CN213092189U - Constant current source excitation sensor circuit - Google Patents
Constant current source excitation sensor circuit Download PDFInfo
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- CN213092189U CN213092189U CN202022054449.XU CN202022054449U CN213092189U CN 213092189 U CN213092189 U CN 213092189U CN 202022054449 U CN202022054449 U CN 202022054449U CN 213092189 U CN213092189 U CN 213092189U
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Abstract
The utility model provides a constant current source excitation sensor circuit, belonging to the sensor power excitation technical field in the measurement and control technology, comprising a constant current source circuit, an electric bridge, a differential amplifying circuit and a signal adjusting circuit, wherein the output end of the constant current source circuit is connected with a bridge power supply end of the electric bridge; one output end of the bridge is connected with the first input end of the differential amplifying circuit, the other output end of the bridge is connected with the second input end of the differential amplifying circuit, and the other bridge power supply end of the bridge is connected with the input end of the signal adjusting circuit; the output end of the signal adjusting circuit is connected with the third input end of the differential amplifying circuit; the differential amplifying circuit and the signal adjusting circuit are respectively provided with an adjustable resistor for accurately adjusting the initial output voltage value and the amplification factor. The sensor circuit has high precision of the output constant current source, is convenient to adjust and has wide application range.
Description
Technical Field
The utility model belongs to the technical field of the sensor power excitation among the measurement and control technique, concretely relates to constant current source excitation sensor circuit.
Background
In the design of power supply excitation circuits of various sensors, the high-precision current constant-current source has very wide application, and has the main advantages of wide frequency spectrum response range, high response speed, high constant-current precision, capability of working stably for a long time, suitability for various loads, and the like. The constant current source circuit is one of the most commonly used power supply circuits in the sensor excitation driving circuit, and one of the most remarkable characteristics of the constant current source circuit is that the output current is constant, namely, the output current does not change along with the change of a load circuit after being constant, so that the constant current source circuit is often applied to the occasions of industrial control, instruments and meters, various component testing circuits, sensor measurement and the like.
At present, the sensors are various in types, the power supply excitation requirements are different, and the sensors are required to be elaborately designed according to the technical requirement indexes to achieve a satisfactory effect. The utility model provides an adopt diffusion type semiconductor pressure sensor's small-size, low-priced pressure transducer's excitation, amplifier circuit design, its advantage is stable adjustable for the high accuracy constant current source of output, and sensor output signal adopts differential amplifier to eliminate common mode error, and this circuit is particularly suitable for exciting and signal amplification to bridge type sensor.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide a: a constant current source excitation sensor circuit is provided, which aims to solve the problems of excitation and signal amplification of a diffusion type semiconductor pressure sensor.
In order to solve the technical problem, the utility model adopts the technical scheme that:
a constant current source excitation sensor circuit comprises a constant current source circuit, an electric bridge, a differential amplification circuit and a signal adjusting circuit, wherein the output end of the constant current source circuit is connected with a bridge power supply end of the electric bridge; one output end of the bridge is connected with the first input end of the differential amplifying circuit, the other output end of the bridge is connected with the second input end of the differential amplifying circuit, and the other bridge power supply end of the bridge is connected with the input end of the signal adjusting circuit; the output end of the signal adjusting circuit is connected with the third input end of the differential amplifying circuit;
the signal adjusting circuit comprises a sixth resistor, a first adjustable resistor and a second operational amplifier, wherein one end of the sixth resistor is used as the input end of the signal adjusting circuit, the output end of the second operational amplifier is used as the output end of the signal adjusting circuit, the other end of the sixth resistor is connected with one end of the first adjustable resistor, the middle end of the first adjustable resistor is connected with the positive phase input end of the second operational amplifier, the other end of the first adjustable resistor is grounded, and the output end of the second operational amplifier is connected with the negative phase input end of the second operational amplifier;
the differential amplifying circuit comprises a third operational amplifier, a fourth operational amplifier, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor and a second adjustable resistor, wherein the positive phase input end of the third operational amplifier is used as the first input end of the differential amplifying circuit, the positive phase input end of the fourth operational amplifier is used as the second input end of the differential amplifying circuit, one end of the seventh resistor is used as the third input end of the differential amplifying circuit, the other end of the seventh resistor is respectively connected with the negative phase input end of the third operational amplifier, one end of the eighth resistor, one end and the middle end of the second adjustable resistor, the other end of the second adjustable resistor is connected with one end of the tenth resistor, the other end of the tenth resistor is connected with the other end of the eighth resistor and the output end of the third operational amplifier, one end of the ninth resistor is connected with the common end of the third operational amplifier, the eighth resistor and the tenth resistor, the other end of the second resistor is connected with the negative phase input end of the fourth operational amplifier and one end of the eleventh resistor, and the other end of the eleventh resistor is connected with the output end of the fourth operational amplifier.
