Intelligent current output sensor signal conditioning circuit and conditioning method
Technical Field
The invention relates to the field of signal communication of aviation, navigation, industrial control and the like, in particular to an intelligent current output sensor signal conditioning circuit and a conditioning method.
Background
The platinum resistor is a temperature sensor with a very wide application range, and when a resistive sensor signal is transmitted, input drift and nonlinearity greatly affect the characteristics of the sensor, so that the input signal needs to be conditioned and converted into available 4-20 mA for transmission. The existing scheme mostly adopts hardware resistance calibration and conditioning, adopts a scheme of hardware resistance compensation, and provides higher requirements for system engineers, each sensor needs to independently adjust a compensation resistance, and simultaneously needs to master the system performance thoroughly, and is externally connected with a high-precision resistance, the precision of the resistance determines the precision of the final whole system, intelligent configuration cannot be carried out, and batch processing is difficult to carry out in production.
Disclosure of Invention
The invention provides an intelligent current output sensor signal conditioning circuit and a conditioning method for solving the technical problems in the background technology, and has the advantages of high integration degree, simplicity in operation, high compensation precision and wide trial range.
The technical solution of the invention is as follows: the invention relates to an intelligent current output sensor signal conditioning circuit, which is characterized in that: the conditioning circuit comprises a platinum resistance temperature sensor RTD, a plurality of precision resistors RZ, a multi-way gate, a first-stage programmable gain amplifier PGA1, a second-stage programmable gain amplifier PGA2, a linearization circuit, an interface SPI and a high-precision voltage-current converter V/I, wherein the platinum resistance temperature sensor RTD is connected with the plurality of precision resistors RZ in parallel, the platinum resistance temperature sensor RTD and the plurality of precision resistors RZ are connected into the first-stage programmable gain amplifier PGA1 through the multi-way gate, the output of the first-stage programmable gain amplifier PGA1 is connected into the input end 387 of the second-stage programmable gain amplifier PGA2, one path of the second-stage programmable gain amplifier PGA2 is connected with the high-precision voltage-current converter V/I, the other path is fed back to the first-stage programmable gain amplifier PGA1 through the linearization circuit, and the interface SPI.
Preferably, the conditioning circuit further comprises memory EEPROM, current DAC1, and current DAC 2; the memory EEPROM is connected with an interface SPI which is connected with the multiplexer through a current DAC1 and is connected between the first-stage programmable gain amplifier PGA1 and the second-stage programmable gain amplifier PGA2 through a current DAC 2.
Preferably, the conditioning circuit further comprises an oscillator OSC, and the oscillator OSC is connected to the interface SPI. The oscillator OSC provides the conditioning circuit with the clock signal required for operation.
Preferably, the current DAC1 is connected to the multiplexer via a two-way current source I1 and a current source I2.
Preferably, the platinum resistance temperature sensor RTD is grounded through a load resistance Rcm.
Preferably, the precision resistance RZ is 5.
A conditioning method for realizing the intelligent current output sensor signal conditioning circuit is characterized in that: the method comprises the following steps:
1) connecting a platinum resistance temperature sensor RTD, configuring different precision resistors Rz according to the application temperature range, and selecting by a multi-channel gate;
2) the input stage carries out differential input on the current flowing through the platinum resistance temperature sensor RTD and the current flowing through the precision resistor Rz, the input signal is subjected to variable gain amplification through a first-stage programmable gain amplifier PGA1 and then is output, and the gain value is controlled by an SPI (serial peripheral interface);
3) after the signal passes through the second-stage programmable gain amplifier PGA2, the output of the sampling part is fed back to the linearization circuit to control the input of the linearization circuit, and the linearization degree of the input signal is adjusted;
4) and outputting the final signal through a second-stage programmable gain amplifier PGA2, and converting the final signal into a required current of 4-20 mA through a high-precision voltage-current converter V/I to be output.
Preferably, the method further comprises a step 5) of writing data to be configured into the internal unit in advance from the memory EEPROM through the interface SPI, and directly loading the data from the internal unit when the platinum resistance temperature sensor RTD is actually used to control the gain of the first-stage programmable gain amplifier PGA1, the size configuration of the current DAC1 and the size configuration of the current DAC 2.
Preferably, the method further comprises the step 6) of providing a clock signal, a reference voltage and a reference current required by the operation of the conditioning circuit by the oscillator OSC and the reference circuit, so as to ensure the circuit accuracy and improve the overall performance of the circuit.
