VI conversion circuit
The sensor signal of the pressure transmitter is converted into linear voltage output through the VI conversion circuit, and a shared dual-channel op amp is used to achieve forward and reverse output, solving the problems of long calibration time and many components in the prior art, and achieving efficient, simplified operation and low-cost transmitter design.
Patent Information
- Application Number
- CN202422292358.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-20
- Publication Date
- 2025-08-01
- Estimated Expiration
- 2034-09-20
AI Technical Summary
The calibration process of existing pressure transmitters takes a long time, has many components and is costly, and is complex in operation, making it difficult to meet the high requirements for the accuracy and stability of the two output signals in fire trucks and high-altitude working platforms.
The VI conversion circuit is adopted to convert the pressure value into millivolt signals through sensors, and amplify and convert it into linear voltage output using conditioning circuits. Forward and reverse output are achieved by sharing a dual-channel op amp, reducing the number of calibration times and components, and simplifying operation.
It realizes the transmitter's volume reduction, short time consumption, high efficiency, simple operation and few components, meeting the output requirements of high precision and stability.
Smart Images
Figure CN223180607U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of circuits, and particularly relates to a VI conversion circuit. Background Art
[0002] Industrially, it is generally necessary to measure various non-electrical physical quantities, such as temperature, pressure, speed, angle, etc. These need to be converted into analog electrical signals before they can be transmitted to a control room or display device hundreds of meters away. The device that converts physical quantities into electrical signals is called a transmitter. Industrially, the most widely used is to use a 4-20 mA current to transmit analog quantities. The current signal is not easily interfered with. And the internal resistance of the current source is infinite, and the wire resistance in series in the loop does not affect the accuracy. It can be transmitted hundreds of meters on ordinary twisted pairs. The spark energy caused by the on-off of the 20 mA current at the upper limit is not enough to ignite gas. The lower limit will not be lower than 4 mA during normal operation. When the transmission line is broken due to a fault, the loop current drops to 0. Usually, 2 mA is taken as the disconnection alarm value. Therefore, the 4-20 mA output pressure transmitter is widely used in industrial control, construction machinery, and automation control occasions.
[0003] Among them, when pressure transmitters are used in fire trucks and aerial work platforms, a pressure signal needs to be accurately converted into two current signals. One is a forward 4-20 mA output, and the other is a 20-4 mA reverse output. The values of the two output signals are used to calculate the platform lifting control and position status feedback. Therefore, there are very high requirements for the accuracy and stability of the two output signals;
[0004] In the existing output circuit, there are the following disadvantages:
[0005] Existing Technology 1: The calibration of the transmitter takes a long time, and each transmitter needs to be calibrated twice.
[0006] Existing Technology 2: There are too many components and the cost is high. Embedded code needs to be written and a calibration host computer is required. The operation is complex and time-consuming.
[0007] Therefore, in view of the above problems, a VI conversion circuit is needed. Summary of the Utility Model
[0008] The purpose of the present utility model is to provide a VI conversion circuit. In the present utility model, a sensor converts the measured pressure value into a millivolt signal, and a conditioning circuit amplifies, conditions, and converts the weak or non-linear electrical signal output by the sensor into a linear voltage output. The VI conversion circuit controls the overall power consumption current according to the output of the signal conditioning circuit; at the same time, a voltage is obtained from the loop and regulated for use by the conditioning circuit and the sensor. A dual-channel operational amplifier is shared with the forward output circuit, and the signals output by the conditioning circuit are respectively sent to the input ends of the forward output and the reverse output. Therefore, only one calibration is required during calibration. The forward and reverse outputs are realized with a small number of peripheral devices, and the outputs do not interfere with each other. The overall volume of the transmitter is reduced, the time consumption is short, the efficiency is high, and there are few components, the operation is simple, time and labor are saved, and the present utility model has strong practicability.
