JP3335144B2 - Liquid level indicator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level gauge using a float / hood type liquid level sensor for measuring a liquid level in a tank.

[0002]

2. Description of the Related Art As a sensor for measuring a liquid level in a tank such as a gas station, for example, Japanese Patent Publication No. Sho 60-356
As disclosed in Japanese Patent Application Laid-Open No. 12, a float / fund type liquid level sensor is used.

FIG. 7 is an overall view of a liquid level sensor of a float fund type. In the drawings, the upper detector is a plan view and the lower tape drum is a sectional view.

[0004] Float 2 floating on the liquid surface in tank 1
Is attached to one end of a float tape 4 that can be wound up or rewound from the tape drum 3, and the float tape 4 moves along a tape guide shaft 5 and a tape guide roller 6, and is attached to the tape drum 3. Winded or unwound.

In the tape drum 3, a fund 8 is attached to one end of a fund tape 7 which can be wound up or rewound from the tape drum 3. The buoyancy of the float 2 and the weight of the fund 8 are balanced.

The float 2 rises or falls following the movement of the liquid level in the tank 1 due to the fluctuation of the liquid level in the tank 1 due to the unloading of the oil, and the tape drum 3 rotates. The tape drum 3 rotates, the potentiometer as the signal converter 10 rotates via the gear 9, the amount of rotation is converted into an electric signal (liquid level signal), and the operation circuit (shown in FIG. Send to

[0007]

However, in the case of the float / hood type liquid level sensor, the gap (backlash) of the gear, the play of the slider inside the signal converter, the frictional resistance due to the rotation of the signal converter, and the like. However, mechanical errors of the liquid level sensor are inevitable. For this reason, when the liquid level is lowered and stopped, and the next time it starts rising, even if the float and the drum move normally according to the liquid level, the rotation amount of the signal converter is reduced by the amount of backlash of the gears and the like. The amount of liquid in the tank cannot be accurately obtained because an error occurs between the measured liquid amount of the liquid level gauge when the liquid is received in the tank and the actually received liquid amount.

[0008] Another mechanical error of the liquid level sensor is caused by the float tape. That is, the liquid level sensor raises and lowers the float due to a change in the liquid level, and winds up the tape attached to the float with the drum.However, as the drum rotates, the diameter of the drum changes by the thickness of the tape. The relationship between the amount of change and the amount of rotation of the drum is not constant, and the liquid level signal output by the signal converter that rotates following the difference is different from the actual liquid level. Error occurs.

Conventionally, in order to avoid this, a method has been adopted in which an error is added to the total capacity value of the tank stored in the arithmetic unit and stored, but the added value differs depending on the size of the tank. The work was troublesome. for that reason,
The amount of liquid in the tank cannot be obtained accurately.

Further, in order to correct a mechanical error of the liquid level sensor, a liquid level gauge is connected to a device (a measuring device or a flow meter) for measuring the amount of liquid flowing into or out of the tank, and the amount of liquid flowing in and out of the tank is measured. The liquid level calculated from the liquid level sensor's liquid level signal has been corrected.However, when the liquid level gauge was installed in the tank, the relationship between the liquid level and the liquid level was not clear. The error between the actual liquid amount and the displayed amount of the liquid level gauge is large, and it takes several months until an accurate liquid amount is obtained. Further, it is necessary to correct the liquid amount evenly from the bottom of the tank to the ceiling, and during this time, the user cannot obtain an accurate liquid amount, which hinders the work.

Furthermore, when the mounting position of the liquid level sensor in the tank is poor, the tape, chain or fund connecting the float comes into contact with the wall of the pipe on which the liquid level sensor is mounted and is caught, and Although the liquid level has changed, the liquid level signal does not change, so that an accurate liquid amount may not be obtained.

Further, when a flow occurs in the liquid in the tank due to unloading to the tank or the like, the float may flow and output a liquid level signal different from the actual one, and the float guide may be used to prevent this. But the cost was high. In the case of a float that moves along a guide,
Foreign matter may adhere to the gap between the guide pipe and the float after many years of use, causing the float to stick, and there is a risk of an overflow accident, especially when the tank is being unloaded.

