JPH0550325U - Liquid level gauge - Google Patents

Abstract

(57) [Summary] [Purpose] Even if the level gauge is not taken out from the tank, it is easy to determine the contact failure of the level gauge. [Configuration] Each contact signal 1 to 4 output from the liquid level gauge is
Since a predetermined pattern is formed according to the state of the liquid level to be detected, the contact signals 1 to 4 are converted into electric signals by the converter 21, and the converted electric signals are AND circuits 22 to 2.
6. It is determined whether or not the contact signals 1 to 4 have the above-described predetermined pattern by performing a logical operation in the logic circuit including the NOR circuit 27, and the contact failure of the liquid level gauge is determined.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a liquid level gauge having a failure determination circuit for determining a failure of a liquid level gauge that detects a liquid level.

[0002]

[Prior Art]

 Conventionally, this type of level gauge has been used to manage water treatment chemicals in cooling water systems, boilers, etc., and for example, a float level gauge has been used to monitor the amount of liquid in a chemical solution tank. In the above float level gauge, a support rod is provided with a plurality of measuring points, each of the above measuring points is provided with a "plow", and the presence / absence of liquid is checked by turning on / off a switch linked to the ups and downs of the "plow". Had detected.

Since this switch has mechanical contacts, if it is used for a long period of time, an electrical or mechanical failure may occur, which may cause the contacts to fail and always turn on or off. In addition, there was a break in the wiring from the liquid level gauge to the monitoring equipment and a failure due to poor connection of the terminals. Conventionally, maintenance personnel remove the level gauge from the tank and submerge the level gauge in the prescribed liquid for each contact to determine the contact failure of the level gauge. I was going.

In recent years, measurement signals of these devices have been communicated with a remote host computer via a telephone line.

[0005]

[Problems to be solved by the device]

 However, in the above judgment, it is necessary to take out the entire liquid level gauge from the inside of the tank, so the work is complicated, and if there is a powerful medicine in the tank, there is a problem that the above taking out work is dangerous. there were. In addition, in order to reduce the cost related to communication, the frequency of data communication requests from the host computer is once per week, which is a fairly long span. It was

The present invention has been made in view of the above problems, and provided with a failure determination circuit capable of easily determining a contact failure of the liquid level meter without taking out the liquid level meter from the tank. The purpose is to provide a liquid level gauge. Another object of the present invention is to provide a liquid level meter suitable for inexpensive online communication of a liquid level meter failure between computers via a telephone line.

In order to achieve the above object, in the present invention, conversion means for converting a contact signal of a liquid level gauge for detecting a predetermined liquid surface into an electric signal, and the above-mentioned conversion electric signal in accordance with the converted electric signal. There is provided a liquid level gauge failure determination circuit comprising a failure level determination circuit for determining a level gauge failure.

[0008]

[Action]

 Since each contact signal output from the liquid level gauge has a predetermined pattern according to the state of the liquid level to be detected, whether or not each contact signal has the above predetermined pattern is determined by, for example, a predetermined logic. The abnormality detection means, which is composed of a circuit, performs a logical operation to determine the failure of the liquid level gauge.

Therefore, it is possible to safely make a failure determination without taking out the liquid level gauge from the inside of the tank.

[0010]

【Example】

 An embodiment of the present invention will be described with reference to the drawing of FIG. FIG. 1 is a circuit diagram showing a circuit configuration of a failure determination circuit according to the present invention. In the figure, the support rod 10 of the float level gauge installed in the tank has four measuring points, for example, the uppermost measuring point 11, the second measuring point 12, and the third measuring point 13 from the upper side in the figure. And the lowest measurement point 14 is provided. Each of the above measurement points is provided with a "plow" (not shown), and contact signals 1 to 4 indicating the presence or absence of liquid are output by turning on / off the float switch that is linked to the ups and downs of the "plow". ing. Here, the contact signal 1 is the output signal from the highest measuring point 11, the contact signal 2 is the output signal from the second measuring point 12, the contact signal 3 is the output signal from the third measuring point 13, and the contact signal is Signal 4 represents the output signal from the lowest measurement point 14.

When the liquid in the tank is discharged, the float level gauge always turns off (or may be turned on) in sequence from the float switch at the highest measurement point 11, so the above measurement The state of the float switch at points 11 to 14 has five patterns shown in the table below.

[0012]

[Table 1] Therefore, when a pattern other than these five patterns occurs, it can be determined that a failure has occurred in the float level gauge. In the present embodiment, the pattern indicating the occurrence of the failure is detected by the logical operation of the logic elements forming the failure determination circuit 20, and the failure determination circuit 20 is shown in FIG.

