However, if the distance is long, it is difficult to take in and out. Therefore, it is convenient if the length of the existing detection tube can be automatically measured even after the detection tube of the bubble type liquid level measuring device is installed in the deep well or when the length of the existing detection tube is unknown.

When the supply of pressurized gas is stopped, if the temperature decreases, the volume in the detector tube contracts and the pressure value detected by the pressure sensor is lower than the actual liquid level, which is mistaken as a drop in liquid level. Increased number of times of supply of pressurized gas. If the corrected pressure value close to the actual liquid level can be output by compensating for the pressure decrease due to the temperature drop, the number of times of supply can be reduced and the life of the pressurized gas supply source that is a pressurized gas supply source can be extended. .

In the following description, the unit of pressure is [mH20]. In this case, when the liquid to be measured is not specific gravity 1.0 such as kerosene, the liquid level of the liquid can be obtained by dividing the measurement pressure by the specific gravity. Therefore, the liquid to be measured is water having a specific gravity of 1.0.
In a pressurized gas supply type liquid level measuring device, a detection tube for immersing the tip in a liquid whose liquid level is to be measured, a pressurized gas supply source for supplying pressurized gas, Control equipped with a pressure sensor for measuring atmospheric pressure, a display unit that displays the depth from the tip of the detection tube to the liquid level as a liquid level, a temperature sensor for pressure correction, and a microcomputer for calculation processing Consisting of units

The invention according to claim 1 refers to FIG. 3 that shows the detected values of the temperature sensor and the pressure sensor over time by calculation processing by a microcomputer. Is obtained, and an accurate measurement value pressure value (P0) of the liquid level obtained when the liquid level fluctuation decreases after the supply is stopped, and a pressure value (P2) is obtained at every first predetermined time (T1) interval. In this case, the slope with respect to (P0) = speed (Sa1) takes an absolute value and Sa1 = | P2-P0 | / T1
When (Sa1) is determined to be larger than the first predetermined speed (S1) set in advance, the pressurized gas is supplied,
With reference to FIG. 5, since the pressurized gas is supplied, the change rate (Sv) of the pressure difference (Pv) of the liquid level obtained at the first predetermined time (T1) interval as time elapses. ) = Pv / T1, and the average speed (Sa2) obtained by adding the change speed (Sv) to the first predetermined number of times (na) and dividing by the number of times (na) is the second predetermined speed ( S2) When it is determined that the pressure has become smaller, the pressurized gas is stopped. Referring to FIG. 6, the change rate (Sv) is added to the second predetermined number (nb), and the number of times ( When the average speed (Sa3) obtained by dividing by nb) is determined to be smaller than the third predetermined speed (S3), it is obtained as an accurate liquid level measurement (P0), and at the same time, the temperature sensor The detected temperature is memorized as the reference temperature (Tp1), and again from the beginning Keep the average speed constantly updated.

According to the second aspect of the present invention, the average speed (Sa4) obtained by adding the change speed (Sv) by the third predetermined number (nc) and dividing by the number (nc) is a rapid change speed. When it is determined that the speed has become higher than a certain fourth predetermined speed (S4), an alarm signal and a control signal associated therewith are output.

The invention according to claim 3 is based on the pressure value detected by the pressure sensor adjacent to the measuring device farthest from the tip of the previous detection tube in a state where the tip of the previous detection tube is immersed in the liquid. First, the pressure difference detected by the pressure sensor from the accurate liquid level measurement value (P0) obtained according to claim 1 to immediately before the supply of pressurized gas is set to (X1), and then The pressure difference from the new accurate liquid level measurement value (P0) obtained after the pressurized gas supply is defined as (X2).
The ratio (Y) of the pressure difference caused by the length of the detection tube is taken as in equation (1).
Y = X1 / X2 (1)
From this ratio (Y), the approximate length (L) of the detection tube is determined by equation (2).
However, the atmospheric pressure here is 10 mH20.
L [m] = (Y−1) × 10 [m] (2)
If the equations (1) and (2) are incorporated in the program software, the approximate length of the detection tube can be automatically measured. Equation (2) is obtained from equations (3) to (10) described below.