The liquid level data based on the analog signal output from the signal converter of the liquid level sensor is input to the arithmetic unit and converted into digital signal liquid level data. In some cases, an analog signal fluctuates and an accurate digital signal cannot be obtained due to, for example, mixing of electrical noise into the signal path of the digital camera. Conventionally, a stable digital signal is obtained by performing filtering with a circuit (hardware) and software, but it is difficult to obtain an accurate digital signal when noise exceeding a limit is generated. For this reason, it is only when the operator notices an abnormality in the liquid amount display during the operation of the tank that the abnormality is recognized and the signal line route is repaired and the like is dealt with. During this time, an accurate liquid volume could not be obtained, which caused a great obstacle to work.

Therefore, the present invention provides a liquid level gauge which can accurately grasp the liquid amount in the tank.

[0015]

According to the liquid level gauge of the present invention, a float is provided at one end of a float tape attached to a tape drum, and a fundo which balances the buoyancy of the float is provided at one end of a fundo tape attached to the tape drum. A float / hood type liquid level sensor provided with a signal converter to which the rotation of a tape drum is transmitted, and (1) storing an error value of a liquid level gauge due to a rise / fall of a liquid level in a tank. An arithmetic circuit for calculating the liquid amount by adding the error value corresponding to the rise / fall of the liquid level to the liquid level signal from the liquid level sensor, or (2) an error due to a change in diameter caused by winding the float tape. an arithmetic circuit for calculating a time of further liquid entering and leaving the tank
The level signal output by the level gauge changes suddenly in a short time.
If the float is
A means is provided that does not perform liquid volume calculation until the liquid level signal returns to normal.
And it said that there were pictures.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the actual amount of liquid in a tank can be displayed on a float tape.

Further, when the liquid level signal output from the liquid level sensor does not change even though the liquid flows in and out of the tank, it is determined that the trouble is caused by the catch of the float, and the allowable variation is determined. If a signal exceeding the threshold value is input, a means for outputting an unmeasurable alarm and / or a printer can be provided.

Also, when the float is flowed while the liquid is flowing in and out of the tank, and when the liquid level signal output by the liquid level sensor changes rapidly in a short time, it is determined that the float is flowing. Then, means for not performing the liquid amount calculation until the liquid level signal returns to the original normal level may be provided.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given of correction of a liquid amount due to a mechanical error of a liquid level gauge.

Due to the mechanical error of the liquid level sensor, especially when the liquid level is lowered and stopped, and then the liquid level sensor starts rising, the float and the drum normally move according to the liquid level, but the backlash of the gears and the like does not occur. , The amount of rotation of the signal converter is reduced. For example, if there is a liquid volume of 1000 liters in the tank and 4000 liters of liquid is put into it, the rotation amount of the signal converter becomes small due to the mechanical error of the liquid level sensor. Instead of 5,000 liters, it is displayed slightly as 4990 liters.

Therefore, an error when the liquid level rises and falls is stored in advance in an arithmetic circuit, and the arithmetic circuit detects the rise and fall of the liquid level and outputs the liquid level signal from the liquid level sensor to the liquid level signal. The liquid amount is calculated by adding an error value corresponding to the rise / fall. That is, the liquid level signal from the liquid level sensor is given an offset value according to the rise / fall of the liquid level, and the liquid level is calculated using the offset value as a true liquid level. When a specific error value is known as a mechanical error unique to the liquid level sensor, the error value is stored in an arithmetic circuit. In the case of an unknown number, the liquid level sensor is actually raised and lowered in advance, and the error is learned.
Remember.

FIG. 1 is a flowchart showing the procedure for correcting the liquid amount. However, it is assumed that the liquid level signal output by the liquid level gauge when the liquid level falls is the correct liquid amount.

(1) The error value d from the drop of the liquid level to the rise is stored (step 101).

(2) A liquid level signal of the liquid level sensor is sampled (step 102).

(3) It is determined whether or not the liquid level has risen (step 103).

(4) If the liquid level rises, an error value d is added to the sampled liquid level to calculate a liquid amount (step 104).

(5) If the liquid level is not rising, it is determined whether or not the liquid level is falling. If the liquid level does not drop, the process returns to step 102 to sample the liquid level signal of the liquid level sensor (step 105).

(6) If the liquid level drops, the liquid amount is calculated from the sampled liquid level (step 106).

