CN101655379A - Ceramic double-capacitance pressure transmitter circuit - Google Patents
Ceramic double-capacitance pressure transmitter circuit Download PDFInfo
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- CN101655379A CN101655379A CN200910144955A CN200910144955A CN101655379A CN 101655379 A CN101655379 A CN 101655379A CN 200910144955 A CN200910144955 A CN 200910144955A CN 200910144955 A CN200910144955 A CN 200910144955A CN 101655379 A CN101655379 A CN 101655379A
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Abstract
The invention discloses a ceramic double-capacitance pressure transmitter circuit which comprises a double-capacitance ceramic pressure-sensitive membrane. A public electrode, a reference electrode and a measurement electrode of the double-capacitance ceramic pressure-sensitive membrane are respectively connected with the input end of a capacitance-voltage conversion chip by down-leads thereof, the output end of the capacitance-voltage conversion chip is connected with the input end of an instrument amplifier, the output end of the instrument amplifier is connected with the input end of a signal operational amplifier, and the output end of the signal operational amplifier is then connected with the input end of a voltage-current conversion chip. In the circuit, the capacitance change caused by voltage change is converted into a voltage signal by the capacitance-voltage conversion chip, the voltage signal is then adjusted by an amplification circuit, the V-I conversion and the nonlinearcorrection of the voltage signal are carried out by the voltage-current conversion chip, and finally, a direct-current signal with 4-20mA is output. The invention has a concise circuit structure, solves the micro-capacitance measurement problem of the ceramic double-capacitance pressure-sensitive membrane better and satisfies the requirement of small-scale production.
Description
Technical field
The present invention relates to Detection of weak and converter technique, refer more particularly to a kind of detection and treatment circuit of ceramic double-capacitance pressure transmitter.
Background technology
The ceramic double-capacitance pressure sensor is that the eighties is invented by U.S. kavlico company, has only several countries such as the U.S., Germany and Switzerland that Related product is arranged at present in the world.The ceramic double-capacitance pressure sensor utilizes electric capacity to become the clearance-type principle, adopt thick film sensing technology and thick film mixing integrated technology to combine, make the sensor of non-topping up air dielectric, it has following characteristics: 1. temperature stability is good, it is very little itself to generate heat, and has low temperature and floats; 2. simple in structure, be easy to make, adaptability is strong, can realize high pressure, HI high impact and overload measurement; 3. dynamic response is good, and the natural frequency height is fit to kinetic measurement; 4. the electrostatic attraction between belt electrode is little, and required input power and intake are little, can realize the minute-pressure test; 5. the loss of medium such as air is little, allows the high frequency multiplication of circuit to amplify, and is highly sensitive.
Present ceramic double-capacitance pressure sensor, and bigger based on the transmitter use amount at home of this sensor, except that being used for pressure survey, be used for the indirect measurement of liquid level mostly.Hefei Intelligent Machinery Inst., Chinese Academy of Scineces at first, also is unique unit that develops the ceramic double-capacitance pressure sensor at home, (seeing Chinese patent ZL200610040162.3 " a kind of preparation method of double capacitance thick film ceramic pressure element "), its transducing part is the two electric capacity pressure-sensitive diaphragms of pottery, structure such as Fig. 1, it makes battery lead plate by ceramic cover plate and ceramic flexible sheet, the pole plate gap is the air dielectric chamber, on ceramic flexible sheet, public electrode is set, coaxial bipolar electrode is set on ceramic cover plate, constitutes two capacitance structures of coaxial ring-type.When flexible sheet is stressed, be subjected to displacement, electric capacity is changed, be converted to exportable electric signal through signal processing circuit.For signal processing circuit, in fact exactly capacitance signal is converted to common voltage or current signal.For the testing circuit of this capacitance signal, do not see relevant report.
The pressure measurement range of ceramic double-capacitance pressure-sensitive diaphragm generally be tens Kpa to hundreds of Kpa, the appearance value of corresponding ceramic condenser is greatly about the 40-100 pico farad, the variable quantity of differential capacitor is several to tens pico farads, this belongs to the small capacitance magnitude.Detection for small capacitance has several different methods, but no matter how, if design, test with discrete component, and then make special-purpose integrated or the mixing integrated chip, the workload of development is very big, expense is also high, because for the capacitive transducer and the transmitter of little electric capacity, not only to consider the stray capacitance of its lead capacitance, circuit design and the influence of environmental change etc., relevant modulate circuit complexity, and, also will influence the measuring accuracy of electric capacity because discrete component is too much.
