Double-current alternating excitation circuit of electromagnetic flowmeter

Abstract

The utility model discloses a double-current alternating excitation circuit of an electromagnetic flowmeter. The circuit comprises a V / I conversion circuit A and a V / I conversion circuit B which are respectively used for converting the voltage of a voltage-stabilized direct-current power supply VCC1 and the voltage of a voltage-stabilized direct-current power supply VCC2 into current, and a current switching circuit which is used for switching and connecting the V / I conversion circuit A and the V / I conversion circuit B into a direction switching circuit, a direction switching circuit for switching a current switching circuit to a current direction and a CPU (Central Processing Unit) are used for switching the current of a V / I conversion circuit A and a V / I conversion circuit B which are accessed by controlling a current switching circuit Q and controlling the direction switching circuit to switch the direction of the current accessed by the current switching circuit, so that a coil of the sensor generates forward and reverse alternating excitation excitation; the problem of insufficient sampling time caused by inductance of a sensor coil can be avoided under high excitation frequency, heating of the excitation circuit can be effectively avoided, and the utilization efficiency of a power supply is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of electromagnetic flowmeters, and in particular relates to a double-current alternating excitation circuit of an electromagnetic flowmeter. Background Art

[0002] Electromagnetic flowmeter is a new type of flow measurement instrument that has developed rapidly with the development of electronic technology. Electromagnetic flowmeter is an instrument that uses the principle of electromagnetic induction to measure the flow rate of conductive fluid according to the electromotive force induced when the conductive fluid passes through an external magnetic field. The advantages of electromagnetic flowmeter are extremely small pressure loss and a large measurable flow range; the output signal is linear with the measured flow rate and has high accuracy. Electromagnetic flowmeter is a flowmeter that measures flow based on Faraday's law of electromagnetic induction, and its structure includes a converter and a sensor. The converter drives the sensor to establish a constant magnetic field, and the amplitude of the electrical signal collected by the sensor electrode reflects the flow rate of the medium passing through the sensor. According to the measurement principle of the electromagnetic flowmeter, in order to ensure the stability of the magnetic field, the general electromagnetic flowmeter adopts constant current excitation. The method is to select a voltage reference source according to the required current value, convert the voltage reference through VI conversion, and convert it into a current source, and then drive the sensor coil to generate a magnetic field through direction switching.

[0003] However, in practical applications, since the sensor coil is generally made of enameled wire and has a large inductance, when the switching frequency of the excitation current is high, the inductive reactance generated by the inductance will be very large. If the power supply voltage of the excitation circuit is low, a longer stabilization time is required to generate a stable magnetic field, resulting in a shortened sampling time; and in order to achieve faster stabilization, the power supply voltage of the excitation circuit must be higher than the actual required voltage, which will cause energy loss in the excitation constant current circuit, causing the circuit to heat up, affecting the performance of the entire machine, and even affecting the measured medium, causing the medium temperature to rise. Utility Model Content

[0004] The utility model aims to overcome the deficiencies in the prior art and provides a double-current alternating excitation circuit for an electromagnetic flowmeter.

[0005] In order to achieve the purpose of the utility model, the utility model is implemented by adopting the following technical solution.

[0006] A double current alternating excitation circuit for an electromagnetic flowmeter, comprising:

[0007] V / I conversion circuit, which can convert the reference voltage into current;

[0008] A regulated DC power supply, used for providing a regulated DC power supply voltage VCC;

[0009] A direction switching circuit is used to drive the coil of the sensor to generate positive and negative alternating excitation;

[0010] The sensor collects the amplitude of the electrical signal through electrodes;

[0011] The dual current alternating excitation circuit also includes a current switching circuit and a CPU;

[0012] The regulated DC power supply includes a regulated DC power supply VCC1 and a regulated DC power supply VCC2, and the voltage of the regulated DC power supply VCC1 is greater than the voltage of the regulated DC power supply VCC2;

[0013] The V / I conversion circuit is composed of a V / I conversion circuit A and a V / I conversion circuit B, wherein: the input end of the V / I conversion circuit A is connected to the output end of the regulated DC power supply VCC1, and the output end of the V / I conversion circuit A is connected to the input end 3 of the current switching circuit; the input end of the V / I conversion circuit B is connected to the output end of the regulated DC power supply VCC2, and the output end of the V / I conversion circuit B is connected to the input end 1 of the current switching circuit;

