CN115389058A - Signal processing circuit, pressure transmitter and pressure transmitting chip - Google Patents
Signal processing circuit, pressure transmitter and pressure transmitting chip Download PDFInfo
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- CN115389058A CN115389058A CN202211189792.2A CN202211189792A CN115389058A CN 115389058 A CN115389058 A CN 115389058A CN 202211189792 A CN202211189792 A CN 202211189792A CN 115389058 A CN115389058 A CN 115389058A
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 6
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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
- G01L1/005—Measuring force or stress, in general by electrical means and not provided for in G01L1/06 - G01L1/22
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L19/00—Details of, or accessories for, apparatus for measuring steady or quasi-steady pressure of a fluent medium insofar as such details or accessories are not special to particular types of pressure gauges
- G01L19/02—Arrangements for preventing, or for compensating for, effects of inclination or acceleration of the measuring device; Zero-setting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
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Abstract
The invention relates to the technical field of pressure transmission, in particular to a signal processing circuit, a pressure transmitter and a pressure transmitting chip. The signal processing circuit includes a null adjustment sub-circuit and a signal conversion sub-circuit. The zero adjustment sub-circuit comprises an operational amplifier U1.4, resistors R7, R8 and R9, a variable resistor P1 and capacitors C1, C2, C3 and C5. The signal conversion sub-circuit comprises operational amplifiers U1.1, U1.2 and U1.3, a variable resistor P2, trios Q1 and Q2, resistors R2, R4, R5 and R10, diodes D2 and D3 and a magnetic bead L2. The differential signal is converted into a single-ended high-potential voltage signal, then the single-ended high-potential voltage signal is converted into a corresponding current signal, and the output current signal and the input differential signal are in a linear relation through linear transformation; when the zero-position sub-circuit is connected with the diffused silicon sensor, the circuit balance of the diffused silicon sensor is not damaged.
Description
Technical Field
The invention relates to the technical field of pressure transmission, in particular to a signal processing circuit, a pressure transmitter and a pressure transmitting chip.
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 in direct proportion to the pressure of a medium, and the resistance value of the sensor changes. When the electronic circuit is designed to detect this change and convert it to output a standard measurement signal corresponding to this pressure, a pressure transmitter is 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 zero adjustment operation. The currently widely used zeroing circuit is to connect an adjusting resistor in parallel to a bridge of a sensor itself, as shown in fig. 1, which is easy to damage the circuit balance of the sensor itself, resulting in a deterioration of the temperature coefficient and accuracy of the finally output signal. In addition, in the conventional method, a precision device is used for converting a weak differential signal into a single-ended current output signal, and the precision device has high unit price and is difficult to obtain, so that the signal conversion cost is high and the difficulty is high.
Disclosure of Invention
Therefore, it is necessary to provide a signal processing circuit, a pressure transmitter, and a pressure transmitting chip to solve the problems of high cost and difficulty in signal conversion in the conventional method.
In order to realize the purpose, the invention adopts the following technical scheme:
a signal processing circuit includes a zero adjustment sub-circuit and a signal conversion sub-circuit. The zero adjustment sub-circuit comprises an operational amplifier U1.4, three resistors R7, R8 and R9, a variable resistor P1 and four capacitors C1, C2, C3 and C5. The signal conversion sub-circuit comprises 3 operational amplifiers U1.1, U1.2 and U1.3, a variable resistor P2, two trios Q1 and Q2, four resistors R2, R4, R5 and R10, diodes D2 and D3 and a magnetic bead L2.