Summary of the invention
The objective of the invention is to provides a kind of transmitter circuit for the two electric capacity pressure-sensitive diaphragms of pottery, this circuit can be converted to the capacitance change of pressure-sensitive diaphragm the transmitter output signal of standard, and require circuit structure succinct relatively, can satisfy the requirement that commercialization is on a small scale produced.
The technical solution used in the present invention is:
The two capacitive pressure transmitters of a kind of pottery detect and translation circuit, comprise two capacitance ceramic pressure-sensitive diaphragms, its public electrode, reference electrode and potential electrode connect with capacitance-voltage conversion chip input end respectively through lead-in wire, capacitance-voltage conversion chip output terminal connects with the input end of instrument amplifier, the output terminal of instrument amplifier connects with single amplifier, and single amplifier output connects with the input end of current-voltage conversion chip.The described pair of capacitance ceramic pressure-sensitive diaphragm causes changes in capacitance amount input capacitance voltage transitions chip with the variation of pressure, the capacitance-voltage conversion chip is converted into voltage form with electric capacity, and with electric resistance partial pressure form input instrument amplifier, adjust signal magnitude through instrument amplifier, transform chip by voltage-to-current again and carry out V-I conversion and non-linear correction, export 4～20mA standard DC current at last.Set up a single operational amplifier in described instrument amplifier output back level and do voltage follower or signal fine setting.Described voltage-to-current conversion chip also is connected with a voltage reference diode.
Described capacitance voltage conversion chip is the XE2004 of Switzerland XEMICS company, and power supply voltage range is 2.4V～5.5V, and its output terminal is set up filter capacitor.
Described instrument amplifier is AD623, and under the situation of single supply, allowing service area is that 3.0V is between the 12V.Also can use the operational amplifier of other single power supply.
Described single operational amplifier is TLV2211 or other little power consumption operational amplifier;
Described electric current and voltage conversion chip is the XTR106 of U.S. BB company,
Described voltage reference diode is the LM385-1.2 of U.S. NS company.
The present invention handles the electric capacitance change that is changed the two ceramic condensers that cause by ambient pressure to be converted into voltage signal by the XE2004 chip, after suitably adjusting, import the XTR106 chip again, carry out linearity correction and voltage-to-current and transform back outputting standard 4～20mA dc current signal.The XTR106 chip designs at piezoresistive transducer, special IC with function integrations such as power supply, amplification, zero point and full scale adjustment, non-linear adjustment, electric current and voltage conversions, the present invention mainly is a function of utilizing its non-linear adjustment and electric current and voltage to transform, for meeting the condition of work of XTR106 chip, the present invention has used a voltage reference diode, promote the zero point that is input to the XTR106 chip and the magnitude of voltage of full scale, make it satisfy the input range requirement of signal.
Beneficial effect of the present invention: can be converted to the small capacitance variable quantity DC current output of standard, have the adjusting of zero point and full scale, non-linear adjustment function, and having overcome influences such as stray capacitance preferably, circuit structure is succinct, volume is less, the requirement in the time of can satisfying small serial production.Non-linear adjustment mode of the present invention also can be used for the sensor of other type.
Description of drawings
The present invention is described in more detail below in conjunction with the drawings and specific embodiments.
Fig. 1 a, b are that two capacitance ceramic pressure-sensitive diaphragm structures are showed synoptic diagram.Among the figure 21, the public electrode lead-in wire, 22, public electrode, 23, the reference electrode lead-in wire, 24, the potential electrode lead-in wire, 25, air hole, 26, medium.
Fig. 2 is circuit theory diagrams.Among the figure, 1 is the capacitance-voltage conversion chip, and 2 is two capacitance ceramic pressure-sensitive diaphragms, and 3 is instrument amplifier, and 4 is single amplifier, and 5 is the voltage-to-current conversion chip, and 6 is the voltage reference diode.
Embodiment
Circuit theory diagrams such as Fig. 2.The capacitance-voltage conversion circuit is selected the XE2004 chip for use, XE2004 chip 10,11,12 pins respectively corresponding three electrodes of two capacitance ceramic pressure-sensitive diaphragms 2, connect by public electrode lead-in wire 21, reference electrode lead-in wire 23 and potential electrode lead-in wire 24, referring to Fig. 1.Make under the useful state, the b among Fig. 1 partly covers on a part in Fig. 1, and on the b part of public electrode 22 in Fig. 1, outer toroid is a medium 26, and air hole 25 is located at a part among Fig. 1.The XE2004 chip internal has can compile amplifier, overload protection and programmable functions, and power supply voltage range is 2.4V～5.5V, and this circuit uses the 5V power supply, reduces cost in order to simplify circuit, chip internal is not programmed, and all adopts default value.Under the situation that two electrode capacitances equate, the theoretical value of voltage output is 2.5V, but the electric capacity at the two poles of the earth can not be equal fully in the middle of the actual conditions, and the zero-point voltage of XE2004 output is about 2.5V.