[0009] The present utility model is implemented as follows:
[0010] A VI conversion circuit, wherein the conditioning circuit is connected to a VI conversion circuit, and the VI conversion current includes a first VI conversion circuit and a second VI conversion circuit that are electrically connected to each other;
[0011] The first VI conversion circuit includes an operational amplifier U2A, and the operational amplifier U2A is connected to a triode Q2. Among them, the operational amplifier U2A and the triode Q2 constitute a forward output. The second VI conversion current includes an operational amplifier U2B, and the amplifier U2B is connected to a triode Q3. The amplifier U2B and the triode Q3 constitute a reverse output. The input end of the operational amplifier U2A is connected to a resistor R6, and the V_OUT signal is input through the resistor R6. The input end of the operational amplifier U2B is connected to a resistor R11, and the V_OUT signal is input through the resistor R11. The input ends of the resistor R11 and the resistor R6 both come from the conditioning circuit;
[0012] The output V_OUT of the conditioning circuit is sent to the non-inverting input end of the operational amplifier U2A, and the inverting input end is connected to the ground reference point. For the reverse 20 - 4mA output signal part, the output V_OUT of the conditioning circuit is sent to the inverting input end of the operational amplifier U2B, and the non-inverting input end is connected to the output AVDD ground of the voltage reference chip U3. Utilizing the virtual short and virtual open characteristics of the operational amplifier, the operational amplifier controls the forward and reverse outputs to make the output reach a steady state.
[0013] The input end of the operational amplifier U2B is further connected to a voltage reference chip U3, and the input end of the voltage reference chip U3 is connected to a capacitor C12.
[0014] Further, a feedback loop is formed by connecting a resistor R9 to the output terminal of the operational amplifier U2A, and a feedback loop is formed by connecting a resistor R16 to the output terminal of the operational amplifier U2B. The resistance values of the resistor R6 and the resistor R11 are both 375K. The sensor outputs a sensor non-linear millivolt signal to the conditioning circuit.
[0015] Further, the working principle of this application is as follows:
[0016] When the circuit works normally, the power supply LOOP_HV+ (DC9 - 32V) of the external transmitter is normal. After the external power supply filters out the interference signals through the capacitor C12, a stable working voltage is provided to the operational amplifier U2 and the reference chip U3.
[0017] The conditioning circuit amplifies the weak or non-linear electrical signals output by the sensor.
[0018] Positive output part: When the pressure measured by the sensor increases or decreases, the output of the conditioning circuit increases or decreases synchronously. The output V_OUT of the conditioning circuit is sent to the positive input terminal of the operational amplifier, and the negative input terminal is connected to the ground reference. Therefore, the output current of the external transmitter also increases or decreases synchronously. The voltage on R9 is obtained through the feedback loop for loop control. This makes the voltage at the negative input terminal approach the voltage at the positive input terminal. In this process, the triode Q2 enters the linear region, the IC current gradually increases, the current flowing through R9 also gradually increases, and the voltage across both ends also gradually increases. Eventually, the voltage at the negative input terminal is equal to the voltage at the positive input terminal, and the circuit enters a stable state.
[0019] Reverse output part: The reverse part is different from the forward circuit. Since the output V_OUT of the conditioning circuit is sent to the negative input terminal of the operational amplifier U2B, and the positive input terminal is connected to the output AVDD of the reference chip U3. The operational amplifier compares the output V_OUT of the conditioning circuit with the output AVDD of the reference chip. Therefore, when the output V_OUT of the conditioning circuit increases, the output of the operational amplifier U2B will decrease in the reverse direction. The voltage on R16 is obtained through the feedback loop for loop control to make the reverse circuit enter a stable state.
[0020] Compared with the prior art, the present utility model shares a dual-channel operational amplifier with the positive output circuit. The signals output by the conditioning circuit are respectively sent to the input terminals of the positive output and the reverse output. Therefore, it only needs to be calibrated once during calibration. The positive and reverse outputs are realized with a small number of peripheral devices, and the outputs do not interfere with each other. The overall volume of the transmitter is reduced, the time consumption is short, the efficiency is high, and there are few components, the operation is simple, time-saving and labor-saving. The present utility model has strong practicability. The present utility model has strong practicability. Description of the Drawings
[0021] To more clearly illustrate the technical solutions of the embodiments of the present utility model, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present utility model, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.