Further, the constant current source circuit includes a dc power supply, a first diode, a second diode, a fifth resistor, and a first operational amplifier, wherein an anode of the dc power supply is connected to an anode of the first diode, a cathode of the dc power supply is grounded, a cathode of the first diode is connected to one end of the fifth resistor, another end of the fifth resistor is connected to a positive input terminal of the first operational amplifier, an anode of the second diode is connected to a cathode of the dc power supply, and a cathode of the second diode is connected to the positive input terminal of the first operational amplifier.
Furthermore, the bridge comprises a first resistor, a second resistor, a third resistor and a fourth resistor, a common end of the first resistor and the second resistor is used as a bridge power supply end of the bridge, a common end of the third resistor and the fourth resistor is used as another bridge power supply end of the bridge, a common end of the first resistor and the third resistor is used as an output end of the bridge, and a common end of the second resistor and the fourth resistor is used as another output end of the bridge.
Further, the second diode is a zener diode.
Further, the first resistor, the second resistor, the third resistor and the fourth resistor are all strain resistors.
Further, the first operational amplifier, the second operational amplifier, the third operational amplifier and the fourth operational amplifier are integrated into a four-operational-amplifier integrated circuit, and the model of the four-operational-amplifier integrated circuit is LM 324N.
Furthermore, the first adjustable resistor and the second adjustable resistor are both precision potentiometers.
Further, the resistance of the seventh resistor is equal to the resistance of the eleventh resistor, and the resistance of the eighth resistor is equal to the resistance of the ninth resistor.
To sum up, owing to adopted above-mentioned technical scheme, the beneficial effects of the utility model are that:
1. the circuit design is simple, the integrated level is high, and the space is very compact during actual installation. In the embodiment, 4 operational amplifiers are packaged together, so that the LM324N is greatly saved in space, and the sensor is very suitable for being arranged in a narrow position;
2. the output constant current source has high precision and wide application range and is convenient to adjust. The same circuit modules are used in this embodiment, and only adjustments to VR1 and VR2 are needed to accommodate different types and ranges of pressure sensors.
Drawings
FIG. 1 is a circuit diagram of the present invention;
FIG. 2 is a pin diagram of a quad-op-amp integrated circuit LM 324N;
in the drawings: 1-constant current source circuit, 2-bridge, 3-differential amplification circuit, D1-first diode, D2-second diode, R1-first resistor, R2-second resistor, R3-third resistor, R4-fourth resistor, R5-fifth resistor, R6-sixth resistor, R7-seventh resistor, R8-eighth resistor, R9-ninth resistor, R10-tenth resistor, R11-eleventh resistor, A1-first operational amplifier, A2-second operational amplifier, A3-third operational amplifier, A4-fourth operational amplifier, VR 1-first adjustable resistor, VR 2-second adjustable resistor.
Detailed Description
The features and properties of the present invention will be described in further detail below with reference to the accompanying drawings and examples.
As shown in fig. 1, the constant current source excitation sensor circuit of the present invention includes a constant current source circuit 1, a bridge 2, a differential amplifier circuit 3 and a signal adjusting circuit 4, wherein the output end of the constant current source circuit 1 is connected to a bridge power supply end of the bridge 2; one output end of the bridge 2 is connected with a first input end of the differential amplifying circuit 3, the other output end of the bridge is connected with a second input end of the differential amplifying circuit 3, and the other bridge power supply end of the bridge 2 is connected with the input end of the signal adjusting circuit 4; the output terminal of the signal adjusting circuit 4 is connected to the third input terminal of the differential amplifying circuit 3.
In the above circuit, the signal adjusting circuit 4 includes a sixth resistor R6, a first adjustable resistor VR1 and a second operational amplifier a2, one end of the sixth resistor R6 is used as the input end of the signal adjusting circuit 4, the output end of the second operational amplifier a2 is used as the output end of the signal adjusting circuit 4, the other end of the sixth resistor 6 is connected with one end of the first adjustable resistor VR1, the middle end of the first adjustable resistor VR1 is connected with the positive phase input end of the second operational amplifier a2, the other end of the first adjustable resistor VR1 is grounded, and the output end of the second operational amplifier a2 is connected with the negative phase input end thereof; the first adjustable resistor VR1 is used to adjust the output value when the input pressure is zero.
