CN114459678A - Self-calibration type strain sensor isolation signal conditioning module - Google Patents
Self-calibration type strain sensor isolation signal conditioning module Download PDFInfo
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- CN114459678A CN114459678A CN202210266265.0A CN202210266265A CN114459678A CN 114459678 A CN114459678 A CN 114459678A CN 202210266265 A CN202210266265 A CN 202210266265A CN 114459678 A CN114459678 A CN 114459678A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L25/00—Testing or calibrating of apparatus for measuring force, torque, work, mechanical power, or mechanical efficiency
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L27/00—Testing or calibrating of apparatus for measuring fluid pressure
- G01L27/002—Calibrating, i.e. establishing true relation between transducer output value and value to be measured, zeroing, linearising or span error determination
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/05—Digital input using the sampling of an analogue quantity at regular intervals of time, input from a/d converter or output to d/a converter
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Abstract
The invention discloses an isolated signal conditioning module of a self-calibration type strain sensor, which comprises an isolated power supply, a micro control unit, an RS485 interface, a digital isolation chip, an isolated three-wire system 4-20mA generating circuit and a self-calibration control circuit, wherein the RS485 interface is connected with the micro control unit to generate an isolated RS485 bus, an output signal of the strain sensor is transmitted to the micro control unit to be subjected to analog-to-digital conversion, then is transmitted to the isolated three-wire system 4-20mA generating circuit through the digital isolation chip to be subjected to digital-to-analog conversion and V/I conversion, and then is output to a current transmitting signal, and the micro control unit adjusts the size of a current transmitting signal output by the isolated three-wire system 4-20mA generating circuit through the self-calibration control circuit. The invention adopts a simple and easily realized digital signal isolation method to realize the isolated output of the analog signal, and simultaneously, the output three-wire system 4-20mA current transmission signal can be automatically calibrated on line.
Description
Technical Field
The invention relates to the field of industrial automation field data acquisition, in particular to a self-calibration type strain sensor isolation signal conditioning module.
Background
The strain sensor is mainly applied to detecting force and force-related application occasions, is one of the most widely applied sensors at present, and is an important component part forming a data acquisition system and an automatic measurement and control system. In some application occasions of the strain gauge sensors, the environment is severe, for example, working occasions comprise large inductive loads, frequency converters, servo drivers and the like, which belong to strong interference sources, if corresponding measures are not taken, output signals of the strain gauge sensors are easily influenced by the interference sources, so that the signal-to-noise ratio is reduced, and even the system can not work normally. At present, anti-interference common methods comprise shielding, isolation and the like, wherein the shielding effect is not ideal in certain occasions, for example, under the interference of a strong magnetic field, certain equipment has poor shielding effect on magnetic signals because of no reliable grounding; the most common signal isolation means of the existing strain gauge sensor adopts an analog isolation method: for example, isolation amplifier isolation, linear optical coupling isolation, transformer type magnetic coupling isolation and the like are generally implemented by using a modulation-demodulation technology, generally, the implementation difficulty is high, the cost is high, meanwhile, the analog isolation methods do not have the intelligent characteristic, and calibration of output transmission signals is generally implemented by matching a manual regulation potentiometer with corresponding detection equipment, but cannot be implemented without detection equipment such as an ammeter.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a self-calibration type strain sensor isolation signal conditioning module, which realizes the isolation output of an analog signal by adopting a simple and easily-realized digital signal isolation method, and meanwhile, the output three-wire system 4-20mA current transmission signal can be automatically calibrated on line.
The technical scheme of the invention is as follows:
a self-calibration type strain sensor isolation signal conditioning module comprises an isolation power supply, a micro control unit, an RS485 interface, a digital isolation chip, an isolation three-wire system 4-20mA generating circuit and a self-calibration control circuit, wherein the isolation power supply is used for supplying power to the micro control unit, the RS485 interface, the digital isolation chip, the isolation three-wire system 4-20mA generating circuit and the self-calibration control circuit;
the RS485 interface comprises an RS485 interface isolation chip, the RS485 interface isolation chip is connected with the mixed signal system-level MCU chip, and an RS485 bus connected to the RS485 interface isolation chip is used for RS485 communication;
the isolation three-wire system 4-20mA generating circuit comprises a sensor conditioning transmitting chip and a V/I conversion circuit, wherein the mixed signal system-level MCU chip is connected with the sensor conditioning transmitting chip through a digital isolation chip, and the voltage signal input end of the V/I conversion circuit is connected with the sensor conditioning transmitting chip;
the self-calibration control circuit comprises a photoelectric coupler, a relay and a precise sampling resistor, wherein the input end of the photoelectric coupler is connected with a mixed signal system-level MCU chip, the output end of the photoelectric coupler is connected with a coil of the relay, the fixed end of a normally open contact of the relay is connected with the current transmission signal output end of a V/I conversion circuit, the movable end of the normally open contact of the relay is connected with one end of the precise sampling resistor, and the other end of the precise sampling resistor is connected with the analog signal input end of a sensor conditioning transmission chip.
