CN115560889A - Signal transmitting circuit and pressure transmitter - Google Patents
Signal transmitting circuit and pressure transmitter Download PDFInfo
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- CN115560889A CN115560889A CN202211189573.4A CN202211189573A CN115560889A CN 115560889 A CN115560889 A CN 115560889A CN 202211189573 A CN202211189573 A CN 202211189573A CN 115560889 A CN115560889 A CN 115560889A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/225—Measuring circuits therefor
- G01L1/2262—Measuring circuits therefor involving simple electrical bridges
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
- G01L9/04—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of resistance-strain gauges
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- Measuring Fluid Pressure (AREA)
Abstract
The invention relates to a signal transmitting circuit and a pressure transmitter. The signal transmitting circuit comprises a signal amplification adjusting sub-circuit and a signal conversion sub-circuit. The signal amplification and adjustment sub-circuit mainly comprises operational amplifiers U1.1, U1.2 and U1.3, adjustable resistors P1 and P2, resistors R6, R7, R10, R11 and R12; the signal conversion sub-circuit comprises an operational amplifier U1.4, a triode Q1 and resistors R1, R2, R3, R4, R5 and R15. According to the invention, the weak differential signals of the sensor can be amplified through the first-stage differential amplification unit composed of U1.2, P2, R6, R7 and U1.3, so that reliable and effective signals are provided for post-stage processing; the null adjustment unit formed by R11, R10, P1 and R12 can maintain the compensation characteristic of the sensor. The signal conversion sub-circuit elaborately completes the conversion of the differential voltage signal into the 4-20mA current.
Description
Technical Field
The invention relates to the technical field of pressure transmission, in particular to a signal transmission circuit and a pressure transmitter.
Background
A pressure transmitter is a device for converting pressure into pneumatic or electric signals for control and remote transmission, and the pressure transmitter usually uses a strain resistor as a sensor for detecting pressure. A diffused silicon pressure sensor is a strain resistor that operates using the principle of piezoresistive effect. Diffused silicon pressure sensors are typically fabricated using integrated process technology and include a wheatstone bridge of a plurality of base resistors. The pressure of the diffused silicon pressure sensor directly acts on a diaphragm of the sensor, so that the diaphragm generates micro displacement which is in direct proportion to the pressure of a medium, and the resistance value of the sensor is changed. When the electronic circuit detects the change and converts and outputs a standard measuring signal corresponding to the pressure, a pressure transmitter can be obtained.
In the conventional pressure transmitter using the diffused silicon pressure sensor, in order to stabilize the signal of the sensor, a wheatstone bridge is subjected to a zeroing operation. The currently widely used zeroing circuit is to connect the adjusting resistor in parallel to the bridge of the sensor itself, as shown in fig. 1, which is easy to destroy the circuit balance of the sensor itself, resulting in a poor temperature coefficient of the finally output signal. The traditional mode adopts a high-end precision device to convert a weak differential signal into a two-wire system current output signal, the high-end precision device is high in price and not easy to obtain, and the cost and difficulty of V/I signal conversion are increased.
Disclosure of Invention
Therefore, it is necessary to provide a signal transmission circuit and a pressure transmitter for solving the problems of high cost and difficulty in V/I signal conversion.
In order to realize the purpose, the invention adopts the following technical scheme:
a signal transmission circuit comprises a signal amplification adjusting sub-circuit and a signal conversion sub-circuit; the signal amplification and adjustment sub-circuit comprises three operational amplifiers U1.1, U1.2 and U1.3, two adjustable resistors P1 and P2, five resistors R6, R7, R10, R11 and R12 and five capacitors C1, C2, C3, C6 and C8. The signal conversion sub-circuit comprises an operational amplifier U1.4, a triode Q1 and six resistors R1, R2, R3, R4, R5 and R15.