[0014] The current switching circuit is composed of a first double-throw electronic analog switch SW1, which is used to switch the current connected to the V / I conversion circuit A and the V / I conversion circuit B;

[0015] The direction switching circuit is composed of a direction switching circuit A and a direction switching circuit B connected in parallel between the current switching circuit and the sensor, and the direction switching circuit A and the direction switching circuit B have the same structure; wherein:

[0016] The direction switching circuit A comprises a second double-throw electronic analog switch SW2;

[0017] The direction switching circuit B comprises a third double-throw electronic analog switch SW3;

[0018] The CPU controls the current switching circuit to connect the current of the V / I conversion circuit A and the V / I conversion circuit B to the direction switching circuit, and controls the direction switching circuit A and the direction switching circuit B to switch the direction of the connected current, so as to drive the coil of the sensor to generate positive and negative alternating excitation.

[0019] As a preferred solution of the present utility model, the IO1 interface of the CPU is connected to the interface 4 of the first double-throw electronic analog switch SW1, its IO2 interface is connected to the interface 4 of the third double-throw electronic analog switch SW3, and its IO3 interface is connected to the interface 4 of the double-throw electronic analog switch SW2.

[0020] As a preferred solution of the utility model, interface 3 of the first double-throw electronic analog switch SW1 is connected to the connecting line between the transistor Q1 and the capacitor C1 in the V / I conversion circuit A, its interface 1 is connected to the connecting line between the transistor Q2 and the capacitor C2 in the V / I conversion circuit B, and its interface 2 is connected to the connecting lines of interface 3 of the second double-throw electronic analog switch SW2 and interface 3 of the third double-throw electronic analog switch SW3.

[0021] As a preferred embodiment of the utility model, the V / I conversion circuit A is composed of a voltage reference chip U1, a resistor R1, a resistor R2 and a resistor R3, a transistor Q1, an operational amplifier U2 and a capacitor C1; the input end of the voltage reference chip U1 is connected to a regulated DC power supply VCC1, and its output end is connected to the non-inverting input end of the operational amplifier U2 through a resistor R2, and its ground end is grounded; the voltage of the regulated DC power supply VCC1 is applied between the inverting input end and the common end of the operational amplifier U2, its inverting input end is connected to the connecting line between the resistor R1 and the emitter of the transistor Q1, its output end is connected to the base of the transistor Q1 through a resistor R3, and its non-inverting input end and the common end are grounded; the collector of the transistor Q1 is grounded through the capacitor C1, and its emitter is connected to the regulated DC power supply voltage VCC1 through the resistor R1.

[0022] As a preferred embodiment of the present utility model, the V / I conversion circuit B is composed of a voltage reference chip U3, a resistor R4, a resistor R5, a resistor R6, a transistor Q2, an operational amplifier U4 and a capacitor C2; the input end of the voltage reference chip U3 is connected to the regulated DC power supply voltage VCC2, and its output end is connected to the non-inverting input end of the operational amplifier U4 through the resistor R5, and its ground end is grounded; the voltage of the regulated DC power supply voltage VCC2 is applied between the inverting input end and the common end of the operational amplifier U4, its inverting input end is connected to the connecting line between the resistor R4 and the emitter of the transistor Q2, its output end is connected to the base of the transistor Q2 through the resistor R6, and its non-inverting input end and the common end are grounded; the collector of the transistor Q2 is grounded through the capacitor C2, and its emitter is connected to the regulated DC power supply voltage VCC2 through the resistor R4.

[0023] As a preferred solution of the utility model, the direction switching circuit A is composed of a second double-throw electronic analog switch SW2 and a resistor R8, the interface 3 of the second double-throw electronic analog switch SW2 is connected to the interface 3 of the third double-throw electronic analog switch SW3, its interface 1 is grounded through the resistor R8, and its interface 2 is connected to the negative pole of the sensor coil.

[0024] As a preferred solution of the utility model, the direction switching circuit B is composed of a third double-throw electronic analog switch SW3 and a resistor R7, the interface 3 of the third double-throw electronic analog switch SW3 is connected to the interface 3 of the second double-throw electronic analog switch SW2, its interface 1 is grounded through the resistor R7, and its interface 2 is connected to the positive pole of the sensor coil.