The isolation power supply comprises a DC/DC isolation power supply chip U1, an LDO power supply chip U2 and an LDO power supply chip U3, the input end of the DC/DC isolation power supply chip U1 is connected with a 24V direct-current power supply 24Vin, the output end of the DC/DC isolation power supply chip U1 outputs 5V direct-current voltage, the input ends of the LDO power supply chip U2 and the LDO power supply chip U3 are both connected with 5V direct-current voltage, the output end of the LDO power supply chip U2 outputs VCC1, the VCC1 supplies power to digital circuits of a mixed signal system-level chip and an RS485 interface isolation chip, the output end of the DO power supply chip U3 outputs VA1, and VA1 is used for supplying power to analog circuits of a sensor, the mixed signal MCU system-level chip and the RS485 interface isolation chip.
And the differential output signals of the strain sensors are respectively filtered by the corresponding second-order RC low-pass filter circuits and then input to the mixed signal system-level MCU chip.
The digital isolation chip is a four-channel high-speed digital isolation chip with the model number of NSi 8241.
The RS485 interface isolation chip is an RS485 interface isolation chip with the model of NiRS 485.
The sensor conditioning transmitting chip is a NSA2860 sensor conditioning transmitting chip.
The voltage regulating end of the sensor conditioning and transmitting chip and the base electrode of the NPN type triode Q1 are connected with 24Vin through a resistor R8, the collector electrode of the NPN type triode Q1 is connected with 24Vin, the emitter electrode of the NPN type triode Q1 outputs a 5V power supply VA2, the power supply input end of the sensor conditioning and transmitting chip is connected with a 5V power supply VA2, and the 5V power supply VA2 generates a digital circuit power supply VCC2 through pi type RC filtering.
The V/I conversion circuit comprises a dual operational amplifier U7, an NPN triode Q2 and an NPN triode Q3, the dual operational amplifier U7 comprises an operational amplifier U7A and an operational amplifier U7B, a positive phase input end of the operational amplifier U7A is connected with a voltage signal output end of the sensor conditioning and transmitting chip, an output end of the operational amplifier U7A is connected with a base electrode of the NPN triode Q2, an inverting input end of the operational amplifier U7A and an emitter electrode of the NPN triode Q2 are connected with an analog ground through a resistor R17, a collector electrode of the NPN triode Q2 is connected with the positive phase input end of the operational amplifier U7B, an output end of the operational amplifier U7B is connected with the base electrode of the NPN triode Q3, a collector electrode of the NPN triode Q3 outputs a current transmitting signal, and an inverting input end of the operational amplifier U7B and an emitter electrode of the NPN triode Q3 are connected with 24 Vin.
The invention has the advantages that:
the analog transmission signals output by the mixed signal system-level MCU chip are isolated by adopting a digital isolation chip NSi824, the digital isolation chip NSi824 supports the insulation and voltage resistance of 5kVrms through UL1577 safety certification, and the data rate of the product is up to 150 Mbps; the RS485 interface of the invention abandons the common high-speed optical coupling isolation method, adopts a more compact and high-reliability RS485 interface isolation chip to generate an isolated RS485 bus, the RS485 interface isolation chip with the model of NiRS485 is an isolated half-duplex RS-485 integrated chip, and supports the insulating and voltage-resisting capability of 3kVrms and strong anti-electromagnetic interference capability through UL1577 safety certification; the invention is provided with a self-calibration control circuit, only corresponding calibration instructions are issued to a micro control unit through an RS485 interface, a voltage difference at two ends of a precise sampling resistor is acquired by using a sensor conditioning and transmitting chip, a mixed signal system-level MCU chip acquires a digital conversion result after analog-to-digital conversion of the sensor conditioning and transmitting chip and calculates the size of a current transmission signal, and the calibration of the analog output transmission signal can be completed by recording corresponding digital quantities of 4mA and 20mA and matching with other parameters.