The differential amplifier circuit 3 includes a third operational amplifier A3, a fourth operational amplifier a4, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, and a second adjustable resistor VR2, wherein a positive phase input terminal of the third operational amplifier A3 is used as a first input terminal of the differential amplifier circuit 3, a positive phase input terminal of the fourth operational amplifier a4 is used as a second input terminal of the differential amplifier circuit 3, one end of the seventh resistor R7 is used as a third input terminal of the differential amplifier circuit 3, the other ends thereof are connected to a negative phase input terminal of the third operational amplifier A3, one end of the eighth resistor R8, one end and a middle end of the second adjustable resistor VR2, the other end of the second adjustable resistor VR2 is connected to one end of the tenth resistor R10, the other end of the tenth resistor R10 is connected to the other end of the eighth resistor R8 and an output terminal of the third operational amplifier A3, one end of the ninth resistor R9 is connected to a common end of the third operational amplifier A3, the eighth resistor R8 and the tenth resistor R10, the other end is connected to a negative phase input terminal of the fourth operational amplifier a4 and one end of the eleventh resistor R11, and the other end of the eleventh resistor R11 is connected to an output terminal of the fourth operational amplifier a 4.
The utility model discloses a theory of operation is: the excitation of the constant current source output from the constant current source circuit 1 is applied to the bridge power supply end of the bridge 2, the optimal value of the magnitude of the constant current source I depends on the type of the strain resistor, and the calculation formula of the magnitude of the constant current source I is
Marking as a formula I, wherein I is the output current value of the constant current source; v is a reference voltage output value, namely a voltage output value of the constant current source circuit 1; r6Is the value of the sixth resistor R6, VR1Is the resistance of the first adjustable resistor VR 1. According to the formula, the size of the output constant current source can be changed by adjusting the resistance value of the first adjustable resistor VR 1. When the input pressure of the bridge 2 is zero, the resistance value of the first adjustable resistor VR1 is adjusted, and the output value of the constant current source excitation sensor circuit can also be adjusted.
The third operational amplifier A3 and the fourth operational amplifier A4 form a differential amplifier having a gain AVIs calculated by the formula
Is expressed as formula two, wherein AVFor differential amplifier gain, R7Is the resistance value of the seventh resistor R78Is the resistance value of the eighth resistor R810Is the resistance value of a tenth resistor R1011Is the resistance value, VR, of the eleventh resistor R112Is a second adjustable resistorResistance value of VR 2. From this equation, the output voltage can be changed by adjusting the resistance of the second adjustable resistor VR 2. Therefore, the output signal range of the sensor circuit excited by the constant current source can be adjusted by adjusting the second adjustable resistor VR 2.
When the input pressure is zero, the resistance value of the first adjustable resistor VR1 is adjusted to obtain the output voltage value at the moment, and the output voltage value is recorded as an initial voltage value. Then, a pressure is applied, the bridge 2 changes from a balanced state to an unbalanced state, and the output voltage value rises, resulting in a pressurized voltage value. The voltage signal proportional to the applied pressure can be obtained from the difference between the pressurization voltage value and the initial voltage value, so as to realize pressure measurement. In actual use, the initial voltage can be adjusted to zero, so that calculation is facilitated.
In addition, the constant current source circuit 1 includes a dc power supply, a first diode D1, a second diode D2, a fifth resistor R5, and a first operational amplifier a1, wherein an anode of the dc power supply is connected to an anode of the first diode D1, a cathode of the dc power supply is grounded, a cathode of the first diode D1 is connected to one end of a fifth resistor R5, another end of the fifth resistor R5 is connected to a non-inverting input terminal of the first operational amplifier a1, an anode of the second diode D2 is connected to a cathode of the dc power supply, and a cathode of the second diode D2 is connected to the non-inverting input terminal of the first operational amplifier a 1. The constant current source circuit has the characteristic of high precision of an output constant current source, the size of the constant current source can be adjusted by VR1, and the constant current source circuit can be suitable for the types of strain resistors in various bridges 2.