For example, when the full-scale height of the tank (from the bottom to the ceiling of the tank) is 1000 and the mechanical error of the liquid level sensor is 1, the liquid level signal of the liquid level gauge is stored when the liquid level rises. When the calculated error value d = 1 is added to convert to a liquid amount, a correct liquid amount can be obtained. Thus, when the liquid is received in the tank, an accurate amount can be obtained.

Next, correction of a tape winding error will be described.

A calculating formula for correcting the tape winding error in advance and storing the true liquid level is stored in the arithmetic unit, and the liquid level including the winding error is converted into the true liquid level based on the calculating formula. I do. Thereby, an accurate liquid amount can be obtained.

Since the winding error increases in proportion to the thickness of the tape and the amount of rotation of the drum, the maximum drum radius Rmax where the tape is wound most, the minimum drum radius Rmin where the tape is not wound, and the liquid level sensor are determined. From the relationship between the sampled liquid levels Hsmp, the true liquid level Ht can be approximately obtained by the following equation.

True liquid level Ht = Hsmp × Rmax / Rmin Further, since the error value actually changes stepwise according to the number of tape windings, it can be obtained in more detail by the following equation.

True liquid level Ht = Hsmp × t × n / Rmin where t is the thickness of the tape, and n is an integer value of the number of windings of the tape.

In order to reduce the error, it is desirable that the thickness of the tape be as small as possible.

FIG. 2 is a flowchart showing a procedure for correcting a tape winding error.

(1) The correction formula is stored. Liquid level Hb = Ha × (1 + t × n / R) after correction value (step 20)
1) (2) The liquid level signal Ha of the liquid level sensor is sampled (step 202).

(3) The corrected liquid level is calculated from the correction formula (step 203).

Next, a procedure for generating an analog signal measurement impossible alarm will be described.

When an analog signal exceeding an allowable variation is input to the arithmetic circuit, a function is provided to determine that measurement is impossible and to output an alarm or a printer to that effect.

Thus, if it is known beforehand that the analog signal has an abnormality before the operation of the tank (when the liquid level gauge is installed), a countermeasure can be taken in advance and the operation such as inventory management of the liquid amount will not be hindered. Also, if you always monitor the state of the analog signal, even if an error occurs in the analog signal during operation,
Abnormalities can be discovered early, and countermeasures can be taken promptly, minimizing business interruptions.

Next, the function of changing the display liquid amount will be described.

To change the displayed liquid amount, the liquid amount at an arbitrary liquid level in the tank is stored in advance on a scale of the float tape or in a tank table indicating the relationship between the standard liquid level and the liquid amount in the tank. For any multiple liquid level points,
The manual adjustment is performed so that the liquid amount is correctly changed and displayed along the scale of the float tape or the tank table.

At the beginning of installation of the liquid level gauge, fine adjustment is made so that an accurate liquid amount close to the actual liquid amount is displayed. For the position signal, the relationship between the liquid level and the liquid amount suitable for the tank is adjusted. This is just a full-scale
In addition to the offset adjustment, adjustment is made at a plurality of points over the height of the tank so as to obtain the correct liquid volume for the liquid level at that time. As a result, it can be used practically in a short time after the installation of the liquid level gauge.

During operation of the tank, the liquid amount calculated from the liquid level signal of the liquid level sensor is corrected based on the liquid amount signal that has entered and exited the tank, such as a refueling signal of the meter.

FIG. 3 is a flowchart showing a procedure for changing the display liquid amount.

When the height of the tank is assumed to be Hn at the beginning of the installation of the liquid level gauge, a point near an arbitrary height such as H _0.1 , H _0.2. This is to make adjustments so that they are displayed.

(1) As a work at the beginning of the installation of the liquid level gauge, the liquid level sensor is set to an arbitrary height Hn (step 30).
1).

(2) The liquid amount Vn of the liquid level Hn is read from the scale or the conversion table showing the relation between the liquid level and the liquid amount of the float tape, and the liquid amount display is manually adjusted so as to be Vn ( (Step 302) (3) The arithmetic unit rewrites the liquid amount data of the liquid level Hn in the tank table stored therein to Vn (Step 3).
03).

(4) The liquid volume between each liquid level arbitrarily set is:
Interpolation is performed with a smooth curve (step 304).