The failure determination circuit 20 includes a conversion unit 21, respective AND circuits 22 to 26, and a NOR circuit 27. The converter 21 is connected to the float switches at the measurement points 11 to 14, converts the contact signals 1 to 4 output from the float switch into electrical signals and outputs the electrical signals to the AND circuits 22 to 26.

The AND circuits 22 to 26 perform a logical product operation of the signals input from the conversion unit 21 and determine whether or not the input signal corresponds to the patterns 1 to 5. That is, the AND circuit 22 detects the pattern 1 state in which all the contact signals 1 to 4 are ON, the AND circuit 23 detects the pattern 2 state in which only the contact signal 1 is OFF, and the AND circuit 24 , The contact signals 1 and 2 detect the state of the pattern 3 of OFF, the AND circuit 25 detects the state of the pattern 4 of which only the contact signal 4 is ON, and the AND circuit 26 detects all the contact signals 1 to 4 are OFF. The state of pattern 5 is detected. When a signal corresponding to any of the patterns 1 to 5 is input, the corresponding AND circuit outputs a level signal of "1" to the NOR circuit 27, and also corresponds to any of the patterns 1 to 5. When no signal is input, each AND circuit 22-26 outputs a level signal of "0" to the NOR circuit 27.

The NOR circuit 27 performs a NOR operation on the signals input from the AND circuits 22 to 26. If any of the input signals is a level signal of "1", it is inverted "0". The level signal of "" is output to an alarm output circuit (not shown) or a communication circuit which is transmitted to a host computer for fault management via a telephone line. Therefore, in this embodiment, when the contact signals 1 to 4 output from the measurement points 11 to 14 have any of the patterns shown in Table 1, any one of the AND circuits 22 to 26 is connected. A "1" level signal is output from the circuit, and the output of the NOR circuit 27 becomes a "0" level signal indicating normality. When the contact signals 1 to 4 do not correspond to any of the patterns shown in Table 1, the AND circuits 22 to 26 output the level signal of "0" and the output of the NOR circuit 27 becomes abnormal. It becomes a level signal of "1" indicating. The alarm output circuit outputs an alarm signal when the level signal indicating the abnormality is fetched from the NOR circuit 27, and the host computer receives the level signal indicating the abnormality and informs the maintenance person of the liquid level meter. Can indicate the occurrence of abnormalities and replacement.

Therefore, in the present embodiment, since the failure determination circuit can automatically determine the failure of the liquid level gauge from the pattern of each contact signal of the liquid level gauge, when a powerful drug is contained in the tank. However, it is possible to safely make a failure determination without taking out the liquid level gauge from the tank. Further, in this embodiment, by using the telephone line, the detected failure can be notified online to the host computer installed far from the computer in the field. Faults can be communicated regardless of the data request from.

In this embodiment, the float liquid level meter having the float switch has been described, but the present invention is not limited to this, and any liquid level meter having a plurality of upper and lower contacts can be applied to the present invention. It can be a target of such a failure determination. Further, the failure judgment circuit according to the present invention is not limited to the logic logic composed of the AND circuit and the NOR circuit shown in FIG. 1, but may be composed of, for example, a NAND circuit or a NOR circuit. Furthermore, it is also possible to carry out arithmetic processing using a microcomputer or the like to make a failure determination.

[0018]

[Effect of the device]

 As described above, according to the present invention, the converting means for converting the contact signal of the liquid level gauge for detecting the predetermined liquid level into an electric signal, and the failure of the liquid level gauge according to the converted electric signal. Since it is provided with a failure determination circuit for determining, it is possible to easily determine the contact failure of the liquid level meter without taking out the liquid level meter from the tank.

Further, since the failure determination circuit is provided, it is possible to detect the failure online, which is effective when communicating the failure of the liquid level gauge through the telephone line.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a circuit configuration of a failure determination circuit according to the present invention.

[Explanation of symbols]

 10 Liquid level gauge support rods 11 to 14 Measurement points 20 Failure determination circuit 21 Conversion unit 22 to 26 AND circuit 27 NOR circuit

Claims (1)

[Scope of utility model registration request] 1. A conversion means for converting a contact signal of a liquid level gauge for detecting a predetermined liquid level into an electrical signal, and a failure determination circuit for determining a failure of the liquid level gauge according to the converted electrical signal. A liquid level gauge characterized by having and.