A liquid level detection device based on temperature transmitter

Abstract

This invention discloses a liquid level detection device based on a temperature transmitter, relating to the field of liquid level detection technology. The liquid level detection device includes: a measuring circuit replacing the temperature sensing element, a temperature transmitter, a circuit board, and a stainless steel tube; the measuring circuit includes: n+1 reed switches K0~K n and n+1 resistors R0 to R1 connected in series n One end of the zero-point resistor R0 is connected to the first input terminal of the temperature transmitter, and the other end is connected to the reed switch K0; the i-th reed switch K0... i One end is connected to resistor R i and R i+1 The circuit is connected to a common connection point, and the other end is connected to the second input terminal of the temperature transmitter; the measuring circuit is fixedly mounted on the circuit board; the circuit board is wrapped with insulating material and inserted into a stainless steel tube; the entire liquid level detection device is fixed on the magnetic float level gauge. This invention enables liquid level measurement without interrupting the production system when the remote level gauge malfunctions.

Description

Technical Field

[0001] This invention relates to the field of liquid level detection technology, and in particular to a liquid level detection device based on a temperature transmitter. Background Technology

[0002] Liquid level detection is indispensable in industrial production systems across various sectors, including petroleum, chemical, power, steel, natural gas, and water conservancy. Process equipment typically has two sets of level gauges: a remote level gauge for automatic control and a local level gauge (usually a magnetic float level gauge) for local indication. There are many types of remote level gauges, including dual-flange level transmitters, radar level gauges, magnetostrictive level gauges, and float level gauges.

[0003] Under ideal process conditions, the aforementioned level detection devices typically function normally. However, when a remote level gauge malfunctions, it cannot accurately measure the level of the process equipment, thus affecting the normal operation of the production system. In an automatic control system where the level signal from the process equipment cannot be transmitted remotely, automatic control of the process equipment is impossible, impacting the normal operation of the production system. This is especially true for level gauges that cannot be replaced while the production system is running, as they cannot be repaired or replaced. Only after shutting down the entire production system, depressurizing, and unloading materials can the malfunctioning remote level gauge be repaired or replaced. This not only delays normal production but also wastes raw materials and sometimes poses safety risks and environmental pollution hazards.

[0004] Therefore, how to provide an emergency liquid level detection device is a technical problem that urgently needs to be solved in the field of liquid level detection. Summary of the Invention

[0005] The purpose of this invention is to provide a liquid level detection device based on a temperature transmitter, which can measure the liquid level without interrupting the production system when the remote liquid level gauge fails.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A liquid level detection device based on a temperature transmitter includes: a measuring circuit replacing the temperature sensing element, a temperature transmitter, a circuit board, and a stainless steel tube; the measuring circuit includes: n+1 reed switches K0~K n and n+1 resistors R0 to R1 connected in series. n Where R0 is the zero-point resistance; R1~R n To detect resistance; one end of the zero-point resistor R0 is connected to the first input terminal of the temperature transmitter, and the other end of the zero-point resistor R0 is connected to the reed switch K0; the i-th reed switch K0... i One end is connected to resistor R i and resistance Ri+1 The common connection point is connected; the i-th reed switch K i The other end is connected to the second input terminal of the temperature transmitter; n-1≥i≥0; resistance R n One end is connected to reed switch K n-1 resistance R n The other end is connected to reed switch K n One end; reed switch K n The other end is connected to the second input terminal of the temperature transmitter;

[0008] The measuring circuit is fixedly mounted on the circuit board; the circuit board is wrapped with insulating material and inserted into the stainless steel tube; the liquid level detection device is fixed on the magnetic float level gauge.

[0009] Optionally, the insulating material is insulating tape or heat shrink tubing.

[0010] Optionally, the stainless steel pipe is a Φ18*1 stainless steel pipe.

[0011] Optionally, the zero-point resistor has a resistance of 100Ω.

[0012] Optionally, the zero-point resistor has a resistance of 1000Ω.

[0013] Optionally, the resistance value of the detection resistor is in the range of 0.5Ω to 2Ω.

[0014] Optionally, the output of the temperature transmitter varies between 4 and 20 mA corresponding to the zero point and full scale of the magnetic float level gauge.

[0015] Optionally, the positive and negative output terminals of the temperature transmitter are connected to the upper control system; the upper control system is used to display the measurement results.

[0016] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0017] This invention provides a liquid level detection device based on a temperature transmitter, comprising: a measuring circuit replacing the temperature sensing element, a temperature transmitter, a circuit board, and a stainless steel tube; wherein the measuring circuit includes: n+1 reed switches K0~K n and n+1 resistors R0 to R1 connected in series. nThe measuring circuit is fixedly mounted on a circuit board; the circuit board is wrapped with insulating material and inserted into a stainless steel tube; the entire liquid level detection device is fixed on a magnetic float level gauge. A measuring circuit consisting of a reed switch and a resistor replaces the input temperature sensing element (RTD or thermocouple) of the temperature transmitter. Through coupling with the magnetic float of the magnetic float level gauge, the purpose of detecting the liquid level using a temperature transmitter is achieved, expanding the application range of the temperature transmitter. This allows for liquid level measurement without interrupting the production system when the remote level gauge malfunctions.

