JPH10281852A - Liquid-level detection sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a liquid level by using a light-emitting diode for a sensor for measuring the liquid level in a container. SOLUTION: In a sealed container where a liquid gas is accommodated inside, an LED(light-emitting diode) 8 is mounted to the lower internal part of a cylindrical body 5 where an opening 11 is provided at a lower edge and is connected to a circuit 10 of a resistor sensor, detecting the liquid level according to the change in the resistance of the circuit by allowing the liquid level in the container to approach the LED. A plurality of LEDs 8 are arranged at a constant interval at the lower internal part of the cylindrical body 5 and each LED is connected to the circuit 10 of the resistor sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detection sensor for a liquid, particularly a liquefied gas.

[0002]

2. Description of the Related Art Conventionally, there are various types of temperature sensors as follows. A sensor using a thermocouple is good for short-time measurement, but is not suitable for long-time measurement, especially when the liquid level and the temperature immediately above the liquid level are the same. The surface could not be detected. In addition, it has been impossible to measure the liquid level in a sealed container because the temperature in the container tends to be uniform. A sensor using a platinum resistor measures the temperature difference between a portion in which the sensor is heated and the temperature is lowered by the latent heat of vaporization when immersed in a liquid, and a gas layer in which the liquefied gas is vaporized. However, it has a disadvantage that the detection sensitivity is low when measuring the liquid surface at a low temperature. A sensor using a carbon resistor has a drawback that the temperature is large and the detection sensitivity when measuring the liquid level is low because the sensor generates heat. Further, there is a problem that the shape of the element is large and the life is short. The ball type float sensor has an advantage that the average of the liquid level can be easily controlled. However, since the element is large and a float such as a ball is used, the entire shape of the sensor is used. However, there is a disadvantage that the size becomes larger. In particular, in the case of a sealed container, there is a problem that it is difficult to take out the vertical movement of the float to the outside. The optical fiber sensor has an advantage that the liquid level can be determined quickly, but when measuring a low-temperature liquid level, if the frost or moisture adheres to the end face of the fiber, the sensor cannot operate. In addition, there is a disadvantage that the handling of connecting the lead wire is troublesome and troublesome.

[0003]

As described above, the conventional temperature sensors have both advantages and disadvantages, and are particularly suitable for a sensor for accurately measuring the liquid level of a liquefied gas. Nothing was found. The present invention relates to L
An object of the present invention is to detect a liquid level by using an ED, that is, a light emitting diode as a sensor for measuring the liquid level.

[0004]

SUMMARY OF THE INVENTION According to the present invention, an LED is mounted inside a cylindrical body having an opening at a lower end in a sealed container containing a liquefied gas therein, and the LED is connected to a resistor sensor. The liquid level is detected by a change in the resistance value of the circuit when the liquid level in the container approaches the LED by connecting to the circuit of-. Further, the container according to the present invention is a container having an upper part opened.
Further, the present invention is characterized in that a plurality of LEDs are arranged and mounted at regular intervals inside a lower part of a cylindrical main body having an opening at a lower end, and each LED is connected to a circuit of a resistor sensor. Is what you do.

[0005]

When a liquid level detecting sensor using an LED comes into contact with the liquid surface of a liquefied gas contained in a container, the LED immediately senses the temperature because it is a point light source, and the temperature is used as a resistor sensor circuit. The liquid level is detected via. Since this LED is inexpensive, a plurality of liquid level detection sensors are provided in multiple stages to detect the liquid level in the container in multiple stages.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a sealed container formed entirely using a heat insulating member, and a liquefied gas such as nitrogen or carbon dioxide is placed in the sealed container 1. A gas outlet 2 to be supplied is mounted on one upper side of the container 1. The gas outlet 2 is connected to a liquid storage tank (not shown) or the like via a pipe 3. The gas outlet 2 is vertically positioned inside the container, and the liquid level detection sensor-4 is attached to and detached from the container 1. Mounted as possible. The liquid level detection sensor 4 is housed in the cylindrical main body 5 so as not to be affected by the flying liquefied gas mixed in the gas layer.

[0007] The cylindrical main body 5 constituting the liquid level detecting sensor-4 is
As shown in FIG. 2, an LED 8 is provided on a support rod 7 disposed below a housing 6 mounted inside the cylindrical main body.
The LED is connected via a lead wire 9 to a known resistor sensor circuit 10 connected to a power supply (not shown).

The LED 8 serving as the sensor has a cylindrical shape around the LED 8 in order to prevent malfunction due to the adhering floating liquefied gas other than the liquid surface 30 of the liquefied gas stored in the container 1. It is covered by the main body 5. An opening 11 is provided at the lower end of the cylindrical main body 5 so that the liquid level 30 that rises due to an increase in the liquefied gas supplied into the container 1 can enter the cylindrical main body 5. Further, the liquefied gas in the container 1 can be distributed to a desired location from the distribution pipe 40.

As shown in FIG. 3, a plurality of LEDs 8a can be mounted on the liquid level sensor 4a to detect the liquid level in multiple stages. That is, a plurality of LEDs 8a, 8a are mounted on a long supporting rod 7a provided at a lower portion of a housing 6a mounted inside the cylindrical main body 5a at fixed or arbitrary intervals, respectively, and individually provided in parallel. Resistor sensor circuit 1
By connecting the LEDs 8a and 8a separately to each other so as to operate the LEDs 8a and 8a separately, the liquid level in the container 1 can be detected and controlled in multiple stages.

That is, as the liquid level 30 that has entered the cylindrical main body 5a rises, it is successively detected by the LED 8a, and the liquid level moving inside the container 1 from outside the sealed container 1 is detected in multiple stages. Can be.