The specific connection mode of the signal transmitting circuit is as follows: the non-inverting input end of U1.2 is connected with one end of C2 and C3, and is used as the input end + S of signal transmission, and the other end of C2 is grounded. The inverting input terminal of U1.2 is connected with the output terminal and is connected with one of the stator pins of P2 and one end of R10. The inverting input end of U1.3 is connected with one end of R6 and R7, the other end of R7 is connected with the output end of U1.3 and one end of C6 and R1, and the other stator pin and the rotor pin of P2 are connected with the other end of R6. The non-inverting input terminal of U1.3 is connected with one end of C8 and the other end of C3 and serves as an input terminal-S of the signal transmitting circuit. The other end of the C8 is grounded and serves as an input end-I of the signal transmitting circuit. The non-inverting input end of U1.1 is connected with the other ends of C6 and R10 and the moving plate pin of P1. One pin of the P1 is connected with one end of the R12, and the other end of the R12 is grounded; the other stator pin of the P1 is connected with one end of the R11, the other end of the R11 is connected with one end of the C1, the other end of the R11 is used as an input end + I of the signal transmitting circuit, and the other end of the C1 is grounded. The inverting input terminal and the output terminal of U1.1 are connected, and are connected with one end of a resistor R3. The voltage input end of U1.1 is used as the voltage-stabilizing input end of the signal transmitting circuit, and the grounding end of U1.1 is grounded. The non-inverting input end of U1.4 is connected with the other end of R3 and one end of R4, and the other end of R4 is connected with one end of R5 and serves as the output end OUT1 of the signal transmitting circuit. And the inverting input end of U1.4 is connected with the other end of R1 and one end of R2. The other end of R2 is grounded with the other end of R5, and is connected with the emitter of Q1. The output end of U1.4 is connected with one end of R15, and the other end of R15 is connected with the base electrode of Q1.
In one embodiment, the signal conversion sub-circuit further comprises a current-limiting protection unit composed of a linear regulator U3 and a resistor R13, and the maximum on-current I of the current-limiting protection unit m The current limiting protection unit is connected in series on a collector of the Q1, wherein the voltage is 1.25V/R13 ≈ 22mA, and the voltage is 1.25V is the inherent reference voltage of U3. Set of Q1The electrode is connected with the adjustable end of the U3 and one end of the R13, the output end of the U3 is connected with the other end of the R13, and the input end of the U3 is connected with a power supply voltage VCC.
In one embodiment, the signal conversion sub-circuit further comprises a stabilizing unit formed by a resistor R17 and a capacitor C9. The existence of the stabilizing unit can effectively eliminate the self-excitation in the circuit. One end of R17 is connected with the base electrode of Q1, the other end of R17 is connected with one end of C9, and the other end of C9 is connected with the emitter electrode of Q1.
In one embodiment, the signal conversion sub-circuit further comprises capacitors C5 and C7. One end of the C5 and the C7 is connected with the input end of the U3, the other end of the C5 is grounded, and the other end of the C7 is connected with one end of the R5 serving as the output end of the signal transmitting circuit. Output current I of signal conversion sub-circuit OUT1 Comprises the following steps: I.C. A OUT1 = (+ Vi-Vi)/R5, wherein + Vi-Vi are differential pressure signals entering the signal conversion sub-circuit
Further, the operational amplifiers U1.2 and U1.3, the variable resistor P2, the resistor R6, and the resistor R7 constitute a first stage differential amplifying unit for amplifying the detection signal of the sensor.
Further, the amplification factor A1 of the first stage differential amplification unit is: a1= R7/(R6 + R) P2 ) Wherein R is P2 Is the resistance of the adjustable resistor P2.
The invention also comprises a pressure transmitter which comprises a sensor, a power circuit and a signal processing circuit. The power supply circuit is used for providing required power supply. The sensor is used for generating a corresponding detection signal in the detection process. The signal processing circuit is used for converting the detection signal into a corresponding current signal; the signal processing circuit employs the aforementioned signal transmitting circuit.