[0022] Figure 1 is a schematic structural diagram of the system of the present utility model;
[0023] Figure 2 is a circuit structure diagram of the present utility model. Specific embodiments
[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present utility model with reference to the drawings in the embodiments of the present utility model. Obviously, the described embodiments are some, but not all, of the embodiments of the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present utility model. Therefore, the following detailed description of the embodiments of the present utility model provided in the drawings is not intended to limit the scope of the present utility model to be protected, but merely represents the selected embodiments of the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present utility model.
[0025] Please refer to Figure 1-2 , a VI conversion circuit, the conditioning circuit is connected to a VI conversion circuit, and the VI conversion current includes a first VI conversion circuit and a second VI conversion circuit that are electrically connected to each other;
[0026] The first VI conversion circuit includes an operational amplifier U2A, and the operational amplifier U2A is connected to a triode Q2. Among them, the operational amplifier U2A and the triode Q2 form a forward output. The second VI conversion current includes an operational amplifier U2B, and the amplifier U2B is connected to a triode Q3. The amplifier U2B and the triode Q3 form a reverse output. The input end of the operational amplifier U2A is connected to a resistor R6, and the V_OUT signal is input through the resistor R6. The input end of the operational amplifier U2B is connected to a resistor R11, and the V_OUT signal is input through the resistor R11. The input ends of the resistor R11 and the resistor R6 both come from the conditioning circuit;
[0027] The output V_OUT of the conditioning circuit is fed into the non-inverting input terminal of operational amplifier U2A, and the inverting input terminal is connected to the ground reference point. For the reverse 20 - 4mA output signal part, the output V_OUT of the conditioning circuit is fed into the inverting input terminal of operational amplifier U2B, and the non-inverting input terminal is connected to the output AVDD ground of voltage reference chip U3. Utilizing the virtual short and virtual open characteristics of the operational amplifier, the operational amplifier controls the forward and reverse outputs to make the output reach a steady state.
[0028] The input terminal of the operational amplifier U2B is also connected to a voltage reference chip U3, and the input terminal of the voltage reference chip U3 is connected to a capacitor C12.
[0029] In this embodiment, the output terminal of the operational amplifier U2A is connected to a resistor R9 to form a feedback loop, the output terminal of the operational amplifier U2B is connected to a resistor R16 to form a feedback loop, and the resistance values of the resistor R6 and the resistor R11 are both 375K. The sensor outputs a sensor non-linear millivolt signal to the conditioning circuit.
[0030] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A VI conversion circuit, comprising a conditioning circuit connected to a sensor, characterized in that: The conditioning circuit is connected to a VI conversion circuit, and the VI conversion circuit includes a first VI conversion circuit and a second VI conversion circuit that are electrically connected to each other; The first VI conversion circuit includes an operational amplifier U2A, and the operational amplifier U2A is connected to a triode Q2. Among them, the operational amplifier U2A and the triode Q2 form a forward output. The second VI conversion circuit includes an operational amplifier U2B, and the amplifier U2B is connected to a triode Q3. The amplifier U2B and the triode Q3 form a reverse output. The input end of the operational amplifier U2A is connected to a resistor R6, and the V_OUT signal is input through the resistor R6. The input end of the operational amplifier U2B is connected to a resistor R11, and the V_OUT signal is input through the resistor R11. The input ends of the resistor R11 and the resistor R6 both come from the conditioning circuit; The input end of the operational amplifier U2B is also connected to a voltage reference chip U3.
2. The VI conversion circuit according to claim 1, wherein The input end of the voltage reference chip U3 is connected to a capacitor C12.
3. The VI conversion circuit according to claim 1, characterized in that The output end of the operational amplifier U2A is connected to a resistor R9 to form a feedback loop, and the output end of the operational amplifier U2B is connected to a resistor R16 to form a feedback loop.
4. A VI conversion circuit according to claim 1, wherein The resistance values of the resistor R6 and the resistor R11 are both 375 KΩ.
5. A VI conversion circuit according to claim 1, characterized in that, The sensor outputs a sensor non-linear millivolt signal to the conditioning circuit.