CN100498865C - Pressure digital acquisition front end - Google Patents
Pressure digital acquisition front end Download PDFInfo
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- CN100498865C CN100498865C CNB2006100480574A CN200610048057A CN100498865C CN 100498865 C CN100498865 C CN 100498865C CN B2006100480574 A CNB2006100480574 A CN B2006100480574A CN 200610048057 A CN200610048057 A CN 200610048057A CN 100498865 C CN100498865 C CN 100498865C
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Abstract
The invention relates to a pressure measurement technology, in particular to a pressure digital acquisition front end, which comprises: two groups of oscillation frequency division circuits with the same structure are connected with the capacitive pressure sensor through a wiring terminal to generate two paths of pulse signals meeting the requirement of accuracy grade; the main control circuit is used for receiving output signals of the two paths of oscillation frequency division circuits, measuring two paths of pulse widths, acquiring front end temperature and sending out a digital electric signal through a 3.3V RS232 link through a wiring terminal; and the direct current power supply is connected with an external power supply through a wiring terminal and provides direct current power supply for the oscillation frequency division circuit and the main control circuit. The invention can convert the pressure signal of the capacitance pressure sensor into a digital electric signal, and can provide the digital pressure/differential pressure electric signal for the pressure/differential pressure transmitter, so that the pressure/differential pressure transmitter can adopt the digital signal processing technology to improve the measurement accuracy grade.
Description
Technical field
The present invention relates to pressure measurement technology, specifically disclose a kind of digital collection front end for pressure that the capacitance pressure transducer, pressure signal is changed into digital signal.
Background technology
Of a great variety because of pressure transducer makes Pressure and Difference Pressure Transmitter kind model numerous.Capacitance pressure transducer, has been realized production domesticization at present, and the capacitance pressure transducer, cost is lower, but homemade Pressure and Difference Pressure Transmitter based on capacitance pressure transducer, still uses the analog signal conversion technology to realize the measurement of pressure/differential pressure, causes degree of accuracy to be difficult to further raising.The higher Pressure and Difference Pressure Transmitter of other accuracy class be import, based on the external product of other higher kind pressure transducer of cost.For the Pressure and Difference Pressure Transmitter that adopts capacitance pressure transducer, provides digitized pressure/differential pressure electric signal, thereby the tonometric technology of realization pinpoint accuracy is not also appeared in the newspapers at present as yet.
Summary of the invention
In order to solve the homemade Pressure and Difference Pressure Transmitter accuracy class problem low than the import like product, the purpose of this invention is to provide a kind of digital collection front end for pressure, for Pressure and Difference Pressure Transmitter provides digitized pressure/differential pressure electric signal, make Pressure and Difference Pressure Transmitter can adopt Digital Signal Processing to improve the accuracy class of measuring.
To achieve these goals, concrete technical scheme of the present invention comprises:
Two groups of oscillation frequency dividing circuits that-structure is identical connect capacitance pressure transducer, through connection terminal, produce the pulse signal that two-way meets the accuracy class requirement;
-governor circuit, the output signal of reception two-way oscillation frequency dividing circuit is measured the two-way pulse width and is gathered the front end temperature, digital signal is sent through connection terminal by 3.3V RS232 link;
-direct supply connects external power source through connection terminal, for oscillation frequency dividing circuit, governor circuit provide direct supply.
