CN115389058B - 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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- CN115389058B CN115389058B CN202211189792.2A CN202211189792A CN115389058B CN 115389058 B CN115389058 B CN 115389058B CN 202211189792 A CN202211189792 A CN 202211189792A CN 115389058 B CN115389058 B CN 115389058B
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- PHEDXBVPIONUQT-RGYGYFBISA-N phorbol 13-acetate 12-myristate Chemical compound C([C@]1(O)C(=O)C(C)=C[C@H]1[C@@]1(O)[C@H](C)[C@H]2OC(=O)CCCCCCCCCCCCC)C(CO)=C[C@H]1[C@H]1[C@]2(OC(C)=O)C1(C)C PHEDXBVPIONUQT-RGYGYFBISA-N 0.000 claims description 4
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 6
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Classifications
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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
Abstract
The invention relates to the technical field of pressure transmission, in particular to a signal processing circuit, a pressure transmitter and a pressure transmission chip. The 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, 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, triodes Q1 and Q2, resistors R2, R4, R5 and R10, diodes D2 and D3 and a magnetic bead L2. The invention firstly converts the differential signal into a single-ended high potential voltage signal, then converts the single-ended high potential voltage signal into a corresponding current signal, and leads the output current signal to be in linear relation with the input differential signal through linear transformation; when the zero sub-circuit is connected with the diffused silicon sensor, the circuit balance of the diffused silicon sensor is not destroyed.
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 transmission chip.
Background
A pressure transducer is a device that converts pressure into a pneumatic or electric signal for control and remote transmission, and typically uses a strain resistance as a sensor for detecting pressure. A diffused silicon pressure sensor is a strain resistor that works on the principle of piezoresistive effect. Diffused silicon pressure sensors are typically fabricated using integrated process technology, which incorporates a wheatstone bridge of a plurality of base resistors. The pressure of the diffusion silicon pressure sensor directly acts on the diaphragm of the sensor, so that the diaphragm generates micro displacement in direct proportion to the pressure of the medium, and the resistance value of the sensor changes. When the change is detected by the designed electronic circuit, a standard measuring signal corresponding to the pressure is converted and output, and then the pressure transmitter can be obtained.
In existing pressure transmitters employing diffused silicon pressure sensors, a wheatstone bridge is zeroed to stabilize the sensor signal. The current widely used zeroing circuit is to connect the adjusting resistor in parallel to the bridge of the sensor itself, as shown in fig. 1, so that the circuit balance of the sensor itself is easily damaged, resulting in the deterioration of the temperature coefficient and accuracy of the finally output signal. In addition, the traditional mode adopts the precision device to convert the weak differential signal into the single-ended current output signal, and the precision device has high unit price and is not easy to acquire, so that the signal conversion cost is high and the difficulty is high.
Disclosure of Invention
Based on the above, it is necessary to provide a signal processing circuit, a pressure transmitter and a pressure transmitting chip, aiming at the problems of high signal conversion cost and great difficulty in the conventional mode.
In order to achieve the above purpose, the present 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 triodes 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 of U1.4 is connected with one end of the output end and 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 movable plate pin of P1 is connected with one end of C5, and one fixed plate pin of P1 is connected with one end of R7. The other end of R7 is used as an 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 commonly grounded with C1, C2 and C3 and serve 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 output end of U1.3 are connected with the moving plate pin and one of the fixed plate pins of P2, and the other fixed 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 the U1.1 is connected with the collector of the Q2 and one end of the R10, the inverting input end of the U1.1 is connected with the emitter of the Q1 and one end of the R5, the voltage input end of the U1.1 is used as one voltage input end of the signal processing circuit, the grounding ground is connected with the ground, and the output end of the U1.1 is connected with the base of the Q1. The collector of Q1 is connected with one end of L2, and the other end of L2 is used as a 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 C7 is connected with the positive electrode of D3, and the other end of C7 is grounded with the other end of 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 negative feedback amplifying unit, and the amplified signals are located at two ends of R10. The amplification factor A1 of the current series negative feedback amplification unit is as follows: a1 =r10/(R) P2 +R4), wherein R is P2 Is the resistance of the variable resistor. The circuit unit converts differential pressure signals (+ Vi-S) into single-ended high-potential signals (V) R10 ). Voltage V across resistor R10 R10 I.e. the voltage of the stage after amplifying the signal.