Furthermore, the power supply circuit comprises a constant-current voltage-stabilizing sub-circuit and a power supply input signal output sub-circuit. The constant-current voltage-stabilizing sub-circuit comprises a linear voltage stabilizer U2, two resistors R9 and R16 and a capacitor C4. The constant current voltage-stabilizing sub-circuit outputs a constant current of 1.5mA for a sensor, and outputs a constant voltage of 5V for an operational amplifier. The power input signal output sub-circuit includes a self-recovery fuse F1 and diodes D1, D2.
The specific connection mode of the power circuit is as follows: an input pin of the U2 is connected with the negative electrodes of the D1 and the D2, and an output pin of the U2 is connected with one end of the R9 and the R16 and is used as a voltage-stabilizing output end of the power supply circuit. The other end of R16 is grounded, C4 is connected with R16 in parallel, and the adjustable pin of U2 is connected with the other end of R9 and is used as the constant current output end of the power supply circuit. The output current + I =1.25V/R9, where 1.25V is the U2 intrinsic reference voltage. The positive pole of the D2 is connected with the output end OUT1 of the signal transmission circuit and is used as the signal output end of the pressure transmitter. The positive pole of the D1 is connected with one end of the F1, and the other end of the F1 is used as a power input end of the pressure transmitter.
In one embodiment, the power input signal output sub-circuit further includes magnetic beads L1, L2. An input pin of the linear voltage stabilizer U2 is connected with one end of the L1, and the other end of the L1 is connected with the cathodes of the D1 and the D2; one end of the L2 is connected to the output terminal OUT1 of the signal transmitting circuit, and the other end is connected to the positive electrode of the D2.
In one embodiment, the sensor comprises a Wheatstone bridge consisting of four voltage variable resistors, and four bridge arms of the Wheatstone bridge are taken as four terminals of the sensor and are respectively connected with input ends + I, -I, + S and-S of the signal transmitting circuit.
The technical scheme provided by the invention has the following beneficial effects:
1. the signal transmitting circuit is arranged to convert weak differential signals of the sensor into corresponding constant-current output signals, and the constant-current output signals and the pressure sensed by the sensor are in a linear relation; the first-stage differential amplification unit composed of U1.2, P2, R6, R7 and U1.3 can amplify the weak differential signals of the sensor; the zero adjustment unit composed of R11, R10, P1 and R12 is positioned on a circuit at the rear end of the first-stage differential amplification unit, so that the compensation characteristic of the sensor can be maintained, and the signal precision output by the signal transmission circuit is higher.
2 the pressure transmitter of the invention utilizes four general low-cost operational amplifiers to complete the process of converting the differential signal of the sensor into a standard current signal; the power supply circuit can provide a constant current source for the sensor and a voltage stabilizing source for the operational amplifier, so that two functions are realized.
3. The R17 and the C9 are arranged to stabilize the circuit, so that the circuit is prevented from self-excitation; u3 and R13 are set to limit the current, so that the maximum value of the current does not exceed a preset value of 22mA, and the circuit is protected; and the magnetic beads L1 and L2 are arranged to improve the anti-electromagnetic interference capability when the pressure transmitter is externally connected.
Drawings
FIG. 1 is a prior art electrical circuit diagram of a conventional nulling circuit and sensor;
FIG. 2 is a circuit diagram of a signal transmitting circuit of the present invention;
FIG. 3 is a circuit diagram based on the signal amplification adjustment sub-circuit of FIG. 2;
FIG. 4 is a circuit diagram based on the signal conversion sub-circuit of FIG. 2;
FIG. 5 is a circuit diagram of the pressure transmitter in embodiment 2;
fig. 6 is a circuit diagram based on the constant current regulator sub-circuit of fig. 5;
FIG. 7 is a circuit diagram of a power input signal output sub-circuit based on FIG. 5;
FIG. 8 is a signal flow diagram based on the pressure transmitter of FIG. 5;
fig. 9 is an overall connection circuit diagram of the pressure transmitter based on fig. 5.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The method and the device solve the problems that differential voltage signals cannot be accurately converted into corresponding output signals and V/I signals cannot be converted due to the fact that the differential voltage signals are not balanced when the amplifier is used for amplifying weak differential signals in the prior art, and are high in cost and difficulty. This embodiment is generally describedThe weak sensor differential signals can be amplified by the first-stage differential amplification unit composed of U1.2, P2, R6, R7 and U1.3. First-stage differential amplification unit A1: a1= R7/(R6 + R) P2 ) Wherein R is P2 Is the resistance value of the adjustable resistor P2. The zero adjusting unit composed of R11, R10, P1 and R12 is positioned on a circuit at the rear end of the first-stage differential amplifying unit and is not directly connected in parallel to a bridge of the sensor, so that the compensation characteristic of the sensor can be maintained, and the signal output by the signal transmitting circuit has higher accuracy.