The specific connection mode of the signal processing circuit is as follows: the inverting input end and the output end of U1.4 are connected with one end of R9, the other end of R9 is connected with the non-inverting input end of U1.2, the non-inverting input end of U1.4 is used as the input end + S of the signal processing circuit, and the non-inverting input end of U1.4 is connected with one end of C1. The pin of the moving plate of P1 is connected with one end of C5, and one pin of the fixed plate of P1 is connected with one end of R7. The other end of R7 is used as the input end + I of the signal processing circuit and is connected with one end of C2. The other stator pin of P1 is connected with one end of R8, and the other ends of C5 and R8 are connected with C1, C2 and C3 in common, and are used as an input end-I of the signal processing circuit. The other end of C3 is used as the input end-S of the signal processing circuit and is connected with the non-inverting input end of U1.3. The inverting input end and the inverting output end of U1.3 are connected with the moving plate pin and one of the stator plate pins of P2, and the other stator plate pin of P2 is connected with one of the ends of R4. The output end of U1.2 is connected with the base electrode of Q2, and the inverting input end of U1.2 is connected with the emitter electrode of Q2 and the other end of R4. The non-inverting input end of U1.1 is connected with the collector of Q2 and one end of R10, the inverting input end of U1.1 is connected with the emitter of Q1 and one end of R5, the voltage input end of U1.1 is used as one voltage input end of the signal processing circuit, the grounding end is grounded, and the output end of U1.1 is connected with the base of Q1. The collector of Q1 is connected with one end of L2, and the other end of L2 is used as the current output end of the signal processing circuit. The other ends of R5 and R10 and one end of R2 are connected with the cathode of a diode D2, the anode of D2 is connected with the cathode of D3, and the anode of D3 is used as the other voltage input end of the signal processing circuit.
Further, the signal conversion sub-circuit further comprises three capacitors C6, C7, C8. C6 is connected in parallel with R2. One end of the C7 is connected with the anode of the D3, and the other end of the C7 is grounded with the other end of the R2. C8 is connected in parallel with R10.
Further, the operational amplifiers U1.2, U1.3, P2, R4, Q2, and R10 form a current series type negative feedback amplifying unit, and the amplified signal is located at two ends of R10. The amplification factor A1 of the current series type negative feedback amplification unit is as follows: a1= R10/(R) P2 + R4), wherein R P2 Is the resistance of the variable resistor. The circuit unit completes the conversion from a differential pressure signal (+ Vi to-S) to a single-ended high potential signal (V) R10 ). Voltage V across resistor R10 R10 I.e. the voltage at which the stage amplifies the signal.
Further, the operational amplifiers U1.1, Q1 and R5 form a conversion unit for converting the voltage signal at the two ends of R10 into the output signal I of 0-10mA OUT current OUT ：I OUT ＝V R10 /R5。
Further, the triode Q1 adopts a PNP triode. The triode Q2 is an NPN triode.
The invention also provides a pressure transmitter which comprises a sensor, a power circuit and a signal conversion 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 conversion circuit is used for converting the detection signal into a corresponding current signal, and the signal conversion circuit adopts the signal processing circuit.
Further, the power supply circuit comprises a linear voltage regulator U2, two resistors R1 and R3, two magnetic beads L1 and L3, a diode D1 and a capacitor C4.
The specific connection mode of the power circuit is as follows: one end of each of the L1 and the L3 is used as an input end of the power supply circuit, the other end of the L1 is connected with the anode of the D1, and the other end of the L3 is connected with one end of the R8 which is grounded. And a voltage output pin of the U2 is connected with one end of the R1 and the R3, and an adjustable pin of the U2 is connected with the other end of the R3 and is used as a constant current output end of the power supply circuit. The voltage input pin of U2 is connected to the cathode of diode D1. The other end of R1 is grounded, and C4 is connected with R1 in parallel.
Further, the linear voltage regulator U2 adopts a three-terminal adjustable voltage-stabilizing integrated circuit LM317, and forms a constant current unit with R1, R3, and C4 to provide a 1.5mA constant current to power the sensor. The output current of the constant current source is as follows: i =1.25V/R3, where 1.25V is the U2 intrinsic reference voltage.
Furthermore, the sensor comprises 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 the input ends + I, -I, + S and-S of the signal processing circuit.
The invention also provides a pressure transmitter chip which is formed by packaging the power circuit and the signal conversion circuit of the pressure transmitter. The pin of the pressure transmitting chip comprises: the first pin is connected with the anode of the diode D1 through the magnetic bead L1. The second pin is connected with one end of a capacitor C5 through a magnetic bead L3. The third pin is connected with the collector of the triode Q2 through the magnetic bead L2. The fourth pin is connected with one of the chip pins of the variable resistor P1 through a resistor R7. The fifth pin is connected to one end of the capacitors C1, C2, C3, which is grounded. The sixth pin is connected to the non-inverting input of operational amplifier U1.4. The seventh pin is connected to one end of a resistor R8 through a capacitor C3.