Further, operational amplifiers U1.1, Q1 andr5 forms a conversion unit for converting the voltage signals at two ends of R10 into 0-10mA OUT current output signals I 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 supply circuit and a signal conversion circuit. The power circuit is used for providing a required power supply. The sensor is used for generating corresponding detection signals in the detection process. The signal conversion circuit is used for converting the detection signal into a corresponding current signal, and the signal processing circuit is adopted by the signal conversion circuit.
Further, the power supply circuit includes 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 supply circuit is as follows: one end of L1 and one end of L3 are respectively used as input ends of a power supply circuit, the other end of L1 is connected with the positive electrode of D1, and the other end of L3 is connected with one end of R8 which is grounded. The voltage output pin of U2 is connected with one end of R1 and R3, and the adjustable pin of U2 is connected with the other end of 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, so as to provide a constant current of 1.5mA for supplying power to the sensor. The constant current source outputs current as follows: i=1.25V/R3, where 1.25V is the U2 intrinsic reference voltage.
Further, the sensor comprises a Wheatstone bridge formed by 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 transmitting chip which is formed by packaging the power supply circuit and the signal conversion circuit of the pressure transmitter. The pin of pressure transmitter chip includes: 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 the collector electrode of the triode Q2 through a magnetic bead L2. The fourth pin is connected to one of the stator pins of the variable resistor P1 through a resistor R7. The fifth pin is connected with one end of the capacitors C1, C2 and C3 which are grounded. The sixth pin is connected to the non-inverting input of the operational amplifier U1.4. The seventh pin is connected to one end of the resistor R8 through the capacitor C3.
The technical scheme provided by the invention has the following beneficial effects:
1. the invention sets the signal processing circuit to convert the differential signal of the sensor into the single-ended high potential voltage signal so as to be in butt joint with the next stage. And then the single-ended high-order voltage signal is converted into a corresponding current signal, and the output current signal and the input signal of the sensor form a linear relation through linear transformation, so that the transmission accuracy is improved. In addition, the zeroing unit formed by U1.4, R7, R8, R9 and P1 is arranged on the circuit at the rear end of the amplifier, so that the compensation characteristic of the sensor is maintained, and the output signal accuracy is higher. The two diodes D2 and D3 are arranged to prevent the output stage from entering the saturation region when in operation, so that the voltage of the input end of the operational amplifier is always lower than 1.4V of the power supply, and the saturation region of the operational amplifier is avoided, so that the operational amplifier always works in the working region. The low-cost universal operational amplifier can be used for converting the weak differential signal into the single-ended current output signal, the cost is low, and the difficulty in acquiring devices is greatly reduced.
2. The pressure transmitter provided by the invention uses a general low-cost four-operational amplifier to complete the process of converting the difference of the sensor into a standard signal of 0-10mA to output, and enables the current signal to be in linear relation with the pressure sensed by the pressure sensor.
3. The pressure transmitter provided by the invention improves the electromagnetic interference resistance of the pressure transmitter when the pressure transmitter is externally connected by arranging the magnetic beads L1, L2 and L3; the diode D1 is arranged to prevent the circuit damage caused by the wrong connection of the power line.
Drawings
FIG. 1 is a circuit diagram of a conventional zeroing 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 of a zero adjust sub-circuit based on FIG. 2;
FIG. 4 is a circuit diagram of a signal conversion sub-circuit based on FIG. 2;
FIG. 5 is a circuit diagram of a pressure transmitter of embodiment 2 of the present invention;
FIG. 6 is a circuit connection diagram based on the power supply 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 diagram of a pressure transmitter chip according to embodiment 3 of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
The signal processing circuit of the embodiment solves the problems of high cost and great difficulty in converting weak differential signals into single-ended current output signals in the prior art. In the embodiment, the zero setting unit formed by U1.4, R7, R8, R9 and P1 is arranged on the circuit at the rear end of the amplifier, so that the compensation characteristic of the sensor is maintained, and the output signal accuracy is higher. In addition, the current series negative feedback amplifying unit is formed by U1.3, P2, R4, U1.2, Q2 and R10, and can convert the sensor differential signal into a single-ended voltage signal V on R10 R10 . The cost is reduced by the low-cost general operational amplifier, and the device is also easy to obtain and is not limited by the supply. In addition, diodes D2 and D3 are arranged to enable the voltage of the input end of the operational amplifier to be always lower than 1.4V of the power supply, avoid the saturation region of the operational amplifier, enable the operational amplifier to always work in the working region, and further overcome the saturationAnd distortion problems.
