CN109781058B - Strain sensor simulator - Google Patents

Abstract

The invention provides a strain sensor simulator, which is characterized by comprising a sensor simulator circuit interface (1), a reverse connection and overvoltage protection circuit (2), a voltage-stabilized power supply circuit (3), a D/A circuit reference voltage divider resistance network (4), a reference voltage switching circuit (5), an output divider resistance network (6), an output divider resistance switching circuit (7), a range selection switch (8), a PWM subdivision circuit (9), an A/D circuit divider resistance network (10), a single chip microcomputer (11), a D/A converter (12), a user program memory EEPROM (13), a temperature sensor (14), a liquid crystal display (15), a communication interface circuit (16) and an operation keyboard (17). The electronic switch replaces a mechanical switch, so that the change of contact resistance caused by oxidation or pollution of a contact of the mechanical switch is eliminated, and the long-term stability of the simulator is improved.

Description

Strain sensor simulator

Technical Field

The invention relates to the field of circuit design, in particular to a strain sensor simulator.

Background

The invention relates to a further development of a high-accuracy strain sensor simulator ZL 03245772.3. The simulator is adapted to a variety of different measuring instruments used in connection with the sensor, and the instruments supply different excitation voltages to the sensor. When the variation range of the sensor excitation voltage input into the simulator is too large, the reference voltage of the DAC exceeds the allowable range, and at this time, a switch circuit is required to switch different voltage division networks to keep the reference voltage of the DAC within a proper range, and a switch is used to switch different output voltage division circuits to keep the ratio of the output voltage to the excitation voltage (i.e. the output value of the sensor) unchanged.

It is conventional practice to switch different voltage divider networks using switches with contacts. When the contact of the switch is oxidized or polluted, the contact resistance is unstable, so that the voltage division ratio of the resistance network is changed, and the output signal of the simulator generates errors.

Disclosure of Invention

In view of the deficiencies in the prior art, it is an object of the present invention to provide a strain sensor simulator.

The invention provides a strain sensor simulator, which comprises a sensor simulator circuit interface, a reverse connection and overvoltage protection circuit, a voltage-stabilized power supply circuit, a D/A circuit reference voltage divider resistance network, a reference voltage switching circuit, an output divider resistance network, an output divider resistance switching circuit, a range selection switch, a PWM subdivision circuit, an A/D circuit divider resistance network, a singlechip, a D/A converter, a user program memory EEPROM, a liquid crystal display, a communication interface circuit and an operation keyboard, wherein the sensor simulator circuit interface is connected with the reverse connection and overvoltage protection circuit;

the sensor simulator circuit interface is connected with a measured instrument, a sensor excitation voltage input by the measured instrument is respectively connected with the input ends of the reverse connection and overvoltage protection circuit, the A/D circuit divider resistance network and the D/A circuit reference voltage divider resistance network through the sensor simulator circuit interface, the output end of the reverse connection and overvoltage protection circuit is connected with the input end of the voltage-stabilized power supply circuit, and the voltage-stabilized power supply circuit (3) provides power; the output end of the A/D circuit divider resistance network is connected with an ADC circuit pin of the singlechip and used for measuring a sensor excitation voltage value output by the instrument to be measured; the voltage dividing ratio of the reference voltage dividing resistor network of the D/A circuit is selected by the reference voltage switching circuit, the output end of the reference voltage dividing resistor network of the D/A circuit is respectively connected with the input ends of the D/A converter and the PWM dividing circuit, the output ends of the D/A converter and the PWM dividing circuit are respectively connected with the input end of the output voltage dividing resistor network, the D/A converter and the PWM subdivision circuit are connected with the singlechip, the D/A converter outputs a voltage value which is in direct proportion to a reference voltage to an output voltage-dividing resistance network according to an instruction of the singlechip, the voltage-dividing ratio of the output voltage-dividing resistance network is controlled by an output voltage-dividing resistance switching circuit, and the voltage output by the output voltage-dividing resistance network after voltage division is superposed with the voltage output by the singlechip-controlled PWM subdivision circuit and then output to a sensor simulator circuit interface to form an output voltage signal of the sensor, and the output voltage signal is transmitted to a signal input end of the measured instrument;

the reference voltage switching circuit and the output voltage dividing resistance switching circuit are respectively connected with a range selection switch and are controlled by the range selection switch, and the range selection switch is connected with the single chip microcomputer to input the state of the single chip microcomputer;

the single chip microcomputer is respectively connected with a user program memory EEPROM, a liquid crystal display, a communication interface circuit and an operation keyboard; the user program memory EEPROM can store user program, the liquid crystal display can display the working state of the simulator, the communication interface circuit can input user program and control instruction of the sensor simulator, and the user operates the sensor simulator to work by operating the keyboard.