As shown in fig. 2, the signal transmitting circuit of the present embodiment includes a signal amplification adjustment sub-circuit and a signal conversion sub-circuit. The signal amplification and adjustment sub-circuit comprises three operational amplifiers U1.1, U1.2 and U1.3, two adjustable resistors P1 and P2, five resistors R6, R7, R10, R11 and R12 and five capacitors C1, C2, C3, C6 and C8. The signal conversion sub-circuit comprises an operational amplifier U1.4, a triode Q1, a linear voltage stabilizer U3, eight resistors R1, R2, R3, R4, R5, R13, R15 and R17 and three capacitors C5, C7 and C9.
As shown in fig. 3, the signal amplification and adjustment sub-circuit includes a first-stage differential amplification unit composed of U1.2, P2, R6, R7, and U1.3, and a null adjustment unit composed of R11, R10, P1, and R12, where U1.1 performs impedance conversion on the signal after null adjustment. Capacitors C5, C7 and C9 act as signal filtering to eliminate noise while increasing interference rejection.
For the selection of the capacitor and the resistor, the embodiment provides a specific way: the patch capacitors 104, namely 0.1 muF capacitors, are selected from the five capacitors C1, C2, C3, C6 and C8. R6 selects a chip resistor 201, namely a 200 omega resistor; r7 and R10 select a chip resistor 202, namely a 2K omega resistor; r11 selects a chip resistor 203, namely a 20K omega resistor; r12 selects the patch resistance 514, i.e. the 51K omega resistance.
As shown in fig. 4, U1.4, R1, R2, R3, R4, R15, Q1, R5 in the signal conversion sub-circuit cooperate to convert the differential signal into a corresponding single-ended signal, so as to achieve the purpose of linear signal conversion. The resistor R17 and the capacitor C9 form a stabilizing unit to prevent the circuit from self-excitation. Current limiting consisting of linear voltage regulator U3 and resistor R13The protection unit enables the maximum value of the current not to exceed a preset value (22 mA), and then the circuit is protected. The preset value is calculated as the maximum on-current I m ：I m =1.25V/R13 ≈ 22ma,1.25v is the U3 intrinsic reference voltage.
For the signal conversion sub-circuit output current I OUT1 The calculating method of (2): I.C. A OUT1 And = (+ Vi to Vi)/R5, where + Vi to Vi are differential pressure signals entering the signal conversion sub-circuit.
The electronic elements of the signal conversion sub-circuit are selected as follows: q1 is an NPN triode, can be selected from model BD237, and has high collector-emitter breakdown voltage characteristic, wherein collector-emitter breakdown voltage (Vceo) is 80V, and collector current (Ic) is 2A. U1.4 may select the same type of operational amplifier as U1.1, U1.2, U1.3. Has the characteristics of low price and universality.
The linear voltage regulator U3 adopts an LDO voltage regulator with adjustable three-terminal positive voltage and is composed of a three-terminal adjustable voltage regulation integrated circuit LM 317. The sensor power supply device skillfully utilizes the special structure of the LM317 to simultaneously complete the output of 1.5mA constant current to supply power for the sensor, and simultaneously outputs 5V regulated power supply to provide stable power supply for the operational amplifier. In particular to an LM317LBDR2G adjustable voltage regulator. It can provide a current of more than 1.5mA in the output voltage range of 1.2V to 37V. It is easy to use and only needs 2 external resistors to set the output voltage. In addition, it also employs internal current limiting, overheat shutdown and safe zone compensation, greatly reducing the possibility of damage. So that it is not substantially damaged.