Wherein: described DC power supply circuit structure comprises: the 6th current-limiting resistance, the first～three filter capacitor, voltage stabilizer is formed, direct supply from the outside is introduced through connection terminal, power cathode links to each other with power cathode through connection terminal, and positive source connects the 6th current-limiting resistance through connection terminal, and the 6th current-limiting resistance connects first filter capacitor and voltage stabilizer input end, behind output termination the second～three filter capacitor of voltage stabilizer, connect the working power of oscillation frequency dividing circuit, governor circuit;
One group of lateral capacitance that connects pressure transducer through connection terminal in described two groups of oscillation frequency dividing circuits, pressure transducer opposite side electric capacity connects another group oscillation frequency dividing circuit through connection terminal, and the public electrode of pressure transducer two lateral capacitances connects power cathode by connection terminal; Every group of oscillation frequency dividing circuit concrete structure is:
The capacitance electrode of pressure transducer connects inverting input, and the in-phase input end of second voltage comparator of first voltage comparator; The output terminal of first voltage comparator connects the input end that is connected to the 3rd Sheffer stroke gate through the 4th Sheffer stroke gate, the output terminal of voltage comparator connects the input end of clock that the 3rd Sheffer stroke gate is connected to binary counter, and current-limiting resistance is connected across between the in-phase end node and the 3rd Sheffer stroke gate output terminal of the first voltage comparator end of oppisite phase and second voltage comparator; The terminal count output of binary counter be connected to respectively governor circuit microprocessor catch end;
Described governor circuit comprises microprocessor, temperature measurement circuit, microprocessor stores control program wherein, microprocessor catch the pulse signal that termination is received two groups of oscillation frequency dividing circuits; Microprocessor is by SPI mouth cut-in temperature sensor; RS232 data terminal integrated circuit board outside connection terminal connects of microprocessor;
Main program flow in the control program is: operation at first begins to reset, I/O port, register, timer, house dog, 3.3V RS232 link to each module in the microprocessor carry out initialization, the input capture port is set to the edge triggering mode, and timer is set to and increases counting mode; Refill and carry calibrating parameters, promptly load total temperature section gamut calibrating parameters, and initialization temperature sensor, setting work starting condition, judge and be limited to when upgrading temperature not, time limit then reads temperature sensor and upgrades temperature value, judges that then the command frame answer finishes not, and the time limit is judged command frame answer end not to directly entering; Command frame is answered and is not finished to upgrade the house dog count value, if answering, command frame finishes to enter whether be the command determination of fetching data, be tissue and transmission data when fetching data order, upgrade the house dog count value, order then judges whether to write the calibrating parameters order if not fetch data, not being to upgrade the house dog count value when writing the calibrating parameters order, is storage calibrating parameters when writing the calibrating parameters order, upgrades the house dog count value; All return after the described renewal house dog count value and judge that upgrading the temperature time limit does not arrive not;
Input capture interrupt service routine flow process in the control program is: adopt first in first out structure numeration stack, be pressed into numeration stack last look after the both sides counting is respectively finished once; Idiographic flow: judge earlier whether this catches counting complete, and the imperfect count initialized variable step that then enters is carried out interruption and returned; When complete count value is pressed into corresponding numeration stack, judges whether that two capture-ports respectively finish once counting, return for not interrupting.Then move numeration stack house Chen Cunxin when being, carry out again and interrupt returning;
Serial ports in the control program receives the interrupt service routine flow process: judge whether to receive the frame banner word earlier, when not receiving the frame banner word, judge whether the word that receives is the frame banner word, not that the execution of frame banner word is interrupted returning, be that the frame banner word is then put the frame banner word and received the position, carry out and interrupt returning; When having received the frame banner word the serial ports buffer zone sent in the word that receives; Judge by length requirement whether receive completely again, return for not interrupting; Judge that received frame by verification denys when being, do not put the communication frame error bit by verification with, the answer frame that says the word is put the running status position during by verification, and the answer frame that says the word is again carried out interruption at last and returned.
Advantage of the present invention:
1. the characteristics that have the signal digitalized output of pressure/differential pressure.Digital collection front end for pressure of the present invention uses 3.3v RS232 link to send by rendezvous protocol the pressure/differential pressure signal, for the digitalization operation of pressure/differential pressure value provides data.Make homemade capacitive pressure/differential pressure transmitter improve the accuracy class of measuring.
2. integrated level height, low in energy consumption.Frequency measurement function of the present invention is used the input capture function of microprocessor, and temp sensing function uses monolithic integrated optical circuit, and the 3.3v RS232 link that serial communication uses is integrated in microprocessor internal equally; The overall work power supply is DC 3.3v, maximum operating currenbt 2.5mA.
3. be widely used, obvious social benefit.In industry spot, pressure unit not only uses in pressure survey, and most of use differential pressure measurement realizes indirectly in the measurement of other values such as flow, liquid level.The life of product of using the present invention not only can prolong capacitance pressure transducer,, and application is also very extensive.
Description of drawings
Fig. 1 is the overall circuit structure diagram of the present invention.
Fig. 2 is a DC power supply circuit schematic diagram among Fig. 1.