In FIG. 4, reference numeral 21 denotes an open container provided with an opening 20 whose upper part is opened by using a heat insulating member, and a gas ejection port 22 for supplying a liquefied gas from the outside is positioned in the container. A pipe 23 is connected to the rear end of the jet port 22. Further, an LED 8 is mounted on a support rod 7 disposed below the inside of the cylindrical main body 5 which is disposed vertically in one side of the container and is connected to a known resistor sensor circuit 10. I have. Further, as shown in FIG. 3, it is of course possible to detect the liquid level 30 in multiple stages using the liquid level detection sensor 4a having a plurality of LEDs 8a.

Next, the operation of the present embodiment will be described. For example, when liquid nitrogen stored in a storage tank (not shown) is transferred to the sealed container 1, the liquid contained in the gas is separated. The liquefied gas is controlled using an automatic valve or the like linked to a sensor made of platinum or a carbon resistor for controlling the liquid level. Since this sensor made of platinum or carbon resistor is expensive, a plurality of sensors are required to control the liquid surface in multiple stages in the container, but it is costly to install a plurality of expensive sensors. Difficult.

FIG. 1 shows a case where the liquid level is detected using a conventional sensor using a platinum resistor or a carbon resistor. In Table 1, E represents a graph showing a change in current, and F represents a current.
Is a graph showing a change in temperature, and a position indicated by H indicates a state where the sensor is located 3 to 5 mm above the liquid level. K indicates the position of the sensor whether or not it is slightly away from the liquid surface, and indicates the voltage output and the temperature change during that time.

[0014]

[Table 1]

The liquid level in the sealed container 1 containing liquid nitrogen at about -196 ° C rises, and the lower end of the liquid level detecting sensor is positioned at about 3 to 5 mm above the liquid level at about -196 ° C. When located, the temperature shown in graph F is around 150 ° C.,
The voltage shown in graph E is an output of about 3V. However, when the sensor comes into contact with the liquid surface, when the sensor does not come into contact with the liquid surface in the range of K, the voltage is about 4.3 V, such as -178 ° C. When the temperature F dropped to −193 ° C., the voltage output was 8.1 V, and a potential difference of about 3.8 V was generated.

When the sensor leaves the liquid level again, the temperature is -184 ° C and the voltage is about 5.1V. When the sensor comes into contact with the liquid level, the temperature drops to -193 ° C and the current is reduced. It becomes 8.1 V, and it can be detected that the sensor is in contact with the liquid level.

[0017]

[Table 2]

Table 2 shows the LED according to the present invention as a sensor.
When the sensor comes into contact with the liquid surface, the temperature drops to -192 ° C., and the graph E shows the voltage.
Indicates 10V. The temperature at which the liquefied gas starts to be supplied into the closed vessel is approximately the atmospheric temperature and the voltage is about 2 V. However, when the sensor comes into contact with the liquid surface, the temperature drops to -196 ° C. It shows an output of 10 V, a potential difference of about 8 V, and a wider range of voltage changes than in the prior art. This has the advantage that the configuration of the resistor sensor circuit can be simplified and hysteresis can be sufficiently obtained.

[0019]

[Table 3]

In the E curve in Table 3, the time from when the LED comes into contact with the liquid surface to when the voltage changes is delayed by a time indicated by 6s in Table 3.

When the LED is operated at an extremely low temperature, for example, at a temperature of about -196 ° C., the light emission amount of the LED is further increased. When the LED is used at a low temperature in this way, it has the advantage of further increasing the amount of light. Therefore, if a window is provided on the wall surface of the above-described cylindrical main body or if the LED is formed of a transparent resin material, the liquid level detection of the LED is performed. Detection can also be made by the amount of light. This case has an advantage in the case of night work or the like.

[0022]

By using the LED according to the present invention as a sensor, the temperature of the liquid surface can be reduced because the conventional platinum or carbon resistor is the source of light, whereas the LED is a point light source. There is no time because it is transmitted instantaneously to the whole of the LED, and the liquid level detection sensor senses immediately when the LED comes into contact with the liquid surface, and immediately senses it. Can be obtained. This LED is extremely inexpensive in terms of cost. Therefore, even if a plurality of sensors are mounted in the container, the cost is hardly high.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a state where a liquid level detection sensor according to the present invention is mounted on a sealed container.

FIG. 2 is an enlarged sectional view of a main part of a liquid level detection sensor having one LED, which is partially broken.

FIG. 3 is an enlarged sectional view of a main part of a liquid level detection sensor including a plurality of LEDs, which is partially broken.

FIG. 4 is a cross-sectional view of a main part in a state where a liquid level detection sensor is mounted inside an open container having an open top.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sealed container 2 Gas ejection port 4 Liquid level sensing sensor 5 Cylindrical main body 7 Support rod 8 LED 8a LED 10 Resistor sensor circuit 11 Opening 30 Liquid level

Claims (3)

[Claims] An LED is provided inside a cylindrical body having an opening at a lower end in a sealed container containing a liquefied gas therein.
And connecting the LED to a circuit of a resistor sensor, and detecting a liquid level by a change in the resistance value of the circuit when the liquid level in the container approaches the LED. Surface detection sensor. 2. The liquid level detecting sensor according to claim 1, wherein the container is a container having an upper part opened. 3. A plurality of LEDs are arranged and mounted at regular intervals inside a lower part of a cylindrical main body having an opening at a lower end.
2. The liquid level detecting sensor according to claim 1, wherein the EDs are connected to respective circuits of the resistor sensor.