Drawings
Fig. 1 is a schematic block diagram of the present invention.
Fig. 2 is a circuit diagram of the isolated power supply of the present invention.
Fig. 3 is a minimal system circuit diagram of the micro control unit of the present invention.
Fig. 4 is a circuit diagram of the RS485 interface of the present invention.
Fig. 5 is a circuit diagram of a digital isolator chip of the present invention.
FIG. 6 is a circuit connection diagram of the isolated three-wire 4-20mA generation circuit and self-calibration control circuit of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, an isolated signal conditioning module of a self-calibration type strain sensor comprises an isolated power supply 1, a micro control unit 2, an RS485 interface 3, a digital isolation chip 4, an isolated three-wire system 4-20mA generating circuit 5 and a self-calibration control circuit 6, wherein the isolated power supply 1 is used for supplying power to the micro control unit 2, the RS485 interface 3, the isolated three-wire system 4-20mA generating circuit 5 and the self-calibration control circuit 6, the RS485 interface 3 is connected with the micro control unit 2 to realize RS485 communication, an output signal of a strain sensor 7 is transmitted to the micro control unit 2, a digital signal obtained after analog-to-digital conversion of the micro control unit 2 is sent to the isolated three-wire system 4-20mA generating circuit 5 through the digital isolation chip 4, the isolated three-wire system 4-20mA generating circuit 5 outputs a current transmission signal after digital-to-analog conversion and V/I conversion, the micro control unit 2 can adjust the current transmission signal output by the isolation three-wire system 4-20mA generating circuit 5 through the self-calibration control circuit 6.
Referring to fig. 2, the isolation power supply includes a DC/DC isolation power supply chip U1, an LDO power supply chip U2, and an LDO power supply chip U3, an input end of the DC/DC isolation power supply chip U1 is connected to a 24V DC power supply 24Vin, an output end of the DC/DC isolation power supply chip U1 outputs 5V DC voltage, input ends of the LDO power supply chip U2 and the LDO power supply chip U3 are both connected to 5V DC voltage, an output end of the LDO power supply chip U2 outputs VCC1, VCC1 supplies power to digital circuits of the mixed signal system-level MCU chip and the RS485 interface isolation chip, an output end of the DO power supply chip U3 outputs VA1, and VA1 is used for supplying power to analog circuits of the sensor, the mixed signal system-level MCU chip, and the RS485 interface isolation chip;
referring to fig. 3, the micro control unit includes a mixed signal system MCU chip U4, and a mixed signal system MCU chip U4 is internally integrated with a high-precision and high-resolution 24-bit ADC and is also integrated with resources such as SPI, UART, and the like; a second-order RC low-pass filter circuit (see a second-order RC low-pass filter circuit consisting of resistors R2 and R4, capacitors C12 and C13 in fig. 3) is connected to an analog signal input end of the mixed signal system-level MCU chip U4, a P3 is a strain sensor interface, differential output signals of the strain sensor are respectively filtered by the corresponding second-order RC low-pass filter circuit and then input to the mixed signal system-level MCU chip U4, and are amplified by PGA in the mixed signal system-level MCU chip U4 and then sent to an internal high-precision ADC for analog-to-digital conversion;
referring to fig. 4, the RS485 interface includes an RS485 interface isolation chip U5 (model is NiRS485), the RS485 interface isolation chip U5 is connected with the mixed signal system MCU chip U4, and an RS485 bus connected to the RS485 interface isolation chip U5 is used for RS485 communication;
referring to fig. 3, 5 and 6, the isolated three-wire 4-20mA generating circuit includes a sensor conditioning and transmitting chip U6 (model number is NSA2860) and a V/I conversion circuit, a voltage regulating terminal of the sensor conditioning and transmitting chip U6 and a base of an NPN transistor Q1 are both connected to 24Vin through a resistor R8, a collector of the NPN transistor Q1 is connected to 24Vin, an emitter of the NPN transistor Q1 outputs a 5V power supply VA2, a power input terminal of the sensor conditioning and transmitting chip is connected to a 5V power supply VA2, the 5V power supply VA2 generates a digital circuit power supply VCC2 through pi-type RC filtering, the mixed signal system MCU chip U4 is connected to the sensor conditioning and transmitting chip U6 through a digital isolation chip U8 (model number is NSi four-channel high-speed digital isolation chip) for data interaction, the sensor conditioning and transmitting chip U6 receives a digital signal of the mixed signal system MCU chip U4 and performs digital-to-analog-to-digital conversion through a DAC to obtain an internal voltage signal, then the current transfer signal is generated by a V/I conversion circuit, the V/I conversion circuit comprises a double-operational amplifier U7, an NPN type triode Q2 and an NPN type triode Q3, wherein the dual operational amplifier U7 