The unit of length is [m], the unit of pressure is [mH20], the temperature is ° C., the inner diameter of the detection tube is the same, and the variables are defined as follows with reference to FIG.
P1: Atmospheric pressure (Atmospheric pressure is equivalent to about 10m for water)
P2: Pressure value detected by the pressure sensor, (X1)
P3: Pressure in the detection tube L: Length of the detection tube h: Distance from the tip of the detection tube to the liquid level (liquid level value)
a: Length of liquid entering from the tip of the detection tube

Since the gauge pressure type pressure sensor outputs a differential pressure with respect to the atmospheric pressure, the pressure value P2 is expressed by Equation (3).
P2 = P3-P1 (3)
Further, the pressure balance equation when the liquid intrudes into the detection tube from the tip of the detection tube in a state where the supply of the pressurized gas is stopped is the equation (4).
P1 + h = P3 + a (4)
Equation (5) is obtained from Equation (3) and Equation (4).
P2 = ha (5)
On the other hand, P1 × L = (P1 + P2) × (L−a) (6) because P1 × L = P3 × (L−a) from Boyle Charles ’law.

P1 × L = (P1 + P2) × (L−h + P2) (7) where “a” is eliminated from the equations (5) and (6) to obtain the equation (7).
By the way, h is a distance (pressure) measured when pressurized gas is supplied and the gas is filled to the tip of the detection tube, and the pressure at that time is X2.
Therefore, Y is Y = h / P2 (9)
Therefore, when the equations (7) and (8) are arranged, the length of the detection tube can be finally obtained from the equation (10).
L = (Y−1) × (P1 + P2) (10)
Here, although the atmospheric pressure P1 is about 10 mH20, when the target depth h of the target liquid level is sufficiently small compared to 10 m, the equation (10) is
L = (Y−1) × 10 (2)
And can.

なる

ボイルシャルルの法則から体積は絶対温度に比例するので、絶対温度を２７３℃として、温度が下降したときの体積の減少率は式（１２）となる
（Ｔ２＋２７３）／（Ｔｐ１＋２７３）・・・（１２）
ここで検出管の内径は同じとしているので体積比は長さ比に相当すると考えることができ、請求項３から計測された検出管の長さ（Ｌ）＝（Ｙ−１）×１０をもとに検出管内に浸入する液体部分の長さ（ａ）は式（１３）になる
ａ＝（Ｙ−１）×１０−（Ｙ−１）×１０×（Ｔｐ２＋２７３）／（Ｔｐ１＋２７３）・・・（１３）
したがって、この値が液面レベル補正分の圧力値に相当することから、検出管内の圧力センサが検出する圧力値（Ｐ２）を加えて、実際の液面のレベルに近い補正圧力値（ＰＬ）は式（１４）になる、
ＰＬ＝Ｐ２＋（Ｙ−１）×１０−（Ｙ−１）×１０（Ｔｐ２＋２７３）／（Ｔｐ１＋２７３）・・・（１４）

ったときに加圧気体供給開始するようにすれば、加圧気体の供給量を少なくできる。
具体的には、式（１１）と式（１４）をプログラムソフトに組み込むことにより可能となる。According to a fourth aspect of the present invention, a predetermined temperature drop is set to Tp3 in advance by a microcomputer in the control unit (7), and the supply of pressurized gas is stopped. To avoid the fact that the pressure of the pressure sensor is detected to be lower than the actual liquid level and the liquid level is measured to be lower than the actual liquid level, and that the liquid volume of the gas contracts, and is mistakenly recognized as a drop in the liquid level. It is.
First, the reference temperature detected by the temperature sensor at the same time when the accurate liquid level (P0) is obtained from claim 1 is stored as Tp1, from which the temperature gradually increases.

Become

Since the volume is proportional to the absolute temperature according to Boyle-Charles' law, the absolute temperature is set to 273 ° C., and the volume decrease rate when the temperature is lowered is expressed by the equation (12) (T2 + 273) / (Tp1 + 273) (12) )
Here, since the inner diameter of the detection tube is the same, the volume ratio can be considered to correspond to the length ratio, and the length (L) = (Y−1) × 10 of the detection tube measured from claim 3 is also obtained. In addition, the length (a) of the liquid portion entering the detection tube is expressed by the following equation (13): a = (Y−1) × 10− (Y−1) × 10 × (Tp2 + 273) / (Tp1 + 273). (13)
Therefore, since this value corresponds to the pressure value corresponding to the liquid level correction, the pressure value (P2) detected by the pressure sensor in the detection tube is added, and the corrected pressure value (PL) close to the actual liquid level. Becomes equation (14),
PL = P2 + (Y−1) × 10− (Y−1) × 10 (Tp2 + 273) / (Tp1 + 273) (14)

If the supply of pressurized gas is started at this time, the supply amount of pressurized gas can be reduced.
Specifically, it becomes possible by incorporating the equations (11) and (14) into the program software.