For the selection of the capacitor and the resistor, the embodiment provides a specific way: r1, R2, R3, R4 and R5 select a chip resistor 203, namely a 20K omega resistor; r13 selects a 56 omega resistor; r15 selects a chip resistor 103, namely a 10K omega resistor; r17 selects the patch resistance 101, i.e., 100 Ω resistance. C5 and C7 select a patch capacitor 104, namely a 0.1 muF capacitor; c9 selects the patch capacitor 105, i.e. 1 μ F capacitor.
The operational amplifiers U1.1, U1.2, U1.3, and U1.4 in the signal transmission circuit are inexpensive general-purpose operational amplifiers. For example: the precision operational amplifier GS8594 has the characteristic of low power consumption, and the performance of the precision operational amplifier GS8594 meets the requirement of a single power supply circuit, so that the precision operational amplifier GS8594 can work together with a sensor in a single power supply. In addition, GS8594 also has the characteristic of zero drift, the drift is close to zero in the whole bearable temperature range, and meanwhile, the operational amplifier is low in price and universal and can completely replace a precise and expensive inlet integrated circuit to complete the functions required by the pressure transmitter. Other operational amplifiers can be selected, and only the requirement that the rated working voltage is more than 7.5V and the static working current is less than 1.5mA is met.
The specific connection method of the electronic components of the signal transmission circuit is as follows: the non-inverting input end of U1.2 is connected with one end of C2 and C3, and is used as the input end + S of signal transmission, and the other end of C2 is grounded. The inverting input terminal of U1.2 is connected with the output terminal and is connected with one of the stator pins of P2 and one end of R10. The inverting input end of U1.3 is connected with one end of R6 and R7, the other end of R7 is connected with the output end of U1.3 and one end of C6 and R1, and the other stator pin and the rotor pin of P2 are connected with the other end of R6. The non-inverting input terminal of U1.3 is connected with one end of C8 and the other end of C3 and serves as an input terminal-S of the signal transmitting circuit. The other end of C8 is grounded and used as the input end-I of the signal transmitting circuit. The non-inverting input end of U1.1 is connected with the other ends of C6 and R10 and the rotor pin of P1. One of the pins of the chip P1 is connected with one end of the R12, and the other end of the R12 is grounded. The other stator pin of the P1 is connected with one end of the R11, the other end of the R11 is connected with one end of the C1, the other end of the R11 is used as an input end + I of the signal transmitting circuit, and the other end of the C1 is grounded. The inverting input terminal and the output terminal of U1.1 are connected, and are connected with one end of a resistor R3. The voltage input end of U1.1 is used as the voltage stabilizing input end of the signal transmitting circuit, and the grounding end of U1.1 is grounded. The non-inverting input end of U1.4 is connected with the other end of R3 and one end of R4, the other end of R4 is connected with one end of R5 and one end of C7, and the non-inverting input end of R4 is used as the output end OUT1 of the signal transmitting circuit. And the inverting input end of U1.4 is connected with the other end of R1 and one end of R2. The other end of R2 is grounded with the other end of R5, and is connected with the emitter of Q1. The output end of U1.4 is connected with one end of R15, and the other end of R15 is connected with the base electrode of Q1. The collector of Q1 links to each other with the adjustable end of U3 and one of them one end of R13, and the output of U3 links to each other with the other end of R13, and supply voltage VCC is connected to the input of U3. One end of R17 is connected with the base electrode of Q1, the other end of R17 is connected with one end of C9, and the other end of C9 is connected with the emitter electrode of Q1. The other end of the C7 is connected with the input end of the U3, and the other end of the C5 is grounded.
