JP2000155041A - Flow measuring method for tank and device for the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a liquid level and a flow rate from a signal by a level gauge alone so as to save costs by introducing a level signal detected by the level gauge to a flow computing unit for converting the level signal into an outflow flow rate. SOLUTION: A sampling unit 11 samples a level signal of a tank 1 detected by a level gauge 2 at a fixed time interval. The sampling signal is introduced into a flow computing unit 13 with a previous sampling signal stored in a memory 12, and an outflow flow rate is found. That is, in the flow computing unit 13, an outflow flow rate is found by computing according to the following expression; outflow flow rate = (previous sampling value - this-time sampling value) × tank internal area/sampling time. A tank internal area is varied by the size of the tank 1, so that it is rewritable. As computing for finding a flow rate cannot be carried out in supply of liquid into the tank 1, a switch 14 serving as a command unit for stopping flow computing is arranged for stopping computing for a flow rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a flow rate of a tank, and more particularly to a method for measuring a liquid level to obtain an amount flowing out of the tank.

[0002]

2. Description of the Related Art FIG. 3 shows a tank facility for high pressure or the like. A tank 1 has a liquid level measuring device 2 comprising a differential pressure transmitter for measuring pressure and a liquid level. Flow rate measuring devices 3 each composed of an electromagnetic flow meter for measuring the amount of outflow from the pipe 1 are provided through respective pipes.

[0003]

In this conventional case,
In order to measure the liquid level and the flow rate of the tank, it is necessary to install a separate measuring device, which is expensive. To measure the flow rate, for example, when an electromagnetic flow meter is used, the length L of the pipe from the tank to the installation point of the electromagnetic flow meter is determined by the rectification of an object flowing through the pipe at the point measured by the electromagnetic flow meter. In order to achieve this, an extra space (3 to 5 times the flowmeter) that is proportional to the inner diameter of the pipe at the measurement point is required, so that an extra space is also required.

[0004]

SUMMARY OF THE INVENTION The present invention has been made as follows in order to solve the above-mentioned problems. That is,
In order to introduce the liquid level signal detected by the liquid level measuring device in the tank and convert it into an outflow flow rate, a sampling section for sampling the liquid level signal at regular time intervals, and a sampling signal from this sampling section for one sampling There is provided a memory for storing, and a flow rate calculation unit including a calculation unit for calculating from the current sampling signal from the sampling unit, the previous sampling signal from the memory, the tank area value, and the sampling time. Further, a flow rate calculation stop command unit is provided so that the calculation function can be arbitrarily stopped at the time of liquid supply to the tank.

[0005]

The method according to the present invention operates as follows. That is, the liquid level signal detected by the liquid level measuring device is introduced into the flow rate calculating section, and the flow rate calculating section calculates the equation (1) to obtain the outflow flow rate.

[0006]

(Equation 1)

Since the tank area value varies depending on the size of the tank, it can be rewritten. In addition, when replenishing the liquid in the tank, since the calculation for obtaining the flow rate value cannot be performed, a command section for stopping the flow rate calculation is provided, and the flow rate calculation is stopped.

[0008]

First Embodiment FIG. 1 shows a first embodiment of the present invention. In the figure, 1 is a tank, 2 is a liquid level measuring device, and there are various liquid level measuring devices 2. For example, a differential pressure transmitter is used. Reference numeral 10 denotes a flow rate calculation unit. The flow rate calculation unit 10 includes a sampling unit 11 and a memory 12.
And an operation unit 13. The sampling unit 11 samples the liquid level signal detected by the liquid level measuring device 2 at a fixed time interval, and is introduced into the arithmetic unit 13 together with the memory 12 storing the previous sampling signal, and the (1) ) Calculate the outflow flow rate by the calculation of the formula. Here, the area value in the tank differs depending on the size of the tank, so that it can be rewritten in the calculation unit.