As shown in fig. 2, the signal processing circuit of the present embodiment includes a zero adjustment sub-circuit and a signal conversion sub-circuit.
As shown in fig. 3, the zero adjustment sub-circuit includes a zero adjustment unit composed of an operational amplifier U1.4, three resistors R7, R8, R9, a variable resistor P1, and four capacitors C1, C2, C3, and C5. Wherein, C1, C2, C3 and C5 play a role in noise filtering and anti-interference capacity increase on weak signals of the pressure sensor. 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 performed.
For numerical selection of each electronic component in the zero adjustment sub-circuit, the embodiment provides a specific scheme: c1, C2, C3 and C5 may select 0.1 μf patch capacitance; r7 and R8 are 510KΩ resistors; r9 is 2KΩ resistor.
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 triodes Q1, Q2, four resistors R2, R4, R5, R10, diodes D2, D3, a magnetic bead L2, and capacitors C7, C6, and C8. The current series negative feedback amplifying unit formed by U1.3, P2, R4, U1.2, Q2 and R10 can convert the sensor differential signal into a single-ended voltage signal (V R10 ) And then the signals on R10 are skillfully converted into corresponding current signals by Q1, R5 and U1.1, and the corresponding current signals are output. Current output signal I OUT The calculation formula of (2) is as follows: i OUT =V R10 R5. The combination perfectly achieves the linear transformation process of converting the differential voltage signal into the current signal, so that the output current is stable and maintains a linear relation with the input signal of the sensor, and the precision of the transmitter is improved. The current signal can be output very well, so that the output circuit has strong load capacity.
The method for calculating the amplification factor A1 of the current series negative feedback amplification unit comprises the following steps: acquiring resistance values of a resistor R4 and an adjustable resistor P2; adding the resistance value of the resistor R4 and the resistance value of 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. Meter with a meter bodyThe calculation formula is as follows: a1 =r10/(p2+r4), where R P2 Is the resistance of the variable resistor.
The operational amplifier is a cheap and general operational amplifier, and the operational amplifier can be replaced by a single power supply circuit with the performance being satisfied and the working power supply voltage being not less than 24V. And all resistance precision is 1% and all capacitance is 32V withstand voltage. Such as LM2902, which is an inexpensive four-way operational amplifier, has 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, the maximum value of the differential input voltage is 26V, which is the same as the maximum value of the power supply voltage. Such as LM324, which is also a low cost four-way operational amplifier with differential inputs, the acceptable operating voltage for the four-way amplifier is 3-32V. The device has the advantages of short-circuit protection and compensation function inside, so that the problem that the working point and the performance drift due to the change of the device along with the temperature environment can be counteracted. LM2902 or LM324 is a 14-pin package having 4 independent op-amps therein, one piece of which meets the requirements of the present circuit (U1.1, U1.2, U1.3, U1.4). Other operational amplifiers that meet the use requirements may also be used.
The diodes D2 and D3 are used to make the voltage at the input end of the operational amplifier always lower than 1.4V of the power supply, so that the saturation region of the operational amplifier is avoided, and the operational amplifier always works in the working region. The types of D2 and D3 are selected according to actual needs, for example, a 1N4148 diode can be selected, the diode can bear 100V reverse withstand voltage and 150mA average forward current, and the diode is low in price, easy to common, strong in universality and quite large in alternative types. The magnetic beads L2 increase the electromagnetic interference resistance of the circuit to external connection. The capacitor plays a role in signal filtering. In addition, Q1 adopts PNP triode, and Q2 adopts NPN triode.
For the numerical selection of each electronic component in the signal conversion sub-circuit, the embodiment provides a specific scheme: c6 and C8 may select 0.1 μf patch capacitance; c7 may choose a capacitance of 2.2 μf. R2 is a 20KΩ resistor; r4 and R5 are 100 omega resistors; r10 is 1.5KΩ resistance.
The specific connection mode of the signal processing circuit is as follows: the inverting input end of U1.4 is connected with one end of the output end and 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 movable plate pin of P1 is connected with one end of C5, and one fixed plate pin of P1 is connected with one end of R7. The other end of R7 is used as an 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 commonly grounded with C1, C2 and C3 and serve 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 output end of U1.3 are connected with the moving plate pin and one of the fixed plate pins of P2, and the other fixed 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 the U1.1 is connected with the collector of the Q2 and one end of the R10, the inverting input end of the U1.1 is connected with the emitter of the Q1 and one end of the R5, the voltage input end of the U1.1 is used as one voltage input end of signal processing power, the grounding ground is connected with the ground, and the output end of the U1.1 is connected with the base of the Q1. The collector of Q1 is connected with one end of L2, and the other end of L2 is used as a 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.