comprises an operational amplifier U7A and an operational amplifier U7B, a positive phase input end of the operational amplifier U7A is connected with a voltage signal output end of the sensor conditioning and transmitting chip, an output end of the operational amplifier U7A is connected with a base electrode of the NPN type triode Q2, an inverting input end of the operational amplifier U7A and an emitter electrode of the NPN type triode Q2 are connected with an analog ground through a resistor R17, a collector electrode of the NPN type triode Q2 is connected with a positive phase input end of the operational amplifier U7B, an output end of the operational amplifier U7B and a base electrode of the NPN type triode Q3, a collector electrode of the NPN type triode Q3 outputs a current transmitting signal, Iout is an output three-wire 4-20mA current transmitting signal, and an inverting input end of the operational amplifier U7B and an emitter electrode of the NPN type triode Q3 are both connected with 24 Vin;
referring to fig. 3 and 6, the self-calibration control circuit comprises a photoelectric coupler U9, a relay J1 and a precision sampling resistor R18, the input end of the photoelectric coupler U9 is connected with the mixed signal system-level MCU chip U4, the output end of the photoelectric coupler U9 is connected with the coil of the relay J1, the fixed end of the normally open contact of the relay J1 is connected with the current transmission signal output end of the V/I conversion circuit, the active end of the normally open contact of the relay J1 is connected with one end of the precision sampling resistor R18, and the other end of the precision sampling resistor R18 is connected with the analog signal input end of the sensor conditioning transmission chip U6.
A calibration instruction is sent to a mixed signal system-level MCU chip U4 through RS485, the mixed signal system-level MCU chip U4 sends a control signal JDQ to a photoelectric coupler U9 after receiving the calibration instruction, a normally open contact of a relay J1 is driven to be closed through the photoelectric coupler U9, a three-wire system 4-20mA current transmission signal Iout is transmitted to one end of a precision sampling resistor R18, a terminal voltage V-CAL output by the other end of the precision sampling resistor R18 is transmitted to a 24-bit ADC in a sensor conditioning transmission chip U6 for analog-to-digital conversion, the mixed signal system-level MCU chip U4 acquires a digital signal after the analog-to-digital conversion through a digital isolation chip U8 and calculates the size of a current transmission signal, then the mixed signal system-level MCU chip U4 controls the size of a digital quantity transmitted to a DAC in the sensor conditioning transmission chip U6 to adjust the size of the output current transmission signal, and records the digital quantities of corresponding 4mA and 20mA to be matched with other parameters to finish the calibration of the analog output transmission signal, the whole process is automatically finished without other detection equipment, and after the calibration is finished, the mixed signal system-level MCU chip U4 sends out a control signal to control the normally open contact of the relay J1 to be disconnected.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (8)
1. The utility model provides a from calibration type strain gauge sensor isolation signal conditioning module which characterized in that: the isolation power supply is used for supplying power to the micro control unit, the RS485 interface, the digital isolation chip, the isolation three-wire system 4-20mA generating circuit and the self-calibration control circuit, an output signal of the strain sensor is transmitted to the micro control unit, and the micro control unit comprises a mixed signal system-level MCU chip;
the RS485 interface comprises an RS485 interface isolation chip, the RS485 interface isolation chip is connected with the mixed signal system-level MCU chip, and an RS485 bus connected to the RS485 interface isolation chip is used for RS485 communication;
the isolation three-wire system 4-20mA generating circuit comprises a sensor conditioning transmitting chip and a V/I conversion circuit, wherein the mixed signal system-level MCU chip is connected with the sensor conditioning transmitting chip through a digital isolation chip, and the voltage signal input end of the V/I conversion circuit is connected with the sensor conditioning transmitting chip;
the self-calibration control circuit comprises a photoelectric coupler, a relay and a precise sampling resistor, wherein the input end of the photoelectric coupler is connected with a mixed signal system-level MCU chip, the output end of the photoelectric coupler is connected with a coil of the relay, the fixed end of a normally open contact of the relay is connected with the current transmission signal output end of a V/I conversion circuit, the movable end of the normally open contact of the relay is connected with one end of the precise sampling resistor, and the other end of the precise sampling resistor is connected with the analog signal input end of a sensor conditioning transmission chip.