The technical scheme provided by the invention has the following beneficial effects:
1. the signal processing circuit can convert the differential signal of the sensor into a single-ended high-potential voltage signal so as to be in butt joint with the next stage. And converting the single-end high-order voltage signal into a corresponding current signal, and enabling the output current signal and the input signal of the sensor to form a linear relation through linear transformation, thereby improving the transformation accuracy. In addition, the zero setting unit composed of U1.4, R7, R8, R9 and P1 is arranged on a circuit at the rear end of the amplifier, so that the compensation characteristic of the sensor is maintained, and the output signal is more accurate. In order to prevent the output stage from entering a saturation region during working, two diodes D2 and D3 are arranged to ensure that the voltage at the input end of the operational amplifier is always lower than the voltage of a power supply 1.4V, and the saturation region of the operational amplifier is avoided, so that the operational amplifier always works in the working region. The function of converting weak differential signals into single-ended current output signals can be completed by adopting a low-cost general operational amplifier, the cost is low, and the difficulty of obtaining devices is greatly reduced.
2. The pressure transmitter provided by the invention uses a universal cheap four-operational amplifier to complete the process of converting the difference of the sensor into a 0-10mA standard signal for output, and makes the current signal have a linear relation with the pressure sensed by the pressure sensor.
3. The anti-electromagnetic interference capability of the pressure transmitter is improved by arranging the magnetic beads L1, L2 and L3 when the pressure transmitter is externally connected; the diode D1 is arranged to prevent the power line from being misconnected to cause circuit damage.
Drawings
FIG. 1 is a circuit diagram of a conventional nulling circuit and sensor in the prior art;
fig. 2 is a circuit diagram of a signal processing circuit according to embodiment 1 of the present invention;
FIG. 3 is a circuit diagram based on the zero 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 a pressure transmitter according to embodiment 2 of the present invention;
FIG. 6 is a circuit diagram of the power circuit of FIG. 5;
FIG. 7 is an overall connection diagram of the pressure transmitter based on FIG. 5;
FIG. 8 is a signal flow diagram based on the pressure transmitter of FIG. 5;
fig. 9 is a schematic structural view of a pressure transmitting chip according to embodiment 3 of the present invention.
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 signal processing circuit of the embodiment solves the problems of high cost and great difficulty in converting a weak differential signal into a single-ended current output signal in the prior art. In the embodiment, the zeroing unit composed of U1.4, R7, R8, R9 and P1 is disposed on the circuit at the rear end of the amplifier, so that the compensation characteristic of the sensor is maintained, and the output signal is more accurate. In addition, a current series negative feedback amplifying unit is formed by U1.3, P2, R4, U1.2, Q2 and R10, and the sensor differential signal can be converted into a single-ended voltage signal V on R10 R10 . The cost is reduced by the cheap general operational amplifier, the device is easy to obtain, and the device is not limited by supply. In addition, the diodes D2 and D3 are arranged to ensure that the voltage at the input end of the operational amplifier is always lower than the voltage of a power supply by 1.4V, and a saturation region of the operational amplifier is avoided, so that the operational amplifier always works in a working region, and the problem of saturation distortion is further solved.
As shown in fig. 2, the signal processing circuit of the present embodiment includes a null adjustment sub-circuit and a signal conversion sub-circuit.
As shown in fig. 3, the null adjustment sub-circuit includes a null adjustment unit composed of an operational amplifier U1.4, three resistors R7, R8, R9, and a variable resistor P1, and four capacitors C1, C2, C3, and C5. Wherein, C1, C2, C3 and C5 play the weak signal to pressure sensor and carry out noise filtering and increase the interference killing feature. The compensation characteristic of the sensor is maintained, so that the accuracy of the output signal is higher. And meanwhile, the large-scale migration can be carried out.
For the value selection of each electronic component in the null adjustment sub-circuit, the embodiment provides a specific scheme: c1, C2, C3 and C5 can select 0.1 muF patch capacitors; selecting 510K omega resistors from R7 and R8; r9 is 2K omega resistance.