In the present invention configured as described above,
The operation will be described. When the liquid level measuring device 2 is a differential pressure type, the pressure in the tank 1 is different from the atmospheric pressure, and when the liquid level fluctuates due to the outflow of the liquid, the pressure in the tank 1 also fluctuates due to the influence. Therefore, the liquid level can be obtained by determining the difference between the gas phase pressure and the pressure at the bottom of the liquid, and measuring the difference. The liquid level measuring device 2 displays one of the detected signals as the liquid level in the tank. For this purpose, it is output to the outside as a liquid level signal and is also output to the sampling unit 11 of the flow rate calculation unit 10. The sampling unit 11 samples the liquid level signal at predetermined time intervals, and
Is output to the operation unit 13. For example, a shift register is used as the memory 12, and when the current sampling signal is input, the previous sampling signal is transmitted. Therefore, the calculation unit 13 calculates the expression (1) using the current sampling value, the previous sampling value, and the previously set tank area value, and calculates m ³ / min or m ³ / sec. The unit is converted and output as a flow measurement value, which is used as a display signal.

When the liquid is replenished in the tank, there is a deviation in the flow rate measurement value. Therefore, a switch 14 which is an operation stop command unit is provided so that the operation can be stopped when the liquid is replenished by an external signal or the like.

FIG. 2 shows a second embodiment of the present invention.

FIG. 1 shows a flow rate calculating unit 10 according to a second embodiment of the present invention, which is different from the first embodiment of the present invention. This is the same as FIG. 1 showing the embodiment.

In FIG. 1, reference numeral 10 denotes a flow rate calculation unit. The flow rate calculation unit 10 includes a sampling unit 11, a memory 12, and a calculation unit 13. The sampling unit 11 samples the liquid level signal at predetermined time intervals as in the first embodiment of the present invention, but the sampling signal is output only to the memory 12 this time. The memory 12 can store at least two of the current and past sampling signals from the latest one. For example, when the current sampling signal and the previous sampling signal are stored, the current sampling signal and the previous sampling signal are output from the memory 12 to the calculation unit 13, and the first embodiment of the invention is used as a flow rate measurement value. Output to In the present embodiment, by storing a large amount of past sampling signals in the memory, it is possible to output an arbitrary sampling signal to the calculation unit and obtain a past flow measurement value or change the length of the sampling time. it can.

[0014]

According to the present invention, since the liquid level and the flow rate can be measured only by the signal of the liquid level measuring instrument, the cost can be saved, and the conventional flow measuring instrument becomes unnecessary. As a result, the piping space can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional liquid level and flow rate measuring device.

[Explanation of symbols]

 Reference Signs List 1 tank 2 liquid level measuring device 3 flow rate measuring device 10 flow rate calculating section 11 sampling section 12 memory 13 calculating section 14 switch

Claims (5)

[Claims] 1. A liquid level measuring device for measuring a liquid level is provided in a tank into which a liquid has been injected, and a liquid level signal detected by the liquid level measuring device is introduced into a flow rate calculating section. A method for measuring the flow rate of a tank, characterized in that the flow rate is converted into an outflow rate. 2. A flow rate calculation unit multiplies a difference between a previous liquid level measurement value and a current liquid level measurement value by an area value in a tank, and calculates a multiplication value between the current liquid level measurement time and the previous liquid level measurement time. 2. The method for measuring the flow rate of a tank according to claim 1, wherein the flow rate is calculated by dividing by a time difference between the two. 3. A flow rate calculator for installing a liquid level measuring device for measuring a liquid level in a tank into which a liquid is injected, introducing a liquid level signal from the liquid level measuring device and converting the signal into an outflow flow rate signal. A sampling unit for sampling the liquid level signal at regular time intervals, a memory for storing the sampling signal from the sampling unit, and a sampling signal for the current sampling from the sampling unit and a memory for storing the sampling signal. A flow rate measuring device for a tank, comprising: a calculating section for introducing a previous sampling signal, multiplying a difference between a previous sampling value and a current sampling value by an area value in a tank, and dividing the multiplied value by a sampling time. apparatus. 4. A method according to claim 1, wherein said arithmetic unit includes a current sampling signal from a sampling unit and a previous sampling signal from a memory. 4. The tank flow rate measuring device according to claim 3, wherein the flow rate is calculated by introducing two sampling signals. 5. The tank flow rate measuring device according to claim 3, wherein the tank is provided with a calculation stop command unit for stopping the calculation of the flow rate calculation unit at the time of liquid supply.