2. The isolated signal conditioning module of claim 1, wherein: the isolation power supply comprises a DC/DC isolation power supply chip U1, an LDO power supply chip U2 and an LDO power supply chip U3, the input end of the DC/DC isolation power supply chip U1 is connected with a 24V direct-current power supply 24Vin, the output end of the DC/DC isolation power supply chip U1 outputs 5V direct-current voltage, the input ends of the LDO power supply chip U2 and the LDO power supply chip U3 are both connected with 5V direct-current voltage, the output end of the LDO power supply chip U2 outputs VCC1, the VCC1 supplies power to digital circuits of a mixed signal system-level chip and an RS485 interface isolation chip, the output end of the DO power supply chip U3 outputs VA1, and VA1 is used for supplying power to analog circuits of a sensor, the mixed signal MCU system-level chip and the RS485 interface isolation chip.
3. The isolated signal conditioning module of claim 1, wherein: and the differential output signals of the strain sensors are respectively filtered by the corresponding second-order RC low-pass filter circuits and then input to the mixed signal system-level MCU chip.
4. The isolated signal conditioning module of claim 1, wherein: the digital isolation chip is a four-channel high-speed digital isolation chip with the model number of NSi 8241.
5. The isolated signal conditioning module of claim 1, wherein: the RS485 interface isolation chip is an RS485 interface isolation chip with the model of NiRS 485.
6. The isolated signal conditioning module of claim 1, wherein: the sensor conditioning transmitting chip is a NSA2860 sensor conditioning transmitting chip.
7. The isolated signal conditioning module of claim 2, wherein: the voltage regulating end of the sensor conditioning and transmitting chip and the base electrode of the NPN type triode Q1 are connected with 24Vin through a resistor R8, the collector electrode of the NPN type triode Q1 is connected with 24Vin, the emitter electrode of the NPN type triode Q1 outputs a 5V power supply VA2, the power supply input end of the sensor conditioning and transmitting chip is connected with a 5V power supply VA2, and the 5V power supply VA2 generates a digital circuit power supply VCC2 through pi type RC filtering.
8. The isolated signal conditioning module of claim 2, wherein: the V/I conversion circuit comprises a dual operational amplifier U7, an NPN triode Q2 and an NPN triode Q3, the dual operational amplifier U7 comprises an operational amplifier U7A and an operational amplifier U7B, a positive phase input end of the operational amplifier U7A is connected with a voltage signal output end of the sensor conditioning and transmitting chip, an output end of the operational amplifier U7A is connected with a base electrode of the NPN triode Q2, an inverting input end of the operational amplifier U7A and an emitter electrode of the NPN triode Q2 are connected with an analog ground through a resistor R17, a collector electrode of the NPN triode Q2 is connected with the positive phase input end of the operational amplifier U7B, an output end of the operational amplifier U7B is connected with the base electrode of the NPN triode Q3, a collector electrode of the NPN triode Q3 outputs a current transmitting signal, and an inverting input end of the operational amplifier U7B and an emitter electrode of the NPN triode Q3 are connected with 24 Vin.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210266265.0A CN114459678A (en) | 2022-03-17 | 2022-03-17 | Self-calibration type strain sensor isolation signal conditioning module |
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| CN202210266265.0A CN114459678A (en) | 2022-03-17 | 2022-03-17 | Self-calibration type strain sensor isolation signal conditioning module |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116087609A (en) * | 2023-02-09 | 2023-05-09 | 电子科技大学 | Voltage sensor based on digital signal isolation |
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2022
- 2022-03-17 CN CN202210266265.0A patent/CN114459678A/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116087609A (en) * | 2023-02-09 | 2023-05-09 | 电子科技大学 | Voltage sensor based on digital signal isolation |
| CN116087609B (en) * | 2023-02-09 | 2023-08-08 | 电子科技大学 | Voltage sensor based on digital signal isolation |
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