As shown in fig. 4, the signal conversion sub-circuit includes 3 operational amplifiers U1.1, U1.2, U1.3, a variable resistor P2, two trios Q1, Q2, four resistors R2, R4, R5, R10, diodes D2, D3, a magnetic bead L2, and capacitors C7, C6, and C8. The current series-type negative feedback amplification unit consisting of U1.3, P2, R4, U1.2, Q2 and R10 can convert the sensor differential signal into a single-ended voltage signal (V) on R10 R10 ) Then Q1, R5 and U1.1 skillfully convert the signal on R10 into a corresponding current signal to be output. Current output signal I OUT The calculation formula of (2) is as follows: i is OUT ＝V R10 and/R5. The combination perfectly achieves the linear conversion process of converting the differential voltage signal into the current signal, so that the output current is stable and keeps a linear relation with the input signal of the sensor, and the precision of the transmitter is improved. The current signal can be better ensured to be output towards the ground, so that the load carrying capacity of the output circuit is strong.
The calculation method of the amplification factor A1 of the current series type negative feedback amplification unit is as follows: acquiring resistance values of the resistor R4 and the adjustable resistor P2; adding the resistance values of the resistor R4 and the adjustable resistor P2 to obtain a total resistance value; and calculating the ratio of the resistance value of the resistor R10 to the total resistance value to obtain the required amplification factor A1. The calculation formula is as follows: a1= R10/(P2 + R4), wherein R P2 Is the resistance of the variable resistor.
The operational amplifier is cheap and universal, and can be replaced by a single power supply circuit with performance not less than 24V. Moreover, all the resistors can meet the precision of 1 percent, and all the capacitors can meet the withstand voltage of 32V. Such as LM2902, which is an inexpensive four-way operational amplifier with a single power supply range of 3-26V and a dual power supply range of ± 1.5V to ± 13V. When the differential signal is received, and the maximum value of the differential input voltage is the same as the maximum value of the power supply voltage, 26V. Such as LM324, which is also a low cost four-way operational amplifier with differential inputs, the acceptable operating voltage of the four-way amplifier is 3-32V. The temperature compensation device has the advantages that short-circuit protection is achieved, the compensation function is achieved, and the problem that the working point and the performance drift due to the change of the device along with the temperature environment can be solved. LM2902 or LM324 is a 14-pin package that contains 4 independent operational amplifiers, and one chip can satisfy the requirements of the circuit (U1.1, U1.2, U1.3, U1.4). Other operational amplifiers may be used to meet the requirements of the application.
The diodes D2 and D3 are used for enabling the voltage of the input end of the operational amplifier to be lower than the voltage of a power supply by 1.4V all the time, so that the saturation region of the operational amplifier is avoided, and the operational amplifier works in the working region all the time. The types of the D2 and the D3 are selected according to actual needs, for example, a 1N4148 diode can be selected, can bear 100V reverse withstand voltage and 150mA average forward current, and is low in price, easy to be common, high in universality and many in substitute types. The magnetic beads L2 increase the anti-electromagnetic interference capability of the external connection of the circuit. The capacitor plays a role in signal filtering. In addition, Q1 adopts PNP triode, and Q2 adopts NPN triode.
For the value selection of each electronic component in the signal conversion sub-circuit, the embodiment provides a specific scheme: c6 and C8 can select 0.1 muF patch capacitor; c7 may be selected to have a capacitance of 2.2 μ F. R2 selects a 20K omega resistor; r4 and R5 are resistors of 100 omega; r10 is a 1.5K omega resistor.