As a result, the liquid amount is calculated to be close to the true liquid amount.
It can be adjusted so that it is displayed.

Next, detection of the catch of the float will be described.

The arithmetic unit monitors the signal of the meter for measuring the amount of liquid flowing into and out of the tank, and the liquid level signal output from the liquid level sensor does not change even though the liquid is flowing in and out of the tank. In such a case, it is determined that the trouble is caused by the catch of the float, and an alarm output and / or a printer output is performed.

As a result, a trouble can be found early,
An overflow accident can be prevented beforehand.

FIG. 4 is a flowchart showing the procedure for detecting the catch of the float.

(1) It is determined whether or not there is a refueling permission signal from the POS (point of sale information processing device) to the weighing machine. If not, return to the original and repeat the determination (step 40
1).

(2) If there is a refueling permission signal, the liquid amount Va is calculated and stored from the liquid level Ha before refueling (step 402).

(3) It is determined whether or not there is a refueling end signal from the weighing machine to the POS. If not, the process returns and repeats the determination (step 403).

(4) When there is a refueling end signal, the liquid amount Vb is calculated from the refueling amount Vk of the measuring machine and the liquid level Hb at that time, and a difference dV = Vb−Va in the liquid amount is obtained (step 40).
4).

(5) It is determined whether or not Vk> dV. N
In the case of o, the process returns to the original state and the determination is repeated (step 40
5).

(6) If Vk> dV, it is determined whether or not Hb ≦ Ha. In the case of No, the process returns to the original and the determination is repeated (Step 406).

(7) When Hb ≦ Ha, if the difference dV in the liquid amount is smaller than the refueling amount Vd of the measuring machine and the liquid level Ha before refueling is equal to or higher than the liquid level Hb after refueling, the float (Step 407).

Next, detection of the flow of the float will be described.

When the float flows, the liquid level signal output from the liquid level sensor changes rapidly in a short time, so that the arithmetic unit determines that there is no sudden change in the liquid level and returns the original normal signal. The liquid volume calculation is not performed until the liquid level signal is returned. Thus, it is possible to prevent the display of the liquid amount different from the actual one.

FIG. 5 is a flowchart for detecting a float flow.

(1) The liquid level signal Ha of the liquid level sensor is stored. The time t is set in the timer T. An allowable change amount Hmax of the liquid level per unit time t is set (step 501).

(2) It is determined whether or not the timer T time t has elapsed. In the case of No, the process returns to the original and the determination is repeated (Step 502).

(3) After the timer T time elapses, the liquid level signal Hb of the liquid level sensor is sampled (50).
3).

(4) It is determined whether or not Hmax <Ha−Hb (step 504). If No, unit time t
Since the liquid level change per hit is less than the allowable change amount Hmax, the liquid level is calculated as a normal liquid level change (step 50).
5).

(5) Allowable change amount Hm per unit time t
Since a change in the liquid level equal to or higher than ax is detected, it is determined that the float has flowed and the liquid amount is not calculated (step 506).

(6) The liquid level signal Hc of the liquid level sensor is sampled (step 507).

(7) It is determined whether or not Hc ≧ Ha (step 508). If No, the process returns to the previous step 507.

(8) Whether the liquid level signal is equal to the original Ha
Otherwise, it is determined that the float has returned to the normal position (step 509). Thereafter, the process returns to step 505.

FIG. 6 is a flowchart of the procedure for generating an analog signal measurement impossible alarm.

(1) Effective range width V of allowable liquid level signal
max is stored. The minimum sample number Nmin of the effective liquid level signal is stored. Number of sampling of liquid level signal N
The smp is stored (step 601).

(2) The liquid level signal of the liquid level sensor is sampled (step 602).

(3) It is determined whether or not sampling is performed Nsmp times. If No, the process returns to the previous step 602 (step 603).

(4) After sampling Nsmp times, V
The sample of the liquid level signal exceeding max is deleted to calculate the effective sample number Nt.

(5) It is determined whether or not Nmin> Nt. If No, an effective number of samples has been obtained, and processing such as liquid volume calculation is performed (step 606).

(6) Assuming that an effective number of samples cannot be obtained and the variation in the liquid level signal is large, alarm output and printer output are performed (step 607).