Fig. 3 is an oscillation frequency dividing circuit schematic diagram among Fig. 1.
Fig. 4 is a governor circuit schematic diagram among Fig. 1.
Fig. 5 is a master control program process flow diagram of the present invention.
Fig. 6 is an input capture interrupt service routine process flow diagram of the present invention.
Fig. 7 receives the interrupt service routine process flow diagram for serial ports of the present invention.
Embodiment
Below in conjunction with accompanying drawing the present invention is described in further detail.
The structure of digital collection front end for pressure (referring to Fig. 1) comprises two groups of identical oscillation frequency dividing circuits of structure, governor circuit, direct supply three partial circuits and connection terminal; Wherein: direct supply connects external power source through connection terminal and provides satisfactory direct supply for digital collection front end; Governor circuit uses 3.3V RS232 link can connect other integrated circuit board (as Harrt agreement instrument etc.) through connection terminal, and digital signal is sent; Two groups of oscillation frequency dividing circuits connect capacitance pressure transducer, through connection terminal, produce the pulse signal that two-way meets the accuracy class requirement; Governor circuit is measured the temperature of two-way pulse width and collection front end and is given and gather the integrated circuit board that front end has the same-interface agreement by 3.3V RS232 link.
As shown in Figure 2, described DC power supply circuit structure comprises: the 6th current-limiting resistance R6, first, two, three filter capacitor C1, C2, C3, voltage stabilizer U6 (adopting linear low pressure reduction type) forms, from the direct supply of outside through connection terminal B3, B4 introduces, power cathode links to each other with collection front end power cathode through connection terminal B4, positive source connects the 6th current-limiting resistance R6 through connection terminal B3, the 6th current-limiting resistance R6 connects the first filter capacitor C1 and voltage stabilizer U6 input end, output termination the second～three filter capacitor C2 of voltage stabilizer U6, behind the C3, connect the working power of other circuit.
As shown in Figure 1, second group of oscillation frequency dividing circuit in two groups of oscillation frequency dividing circuits uses the 3rd connection terminal A3 to connect a lateral capacitance of pressure transducer.As shown in Figure 3, pressure transducer opposite side electric capacity connects the S1 point of first group of oscillation frequency dividing circuit through the first connection terminal A1, and the public electrode of pressure transducer two lateral capacitances connects the power cathode of digital collection front end for pressure by the second connection terminal A2; Every group of oscillation frequency dividing circuit concrete structure is (is the example explanation with first group):
The capacitance electrode that the first connection terminal A1 inserts connects inverting input, and the in-phase input end of the second voltage comparator U2 of the first voltage comparator U1; The in-phase input end of the first voltage comparator U1 meets voltage-reference VH (for the high voltage benchmark of standard of precision voltage source LM285-2.5 generation), it (is two big resistance resistance: 100K and 200K that the inverting input of the second voltage comparator U2 meets voltage-reference VL, with the low voltage reference that produces after the VH dividing potential drop), the output terminal of the first voltage comparator U1 connects the input end a of the 4th Sheffer stroke gate U4, the output terminal of the second voltage comparator U2 connects the input end b of the 3rd Sheffer stroke gate U3, the input end a of the 3rd Sheffer stroke gate U3 connects the output terminal of the 4th Sheffer stroke gate U4, the output terminal of the 3rd Sheffer stroke gate U3 connects the end of the first current-limiting resistance R1, the input end b of the 4th Sheffer stroke gate U4, as the input end of clock of the frequency divider U5 of binary counter, the other end of the first current-limiting resistance R1 links to each other with the node of the in-phase end of the first voltage comparator U1 end of oppisite phase and the second voltage comparator U2; Four terminal count outputs of binary counter U5 connect the end of the second～five resistance R 2, R3, R4, R5 respectively; The be connected end of catching of governor circuit microprocessor U7 of the other end of the second～five resistance R 2, R3, R4, R5.