According to the invention having the first feature, the liquid level change is monitored by constantly capturing the pressure change rate based on the pressure value detected by the pressure sensor even while the supply of the pressurized gas is stopped. Therefore, if the liquid level exceeds the predetermined pressure change rate, pressurized gas can be supplied, and when the pressure rises due to the supply of pressurized gas, the rising rate is continuously monitored at short intervals, so the pressure level is When the rate of change becomes moderate, the supply of pressurized gas can be stopped accurately and the supply amount of pressurized gas can be reduced. In addition, since the pressure change rate at the time of pressure drop is continuously monitored after a short time interval after the supply of pressurized gas is stopped, it is always unaffected by the thickness and length of the detection tube and the depth of the liquid to be measured. An accurate liquid level (P0) is obtained.
Further, by knowing the pressure change rate, that is, the liquid level change rate, it is possible to display the time until the kerosene has been used up or to convert the current consumption rate into C02.

According to the invention having the second feature, since control and warning can be issued by a rapid change in the liquid level, for example, a warning alarm due to a sudden rise in the river or the sea level or liquid in the tank due to theft of kerosene or the like A burglar alarm can be issued due to a sudden drop in the surface.

According to the invention having the third feature, if the tip of the detection tube is immersed in a liquid and the inner diameter of the detection tube is the same, the measurement time varies depending on the length of the detection tube, but pressurized gas is supplied. Then, the temperature is measured at an interval time between the accurate liquid level measurement value (P0) obtained when the liquid level change almost disappears after the pressurized gas is stopped and the accurate liquid level (P0) before update. The length of the detector tube can be automatically measured with little change, and even if the length of the detector tube installed in the deep well is unknown, it is only necessary to measure the length of the detector tube on the ground later The distance from the ground surface to the water surface of the deep well can be grasped.

According to the invention having the fourth feature, the pressure value close to the actual liquid level is corrected or displayed for the volume decrease in the detection tube when the temperature drops in the detection tube in the pressurized gas supply stop state. The number of times the pressurized gas is supplied can be greatly reduced, and when the remaining amount of edible oil is monitored, the edible oil is hardly oxidized by the pressurized gas supply.

It is a figure for calculating | requiring the correlation of the detection value of a pressure sensor, a liquid level measurement value, and the length of a detection pipe | tube when measuring a liquid level. 1 is an overall configuration diagram for implementing a liquid level measuring device. FIG. It is a figure showing the detected value of a temperature sensor and a pressure sensor when a pump drives over time. It is a figure showing the pressure change when pressurized gas starts supply. It is a figure showing the pressure change when pressurized gas stops supply. It is a figure showing the pressure change when obtaining the exact measured value of a liquid level at the time of the pressure fall after a pressurization gas supply stop. It is a figure showing the timing which acquires an alarm signal when a pressure rises rapidly. It is a block diagram of the whole for a liquid level measuring apparatus to be implemented, and is a flowchart.

1 Measurement object (container) when measuring liquid level
2 Pressurized air supply source (pump)
3 Detection Tube 3a Branch Valve 4 Check Valve 5 Pressure Sensor 6 Control Panel 7 Control Unit 8 Display 9 Alarm 10 Temperature Sensor

図６を参照にして、連続する前記１回分の変化速度（Ｓｖ）を第２の所定回数（ｎｂ）例えば４回加算し４回で割ることで得た平均速度（Ｓａ３）が例えば０．９ｍｍ／秒になった場合第３の所定速度（Ｓ３）例えば１ｍｍ／秒に設定しておいた場合はより小さくなったと判断される場合に正確な液面レベル測定値（Ｐ０）例えば１．５ｍＨ２０として得られ、

