JPH07234146A - Liquid level detector - Google Patents

Abstract

PURPOSE:To provide a liquid level detector requiring no maintenance and inspection and capable of being produced inexpensively. CONSTITUTION:A liquid level detector is equipped a detector 1 having a central electrode wire 13 and the electrode wires 12, 14 parallelly arranged on both sides of the central electrode wire 13 and connected at one terminal parts thereof to be formed into a U-shape, an oscillator 2 applying high frequency power from the opened terminal part of the electrode wire 12 and a detector 3 detecting the high frequency power outputted from the opened terminal part of the electrode wire 14 and the output of this detector is allowed to correspond to the depth of a liquid. The detector 1 is arranged along the outside wall of a container formed from an insulating material and sealed by an insulating material to be vertically arranged in the container to be utilized in the detection of a liquid level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detector for electrically detecting a liquid level, and is particularly constructed so that maintenance and inspection are not required.

[0002]

2. Description of the Related Art As a detector for electrically detecting the liquid level of a liquid such as water contained in a container or tank, a plurality of electrode rods are suspended in the liquid to detect the conduction state between the electrode rods due to the liquid. To detect the liquid level, a device that emits ultrasonic pulses from the top of the container or tank and detects the reflected wave from the liquid level to detect the liquid level, and a pressure gauge attached to the bottom of the container or tank. A device for detecting the liquid level is known.

[0003]

In such a conventional liquid level detector, some kind of detection member must be installed in the container or tank. In addition, such a detection member tends to be expensive because it must operate stably for a long period of time without being corroded or altered.

Therefore, according to the present invention, the liquid level can be detected by attaching the detecting member to the outer surface of the container or the tank without attaching the detecting member to the container or the tank, and
The purpose of the invention is to provide a liquid level detector that can be manufactured inexpensively without requiring maintenance and inspection.

[0005]

[Means for Solving the Problems] Central electrode wire, and
A detector provided with a U-shaped electrode wire connected in parallel to both sides of the central electrode wire and having one end connected, and a detector arranged in the depth direction of the liquid to be detected, and opening of the U-shaped electrode wire. An oscillator for applying high-frequency power from one of the open ends and a detector for detecting high-frequency power output from the other open end of the U-shaped electrode wire. Configure to accommodate depth.

The detector is placed along the outer wall of the container made of an insulator, or the detector is sealed with an insulator and placed upright in the container to detect the liquid level.

[0007]

EXAMPLE As shown in FIG. 1, a detector 1 installed along the outer surface of an insulating container or tank 5 made of a synthetic resin such as polyethylene, and the detector 1 via a capacitor 6 are weak. An oscillator 2 for applying a high frequency power and a detector 1
The high-frequency power that is attenuated by and detected through the capacitor 7 is detected, and the detector 3 that obtains a signal corresponding to the level is compared with the reference voltage (ref) to detect the output. When the output of the unit 3 exceeds the reference voltage, and /
Alternatively, it is provided with a comparison circuit 4 that generates an output when the voltage drops below the reference voltage.

The detector 1, as shown in the plan view of FIG.
Striations 12, 13 arranged parallel to the surface of the elongated insulating plate 11,
14 and the filaments 12, 14 on both sides have a line 15 at its lower end.
Are connected to form a U-shaped electrode wire, the upper end of one of the wire rods 12 is connected to the oscillator 2, the upper end of the other wire rod 14 is connected to the detector 3, and the center wire is connected. The upper end of Article 13 is grounded.

The detector 1 having a distance of 7 mm between the filaments 12, 13 and 14 and a length of 160 mm is attached to a polyethylene tank 5 having a side wall thickness of 2 mm. The DC signal level obtained by detecting the output generated from the upper end of the wire 13 with the detector 3 by applying a high-impedance high-frequency power of 2.5 V with a rectangular wave having a frequency of 5 MHz and the tank 5 When the relationship with the water surface inside was examined, the high frequency power was lost due to the water inside the tank 5, so the characteristics shown in FIG. 3 were obtained. As is clear from this characteristic curve, by appropriately setting the intervals and lengths of the filaments 12, 13, 14 and the frequency of the applied high frequency power, the level of the DC signal output from the detector 3 is It has become clear that the relationship changes while maintaining a linear relationship.

Therefore, in the comparison circuit 4, the output of the detector 3 is compared with the reference voltage (ref), and when the output of the detector 3 exceeds the reference voltage (ref) and / or the output voltage drops below the reference voltage. When this occurs, an output is generated to control the utilization device, such as a pump or a solenoid valve, so that the liquid level in the tank 5 can be properly maintained.

In the embodiment described above, the liquid level is detected by the detector 1 attached to the outside of the container or tank. However, the detector 1 is sandwiched between synthetic resin sheets such as polyethylene for waterproofing. Alternatively, the detector 1 may be suspended in a container made of synthetic resin, or may be suspended in a container or tank, or may be erected at the bottom of the container or tank and used to detect the liquid level.

When a human body or an object approaches the detector 1, the level of the DC signal output from the detector 3 may fluctuate. To prevent such fluctuation, the back surface of the detector 1 It suffices to provide a shield electrode along the line and ground this shield electrode together with the central line 13.

[0013]

As is apparent from the description based on the above embodiments, according to the liquid level detector of the present invention, since the electrodes of the detector do not come into direct contact with liquid such as water, maintenance and inspection are required. It can be operated stably for a long time without.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a liquid level detector of the present invention,

FIG. 2 is a plan view of a detector used in the liquid level detector shown in FIG.

FIG. 3 is a characteristic curve diagram used to explain the operation of the liquid level detector shown in FIG.

[Explanation of symbols]

 1 Detector 13 Center electrode wire 12, 14, 15 U-shaped electrode wire 2 Oscillator 3 Detector 4 Comparison circuit

Claims (3)

[Claims] 1. A central electrode wire, and a U-shaped electrode wire that is arranged in parallel on both sides of the central electrode wire and has one end connected to it, and is arranged in the depth direction of the liquid to be detected. Detector, an oscillator for applying high-frequency power from one of the open ends of the U-shaped electrode wire, and a detection for detecting high-frequency power output from the other open end of the U-shaped electrode wire. And a liquid level detector which makes the output of the detector correspond to the depth of the liquid. 2. The liquid level detector according to claim 1, wherein the detector is arranged along the outer wall of the container made of an insulating material. 3. The liquid level detector according to claim 1, wherein the detector is sealed with an insulator and installed vertically in a container.