The first voltage comparator U1 shown in Fig. 3, the second voltage comparator U2, the 3rd Sheffer stroke gate U3, the 4th Sheffer stroke gate U4, the first current-limiting resistance R1 and be connected on the sensor capacitance that S1 orders and form the bistable oscillation circuit, along with the cycle charge-discharge of pressure transducer electric capacity, will at the S5 point output terminal generation square wave identical of the 3rd Sheffer stroke gate U3 with the capacitor charge and discharge cycle according to truth table table 1.This square wave enters its CLK input end as the clock source of frequency divider U5.Frequency divider U5 adopts binary counter 74HC393, to produce two, four, eight, 16 times of pulse P1 that charge and discharge the cycle to electric capacity respectively at its Q0, Q1, Q2, Q3 end, can choose one as required wantonly to select different divide ratios during four resistance welded of the second～five resistance R, 2～R5 among the figure, selecting the 5th resistance R 5 among the present invention, is 16 frequency divisions.Second group of oscillation frequency dividing circuit principle of work is same as first group, only imports another pressure sensing electric capacity of termination, and divide ratio is identical, and the pulse P2 of generation connects another input capture end of the microprocessor U7 of digital governor circuit.
Bistable oscillation circuit truth table in truth table 1 oscillation frequency dividing circuit
Annotate: the current potential that S1 is ordered in the VS1 presentation graphs 3.
Referring to Fig. 4, governor circuit comprises microcontroller circuit U7, temperature measurement circuit U8, is integrated with 3.3V RS232 link among the microprocessor U7.Wherein microprocessor U7 storage control program carries temperature sensor U8 by SPI mouth web joint.Directly receive the input capture end of microprocessor U7 from the pulse signal of two groups of oscillation frequency dividing circuits; Temperature measurement circuit is the Totally integrated digital chip of band standard SPI interface, directly links to each other with microprocessor U7 by three buses; The data input pin of RS232 link layer and output terminal integrated circuit board outside connection terminal B1, B2 connect among the microprocessor U7.
Microprocessor U7 adopts MSP430F123, two groups of outputs of vibration frequency division P1, P2 are inserted its input capture end 1, input capture end 2 respectively, and two acquisition modes are set is that negative edge is caught, the difference of the count value that twice input capture interruption obtained is the count value of microprocessor in 16 capacitor charge and discharge cycles, and this count value multiply by the periodic quantity that is 16 capacitor charge and discharges oscillation period of microprocessor.The opposite variation of trend appears in two capacitances when pressure/differential pressure changes, and the opposite variation of trend can appear in two count values that microprocessor U7 records equally.
Temperature measurement circuit U8 is the Totally integrated digital chip DS1722 of band standard SPI interface, and microprocessor U7 reads the real time temperature value every 2 seconds one time from U8.And count value and temperature value are sent by the RS232 link.
Main program flow in the master control program (referring to Fig. 5) is: operation at first begins to reset, I/O port, register, timer, 3.3V RS232 link, house dog to each module in the microprocessor U7 carry out initialization, the input capture port is set to the edge triggering mode, and timer is set to and increases counting mode; Temperature measurement circuit U8 reinitializes; Load total temperature section gamut calibrating parameters, and the initialization temperature sensor, set the work starting condition, judge and be limited to when reading temperature not, time limit then reads temperature sensor and upgrades temperature value, judges that then the command frame answer finishes not, and the time limit is judged command frame answer end not to directly entering; Frame is answered and is not finished to upgrade the house dog count value, if answering, frame finishes to enter the command determination of whether fetching data, be tissue and transmission data when fetching data order, upgrade the house dog count value, order then judges whether to write the calibrating parameters order if not fetch data, not being to upgrade the house dog count value when writing the calibrating parameters order, is storage calibrating parameters when writing the calibrating parameters order, upgrades the house dog count value; All return after the described renewal house dog count value and judge that upgrading the temperature time limit does not arrive not.
Input capture interrupt service routine flow process (referring to Fig. 6) is that the numeration stack is that first in first out (FIFO) structure is pressed into numeration stack last look after the both sides counting is respectively finished once; Idiographic flow: judge earlier whether this catches counting complete, and the imperfect count initialized variable step that then enters is carried out interruption and returned; When complete count value is pressed into corresponding numeration stack, judges whether that two catch end and respectively finish once counting, return for not interrupting.Then move numeration stack house Chen Cunxin when being, carry out again and interrupt returning.