[0018] This invention adds a liquid level detection device, consisting of a temperature transmitter as the main component, to a field magnetic float level gauge for measuring the liquid level in industrial equipment. It can also transmit the liquid level measurement signal to a higher-level control system for liquid level detection of process equipment in operation. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A schematic diagram of the measurement circuit structure and working principle of the liquid level detection device based on a temperature transmitter provided by the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The purpose of this invention is to provide a liquid level detection device based on a temperature transmitter, which can measure the liquid level without interrupting the production system when the remote liquid level gauge fails.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Figure 1 This is a schematic diagram of the liquid level detection device based on a temperature transmitter provided by the present invention. Figure 1As shown, the present invention discloses a liquid level detection device based on a temperature transmitter, comprising: a measuring circuit replacing the temperature sensing element, a temperature transmitter, a circuit board, and a stainless steel tube.

[0025] A temperature transmitter is an instrument that converts temperature variables into standardized, transmittable output signals. It is primarily used for measuring and controlling temperature parameters in industrial processes. Temperature transmitters use thermocouples or resistance temperature detectors (RTDs) as sensing elements. The signal from the sensing element is sent to the transmitter and processed through circuits including voltage regulation and filtering, operational amplification, nonlinear correction, V / I conversion, constant current, and reverse protection. The signal is then converted into a 4–20mA current signal, a 0-5V / 0-10V voltage signal, or an RS485 digital signal output, all linearly related to temperature.

[0026] This invention replaces the temperature sensing element of a temperature transmitter with a measuring circuit, proposing an extended application of the temperature transmitter to enable it to be used for liquid level measurement. For example... Figure 1 As shown, the measurement circuit includes: n+1 reed switches K0 to K1 n and n+1 resistors R0 to R1 connected in series. n Where R0 is the zero-point resistance; R1~R n To detect resistance. A reed switch, also called a magnetic reed switch, is an electrical switch that is operated by an applied magnetic field. When a magnetic field is near, the reed switch conducts; when the magnetic field is far away, the reed switch opens.

[0027] This invention uses n+1 reed switches K0 to K n and n+1 resistors R0 to R1 connected in series. n according to Figure 1 As shown, it is soldered onto a long strip circuit board. Specifically, one end of the zero-point resistor R0 ( Figure 1 Point B in the diagram) and the first input terminal of the temperature transmitter ( Figure 1 Terminal 3) is connected, and the other end of the zero-point resistor R0 is connected to the reed switch K0. The i-th reed switch K i One end is connected to resistor R i and resistance R i+1 The common connection point is connected; the i-th reed switch K i The other end ( Figure 1 Point A in the diagram) and the second input terminal of the temperature transmitter ( Figure 1 Terminal 2) is connected; n-1≥i≥0. Resistor R n One end is connected to reed switch K n-1 resistance R n The other end is connected to reed switch K n One end; reed switch K n The other end is connected to the second input terminal of the temperature transmitter.

[0028] The soldered circuit board is insulated by wrapping it with insulating material (insulating tape or heat shrink tubing) and then inserted into a stainless steel tube of suitable diameter to form the liquid level detection device of this invention. A Φ18*1 stainless steel tube is typically used.

[0029] During liquid level measurement, the liquid level detection device is fixed to the magnetic float level gauge. When the magnetic float of the magnetic float level gauge approaches the liquid level detection device of this invention, the magnetic field of the magnetic float poles will cause the reed switch at the corresponding position of the liquid level detection device to activate (close). Since the magnetic float of the magnetic float level gauge will float up and down with the change of liquid level height, it controls the activation of the reed switches at different positions in the liquid level detection device, thereby causing the resistance between points A and B to change with the change of liquid level height. Thus, the resistance between input terminals 2 and 3 of the temperature transmitter is the sum of the zero-point resistance R0 and the detection resistance below the activation point (closed reed switch), which serves as the input resistance of the temperature transmitter. The temperature transmitter converts the input resistance signal into a standard 4-20mA current signal, which is output from the positive and negative output terminals of the temperature transmitter to the upper control system, which is used to display the measurement results.

[0030] For example, when the magnetic field of the magnetic float approaches the reed switch K2, the reed switch K2 is activated, and the resistance between points A and B becomes R0 + R1 + R2. n-2 At that time, reed switch K n-2 When the magnets are engaged, the resistance between points A and B is R0 + R1 + R2 + ... + R n-2 Similarly, the resistance between point A and point B is the input resistance of the temperature transmitter.