[0025] Compared with the prior art, the beneficial effects achieved by the utility model are:

[0026] In the utility model, by setting reference circuits and V / I conversion circuits with different high and low voltages, the CPU switches constant current excitation through a current switching circuit, and the CPU switches the excitation direction through a direction switching circuit to excite the sensor. In the initial stage of switching the excitation, the CPU controls high voltage excitation, and switches to low voltage excitation in the later stage. This can effectively avoid the problem of insufficient sampling time caused by the inductance of the sensor coil at a high excitation frequency, and can effectively avoid heating of the excitation circuit, thereby improving the power supply utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the circuit structure of the utility model. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0029] As an embodiment of the present utility model, Figure 1 As shown, the dual current alternating excitation circuit of the electromagnetic flowmeter comprises:

[0030] A double current alternating excitation circuit for an electromagnetic flowmeter, comprising:

[0031] V / I conversion circuit, which can convert the reference voltage into current;

[0032] A regulated DC power supply, used for providing a regulated DC power supply voltage VCC;

[0033] A direction switching circuit is used to drive the coil of the sensor to generate positive and negative alternating excitation;

[0034] The sensor collects the amplitude of the electrical signal through electrodes;

[0035] The dual current alternating excitation circuit also includes a current switching circuit and a CPU;

[0036] The regulated DC power supply includes a regulated DC power supply VCC1 and a regulated DC power supply VCC2, and the voltage of the regulated DC power supply VCC1 is greater than the voltage of the regulated DC power supply VCC2;

[0037] The V / I conversion circuit is composed of two V / I conversion circuits A and B connected in parallel between the regulated DC power supply VCC1 and the regulated DC power supply VCC2 and the current switching circuit, and having the same connection structure;

[0038] The current switching circuit is composed of a first double-throw electronic analog switch SW1, which is used to switch the current of the V / I conversion circuit A and the V / I conversion circuit B connected to the direction switching circuit;

[0039] The direction switching circuit is composed of two direction switching circuits A and B connected in parallel between the current switching circuit and the sensor and having the same connection structure, wherein:

[0040] The direction switching circuit A comprises a second double-throw electronic analog switch SW2;

[0041] The direction switching circuit B comprises a third double-throw electronic analog switch SW3;

[0042] The CPU controls the current switching circuit to connect the current of the V / I conversion circuit A and the V / I conversion circuit B to the direction switching circuit, and controls the direction switching circuit A and the direction switching circuit B to switch the direction of the connected current, so as to achieve positive and reverse alternating excitation of the coil of the sensor.

[0043] As a preferred embodiment of the present invention, Figure 1 As shown, interface 3 of the first double-throw electronic analog switch SW1 is connected to the connection line between transistor Q1 and capacitor C1 in the V / I conversion circuit A, its interface 1 is connected to the connection line between transistor Q2 and capacitor C2 in the V / I conversion circuit B, and its interface 2 is connected to the connection lines of interface 3 of the second double-throw electronic analog switch SW2 and interface 3 of the third double-throw electronic analog switch SW3.

[0044] As an embodiment of the present utility model, Figure 1 As shown, interface 3 of the first double-throw electronic analog switch SW1 is connected to the connection line between transistor Q1 and capacitor C1 in the V / I conversion circuit A, its interface 1 is connected to the connection line between transistor Q2 and capacitor C2 in the V / I conversion circuit B, and its interface 2 is connected to the connection lines of interface 3 of the second double-throw electronic analog switch SW2 and interface 3 of the third double-throw electronic analog switch SW3.

[0045] As an embodiment of the present utility model, Figure 1 As shown, the V / I conversion circuit A is composed of a voltage reference chip U1, a resistor R1, a resistor R2 and a resistor R3, a transistor Q1, an operational amplifier U2 and a capacitor C1; the input end of the voltage reference chip U1 is connected to a regulated DC power supply VCC1, and its output end is connected to the non-inverting input end of the operational amplifier U2 through a resistor R2, and its ground end is grounded; the voltage of the regulated DC power supply VCC1 is applied between the inverting input end and the common end of the operational amplifier U2, its inverting input end is connected to the connection line between the resistor R1 and the emitter of the transistor Q1, its output end is connected to the base of the transistor Q1 through a resistor R3, and its non-inverting input end and the common end are grounded; the collector of the transistor Q1 is grounded through a capacitor C1, and its emitter is connected to the regulated DC power supply voltage VCC1 through a resistor R1. As an embodiment of the utility model, Figure 1 As shown, the V / I conversion circuit B is composed of a voltage reference chip U3, a resistor R4, a resistor R5, a resistor R6, a transistor Q2, an operational amplifier U4 and a capacitor C2; the input end of the voltage reference chip U3 is connected to the regulated DC power supply voltage VCC2, the output end thereof is connected to the non-inverting input end of the operational amplifier U4 through the resistor R5, and the ground end thereof is grounded; the voltage of the regulated DC power supply voltage VCC2 is applied between the inverting input end and the common end of the operational amplifier U4, the inverting input end thereof is connected to the connecting line between the resistor R4 and the emitter of the transistor Q2, the output end thereof is connected to the base of the transistor Q2 through the resistor R6, and the non-inverting input end thereof is grounded to the common end; the collector of the transistor Q2 is grounded through the capacitor C2, and the emitter thereof is connected to the regulated DC power supply voltage VCC2 through the resistor R4.