同時に温度センサが検出する温度を基準温度（Ｔｐ１）として記憶させるようにさせる。First, in FIG. 2, a liquid substance is stored in a container (1) which is an object of a liquid level measuring apparatus, and a detection tube (3) is used to measure the liquid level (h) in the container. Is inserted to a position close to the bottom (1a) of the container (1).
On the other hand, a pressurized gas supply source (2) which is a pressurized gas supply source is fixedly disposed outside the container (1), and the pressurized gas supply source (2) is connected to the pressurized gas supply source (2). 2) Connected to the detection tube (3) via a check valve (4) that prevents backflow to the side. The pressure sensor (5) for detecting the pressure in the detection pipe (3) is connected to the branch pipe (3a) branched from the detection pipe (3) downstream of the check valve (4). It is connected to the position farthest from the tip of 3).
The drive of the pressurized gas supply source (2) is controlled by a control unit (7) comprising a microcomputer, and the control unit (7) includes the pressure sensor (5), a display (8), and It is connected with the alarm (9). Further, a temperature sensor (10) is fixedly arranged near the detection tube (3) where the temperature change is large, and this is also connected to the control unit (7).
The control unit (7) is composed of a calculation processing by a microcomputer and a control circuit.
From FIG. 4, the accurate measurement value (P0) of the liquid level obtained when the pressurized gas is supplied from the pressurized gas supply source and the fluctuation in the liquid level decreases after the supply is stopped, The pressure value (P2) obtained intermittently at a predetermined time (T1) of, for example, 1.0 second is, for example, 1521 mmH20, and the pressure value is always based on the accurate measured value (P0) of, for example, 1500 mmH20 The inclination speed (Sa1) takes the absolute value of the speed and Sa1 = | P2-P0 | / T1 to | 1500-1521 | / 1 = 21 (mmH20 / sec)
Thus, the pressurized gas supply source (2) is driven so that the intermittent pre-tilt speed (Sa1) is greater than a preset first predetermined speed (S1), for example, 20 mmH20 / sec. = | P2-P0 | / T1, if Sa1> S1, the pressurized gas supply source is driven. Referring to FIG. 5, the first predetermined time (T1), e.g. The change rate for one time (Sv) = Pv / T1 based on the pressure difference (Pv) detected by the pressure sensor generated from the pressure difference at the liquid level obtained before and after the above is obtained. When the average speed (Sa2) obtained by adding (Sv) to the first predetermined number of times (na), for example, 2 and dividing by (times) 2 (na) is, for example, 9.9 mm / second, the second predetermined number When the speed (S2) is set to 10 mm / second, for example And the pressurized gas supply source (2) is stopped.

Referring to FIG. 6, the average speed (Sa3) obtained by adding the second predetermined number of times (nb), for example, four times and dividing by four times is obtained, for example, 0.9 mm. When the third predetermined speed (S3), for example, 1 mm / second is set, the accurate liquid level measurement value (P0), for example, 1.5 mH20 is determined. Obtained,

At the same time, the temperature detected by the temperature sensor is stored as the reference temperature (Tp1).

また、前記加圧気体供給源（２）が駆動中のときは、圧力が暴れるため警報器（９）のブザーが鳴らないように比較回路を遮断するなどして止めておく。Referring to FIG. 7, the average speed (Sa4) obtained by dividing the change speed (Sv) for one time by the first predetermined number (nc), for example, the number of times obtained by adding four times (nc) four times is, for example, The fourth predetermined speed (S4) in which the average speed obtained by dividing the case of 2.1 mm / second by the number of times (nc) obtained by adding the third predetermined number (nc) is an abrupt change speed. It is determined that the speed is higher than 0 mm / second, and the held alarm signal is sent, and the buzzer of the alarm device (9) continues to sound.

Further, when the pressurized gas supply source (2) is being driven, the pressure is violated, so that the buzzer of the alarm (9) is not turned off by shutting off the comparison circuit.