The signal amplification and adjustment sub-circuit of the embodiment amplifies the weak differential signal of the sensor, and the signal conversion sub-circuit then performs a conversion process of converting the differential signal into a current signal. . The zero adjusting unit is positioned behind the first-stage differential amplifying unit, the circuit balance of the sensor is not damaged, the signal conversion sub-circuit can convert the differential voltage signal into a corresponding constant current output signal, and the signal and a pressure value sensed by the pressure sensor are in a linear relation.
Example 2
As shown in fig. 5, the present embodiment describes a pressure sensor including a sensor, a power supply circuit, and a signal processing circuit. The power supply circuit is used for providing required power supply. The sensor is used for generating a corresponding detection signal in the detection process. The signal processing circuit is used for converting the detection signal into a corresponding current signal. The signal processing circuit employs the signal transmitting circuit in embodiment 1.
The sensor is composed of a Wheatstone bridge consisting of four voltage variable resistors, and four bridge arms of the Wheatstone bridge are used as four wiring terminals of the sensor and are respectively connected with input ends + I, -I, + S and-S of the signal transmitting circuit.
The power supply circuit comprises a constant-current voltage-stabilizing sub-circuit and a power supply input signal output sub-circuit. As shown in fig. 6, the constant current regulator sub-circuit includes a linear regulator U2, two resistors R9 and R16, and a capacitor C4. The constant current voltage-stabilizing sub-circuit outputs a constant current of 1.5mA for a sensor, and outputs a constant voltage of 5V for an operational amplifier. As shown in fig. 7, the power input signal output sub-circuit includes a self-recovery fuse F1, diodes D1 and D2, and magnetic beads L1 and L2, and is used for protecting the circuit.
The electronic components of the power supply circuit are selected as follows: the linear voltage stabilizer U2 selects the model which is the LM317 and is the same as the model of the U3, and skillfully achieves two functions, namely providing a 1.5mA constant current source for the sensor and providing a 5V constant voltage source for the operational amplifier. F1 is used for preventing damage caused by current surge and overheating, limiting large current to flow, and reducing maintenance times because it can be reset after circuit fault clearing and power supply disconnection. F1 may be model ASMD1206-005, holding current 0.05A.
D1 is a reverse protection diode and plays a role in circuit protection, and the model of D1 can be 1N4148, so that the circuit protection device has the characteristics of easiness in obtaining, low price and wide universality. D2 is an overvoltage protection TVS diode, and the protection voltage is 26V. Model SMBJ26AQ was chosen with a reverse cutoff voltage (Vrwm) of 26V. D2 may select other types of overvoltage protection TVS diodes, but the protection voltage 26V needs to be satisfied. The direct current impedance of the magnetic beads L1 and L2 is zero, the magnetic beads have certain inductive reactance to high frequency, and the MMZ1608Q601 can be selected, the working temperature of the magnetic beads is-20-90 ℃, and the daily use environment is met.
For the selection of the resistor and the capacitor, the embodiment provides a specific way: r9 selects the patch resistor 821, i.e., 820 Ω resistor; r16 selects the patch resistance 103, i.e. the 10K omega resistance. C4 selects the patch capacitance 225, i.e., the 2.2 μ F capacitance.
The specific connection mode of each electronic element in the power circuit is as follows: an input pin of the U2 is connected with the negative electrodes of the D1 and the D2, and an output pin of the U2 is connected with one end of the R9 and the R16 and is used as a voltage-stabilizing output end of the power supply circuit. The other end of the R16 is grounded, the C4 is connected with the R16 in parallel, the adjustable pin of the U2 is connected with the other end of the R9 and serves as a constant current output end of the power supply circuit, the output current + I =1.25V/R9, and 1.25V is the inherent reference voltage of the U2. The positive pole of the D2 is connected with the output end OUT1 of the signal transmission circuit and is used as the signal output end of the pressure transmitter. The anode of the D1 is connected with one end of the F1, and the other end of the F1 is used as a power input end of the pressure transmitter. An input pin of the U2 is connected with one end of the L1, and the other end of the L1 is connected with the cathodes of the D1 and the D2. One end of the L2 is connected to the output terminal OUT1 of the signal transmitting circuit, and the other end is connected to the positive electrode of the D2.