In addition, the bridge 2 includes a first resistor R1, a second resistor R2, a third resistor R3 and a fourth resistor R4, a common end of the first resistor R1 and the second resistor R2 serves as a bridge power supply end of the bridge 2, a common end of the third resistor R3 and the fourth resistor R4 serves as another bridge power supply end of the bridge 2, a common end of the first resistor R1 and the third resistor R3 serves as an output end of the bridge 2, and a common end of the second resistor R2 and the fourth resistor R4 serves as another output end of the bridge 2. The first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4 are all strain resistors. The bridge 2 is formed by strain resistors diffused on a silicon wafer. The second diode D2 is a zener diode. The voltage stabilizing diode has the function of enabling the constant current source to output the reference voltage to be more constant. The first operational amplifier A1, the second operational amplifier A2, the third operational amplifier and the fourth operational amplifier are integrated into a four-operational-amplifier integrated circuit, and the model of the four-operational-amplifier integrated circuit is LM 324N. In practical application, the four-operational-amplifier integrated circuit with the model number LM324N can be selected to replace the operation of the operational amplifier A1-A4, so that the sensor circuit has the advantages of high integration level and space saving, and is very suitable for arranging the sensor using the sensor circuit at a position with narrow space. The first adjustable resistor and the second adjustable resistor are both precision potentiometers. The precise potentiometer can conveniently and accurately adjust the resistance value. In order to ensure the symmetry of the differential amplifier circuit 3, it is necessary to set the resistance of the seventh resistor equal to the resistance of the eleventh resistor, and the resistance of the eighth resistor equal to the resistance of the ninth resistor.
Example 1
A15-30V direct current power supply DC is provided, the model of the first diode D1 is selected to be 1N5817, and the model of the second diode D2 is selected to be LM 385Z-2.5V. As shown in fig. 2, a four-op-amp integrated circuit LM 324N. Four strain resistors. Seven resistors, wherein R5 has a resistance of 24 kilo-ohms, R6 has a resistance of 500 ohms, R7 has a resistance of 100 kilo-ohms, R8 has a resistance of 10 kilo-ohms, R9 has a resistance of 10 kilo-ohms, R10 has a resistance of 3 kilo-ohms, and R11 has a resistance of 100 kilo-ohms. The resistance value of a first adjustable resistor VR1 is 2 kilo-ohms, and the resistance value of VR2 is 5 kilo-ohms.
The positive pole of the direct current power supply DC is connected with the positive pole of a first diode D1, the negative pole of the direct current power supply DC is grounded, the negative pole of a first diode D1 is connected with one end of a fifth resistor R5, the other end of the fifth resistor R5 is connected with pin 3 of a four-operational amplifier integrated circuit LM324N, the positive pole of a second diode D2 is connected with the negative pole of the direct current power supply, and the negative pole of the second diode D5 is connected with pin 3 of the four-operational amplifier integrated circuit LM 324N. Pin 1 of the four-operational-amplifier integrated circuit LM324N is connected to one bridge power supply terminal of the bridge 2, the other bridge power supply terminal of the bridge 2 is connected to one end of the R6 of the sixth resistor, one output terminal of the bridge 2 is connected to pin 10 of the four-operational-amplifier integrated circuit LM324N, and the other output terminal of the bridge 2 is connected to pin 12 of the four-operational-amplifier integrated circuit LM 324N. The other end of the sixth resistor 6 is connected with one end of a first adjustable resistor VR1, the middle end of the first adjustable resistor VR1 is connected with a pin 5 of a four-operational amplifier integrated circuit LM324N, the other end of the first adjustable resistor VR1 is grounded, pins 6 and 7 of the four-operational amplifier integrated circuit LM324N are connected, a pin 7 is further connected with one end of a seventh resistor R7, the other ends of the seventh resistor R7 are respectively connected with one end of a pin 9, one end of an eighth resistor R8, one end and the middle end of a second adjustable resistor VR2, the other end of the second adjustable resistor VR2 is connected with one end of a tenth resistor R10, the other end of the tenth resistor R10 is connected with the other end of an eighth resistor R8 and a pin 8, one end of a ninth resistor R9 is connected with a pin 8, the common end of an eighth resistor R8 and the tenth resistor R10, the other end of the pin 13 and one end of the eleventh resistor R11, and the other end of the eleventh resistor R11 is connected with a pin 14. The four-operational-amplifier integrated circuit LM324N is powered by the DC power supply DC, i.e., pin 4 is connected to the positive pole of the DC power supply DC, and pin 11 is connected to ground.