According to the embodiment, the zero adjustment sub-circuit is matched with the signal conversion sub-circuit, so that the zero adjustment can be performed while the circuit balance of the sensor is maintained, the problem that the zero position is not zero is solved, meanwhile, the differential conversion of the sensor into the standard current signal output is completed by using the universal and low-cost four operational amplifier, and the current signal and the pressure value sensed by the pressure sensor are in a linear relation.
Example 2
As shown in fig. 5, this embodiment describes a pressure transmitter that includes a sensor, power circuitry, and signal conversion circuitry. The power circuit is used for providing a required power supply. The sensor is used for generating corresponding detection signals 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 voltage regulator U2, two resistors R1, R3, two magnetic beads L1, L3, a diode D1, and a capacitor C4. U2, R1, R3 and C4 form a constant current unit, and the output current of the constant current source is as follows: i=1.25V/R3 (1.25V is the U2 intrinsic reference voltage) for 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 the sensor outputs a differential signal to obtain a current signal of 0-10mA corresponding to the detection signal of the sensor through a signal change circuit. D1, L1 and L3 form a protection anti-interference unit, eliminate the interference of high-frequency electromagnetic waves and protect a circuit.
The selection of the electronic components in the power supply circuit is as follows: the linear voltage regulator U2 adopts an adjustable three-terminal positive voltage LDO voltage regulator and can be formed by a three-terminal adjustable voltage stabilizing integrated circuit LM 317. The special structure of the LM317 is skillfully utilized to simultaneously complete the constant current source to output 1.5mA current to supply power to the sensor through the R2, and meanwhile, the 5V regulated power supply operational amplifier is output to provide stable power supply. The specific model is LM317LBDR2G adjustable voltage stabilizer. It is capable of providing a current greater than 1.5mA in the output voltage range of 1.2V to 37V. The output voltage can be set by only 2 external resistors, and the use is easy. In addition, it also adopts internal current limitation, overheat shutdown and safe area compensation, so as to greatly reduce the possibility of damage. So that it is not substantially damaged.
L1 and L3 can be of the same model, L2 in the signal processing circuit can be selected to be consistent with L1 and L3, and the working temperatures of MMZ1608Q601 and MMZ1608Q601 can be between-20 ℃ and 90 ℃ so as to eliminate high-frequency electromagnetic interference. The magnetic beads L1, L2 and L3 have zero direct current impedance and certain inductance to high frequency. The diode D1 serves to prevent circuit damage caused by miswiring of the power supply line.
The values of capacitance and resistance are selected as follows: c4 selects 2.2 mu F capacitance; r1 is 5.1KΩ resistor, and R3 is 820 KΩ resistor.
The specific connection mode of the power supply circuit is as follows: one end of L1 and one end of L3 are respectively used as input ends of a power supply circuit, the other end of L1 is connected with the positive electrode of D1, and the other end of L3 is connected with one end of R8 which is grounded; the voltage output pin of the U2 is connected with one end of the R1 and the R3, and the 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 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 terminals of the sensor and are respectively connected with the input ends +I, -I, +S and-S of the signal processing circuit, and the sensor corresponds to the induced pressure change through the change of the resistance so as to transmit differential signals to the signal processing circuit.
As shown in fig. 8, the power supply circuit provides a constant current source of 1.5mA for the sensor, and the signal processing circuit acquires differential signals (detection signals) transmitted by the sensor in combination with fig. 7, firstly converts the differential signals into single-ended voltage signals, and then converts the single-ended voltage signals into corresponding current signals to output, wherein the current signals are standard 0-10mA current signals
The embodiment realizes that the differential conversion of the sensor into the 0-10mA standard signal output is perfectly finished by using the universal and low-cost four-operational amplifier, and the current signal and the pressure sensed by the pressure sensor are in a linear relation.
Example 3
As shown in fig. 9, this embodiment describes a pressure transmitter chip that 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 the capacitor C5 through the magnetic bead L3. The third pin is connected with the collector electrode of the triode Q2 through a magnetic bead L2. The fourth pin is connected to one of the stator pins of the variable resistor P1 through a resistor R7. The fifth pin is connected with one end of the capacitors C1, C2 and C3 which are grounded. The sixth pin is connected to the non-inverting input of the operational amplifier U1.4. The seventh pin is connected to one end of the resistor R8 through the capacitor C3.