As shown in fig. 8, the power supply circuit can provide a 1.5mA constant current source for the sensor, provide a 5V regulated voltage source for the signal transmitting circuit, amplify the differential voltage signal (detection signal) of the sensor by the signal transmitting circuit, then adjust the zero position, and finally convert the differential voltage signal into a single-ended current signal linearly, and output a standard 4-20mA current signal through the power supply circuit.
In the embodiment, a universal and cheap four operational amplifier is used for perfectly converting the differential signal of the sensor into the standard signal of 4-20mA, so that the current signal and the pressure value sensed by the pressure sensor are in a linear relation, and the accuracy of the output current signal is improved.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that various changes and modifications can be made by those skilled in the art without departing from the spirit of the invention, and these changes and modifications are all within the scope of the invention. Therefore, the protection scope of the present patent should be subject to the appended claims.
Claims (10)
1. A signal transmitting circuit is used for collecting a detection signal of a sensor and generating a current signal corresponding to a detection amount according to the detection signal of the sensor, and is characterized by comprising a signal amplification adjusting sub-circuit and a signal conversion sub-circuit; the signal amplification and adjustment sub-circuit comprises three operational amplifiers U1.1, U1.2 and U1.3, two adjustable resistors P1 and P2, five resistors R6, R7, R10, R11 and R12 and five capacitors C1, C2, C3, C6 and C8; the signal conversion sub-circuit comprises an operational amplifier U1.4, a triode Q1 and six resistors R1, R2, R3, R4, R5 and R15;
the non-inverting input end of U1.2 is connected with one end of C2 and C3, and is used as the input end + S of the signal transmission, and the other end of C2 is grounded; the inverting input end of U1.2 is connected with the output end and is connected with one of the stator pins of P2 and one end of R10; the inverting input end of U1.3 is connected with one end of R6 and R7, the other end of R7 is connected with the output end of U1.3 and one end of C6 and R1, and the other stator pin and the rotor pin of P2 are connected with the other end of R6; the non-inverting input end of U1.3 is connected with one end of C8 and the other end of C3 and is used as the input end-S of the signal transmitting circuit; the other end of the C8 is grounded and is used as an input end-I of the signal transmitting circuit; the non-inverting input end of U1.1 is connected with the other ends of C6 and R10 and the moving plate pin of P1; one pin of the P1 is connected with one end of the R12, and the other end of the R12 is grounded; the other stator pin of the P1 is connected with one end of the R11, the other end of the R11 is connected with one end of the C1 and is used as an input end + I of the signal transmitting circuit, and the other end of the C1 is grounded; the inverting input end and the inverting output end of the U1.1 are connected, and are connected with one end of the R3; the voltage input end of U1.1 is used as the voltage stabilizing input end of the signal transmitting circuit, and the grounding end of U1.1 is grounded; the non-inverting input end of U1.4 is connected with the other end of R3 and one end of R4, the other end of R4 is connected with one end of R5, and the non-inverting input end of R4 is used as the output end OUT1 of the signal transmitting circuit; the inverting input end of U1.4 is connected with the other end of R1 and one end of R2; the other end of the R2 is grounded with the other end of the R5 and is connected with the emitting electrode of the Q1; the output end of U1.4 is connected with one end of R15, and the other end of R15 is connected with the base electrode of Q1.
2. The signal transmission circuit according to claim 1, wherein the signal conversion sub-circuit further comprises a current-limiting protection unit composed of a linear regulator U3 and a resistor R13, the current-limiting protection unit being connected in series to the collector of Q1; the collector of Q1 links to each other with the adjustable end of U3 and one of them one end of R13, and the output of U3 links to each other with the other end of R13, and supply voltage VCC is connected to the input of U3.