The following formulas (1) and (2) obtained in the above means for solving are used. Finally, the approximate length (L) of the detection tube is obtained. Y = X1 / X2 (1)
L [m] = (Y-1) × 10 [m] (2)
X1 is a pressure difference detected by the pressure sensor and rises, for example, 6 mm from the accurate liquid level value, and the pressurized gas supply source (2) is driven. On the other hand, X2 is assumed to be 2 mm, for example, as a pressure difference between the accurate liquid level values before and after the pressurized gas supply source (2) is driven. X1 and X2 are pressure difference ratios due to the length of the detection tube. From the equation (1), the ratio Y = X2 / X1 is substituted into the equation (2), and L = (3-1) × 10 = That is, the length of the detection tube is obtained by driving the pressurized gas supply source (2) to obtain X1 and X2, and the automatically measured values are stored and the indicator (8 ) Can be displayed.

となる。
また、（Ｙ−１）×１０は検出管の長さを自動的に求める式で上記と同じ条件のまま引き継いだとすれば約２０ｍである。
前記基準温度２０℃から温度が２℃低下したときの圧力センサが検出した圧力値（ＰＳ）が例えば２．３ｍとすれば
式（１４）に上で得られた（Ｙ−１）×１０＝２０、Ｔｐ２＝１８、Ｐ２＝２．３を代入すると、実際の液面のレベルに近い補正圧力値（ＰＬ）は
ＰＬ＝Ｐ２＋（Ｙ−１）×１０−（Ｙ−１）×１０（Ｔｐ２＋２７３）／（Ｔｐ１＋２７３）・・（１４）
ＰＬ＝２．３＋２０−２０×（１８＋２７３）／（２０＋２７３）
＝２．４４ｍ
となる。
予め前記所定の下降補正温度（Ｔｐ３）℃を例えば２℃に設定すれば、前期下降

うにすればよい。
もし温度による圧力補正をしなかった場合には、２℃の温度低下で２．４４−２．３＝０．１４ｍの圧力誤差を生じることになる。また、前記加圧気体供給源（２）が駆動するための第１の所定速度（Ｓ１）を例えば５ｍｍ／秒、つまり０．００５ｍ／秒に設定しておいた場合には
本来は０．１４／０．００５＝２８回前記加圧気体供給源（２）が駆動するが、温度による圧力補正をすることで駆動する回数が１回で済むことになる。The reference temperature (Tp1) stored at the moment when the accurate liquid level measurement value (P0) is obtained based on the equations (11) and (14) obtained at the means for solving the problem. For example, the temperature (Tp2) when the temperature is gradually lowered at 20 ° C., for example

It becomes.
Further, (Y-1) × 10 is an expression for automatically obtaining the length of the detection tube, and is about 20 m if the same conditions as described above are taken over.
If the pressure value (PS) detected by the pressure sensor when the temperature drops from the reference temperature of 20 ° C. by 2 ° C. is 2.3 m, for example, (Y−1) × 10 = Substituting 20, Tp2 = 18, and P2 = 2.3, the correction pressure value (PL) close to the actual liquid level is PL = P2 + (Y−1) × 10− (Y−1) × 10 (Tp2 + 273). ) / (Tp1 + 273) (14)
PL = 2.3 + 20−20 × (18 + 273) / (20 + 273)
= 2.44m
It becomes.
If the predetermined lowering correction temperature (Tp3) ° C. is set to 2 ° C. in advance, the previous lowering

Just do it.
If the pressure is not corrected by the temperature, a pressure error of 2.44−2.3 = 0.14 m is generated at a temperature drop of 2 ° C. When the first predetermined speed (S1) for driving the pressurized gas supply source (2) is set to, for example, 5 mm / second, that is, 0.005 m / second, it is originally 0.14. /0.005=28 times The pressurized gas supply source (2) is driven. However, the number of times of driving is only one by correcting the pressure by the temperature.

Claims (4)