Serial ports receives the interrupt service routine flow process: judge whether to receive the frame banner word earlier, when not receiving the frame banner word, judging whether the word that receives is the frame banner word, is not that the execution of frame banner word is interrupted returning, be that the frame banner word is then put the hardwood banner word and received the position, carry out and interrupt returning; When frame receives the frame banner word the serial ports buffer zone sent in the word that receives; Judge by length requirement whether receive completely again, return for not interrupting; Judge that received frame by verification denys when being, do not put the communication frame error bit by verification with, the answer frame that says the word is put the running status position during by verification, and the answer frame that says the word is again carried out interruption at last and returned.
3.3v the RS232 link is operated in master-slave mode half-duplex operation mode, when external integrated circuit board fetched data command frame, digital collection front end for pressure organized real time data to issue external integrated circuit board after the frame of confirming to receive is correct.
Claims (8)
1. digital collection front end for pressure is characterized in that comprising:
Two groups of oscillation frequency dividing circuits that-structure is identical connect capacitance pressure transducer, through connection terminal, produce the pulse signal that two-way meets the accuracy class requirement;
-governor circuit, the output signal of reception two-way oscillation frequency dividing circuit is measured the two-way pulse width and is gathered the front end temperature, digital signal is sent through connection terminal by 3.3V RS232 link;
-direct supply connects external power source through connection terminal, for oscillation frequency dividing circuit, governor circuit provide direct supply.
2. according to the described digital collection front end for pressure of claim 1, it is characterized in that: described DC power supply circuit structure is by the 6th current-limiting resistance (R6), the first～three filter capacitor (C1～C3), voltage stabilizer (U6) is formed, direct supply from the outside is introduced through connection terminal, the external dc power negative pole links to each other with dc power cathode in gathering front end through connection terminal, the external dc power positive pole connects the 6th current-limiting resistance (R6) through connection terminal, the 6th current-limiting resistance (R6) connects first filter capacitor (C1) and voltage stabilizer (U6) input end, output termination the second～three filter capacitor of voltage stabilizer (U6) (behind the C2～C3), connects oscillation frequency dividing circuit, the working power of governor circuit.
3. according to the described digital collection front end for pressure of claim 1, it is characterized in that: described voltage stabilizer (U6) adopts linear low pressure reduction type.
4. according to the described digital collection front end for pressure of claim 1, it is characterized in that: one group of lateral capacitance that connects pressure transducer through connection terminal in described two groups of oscillation frequency dividing circuits, pressure transducer opposite side electric capacity connects another group oscillation frequency dividing circuit through connection terminal, and the public electrode of pressure transducer two lateral capacitances connects power cathode by connection terminal; Every group of oscillation frequency dividing circuit concrete structure is:
The capacitance electrode of pressure transducer connects inverting input, and the in-phase input end of second voltage comparator (U2) of first voltage comparator (U1); The output terminal of first voltage comparator (U1) connects the input end that is connected to the 3rd Sheffer stroke gate (U3) through the 4th Sheffer stroke gate (U4), the output terminal of voltage comparator (U2) connects the input end of clock that the 3rd Sheffer stroke gate (U3) is connected to binary counter (U5), and current-limiting resistance (R1) is connected across between the in-phase end node and the 3rd Sheffer stroke gate (U3) output terminal of first voltage comparator (U1) end of oppisite phase and second voltage comparator (U2); The terminal count output of binary counter (U5) be connected to respectively governor circuit microprocessor (U7) catch end.
5. according to the described digital collection front end for pressure of claim 1, it is characterized in that: described governor circuit comprises microprocessor (U7), temperature measurement circuit (U8), microprocessor (U7) storage control program wherein, microprocessor (U7) catch the pulse signal that termination is received two groups of oscillation frequency dividing circuits; Microprocessor (U7) is by SPI mouth cut-in temperature sensor; RS232 data terminal integrated circuit board outside connection terminal connects of microprocessor (U7).