3. The signal transmission circuit according to claim 2, wherein the signal conversion sub-circuit further comprises a stabilization unit constituted by a resistor R17 and a capacitor C9; one end of R17 is connected with the base electrode of Q1, the other end of R17 is connected with one end of C9, and the other end of C9 is connected with the emitter electrode of Q1.
4. The signal transmission circuit of claim 3, wherein the signal conversion sub-circuit further comprises capacitors C5 and C7; one end of the C5 and the C7 is connected with the input end of the U3, the other end of the C5 is grounded, and the other end of the C7 is connected with one end of the R5 serving as the output end of the signal transmitting circuit.
5. The signal transmitting circuit according to claim 1, wherein the operational amplifiers U1.2 and U1.3, the variable resistor P2, the resistor R6, and the resistor R7 constitute a first stage differential amplifying unit for amplifying the detection signal of the sensor; the amplification factor A1 of the first-stage differential amplification unit is as follows: a1= R7/(R6 + R) P2 ) Wherein R is P2 Is the resistance value of the adjustable resistor P2.
6. The signal transmission circuit according to claim 5, wherein the amplification factor A1 of the first stage differential amplification unit is: a1= R7/(R6 + R) P2 ) Wherein R is P2 Is the resistance of the adjustable resistor P2.
7. A pressure transmitter includes a sensor, a power circuit, and a signal processing circuit; the power supply circuit is used for providing required power supply; the sensor is used for generating a corresponding detection signal in a detection process; the signal processing circuit is used for converting the detection signal into a corresponding current signal; the method is characterized in that:
the signal processing circuit employs the signal transmitting circuit as claimed in any one of claims 1 to 6.
8. The pressure transmitter of claim 7 wherein the power circuit includes a constant current regulator sub-circuit and a power input signal output sub-circuit; the constant-current voltage-stabilizing sub-circuit comprises a linear voltage stabilizer U2, two resistors R9 and R16 and a capacitor C4; the power input signal output sub-circuit comprises a self-recovery fuse F1 and diodes D1 and D2;
an input pin of the U2 is connected with the negative electrodes of the D1 and the D2, an output pin of the U2 is connected with one end of the R9 or the R16 and is used as a voltage-stabilizing output end of the power supply circuit; the other end of the R16 is grounded, the C4 is connected with the R16 in parallel, and an adjustable pin of the U2 is connected with the other end of the R9 and is used as a constant current output end of the power circuit; the positive electrode of the D2 is connected with the output end OUT1 of the signal transmission circuit and is used as the signal output end of the pressure transmitter; the anode of the D1 is connected with one end of the F1, and the other end of the F1 is used as a power input end of the pressure transmitter.
9. The pressure transmitter of claim 8, wherein the power input signal output sub-circuit further comprises magnetic beads L1, L2; an input pin of the linear voltage stabilizer U2 is connected with one end of the L1, and the other end of the L1 is connected with the cathodes of the D1 and the D2; one end of the L2 is connected to the output terminal OUT1 of the signal transmitting circuit, and the other end is connected to the positive electrode of the D2.
10. The pressure transmitter of claim 7, wherein the sensor comprises a wheatstone bridge of four voltage-variable resistors, four arms of the wheatstone bridge serving as four terminals of the sensor are connected to the input terminals + I, -I, + S, and-S of the signal transmitting circuit, respectively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211189573.4A CN115560889A (en) | 2022-09-28 | 2022-09-28 | Signal transmitting circuit and pressure transmitter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211189573.4A CN115560889A (en) | 2022-09-28 | 2022-09-28 | Signal transmitting circuit and pressure transmitter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115560889A true CN115560889A (en) | 2023-01-03 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211189573.4A Pending CN115560889A (en) | 2022-09-28 | 2022-09-28 | Signal transmitting circuit and pressure transmitter |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115560889A (en) |
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2022
- 2022-09-28 CN CN202211189573.4A patent/CN115560889A/en active Pending
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