Also, the float tape connecting the float of the liquid level sensor is provided with a scale on which a liquid amount corresponding to the liquid level is written, so that it can be visually confirmed. Since this is a completely mechanical movement, it is not affected by a power failure, an electrical failure, or the like, and does not hinder business.

[0082]

According to the present invention, the following effects can be obtained.

(1) By correcting the liquid amount due to a mechanical error of the liquid level sensor, an accurate amount of liquid can be obtained when the liquid is received in the tank.

(2) At the beginning of the installation of the liquid level gauge, fine adjustment is made so as to display an accurate liquid level close to the actual liquid level. .

(3) If the liquid level signal output from the liquid level sensor does not change even though the liquid is flowing in and out of the tank, it is determined that a trouble is caused by the float being caught, and an alarm output and / or an alarm is issued. By performing printer output, a trouble can be found at an early stage, and an overflow accident can be prevented.

(4) When the liquid level signal suddenly changes in a short time due to the flow of the float, the liquid volume calculation is not performed until the original normal liquid level signal is returned. The display of the liquid amount can be prevented.

(5) An accurate liquid amount can be obtained by correcting a tape winding error.

(6) By constantly monitoring the state of the analog signal, even if an abnormality occurs in the analog signal, the abnormality can be detected at an early stage, and a countermeasure can be taken promptly, thereby minimizing the trouble in business. it can.

(7) The scale of the float tape can be scaled to allow the amount of liquid to be visually checked.
It will not be affected by electrical failures, etc., and will not hinder business.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a procedure for correcting a liquid amount.

FIG. 2 is a flowchart illustrating a procedure for correcting a tape winding error.

FIG. 3 is a flowchart showing a procedure for changing a display liquid amount.

FIG. 4 is a flowchart showing a procedure for detecting the catch of a float.

FIG. 5 is a flowchart showing a procedure for detecting a float flow.

FIG. 6 is a flowchart of an analog signal measurement inability alarm generation procedure.

FIG. 7 is an overall view of a float / fund type liquid level gauge.

[Explanation of symbols]

 1: tank 2: float 3: tape drum 4: float tape 5: tape guide shaft 6: tape guide roller 7: fund tape 8: fund 9: gear 10: signal converter 11: terminal box

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01F 23/00-25/00

Claims (5)

(57) [Claims] A float is provided at one end of a float tape attached to a tape drum, and a fundo that balances the buoyancy of the float is provided at one end of a fundo tape attached to the tape drum, and a signal for transmitting rotation of the tape drum is provided. This is a liquid level sensor equipped with a converter, which stores the error value of the liquid level gauge due to the rise and fall of the liquid level in the tank, and detects the rise and fall of the liquid level in the liquid level signal from the liquid level sensor. An arithmetic circuit for calculating the liquid amount by adding the error value corresponding thereto , and further when the liquid is flowing in and out of the tank.
The level signal output by the level gauge changes suddenly in a short time.
If the float is
A means is provided that does not perform liquid volume calculation until the liquid level signal returns to normal.
Liquid level meter, characterized in that there was e. 2. A float provided at one end of a float tape attached to the tape drum, and a fundo provided at one end of the fundo tape attached to the tape drum to balance the buoyancy of the float, and a signal for transmitting the rotation of the tape drum. A liquid level sensor provided with a converter, comprising an arithmetic circuit for calculating an error due to a change in diameter due to winding of a float tape and calculating a liquid amount , and further comprising a liquid tank.
Level signal output by the level gauge when entering or exiting
If the water changes drastically in a short time, the float
Fluid level until it returns to the original normal level signal.
A liquid level gauge comprising means for performing no calculation . 3. When the liquid level signal output from the liquid level gauge does not change even though the liquid flows in and out of the tank, it is determined that the trouble is caused by the catch of the float, and the alarm output and / or the printer is output. 3. The liquid level gauge according to claim 1, further comprising means for performing output. 4. A signal exceeding an allowable variation is input.
If a warning is output and / or a printer
4. The liquid level gauge according to claim 1, further comprising means for performing a force . 5. A float tape for measuring an actual liquid amount in a tank.
4. The display according to claim 1, wherein the display is scaled.
Or the liquid level gauge according to 4 .