Preferably, the temperature sensor is connected with the single chip microcomputer, and the single chip microcomputer compensates the circuit board temperature measured by the temperature sensor and outputs the compensated circuit board temperature.

Preferably, the maximum output voltage of the PWM sub-division circuit is the minimum resolution voltage of the D/a converter.

Preferably, the sensorsimulator circuit interface 1 comprises a connector J1, a filter C1, a filter C2, a filter C3 and a filter C4, the reverse connection and overvoltage protection circuit comprises a self-recovery fuse F1 and a TVS tube D1, the regulated power supply circuit comprises a voltage stabilizer U1, a resistor R16, a resistor R18, a capacitor C7 and a capacitor C8, the D/A circuit reference voltage divider resistor network comprises a precision resistor network RM1, the reference voltage switching circuit comprises a MOSFET tube Q2, the output divider resistor network comprises a precision resistor R3, a precision resistor R10, a precision resistor network RM2 and a precision resistor network RM3, the output divider resistor switching circuit comprises a MOSFET tube Q3, a MOSFET tube Q4, a resistor R34, a resistor R35 and a voltage stabilizing diode D8, the range selection switch comprises K1A and K1B, and the PWM subdivision circuit comprises a MOSFET tube Q1, a resistor R1, a resistor R2 and a resistor R5983, The A/D circuit voltage-dividing resistor network comprises a resistor R4, a resistor R5, a resistor R6, a resistor R8 and a capacitor C17, and the A/D circuit voltage-dividing resistor network comprises a resistor R12 and a resistor R13.

Preferably, the MOSFET tube Q1, the MOSFET tube Q2, the MOSFET tube Q3 and the MOSFET tube Q4 adopt AO3400, the D/a converter adopts AD5060, the single chip microcomputer adopts PIC18F1320, the temperature sensor adopts TC77, the user program memory EEPROM adopts 24C512, and the voltage stabilizer U1 adopts TPS 71501.

Compared with the prior art, the invention has the following beneficial effects:

1. the electronic switch replaces a mechanical switch, so that the change of contact resistance caused by oxidation or pollution of a contact of the mechanical switch is eliminated, and the long-term stability of the simulator is improved.

2. The invention uses the voltage regulator tube to ensure that the MOSFET (field effect tube) has enough starting voltage and can not exceed the allowable grid source voltage limit value of the MOSFET.

3. In the voltage division circuit, a fixed resistor and the switching between two states of the fixed resistor and the other disconnectable resistor in parallel are used for replacing the switching between the two resistors, so that the influence caused by the change of the on-resistance of the MOSFET is reduced.

4. The invention uses the combination of the DAC circuit and the PWM circuit to improve the resolution of the DAC circuit and improve the performance of the simulator.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

fig. 1 is a schematic block diagram of the present invention.

Fig. 2 is an electrical schematic of the present invention.

The figures show that:

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.

The present invention relates to a device for detecting or calibrating instruments and control systems, which is used for outputting specified standard signals by an analog strain sensor. The output signal of the strain sensor is proportional to the product of the input to the sensor and the excitation voltage of the sensor.