The power supply circuit and the signal conversion circuit are packaged into a chip, and the power supply circuit and the signal conversion circuit are connected with the sensor and the chip in actual use, so that the power supply circuit and the signal conversion circuit are convenient to popularize in the market and can be rapidly used by those skilled in the art, and only the power supply circuit and the signal conversion circuit are required to be connected with a product instruction book in a line mode.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (10)
1. A signal processing circuit 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, characterized in that the signal processing circuit comprises 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 the U1.4 are connected with one end of the R9, the other end of the R9 is connected with the non-inverting input end of the U1.2, the non-inverting input end of the U1.4 is used as an input end +S of the signal processing circuit, and the non-inverting input end of the U1.4 is connected with one end of the C1; the pin of the moving plate of P1 is connected with one end of C5, and one pin of the moving plate of P1 is connected with one end of R7; the other end of R7 is used as an 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, the other ends of C5 and R8 are commonly grounded with C1, C2 and C3, and the other ends are used as an input end-I of the signal processing circuit; the other end of C3 is used as an input end-S of the signal processing circuit and is connected with a non-inverting input end of U1.3; the inverting input end and the output end of the U1.3 are connected with a moving plate pin and one fixed plate pin of the P2, and the other fixed plate pin of the P2 is connected with one end of the R4; the output end of the U1.2 is connected with the base electrode of the Q2, and the inverting input end of the U1.2 is connected with the emitter electrode of the Q2 and the other end of the R4; the non-inverting input end of the U1.1 is connected with the collector of the Q2 and one end of the R10, the inverting input end of the U1.1 is connected with the emitter of the Q1 and one end of the R5, the voltage input end of the U1.1 is used as one voltage input end of the signal processing circuit, the grounding ground is connected with the ground, and the output end of the U1.1 is connected with the base electrode of the Q1; the collector of the Q1 is connected with one end of the L2, and the other end of the L2 is used as a 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.
2. The signal processing circuit of claim 1, wherein the signal conversion subcircuit further comprises three capacitors C6, C7, C8; c6 is connected with R2 in parallel; one end of C7 is connected with the positive electrode of D3, and the other end of C7 is grounded with the other end of R2; c8 is connected in parallel with R10.
3. The signal processing circuit of claim 1, the operational amplifiers U1.2, U1.3, P2, R4, Q2, and R10 constitute a current series negative feedback amplification unit; the current series negative feedback amplifying unit has the amplification factor A1: a1 =r10/(R) P2 +R4), wherein R is P2 Is the resistance of the variable resistor.
4.The signal processing circuit of claim 1, the operational amplifiers U1.1, Q1 and R5 form a conversion unit, the output current I of the conversion unit OUT ：I OUT =V R10 R5, wherein V R10 Is the voltage across resistor R10.
5. The signal processing circuit of claim 1, wherein the transistor Q1 is a PNP transistor; the triode Q2 adopts an NPN triode.
6. A pressure transmitter comprising a sensor, a power circuit, and a signal conversion circuit; the power circuit is used for providing a required power supply; the sensor is used for generating corresponding detection signals in the 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 according to 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 magnetic beads L1, L3, a diode D1, and a capacitor C4;
one end of each of L1 and L3 is used as an input end of a power supply circuit, the other end of each of L1 is connected with the positive electrode of each of D1, and the other end of each of L3 is connected with one grounded end of each of R8; the voltage output pin of the U2 is connected with one end of the R1 and the R3, and the 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 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 regulated 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 of four voltage-variable resistors, the four legs of the wheatstone bridge being connected as four terminals of the sensor to inputs +i, -I, +s and-S of the signal processing circuit, respectively.
10. A pressure transmitter chip, characterized in that it is packaged by the power circuit and signal conversion circuit of the pressure transmitter according to any one of claims 6-9; the pin of pressure transmitter chip includes:
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 a magnetic bead L3;
the third pin is connected with the collector electrode of the triode Q2 through a magnetic bead L2;
a fourth pin connected to one of the stator pins of the variable resistor P1 through a resistor R7;
the fifth pin is connected with one end of the capacitors C1, C2 and C3 which are grounded;
a sixth pin connected to the non-inverting input of the operational amplifier U1.4;
and a seventh pin connected to one end of the resistor R8 through a capacitor C3.
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| CN117129114B (en) * | 2023-10-23 | 2024-01-26 | 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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