[0031] When the required liquid level gauge range is small in practical applications, the selected zero-point resistor R0 is also small; when the required liquid level gauge range is large, the selected zero-point resistor R0 is also large. For ease of setting up the temperature transmitter and simplifying calculations, a 100Ω resistor is typically chosen for the zero-point resistor R0 when the required liquid level gauge range is small. When the required liquid level gauge range is large, a 1000Ω resistor is typically chosen for the zero-point resistor R0.

[0032] Based on the required level gauge range and the calibration number of the temperature transmitter, the detection resistances R1 to R2 are determined. n The resistance value is typically selected between 0.5Ω and 2Ω. After determining the resistance value of the sensing resistor, calculate the sum of the sensing resistor and the zero-point resistance, and then set the measurement range of the temperature transmitter so that the output of the temperature transmitter corresponds to the zero point and full scale of the level gauge varying between 4 and 20mA.

[0033] For example, if the resistance of the sensing resistor is selected as 1Ω and the required range of the level gauge is 500mm, a resistor is usually set every 5mm, so 100 sensing resistors are needed. The resistance change of the level gauge across its full range is 100Ω. If the temperature transmitter's calibration number is set to PT100, according to the temperature resistance value correspondence table for PT100 thermal resistors, the temperature transmitter's measurement range can be set to 0~267℃. That is to say, when the liquid level is at zero, the magnetic field of the magnetic float approaches the reed switch K0, the reed switch K0 is activated, the input resistance of the temperature transmitter is 100Ω, and the output current of the temperature transmitter is 4mA; when the level gauge is at full scale, the magnetic field of the magnetic float approaches the reed switch K0. 100 reed switch K 100 When engaged, the temperature transmitter has an input resistance of 200Ω and an output current of 20mA.

[0034] Based on the above principles, the liquid level detection device of this invention can convert changes in liquid level into changes in standard current, and then send the changing current signal to the upper control system for display, thereby realizing real-time monitoring of liquid level.

[0035] This invention expands the application scope of temperature transmitters by using them to detect liquid levels. This allows temperature transmitters to be used not only for temperature measurement but also for liquid level measurement. Furthermore, the liquid level detection device based on temperature transmitters provided by this invention can achieve relatively accurate liquid level measurement without interrupting the production system when the remote liquid level gauge malfunctions.

[0036] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0037] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A liquid level detection device based on a temperature transmitter, characterized in that, include: The measuring circuit, temperature transmitter, circuit board, and stainless steel tube are used to replace the temperature sensing element. The measurement circuit includes: n+1 reed switches. ~ and n+1 resistors connected in series ~ ;in Zero-point resistance; ~ For detecting resistance; zero-point resistance One end is connected to the first input terminal of the temperature transmitter, and the zero-point resistor The other end is connected to a reed switch The i-th reed switch One end is connected to the resistor and resistance The common connection point is connected; the i-th reed switch The other end is connected to the second input terminal of the temperature transmitter; n-1≥i≥0; resistance One end is connected to a reed switch ,resistance The other end is connected to a reed switch One end; reed switch The other end is connected to the second input terminal of the temperature transmitter; The measuring circuit is fixedly mounted on the circuit board; the circuit board is wrapped with insulating material and inserted into the stainless steel tube; the liquid level detection device is fixed on the magnetic float level gauge; The measuring circuit replaces the input temperature measuring element of the temperature transmitter, and the measuring circuit is coupled to the magnetic float of the magnetic level gauge, so that the temperature transmitter can be used for level detection. The output of the temperature transmitter corresponds to the zero point and full scale of the magnetic float level gauge, which vary between 4 and 20 mA. Determine the resistance value of the sensing resistor based on the required range of the level gauge and the graduation number of the temperature transmitter. After determining the resistance value of the sensing resistor, calculate the sum of the sensing resistor and the zero-point resistance, and then set the measurement range of the temperature transmitter so that the output of the temperature transmitter corresponds to the zero point and full scale of the level gauge between 4 and 20 mA.

2. The liquid level detection device according to claim 1, characterized in that, The insulating material is insulating tape or heat shrink tubing.

3. The liquid level detection device according to claim 1, characterized in that, The stainless steel pipe is a Φ18*1 stainless steel pipe.

4. The liquid level detection device according to claim 1, characterized in that, The zero-point resistor has a resistance of 100Ω.

5. The liquid level detection device according to claim 1, characterized in that, The zero-point resistor has a resistance of 1000Ω.

6. The liquid level detection device according to claim 1, characterized in that, The resistance value of the detection resistor is in the range of 0.5Ω to 2Ω.

7. The liquid level detection device according to claim 1, characterized in that, The positive and negative output terminals of the temperature transmitter are connected to the upper control system; the upper control system is used to display the measurement results.

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