The strain sensor simulator provided by the invention comprises a sensorsimulator circuit interface 1, a reverse connection andovervoltage protection circuit 2, a voltage-stabilizedpower supply circuit 3, a D/A circuit reference voltagedivider resistance network 4, a referencevoltage switching circuit 5, an outputdivider resistance network 6, an output dividerresistance switching circuit 7, arange selection switch 8, aPWM subdivision circuit 9, an A/D circuitdivider resistance network 10, asingle chip microcomputer 11, a D/A converter 12, a user program memory EEPROM13, aliquid crystal display 15, acommunication interface circuit 16 and anoperation keyboard 17, wherein the sensorsimulator circuit interface 1 is connected with a voltage-stabilizedpower supply circuit 3;

the sensorsimulator circuit interface 1 is connected with a measured instrument, a sensor excitation voltage input by the measured instrument is respectively connected with the input ends of the reverse connection andovervoltage protection circuit 2, the A/D circuitdivider resistance network 10 and the D/A circuit reference voltagedivider resistance network 4 through the sensorsimulator circuit interface 1, the output end of the reverse connection andovervoltage protection circuit 2 is connected with the input end of the voltage-stabilizedpower supply circuit 3, and the voltage-stabilizedpower supply circuit 3 provides power; the output end of the A/D circuitdivider resistance network 10 is connected with an ADC circuit pin of thesinglechip 11 and is used for measuring a sensor excitation voltage value output by a measured instrument; the voltage division ratio of the reference voltagedivider resistance network 4 of the D/A circuit is selected by the referencevoltage switching circuit 5, the output end of the reference voltagedivider resistance network 4 of the D/A circuit is respectively connected with the input ends of the D/A converter 12 and thePWM subdivision circuit 9, the output ends of the D/A converter 12 and thePWM subdivision circuit 9 are respectively connected with the input end of the outputdivider resistance network 6, the D/A converter 12 and thePWM subdivision circuit 9 are connected with thesinglechip 11, the D/A converter 12 outputs a voltage value which is in direct proportion to the reference voltage to the outputdivider resistance network 6 according to the instruction of thesinglechip 11, the voltage division ratio of the outputdivider resistance network 6 is controlled by the output dividerresistance switching circuit 7, the voltage output after the voltage division of the outputdivider resistance network 6 is superposed with the voltage output by thesinglechip 11 controlling thePWM subdivision circuit 9 and then is output to the sensorsimulator circuit interface 1 to form an output voltage signal of the sensor which is A number input;

the referencevoltage switching circuit 5 and the output voltage-dividingresistance switching circuit 7 are respectively connected with arange selection switch 8 and are controlled by therange selection switch 8, and therange selection switch 8 is connected with thesinglechip 11 to input the self state into thesinglechip 11;

thesingle chip microcomputer 11 is respectively connected with a user program memory EEPROM13, aliquid crystal display 15, acommunication interface circuit 16 and anoperation keyboard 17; the user program memory EEPROM13 can store user program, theliquid crystal display 15 can display the simulator operating status, thecommunication interface circuit 16 can input user program and sensor simulator control instructions, and the user operates the sensor simulator to operate by operating thekeypad 17. Thetemperature sensor 14 is connected with thesingle chip microcomputer 11, and thesingle chip microcomputer 11 compensates the circuit board temperature measured by thetemperature sensor 14 and outputs the compensated circuit board temperature.

The maximum output voltage of thePWM sub-division circuit 9 is the minimum resolution voltage of the D/a converter 12. The combination of the D/a converter 12 and thePWM sub-division circuit 9 thus improves the resolution of the simulator. The resolution of twenty bits can be achieved by using the sixteen-bit D/A device and the four-bit PWM circuit to work in combination.