A device for measuring a liquid level (h) of a liquid substance, the detection tube (3) having a tip immersed in a bottom (1a) in the liquid, which is an object (1) for measuring the liquid level; A pressurized gas supply source (2) and a check valve (4) connected to the detection pipe (3) to leak pressurized gas from the tip of the detection pipe (3); A pressure sensor (5) connected to the detection pipe (3) so as to detect pressure, and a display for displaying a liquid level and an alarm display based on the pressure value detected from the pressure sensor (5) In the device for measuring the liquid level (h) on the basis of the pressure value of the pressure sensor (5), the vessel (8) has a temperature sensor (10) attached outside the liquid level device.
A first predetermined time (T1), a first predetermined number of times (na), a second predetermined number of times (nb), a third predetermined number of times (nc), a first predetermined time (T1) by a microcomputer in the control unit (7). In the state where the set values of the predetermined speed (S1), the second predetermined speed (S2), and the third predetermined speed (S3) are stored and the supply of pressurized gas is stopped, the change speed of the liquid level is changed. It is a liquid level measuring device that performs control processing by a microcomputer from the pressure detected by the pressure sensor (5) for constant monitoring. The liquid level is supplied after a pressurized gas is supplied from a pressurized gas supply source and the supply is stopped. With respect to the reference pressure value (P0) obtained when the fluctuation is reduced, the pressure value is obtained at a predetermined interval (T1), and the inclination speed of the pressure value always obtained at a predetermined interval compared with the reference pressure value ( Sa1) When it is determined that the speed has become higher than the set first predetermined speed (S1), the pressurized gas is supplied, and then the first predetermined time (T1) is mutually passed while the time has passed. The pressure change rate (Sv) for one time serving as a reference is calculated from the pressure difference before and after the gap,
The average speed (Sa2) obtained by adding the first predetermined number of times (na) to the pressure change speed (Sv) for one time and dividing by the number of times (na) is smaller than the second predetermined speed (S2). When the determination is made, that is, when the pressurized gas leaks from the tip of the detection tube (3) and the pressure fluctuation in the detection tube (3) becomes small, the pressurized gas is supplied from the pressurized gas supply source (2). The average speed (Sa3) obtained by adding the second predetermined number of times (nb) and dividing by the number of times (nb) is slightly changed. When it is determined that the speed has become smaller than the third predetermined speed (S3), that is, when the liquid level change is almost eliminated at the time of the pressure drop, an accurate liquid level measurement value (P0) is obtained, and at the same time, the temperature sensor Is the reference temperature (Tp1 So as to be stored as characterized by their ability to constantly controlled while monitoring the state of change of the liquid level by going to update the tilt speed (Sa1) again. The setting values of the fourth predetermined speed (S4) and the fourth predetermined number of times (nd) are stored in advance by the microcomputer in the control unit (7), and the speed for the previous period is the same as in claim 1. The average speed (Sa4) obtained by adding (Sv) to the fourth predetermined number of times (nd) and dividing by the number of times (nd) exceeds the fourth predetermined speed (S4) which is a reference for the rapid change speed. 2. The liquid level measuring apparatus according to claim 1, wherein control or an alarm can be issued when it is determined that the liquid level is abrupt, that is, when a sudden change in the liquid level occurs. The length from the pressure sensor adjacent to or built in the liquid level device to the tip of the detection tube is based on the pressure value detected by the pressure sensor.
The pressure difference between immediately after obtaining the accurate liquid level measurement value (P0) according to claim 1 and immediately before the start of supply of pressurized gas from the pressurized gas supply source (2) is defined as (X1), A pressure difference between (P0) corresponding to the accurate liquid level measurement values before and after being updated at this time is defined as (X2), and X2 / X1 is defined as Y. Y = X2 / X1
From this ratio (Y), the approximate length (L) of the detection tube is determined by the following equation: L [m] = (Y−1) × 10 [m]
3. The liquid level measuring device according to claim 1, wherein the equation is incorporated in the program software and the approximate length of the detection tube can be automatically measured. A predetermined decrease correction temperature (Tp3) is stored in advance by a microcomputer in the control unit (7), and the temperature sensor (5) is installed near a detection tube having a large air temperature change so that the actual temperature is decreased. The variables for obtaining the corrected pressure value close to the liquid level are as follows, and are all automatically calculated values. Therefore, when the absolute temperature is 273 ° C., the corrected pressure value (PL) is calculated by the equation (14). Obtained Tp2: Temperature Tp1 detected by the temperature sensor at the time of temperature drop 1: Reference temperature obtained from claim 1

P2: Pressure value detected by the pressure sensor (Y-1) × 10: Length of detection tube obtained from claim 4 (L)
PL = P2 + (Y−1) × 10− (Y−1) × 10 (Tp2 + 273) / (Tp1 + 273) (14)
Formula (14) is incorporated into the program software to automatically obtain the corrected pressure value (PL).

The number of times of supply can be greatly reduced by supplying the pressurized gas from the pressurized gas supply source (2) only when the pressure exceeds it. Liquid level measuring device.

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