[0046] As an embodiment of the present utility model, Figure 1 As shown, the direction switching circuit A is composed of a second double-throw electronic analog switch SW2 and a resistor R8, wherein the interface 3 of the second double-throw electronic analog switch SW2 is connected to the interface 3 of the third double-throw electronic analog switch SW3, wherein the interface 1 is grounded through the resistor R8, and the interface 2 is connected to the negative pole of the sensor coil.

[0047] As an embodiment of the present utility model, Figure 1 As shown, the direction switching circuit B is composed of a third double-throw electronic analog switch SW3 and a resistor R7, the interface 3 of the third double-throw electronic analog switch SW3 is connected to the interface 3 of the second double-throw electronic analog switch SW2, its interface 1 is grounded through the resistor R7, and its interface 2 is connected to the positive pole of the sensor coil.

[0048] The working principle of this utility model:

[0049] The utility model sets a reference circuit of a voltage-stabilized DC power supply VCC1 and a voltage-stabilized DC power supply VCC2, a V / I conversion circuit A and a V / I conversion circuit B, sets the voltage of the voltage-stabilized DC power supply VCC1 to be greater than the voltage of the voltage-stabilized DC power supply VCC2, and the CPU controls the current switching circuit to switch the current access direction switching circuit of the V / I conversion circuit A and the V / I conversion circuit B, and controls the direction switching circuit A and the direction switching circuit B to switch the current direction to realize the positive and negative alternating excitation of the sensor coil.

[0050] In actual operation, at the initial stage of switching the current direction, the reference circuit of the higher voltage regulated DC power supply VCC1 and the V / I conversion circuit A drive the sensor excitation through the direction switching circuit A, and at the later stage of switching the current direction, the reference circuit of the lower voltage regulated DC power supply VCC2 and the V / I conversion circuit B drive the sensor excitation through the direction switching circuit B. Thus, at the initial stage of switching the current, the influence of the inductive reactance is quickly eliminated, and the excitation current is pushed into the constant current excitation stage. At the later stage of switching the current, the power supply voltage is reduced to avoid energy waste and heating of the circuit.

Claims

1. A double current alternating excitation circuit for an electromagnetic flowmeter, comprising: V / I conversion circuit, which can convert the reference voltage into current; A regulated DC power supply, used for providing a regulated DC power supply voltage VCC; A direction switching circuit is used to drive the coil of the sensor to generate positive and reverse alternating excitation; The sensor collects the amplitude of the electrical signal through electrodes; Features: The dual current alternating excitation circuit also includes a current switching circuit and a CPU; The regulated DC power supply includes a regulated DC power supply VCC1 and a regulated DC power supply VCC2, and the voltage of the regulated DC power supply VCC1 is greater than the voltage of the regulated DC power supply VCC2; The V / I conversion circuit is composed of a V / I conversion circuit A and a V / I conversion circuit B, wherein: the input end of the V / I conversion circuit A is connected to the output end of the regulated DC power supply VCC1, and the output end of the V / I conversion circuit A is connected to the input end 3 of the current switching circuit; the input end of the V / I conversion circuit B is connected to the output end of the regulated DC power supply VCC2, and the output end of the V / I conversion circuit B is connected to the input end 1 of the current switching circuit; The current switching circuit is composed of a first double-throw electronic analog switch SW1, which is used to switch the current connected to the V / I conversion circuit A and the V / I conversion circuit B; The direction switching circuit is composed of a direction switching circuit A and a direction switching circuit B connected in parallel between the current switching circuit and the sensor, and the direction switching circuit A and the direction switching circuit B have the same structure; wherein: The direction switching circuit A comprises a second double-throw electronic analog switch SW2; The direction switching circuit B comprises a third double-throw electronic analog switch SW3; The CPU controls the current switching circuit to connect the current of the V / I conversion circuit A and the V / I conversion circuit B to the direction switching circuit, and controls the direction switching circuit A and the direction switching circuit B to switch the direction of the connected current, so as to drive the coil of the sensor to generate positive and negative alternating excitation.