The specific connection mode of the signal processing circuit is as follows: the inverting input end and the output end of U1.4 are connected with one end of R9, the other end of R9 is connected with the non-inverting input end of U1.2, the non-inverting input end of U1.4 is used as the input end + S of the signal processing circuit, and the non-inverting input end of U1.4 is connected with one end of C1. The pin of the moving plate of P1 is connected with one end of C5, and one pin of the fixed plate of P1 is connected with one end of R7. The other end of R7 is used as the input end + I of the signal processing circuit and is connected with one end of C2. The other stator pin of P1 is connected with one end of R8, and the other ends of C5 and R8 are connected with C1, C2 and C3 in common, and are used as an input end-I of the signal processing circuit. The other end of C3 is used as the input end-S of the signal processing circuit and is connected with the non-inverting input end of U1.3. The inverting input end and the inverting output end of U1.3 are connected with the moving plate pin and one of the stator plate pins of P2, and the other stator plate pin of P2 is connected with one of the ends of R4. The output end of U1.2 is connected with the base electrode of Q2, and the inverting input end of U1.2 is connected with the emitter electrode of Q2 and the other end of R4. The non-inverting input end of U1.1 is connected with the collector of Q2 and one end of R10, the inverting input end of U1.1 is connected with the emitter of Q1 and one end of R5, the voltage input end of U1.1 is used as one voltage input end of signal processing power, the grounding end is grounded, and the output end of U1.1 is connected with the base of Q1. The collector of Q1 is connected with one end of L2, and the other end of L2 is used as the current output end of the signal processing circuit. The other ends of R5 and R10 and one end of R2 are connected with the cathode of a diode D2, the anode of D2 is connected with the cathode of D3, and the anode of D3 and one end of C7 are used as the other voltage input end of the signal processing circuit. The other end of C7 is grounded with the other end of R2. C6 is connected in parallel with R2. C8 is connected in parallel with R10.
This embodiment is through zero adjustment sub-circuit and signal conversion sub-circuit cooperation, not only can carry out zero adjustment when maintaining sensor self circuit balance, solves the zero-bit to the problem of not having zero, and the difference of utilizing general low-priced four to have simultaneously put and has accomplished by the sensor converts standard current signal output to make this current signal and the pressure value that pressure sensor sensed linear relation.
Example 2
As shown in fig. 5, the present embodiment describes a pressure transmitter including a sensor, a power supply circuit, and a signal conversion circuit. The power circuit is used for providing required power. The sensor is used for generating a corresponding detection signal in the detection process. The signal conversion circuit is used for converting the detection signal into a corresponding current signal. The signal conversion circuit employs the signal processing circuit in embodiment 1.
As shown in fig. 6, the power supply circuit includes a linear regulator U2, two resistors R1 and R3, two magnetic beads L1 and L3, a diode D1, and a capacitor C4. U2 constitutes constant current unit with R1, R3 and C4, and the constant current source output current is: i =1.25V/R3 (1.25V is the U2 intrinsic reference voltage) for use with the sensor. The constant current unit provides a constant current of 1.5mA to the sensor through a constant current output end (+ I end), and a differential signal output by the sensor passes through a signal change circuit to obtain a current signal which outputs 0-10mA corresponding to a detection signal of the sensor. D1, L3 constitute the protection anti-interference unit, eliminate the interference of high frequency electromagnetism, protection circuit.
The selection of the electronic components in the power supply circuit is as follows: the linear voltage regulator U2 is an LDO voltage regulator with adjustable three-terminal positive voltage, and can be 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 power supply of the sensor by outputting 1.5mA current from the constant current source through the R2 and outputting 5V stabilized power supply operational amplifier to provide stable power supply. The specific model is LM317LBDR2G adjustable voltage stabilizer. 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.
L1 and L3 can adopt the same model, L2 in the signal processing circuit can be selected to be consistent with L1 and L3, preferably MMZ Q601, MMZ1608Q601 can work at the temperature of-20-90 ℃, and can eliminate the interference of high-frequency electromagnetism. The magnetic beads L1, L2, and L3 have a zero dc impedance and a certain inductance to high frequencies. The diode D1 plays a role in preventing the power line from being misconnected to cause circuit damage.
The values of the capacitance and resistance were chosen as follows: c4, selecting a capacitor of 2.2 mu F; r1 is a 5.1K Ω resistor, and R3 is a 820 Ω resistor.
The specific connection mode of the power circuit is as follows: one end of each of the L1 and the L3 is respectively used as an input end of the power circuit, the other end of the L1 is connected with the anode of the D1, and the other end of the L3 is connected with one end of the R8 which is grounded; a voltage output pin of the U2 is connected with one end of the R1 and the R3, and an adjustable pin of the U2 is connected with the other end of the R3 and is used as a constant current output end of the power circuit; a voltage input pin of the U2 is connected with the cathode of the diode D1; the other end of R1 is grounded, and C4 is connected with R1 in parallel.