6. according to the described digital collection front end for pressure of claim 5, it is characterized in that: the main program flow in the control program is: operation at first begins to reset, I/O port, register, timer, house dog, 3.3V RS232 link to each module in the microprocessor carry out initialization, the input capture port is set to the edge triggering mode, and timer is set to and increases counting mode; Refill and carry calibrating parameters, promptly load total temperature section gamut calibrating parameters, and initialization temperature sensor, setting work starting condition, judge and be limited to when upgrading temperature not, time limit then reads temperature sensor and upgrades temperature value, judges that then the command frame answer finishes not, and the time limit is judged command frame answer end not to directly entering; Command frame is answered and is not finished to upgrade the house dog count value, if answering, command frame finishes to enter whether be the command determination of fetching data, be tissue and transmission data when fetching data order, upgrade the house dog count value, order then judges whether to write the calibrating parameters order if not fetch data, not being to upgrade the house dog count value when writing the calibrating parameters order, is storage calibrating parameters when writing the calibrating parameters order, upgrades the house dog count value; All return after the described renewal house dog count value and judge that upgrading the temperature time limit does not arrive not.
7. according to the described digital collection front end for pressure of claim 5, it is characterized in that: the input capture interrupt service routine flow process in the control program is: adopt first in first out structure numeration stack, be pressed into numeration stack last look after the both sides counting is respectively finished once; Idiographic flow: judge earlier whether this catches counting complete, and the imperfect count initialized variable step that then enters is carried out interruption and returned; When complete count value is pressed into corresponding numeration stack, judges whether that two capture-ports respectively finish once counting, return for not interrupting.Then move numeration stack house Chen Cunxin when being, carry out again and interrupt returning.
8. according to the described digital collection front end for pressure of claim 5, it is characterized in that: the serial ports in the control program receives the interrupt service routine flow process and is: judge whether to receive the frame banner word earlier, when not receiving the frame banner word, judge whether the word that receives is the frame banner word, not that the execution of frame banner word is interrupted returning, be that the frame banner word is then put the frame banner word and received the position, carry out and interrupt returning; When having received the frame banner word the serial ports buffer zone sent in the word that receives; Judge by length requirement whether receive completely again, return for not interrupting; Judge that received frame by verification denys when being, do not put the communication frame error bit by verification with, the answer frame that says the word is put the running status position during by verification, and the answer frame that says the word is again carried out interruption at last and returned.
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| Application Number | Priority Date | Filing Date | Title |
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| CNB2006100480574A CN100498865C (en) | 2006-10-20 | 2006-10-20 | Pressure digital acquisition front end |
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| Application Number | Priority Date | Filing Date | Title |
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| CNB2006100480574A CN100498865C (en) | 2006-10-20 | 2006-10-20 | Pressure digital acquisition front end |
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| CN100498865C true CN100498865C (en) | 2009-06-10 |
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| GB201102070D0 (en) * | 2011-02-07 | 2011-03-23 | Nordic Semiconductor Asa | Semiconductor temperature sensors |
| US11715322B2 (en) * | 2020-11-20 | 2023-08-01 | Novatek Microelectronics Corp. | Fingerprint sensing apparatus, fingerprint readout circuit, and touch display panel |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5641911A (en) * | 1993-10-08 | 1997-06-24 | Vaisala Oy | Method and apparatus for feedback-control of an asymmetric differential pressure transducer |
| JP2001304994A (en) * | 2000-04-25 | 2001-10-31 | Matsushita Electric Works Ltd | Pressure sensor circuit |
| CN1419114A (en) * | 2002-12-26 | 2003-05-21 | 天津师范大学 | Direct digitalized pressure transmitter and measuring method thereof |
| CN200969147Y (en) * | 2006-10-20 | 2007-10-31 | 沈阳中科博微自动化技术有限公司 | Pressure digital acquisition front end |
-
2006
- 2006-10-20 CN CNB2006100480574A patent/CN100498865C/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5641911A (en) * | 1993-10-08 | 1997-06-24 | Vaisala Oy | Method and apparatus for feedback-control of an asymmetric differential pressure transducer |
| JP2001304994A (en) * | 2000-04-25 | 2001-10-31 | Matsushita Electric Works Ltd | Pressure sensor circuit |
| CN1419114A (en) * | 2002-12-26 | 2003-05-21 | 天津师范大学 | Direct digitalized pressure transmitter and measuring method thereof |
| CN200969147Y (en) * | 2006-10-20 | 2007-10-31 | 沈阳中科博微自动化技术有限公司 | Pressure digital acquisition front end |
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Granted publication date: 20090610 Termination date: 20161020 |