As shown in fig. 2, the sensorsimulator circuit interface 1 includes a connector J1, a filter C1, a filter C2, a filter C3 and a filter C4, the reverse connection andovervoltage protection circuit 2 includes a self-recovery fuse F1 and a TVS tube D1, the regulatedpower supply circuit 3 includes a regulator U1, a resistor R16, a resistor R18, a capacitor C7 and a capacitor C8, the D/a circuit reference voltagedivider resistor network 4 includes a precision resistor network RM1, the referencevoltage switching circuit 5 includes a MOSFET tube Q2, the outputdivider resistor network 6 includes a precision resistor R3, a precision resistor R10, a precision resistor network RM2 and a precision resistor network RM3, the output dividerresistor switching circuit 7 includes a MOSFET tube Q3, a MOSFET tube Q4, a resistor R34, a resistor R35 and a regulator diode D35, therange selection switch 8 includes aMOSFET 1 35 and a PWM 35, and the PWM subdivision circuit 369 includes a tube Q72, The A/D circuit voltage-dividingresistor network 10 comprises a resistor R1, a resistor R2, a resistor R4, a resistor R5, a resistor R6, a resistor R8 and a capacitor C17, and the resistor R12 and the resistor R13. Therange selection switches 8 are K1A and K1B, when the switches are in a 5-10V gear, the grid sources of Q2, Q3 and Q4 are all in short circuit, and Q2, Q3 and Q4 are all cut off; when the switch is in a 10-20V gear, Q2, Q3 and Q4 are all conducted, 2-3 pin resistors and 2-4 pin resistors of a precision resistor network RM1 in the D/A circuit reference voltagedivider resistor network 4 are connected in parallel, 1-3 pin resistors and 1-4 pin resistors in the precision resistor network RM2 in the outputdivider resistor network 6 are connected in parallel, and 1-3 pin resistors and 1-4 pin resistors in a precision resistor network RM3 in the outputdivider resistor network 6 are connected in parallel, so that the voltage division ratio of the D/A circuit reference voltagedivider resistor network 4 and the outputdivider resistor network 6 is changed. Thesinglechip 11 is U5, the D/A converter 12 is U4, the user program memory EEPROM13 is U3, and thetemperature sensor 14 is U2.

The MOSFET tube Q1, the MOSFET tube Q2, the MOSFET tube Q3 and the MOSFET tube Q4 adopt AO3400, the D/A converter 12 adopts AD5060, thesinglechip 11 adopts PIC18F1320, thetemperature sensor 14 adopts TC77, the user program memory EEPROM13 adopts 24C512, and the voltage stabilizer U1 adopts TPS 71501.

Preferably, the connection mode of the sensorsimulator circuit interface 1 is similar to that of various strain sensors, the input sensor excitation voltage is supplied to various electric components from a stabilized voltagepower supply circuit 3 through a reverse connection andovervoltage protection circuit 2, and is transmitted to an ADC circuit pin of asinglechip 11 through an A/D circuitdivider resistance network 10 for measuring the excitation voltage value input by the interface; the voltage is divided by a D/A circuit reference voltagedivider resistance network 4 and then sent to a reference voltage input pin of a D/A converter 12 and aPWM subdivision circuit 9. The D/a circuit reference voltage dividingresistor network 4 selects a dividing ratio by the referencevoltage switching circuit 5 so that the reference voltage of the D/aconverter 12 is kept within an appropriate range. The D/A converter 12 outputs a voltage value which is in proportion to the reference voltage according to the instruction of thesinglechip 11, the voltage is sent to the output voltage-dividingresistance network 6, the output voltage-dividingresistance network 6 controls the voltage-dividing ratio by the output voltage-dividingresistance switching circuit 7, the output voltage after voltage division is superposed with the output voltage value of thePWM subdivision circuit 9 controlled by thesinglechip 11 and then is output to the sensorsimulator circuit interface 1, and an output voltage signal of the sensor is formed. The referencevoltage switching circuit 5 and the output voltage-dividingresistance switching circuit 7 are both controlled by arange selection switch 8, and the state of therange control switch 8 is also input to thesinglechip 11.

The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims (7)

1. A strain sensor simulator is characterized by comprising a sensor simulator circuit interface (1), a reverse connection and overvoltage protection circuit (2), a voltage-stabilized power supply circuit (3), a D/A circuit reference voltage divider resistance network (4), a reference voltage switching circuit (5), an output divider resistance network (6), an output divider resistance switching circuit (7), a range selection switch (8), a PWM subdivision circuit (9), an A/D circuit divider resistance network (10), a singlechip (11), a D/A converter (12), a user program memory EEPROM (13), a liquid crystal display (15), a communication interface circuit (16) and an operation keyboard (17);