The platinum resistor is used as a temperature sensor, certain output error and nonlinearity exist, the intelligent signal conditioning circuit and the conditioning method of the current output sensor provided by the invention process the nonlinearity of the platinum resistor while amplifying and converting the signal, supply power to the platinum resistor at a constant current, amplify a small signal at an input end, and then convert the small signal into high-precision controllable current output, wherein the gain and nonlinear feedback output are controlled by a digital circuit part, so the invention has the following advantages:
1. according to the invention, through an intelligent current output sensor signal conditioning circuit framework, the single-chip integrated circuit is adopted, amplification, storage and nonlinear calibration are all integrated in one chip, and the integration degree is high.
2. The invention selects different zero setting resistors Rz through different application ranges, can realize the intelligent transmission of the configuration of the platinum resistor through digital configuration, and has the advantages of simple operation, high compensation precision and wide trial range.
Drawings
Fig. 1 is a circuit schematic of the present invention.
Detailed Description
The technical solution of the present invention is further described in detail with reference to the accompanying drawings and specific embodiments.
Referring to fig. 1, the structure of the embodiment of the present invention includes a platinum resistance temperature sensor RTD, a plurality of precision resistors RZ, a multiplexer, a first stage programmable gain amplifier PGA1, a second stage programmable gain amplifier PGA2, a linearizer, an interface SPI, a memory EEPROM, a current DAC1, a current DAC2, an oscillator OSC, and a high precision voltage-to-current converter V/I, the platinum resistance temperature sensor RTD is connected in parallel with the plurality of precision resistors RZ, in the embodiment, the number of precision resistors RZ configured according to the application temperature range of the platinum resistance temperature sensor RTD is 5, and is divided into RZ 1-RZ 5, one end of the platinum resistance temperature sensor RTD is grounded through a load resistor Rcm, the other end and the 5 precision resistors RZ 1-RZ 5 are connected to the first stage programmable gain amplifier PGA1 through the multiplexer, the output of the first stage programmable gain amplifier 1 is connected to the input end of the second stage programmable gain amplifier PGA2, one path of the second-stage programmable gain amplifier PGA2 is connected with the high-precision voltage-current converter V/I, the other path is fed back to the first-stage programmable gain amplifier PGA1 through the linearization circuit, the memory EEPROM is connected with the interface SPI, the interface SPI is divided into three paths, the first path is connected with the multi-path gate through the current DAC1, the current DAC1 is connected with the multi-path gate through the two paths of the current source I1 and the current source I2, the second path is connected with the first-stage programmable gain amplifier PGA1, the third path is connected between the first-stage programmable gain amplifier PGA1 and the second-stage programmable gain amplifier PGA2 through the current DAC2, and the oscillator OSC.
Wherein the linearizer is an existing linearizer.
The invention also provides a conditioning method of the intelligent current output sensor signal conditioning circuit for realizing the specific embodiment, which comprises the following steps:
1) connecting a platinum resistance temperature sensor RTD, configuring different precision resistors Rz according to the application temperature range, and selecting by a multi-channel gate;
2) the input stage carries out differential input on the current flowing through the platinum resistance temperature sensor RTD and the current flowing through the precision resistor Rz, the input signal is subjected to variable gain amplification through a first-stage programmable gain amplifier PGA1 and then is output, and the gain value is controlled by an SPI (serial peripheral interface);
3) after the signal passes through the second-stage programmable gain amplifier PGA2, the output of the sampling part is fed back to the linearization circuit to control the input of the linearization circuit, and the linearization degree of the input signal is adjusted;
4) the final signal is output through a second-stage programmable gain amplifier PGA2, and then converted into the required 4-20 mA current output through a high-precision voltage-current converter V/I;
5) data needing to be configured is written into an internal unit in advance through an interface SPI by a memory EEPROM, the internal unit is directly loaded when the platinum resistance temperature sensor RTD is actually applied, and the gain of a first-stage programmable gain amplifier PGA1, the size configuration of a current DAC1 and the size configuration of a current DAC2 are controlled;
6) clock signals, reference voltage and reference current required by the working of the conditioning circuit are provided by the oscillator OSC and the reference circuit, so that the overall performance of the circuit is improved while the circuit precision is ensured.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.