In practical application, the reference voltage output value of the constant current source circuit 1 is 2.5v, and the first adjustable resistor VR1 is adjusted to make the output voltage signal zero when the input pressure is zero. Adjusting VR2 to make differential amplifier gain AV40 and 50 respectively. The data measured for the present sensor circuit are as follows:
Claims (8)
1. a constant current source stimulated sensor circuit, characterized by: the device comprises a constant current source circuit (1), an electric bridge (2), a differential amplification circuit (3) and a signal adjusting circuit (4), wherein the output end of the constant current source circuit (1) is connected with a bridge power supply end of the electric bridge (2); one output end of the electric bridge (2) is connected with a first input end of the differential amplifying circuit (3), the other output end of the electric bridge is connected with a second input end of the differential amplifying circuit (3), and the other bridge power supply end of the electric bridge (2) is connected with the input end of the signal adjusting circuit (4); the output end of the signal adjusting circuit (4) is connected with the third input end of the differential amplifying circuit (3);
the signal adjusting circuit (4) comprises a sixth resistor, a first adjustable resistor and a second operational amplifier, one end of the sixth resistor is used as the input end of the signal adjusting circuit (4), the output end of the second operational amplifier is used as the output end of the signal adjusting circuit (4), the other end of the sixth resistor is connected with one end of the first adjustable resistor, the middle end of the first adjustable resistor is connected with the positive phase input end of the second operational amplifier, the other end of the first adjustable resistor is grounded, and the output end of the second operational amplifier is connected with the negative phase input end of the second operational amplifier;
the differential amplifying circuit (3) comprises a third operational amplifier, a fourth operational amplifier, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor and a second adjustable resistor, wherein a positive phase input end of the third operational amplifier is used as a first input end of the differential amplifying circuit (3), a positive phase input end of the fourth operational amplifier is used as a second input end of the differential amplifying circuit (3), one end of the seventh resistor is used as a third input end of the differential amplifying circuit (3), the other end of the seventh resistor is respectively connected with a negative phase input end of the third operational amplifier, one end of the eighth resistor, one end and a middle end of the second adjustable resistor, the other end of the second adjustable resistor is connected with one end of the tenth resistor, the other end of the tenth resistor is connected with the other end of the eighth resistor and an output end of the third operational amplifier, one end of the ninth resistor is connected with the third operational amplifier, And the other end of the eleventh resistor is connected with the output end of the fourth operational amplifier.
2. A constant current source excitation sensor circuit as claimed in claim 1, wherein: the constant current source circuit (1) comprises a direct current power supply, a first diode, a second diode, a fifth resistor and a first operational amplifier, wherein the anode of the direct current power supply is connected with the anode of the first diode, the cathode of the direct current power supply is grounded, the cathode of the first diode is connected with one end of the fifth resistor, the other end of the fifth resistor is connected with the positive phase input end of the first operational amplifier, the anode of the second diode is connected with the cathode of the direct current power supply, and the cathode of the second diode is connected with the positive phase input end of the first operational amplifier.
3. A constant current source excitation sensor circuit as claimed in claim 1, wherein: the bridge (2) comprises a first resistor, a second resistor, a third resistor and a fourth resistor, wherein the common end of the first resistor and the second resistor is used as one bridge power supply end of the bridge (2), the common end of the third resistor and the fourth resistor is used as the other bridge power supply end of the bridge (2), the common end of the first resistor and the third resistor is used as one output end of the bridge (2), and the common end of the second resistor and the fourth resistor is used as the other output end of the bridge (2).
4. A constant current source excitation sensor circuit as claimed in claim 2, wherein: the second diode is a zener diode.
5. A constant current source excitation sensor circuit as recited in claim 3, wherein: the first resistor, the second resistor, the third resistor and the fourth resistor are all strain resistors.
6. A constant current source excitation sensor circuit as claimed in claim 2, wherein: the first operational amplifier, the second operational amplifier, the third operational amplifier and the fourth operational amplifier are integrated into a four-operational-amplifier integrated circuit, and the model of the four-operational-amplifier integrated circuit is LM 324N.
7. A constant current source excitation sensor circuit as claimed in claim 1, wherein: the first adjustable resistor and the second adjustable resistor are both precision potentiometers.
8. A constant current source excitation sensor circuit as claimed in claim 1, wherein: the resistance value of the seventh resistor is equal to that of the eleventh resistor, and the resistance value of the eighth resistor is equal to that of the ninth resistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202022054449.XU CN213092189U (en) | 2020-09-18 | 2020-09-18 | Constant current source excitation sensor circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202022054449.XU CN213092189U (en) | 2020-09-18 | 2020-09-18 | Constant current source excitation sensor circuit |
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| CN213092189U true CN213092189U (en) | 2021-04-30 |
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| CN202022054449.XU Active CN213092189U (en) | 2020-09-18 | 2020-09-18 | Constant current source excitation sensor circuit |
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