the sensor simulator circuit interface (1) is connected with a measured instrument, a sensor excitation voltage input by the measured instrument is respectively connected with the input ends of the reverse connection and overvoltage protection circuit (2), the A/D circuit divider resistance network (10) and the D/A circuit reference voltage divider resistance network (4) through the sensor simulator circuit interface (1), the output end of the reverse connection and overvoltage protection circuit (2) is connected with the input end of the voltage-stabilized power supply circuit (3), and the voltage-stabilized power supply circuit (3) provides power; the output end of the A/D circuit divider resistance network (10) is connected with an ADC circuit pin of the singlechip (11) and is used for measuring a sensor excitation voltage value output by the instrument to be measured; the voltage dividing ratio of the reference voltage divider resistance network (4) of the D/A circuit is selected through the reference voltage switching circuit (5), the output end of the reference voltage divider resistance network (4) of the D/A circuit is respectively connected with the input ends of the D/A converter (12) and the PWM subdivision circuit (9), the output ends of the D/A converter (12) and the PWM subdivision circuit (9) are respectively connected with the input end of the output divider resistance network (6), the D/A converter (12) and the PWM subdivision circuit (9) are connected with the singlechip (11), the D/A converter (12) outputs a voltage value which is in direct proportion to the reference voltage to the output divider resistance network (6) according to the instruction of the singlechip (11), the voltage dividing ratio of the output divider resistance network (6) is controlled through the output divider resistance switching circuit (7), and the voltage output after the voltage division of the output divider resistance network (6) and the voltage output by the PWM subdivision circuit (9) controlled by the singlechip (11) After being pressed and overlapped, the voltage is output to a circuit interface (1) of a sensor simulator to form an output voltage signal of the sensor and the output voltage signal is sent to a signal input end of a measured instrument;

the reference voltage switching circuit (5) and the output voltage dividing resistance switching circuit (7) are respectively connected with a range selection switch (8) and are controlled by the range selection switch (8), and the range selection switch (8) is connected with the singlechip (11) to input the self state into the singlechip (11);

the single chip microcomputer (11) is respectively connected with a user program memory EEPROM (13), a liquid crystal display (15), a communication interface circuit (16) and an operation keyboard (17); the user program memory EEPROM (13) can store user program, the liquid crystal display (15) can display the working state of the simulator, the communication interface circuit (16) can input user program and control command of the sensor simulator, and the user operates the sensor simulator by operating the keyboard (17).

2. The strain sensor simulator according to claim 1, further comprising a temperature sensor (14), wherein the temperature sensor (14) is connected to the single chip microcomputer (11), and the single chip microcomputer (11) compensates and outputs the circuit board temperature measured by the temperature sensor (14).

3. Strain sensor simulator according to claim 1, characterized in that the maximum output voltage of the PWM subdivision circuit (9) is the minimum resolution voltage of the D/a converter (12).

4. The strain sensor simulator according to claim 1, wherein the sensor simulator circuit interface (1) comprises a connector J1, a filter C1, a filter C2, a filter C3 and a filter C4, the reverse connection and overvoltage protection circuit (2) comprises a self-recovery fuse F1 and a TVS tube D1, the regulated power supply circuit (3) comprises a regulator U1, a resistor R16, a resistor R18, a capacitor C7 and a capacitor C8, the D/a circuit reference voltage divider resistor network (4) comprises a precision resistor network RM1, the reference voltage switching circuit (5) comprises a MOSFET tube Q2, the output divider resistor network (6) comprises a precision resistor R3, a precision resistor R10, a precision resistor network RM2 and a precision resistor network RM3, the output resistor divider switching circuit (7) comprises a MOSFET tube Q3, a MOSFET tube Q4, a resistor R34 and a resistor R35, The voltage stabilizing diode D8, the span selection switch (8) comprises K1A and K1B, the PWM subdivision circuit (9) comprises a MOSFET tube Q1, a resistor R1, a resistor R2, a resistor R4, a resistor R5, a resistor R6, a resistor R8 and a capacitor C17, and the A/D circuit voltage dividing resistor network (10) comprises a resistor R12 and a resistor R13.

5. The strain sensor simulator according to claim 1, wherein the D/a converter (12) is AD5060, the single-chip microcomputer (11) is PIC18F1320, and the user program memory EEPROM (13) is 24C 512.

6. The strain sensor simulator according to claim 2, characterized in that the temperature sensor (14) employs TC 77.

7. The strain sensor simulator of claim 4, wherein the MOSFET transistor Q1, the MOSFET transistor Q2, the MOSFET transistor Q3, the MOSFET transistor Q4 are AO3400, and the voltage regulator U1 is TPS 71501.

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