The sensor comprises a Wheatstone bridge consisting of four voltage variable resistors, four bridge arms of the Wheatstone bridge are used as four wiring ends of the sensor and are respectively connected with input ends + I, -I, + S and-S of the signal processing circuit, the sensor responds to the sensed pressure change through the change of the resistors, and then differential signals are transmitted to the signal processing circuit.
As shown in fig. 8, the power circuit provides a constant current source of 1.5mA to the sensor, and in conjunction with fig. 7, the signal processing circuit collects the differential signal (detection signal) transmitted by the sensor, converts the differential signal into a single-ended voltage signal, and then converts the single-ended voltage signal into a corresponding current signal, which is a standard 0-10mA current signal for output
The embodiment perfectly converts the difference of the sensor into a standard signal of 0-10mA, and outputs the standard signal by using the universal cheap four-operational amplifier, and makes the current signal have a linear relation with the pressure sensed by the pressure sensor.
Example 3
As shown in fig. 9, this embodiment describes a pressure transmitting chip, which is packaged by the power supply circuit and the signal conversion circuit in embodiment 2. The pins of the pressure transmitting chip are as follows: the first pin is connected with the anode of the diode D1 through the magnetic bead L1. The second pin is connected with one end of a capacitor C5 through a magnetic bead L3. The third pin is connected with the collector of the triode Q2 through the magnetic bead L2. The fourth pin is connected with one of the chip pins of the variable resistor P1 through a resistor R7. The fifth pin is connected to one end of the capacitors C1, C2, C3, which is grounded. The sixth pin is connected to the non-inverting input of operational amplifier U1.4. The seventh pin is connected to one end of a resistor R8 through a capacitor C3.
The power circuit and the signal conversion circuit are packaged into a chip, and only the sensor and the chip need to be connected during actual use, so that the power circuit and the signal conversion circuit are convenient to popularize in the market and can be quickly used by technicians in the field, and only the product specification needs to be faced, and the circuit connection is carried out.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within 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 more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A signal processing circuit is used for collecting a detection signal of a sensor and generating a current signal corresponding to a detection quantity according to the detection signal of the sensor, and is characterized by comprising a zero adjustment sub-circuit and a signal conversion sub-circuit; the zero adjustment sub-circuit comprises an operational amplifier U1.4, three resistors R7, R8 and R9, a variable resistor P1 and four capacitors C1, C2, C3 and C5; the signal conversion sub-circuit comprises 3 operational amplifiers U1.1, U1.2 and U1.3, a variable resistor P2, two triodes Q1 and Q2, four resistors R2, R4, R5 and R10, diodes D2 and D3 and a magnetic bead L2;
the inverting input end and the output end of U1.4 are connected with one end of R9, the other end of R9 is connected with the non-inverting input end of U1.2, the non-inverting input end of U1.4 serves as the input end + S of the signal processing circuit, and the non-inverting input end of U1.4 is connected with one end of C1; the pin of the moving plate of P1 is connected with one end of the C5, and one pin of the fixed plate of P1 is connected with one end of the R7; the other end of the R7 is used as the input end + I of the signal processing circuit and is connected with one end of the C2; the other stator pin of P1 is connected with one end of R8, and the other ends of C5 and R8 are grounded with C1, C2 and C3 and used as the input end-I of the signal processing circuit; the other end of the C3 is used as an input end-S of the signal processing circuit and is connected with the in-phase input end of the U1.3; the inverting input end and the inverting output end of U1.3 are connected with the moving plate pin and one stator plate pin of P2, and the other stator plate pin of P2 is connected with one end of R4; the output end of U1.2 is connected with the base electrode of Q2, and the inverting input end of U1.2 is connected with the emitter electrode of Q2 and the other end of R4; the non-inverting input end of U1.1 is connected with the collector of Q2 and one end of R10, the inverting input end of U1.1 is connected with the emitter of Q1 and one end of R5, the voltage input end of U1.1 is used as one voltage input end of the signal processing circuit, the grounding end is grounded, and the output end of U1.1 is connected with the base of Q1; the collector of Q1 is connected with one end of L2, and the other end of L2 is used as the current output end of the signal processing circuit; the other ends of the R5 and the R10 and one end of the R2 are connected with the cathode of the diode D2, the anode of the D2 is connected with the cathode of the D3, and the anode of the D3 is used as the other voltage input end of the signal processing circuit.