2. A double current alternating excitation circuit for an electromagnetic flowmeter according to claim 1, characterized in that: The IO1 interface of the CPU is connected to the interface 4 of the first double-throw electronic analog switch SW1, its IO2 interface is connected to the interface 4 of the third double-throw electronic analog switch SW3, and its IO3 interface is connected to the interface 4 of the double-throw electronic analog switch SW2.

3. The double current alternating excitation circuit of an electromagnetic flowmeter according to claim 1, characterized in that: Interface 3 of the first double-throw electronic analog switch SW1 is connected to the connecting line between the transistor Q1 and the capacitor C1 in the V / I conversion circuit A, its interface 1 is connected to the connecting line between the transistor Q2 and the capacitor C2 in the V / I conversion circuit B, and its interface 2 is connected to the connecting lines of interface 3 of the second double-throw electronic analog switch SW2 and interface 3 of the third double-throw electronic analog switch SW3.

4. A double current alternating excitation circuit for an electromagnetic flowmeter according to claim 1 or 3, characterized in that: The V / I conversion circuit A is composed of a voltage reference chip U1, a resistor R1, a resistor R2 and a resistor R3, a transistor Q1, an operational amplifier U2 and a capacitor C1; the input end of the voltage reference chip U1 is connected to a regulated DC power supply VCC1, the output end thereof is connected to the non-inverting input end of the operational amplifier U2 through a resistor R2, and the ground end thereof is grounded; the voltage of the regulated DC power supply VCC1 is applied between the inverting input end and the common end of the operational amplifier U2, the inverting input end thereof is connected to the connecting line between the resistor R1 and the emitter of the transistor Q1, the output end thereof is connected to the base of the transistor Q1 through a resistor R3, and the non-inverting input end thereof is grounded to the common end; the collector of the transistor Q1 is grounded through a capacitor C1, and the emitter thereof is connected to the regulated DC power supply VCC1 through a resistor R1.

5. A double current alternating excitation circuit for an electromagnetic flowmeter according to claim 1 or 3, characterized in that: The V / I conversion circuit B is composed of a voltage reference chip U3, a resistor R4, a resistor R5, a resistor R6, a transistor Q2, an operational amplifier U4 and a capacitor C2; the input end of the voltage reference chip U3 is connected to a regulated DC power supply VCC2, the output end thereof is connected to the non-inverting input end of the operational amplifier U4 through a resistor R5, and the ground end thereof is grounded; the voltage of the regulated DC power supply VCC2 is applied between the inverting input end and the common end of the operational amplifier U4, the inverting input end thereof is connected to the connecting line between the resistor R4 and the emitter of the transistor Q2, the output end thereof is connected to the base of the transistor Q2 through a resistor R6, and the non-inverting input end thereof is grounded to the common end; the collector of the transistor Q2 is grounded through a capacitor C2, and the emitter thereof is connected to the regulated DC power supply VCC2 through a resistor R4.

6. A double current alternating excitation circuit for an electromagnetic flowmeter according to claim 1 or 2, characterized in that: The direction switching circuit A is composed of a second double-throw electronic analog switch SW2 and a resistor R8, wherein the interface 3 of the second double-throw electronic analog switch SW2 is connected to the interface 3 of the third double-throw electronic analog switch SW3, wherein the interface 1 is grounded through the resistor R8, and the interface 2 is connected to the negative pole of the sensor coil.

7. A double current alternating excitation circuit for an electromagnetic flowmeter according to claim 1 or 2, characterized in that: The direction switching circuit B is composed of a third double-throw electronic analog switch SW3 and a resistor R7. Interface 3 of the third double-throw electronic analog switch SW3 is connected to interface 3 of the second double-throw electronic analog switch SW2, its interface 1 is grounded through resistor R7, and its interface 2 is connected to the positive pole of the sensor coil.

Images