2. The signal processing circuit of claim 1, wherein the signal conversion sub-circuit further comprises three capacitors C6, C7, C8; c6 is connected with R2 in parallel; one end of the C7 is connected with the anode of the D3, and the other end of the C7 is grounded with the other end of the R2; c8 is connected in parallel with R10.
3. The signal processing circuit according to claim 1, wherein the operational amplifiers U1.2, U1.3, P2, R4, Q2 and R10 constitute a current series type negative feedback amplification unit; the amplification factor A1 of the current series type negative feedback amplification unit is: a1= R10/(R) P2 + R4), wherein R P2 Is the resistance of the variable resistor.
4. The signal processing circuit of claim 1, the operational amplifiers U1.1, Q1 and R5 constituting a conversion unit, the output current I of the conversion unit OUT ：I OUT ＝V R10 R5, wherein V R10 Is the value of the voltage across resistor R10.
5. The signal processing circuit of claim 1, wherein the transistor Q1 employs a PNP triode; the triode Q2 is an NPN triode.
6. A pressure transmitter includes a sensor, a power circuit and a signal conversion 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 conversion circuit is used for converting the detection signal into a corresponding current signal; the method is characterized in that:
the signal conversion circuit employs the signal processing circuit as claimed in any one of claims 1 to 5.
7. The pressure transmitter of claim 6, wherein the power circuit comprises a linear regulator U2, two resistors R1, R3, two beads L1, L3, a diode D1, and a capacitor C4;
one end of each of the L1 and the L3 is respectively used as an input end of the power circuit, the other end of the L1 is connected with the anode of the D1, and the other end of the L3 is connected with one end of the R8 which is grounded; a voltage output pin of the U2 is connected with one end of the R1 and the R3, and an adjustable pin of the U2 is connected with the other end of the R3 and is used as a constant current output end of the power circuit; a voltage input pin of the U2 is connected with the cathode of the diode D1; the other end of R1 is grounded, and C4 is connected with R1 in parallel.
8. The pressure transmitter of claim 7, wherein the linear regulator U2 employs a three-terminal adjustable voltage regulator integrated circuit LM317, and forms a constant current unit with R1, R3, and C4 to provide a constant current of 1.5mA to power the sensor.
9. The pressure transmitter of claim 6, wherein the sensor comprises a wheatstone bridge consisting of four voltage-variable resistors, and four arms of the wheatstone bridge serve as four terminals of the sensor and are respectively connected to the input terminals + I, -I, + S, and-S of the signal processing circuit.
10. A pressure transmitter chip, which is packaged by the power supply circuit and the signal conversion circuit of the pressure transmitter according to any one of claims 6 to 9; the pin of the pressure transmitting chip comprises:
the first pin is connected with the anode of the diode D1 through the magnetic bead L1;
the second pin is connected with one end of the capacitor C5 through the magnetic bead L3;
the third pin is connected with a collector electrode of the triode Q2 through a magnetic bead L2;
the fourth pin is connected with one of the pins of the variable resistor P1 through a resistor R7;
a fifth pin connected to one end of the capacitors C1, C2, and C3, which is grounded;
a sixth pin connected to the non-inverting input of operational amplifier U1.4;
and a seventh pin connected to one end of the resistor R8 through the capacitor C3.
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| CN202211189792.2A CN115389058B (en) | 2022-09-28 | 2022-09-28 | Signal processing circuit, pressure transmitter and pressure transmitting chip |
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| CN202211189792.2A CN115389058B (en) | 2022-09-28 | 2022-09-28 | Signal processing circuit, pressure transmitter and pressure transmitting chip |
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| CN115389058B CN115389058B (en) | 2023-11-03 |
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| CN117129114A (en) * | 2023-10-23 | 2023-11-28 | 无锡芯感智半导体有限公司 | High-precision pressure sensor with temperature compensation open loop bridge balance structure |
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| CN115389058B (en) | 2023-11-03 |
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