The Output Voltage Formula of XE2004 is:
Under the situation of acquiescence, Ccomp and Voff are zero, and K is the inner enlargement factor compiled, and default value is 8, and Vref is 2.5V under the situation of 5V power supply.
XE2004 is converted into voltage inside with electric capacity has certain oscillator signal to need to carry out filtering at C1 electric capacity of output terminal increase.In this circuit, use the 5V reference edge of XTR106 to power as XE2004, the 5V power voltage supply makes XE2004 be output as about 2.5V, again output is connected amplifier input terminal, and instrument amplifier AD623 can single dual power supply, this circuit is selected single power supply for use, negativing ending grounding.D1 provides voltage to AD623 by voltage stabilizing diode, under the situation of single supply, the permission service area of AD623 be 3.0V between the 12V, enlargement factor can be adjusted between 1～1000, and only needs a resistance.
Draw reference voltage from the Voltage Reference end of XE2004, provide common-mode signal by resistance R 3 and R4, R5 dividing potential drop for AD623 with this voltage, this magnitude of voltage is Vref=(VDD-VSS)/2, Vss ground connection, and Vref is 2.5V.The enlargement factor of AD623 has been subjected to the restriction of common-mode signal and supply voltage, can only reach 4.296V, but can meet the demands, for having increased a single amplifier, the driving force output that increases output voltage makes voltage follower, two electric capacity of pottery and the non-linear of circuit are not adjusted, and have simplified the difficulty of circuit debugging greatly.
Non-linear adjustment transforms chip XTR106 by voltage-to-current and carries out.The power supply voltage range of XTR106 chip is between 7.5V～36V, power with reference to being output as XE2004 with its 5V, supply voltage minimum to the XTR106 chip should be 8V, use 2.5V with reference to the time XTR106 chip non-linear domain-2.5%～+ 5% that can regulate, under the situation of 5V power supply, the non-linear domain that the XTR106 chip can be regulated is ± 5%, and regulation can reach 20: 1.XTR106 processing signals scope is between 1.1～3.5V, variable quantity is in 2.4V, the voltage range of the output of XE2004 can not satisfy the requirement of XTR106, use LM385-1.2 to provide the Voltage Reference of 1.2V to promote zero point and full scale simultaneously, when input XTR106, carry out the electric resistance partial pressure adjustment, behind conditioned suitable output voltage, determine the linearity and the linear polarity of output voltage, output is that negative wire then is connected 1 pin of chip with 12 pin, inserts linear resistance then between 1 pin and 11 pin; Linear positive then is connected 6 pin with 12 pin in this way, and 1 pin is connected with 11 pin.
The computing formula of linear resistance is:
B sensor non-linear, K
LinBeing non-linear factor, is 6645 Ω under the reference voltage of 5V; Under the 2.5V reference voltage 9905 Ω.
Again demarcate zero point and full scale, the linearity of calculating sensor, as do not reach requirement and on this basis, finely tune linear resistance and demarcate again up to reaching requirement.By top method debugging, circuit is simple, cost is low, volume is little, easy realization.
Embodiment
In the circuit of Fig. 2, the output signal of zero point and full scale is after through instrument amplifier, single amplifier, greatly between 0.3V～3.2V, this voltage range can not satisfy the input requirement of XTR106 chip, for this reason, use the voltage reference diode of a 1.2V in this circuit, improved the voltage relative value of zero point and full scale.Adjust through the prime dividing potential drop, make the voltage range that is input to the XTR106 chip be seated between 1.1～3.5V, regulate the adjustable rheostat RPT2 of Fig. 2 and adjust zero point, RPT1 adjusts full scale, make zero point and full scale reach 4.0～20.0mA at last, and then calculate non-linear and definite non-linear polarity, this example is a negative wire, then 1 pin with XTR106 is connected with 12 pin, between 1 pin and 11 pin, insert linear resistance then, select suitable linear resistance according to formula, adjust non-linearly, experiment shows, this circuit can be improved to the capacitance signal of the non-linear two electric capacity pressure-sensitive diaphragms of pottery about ± 5% non-linear ± 0.2% with interior current signal.Table 1 is an experimental example.
The non-linear unit of adjustment of table 1 transmitter: pressure (Kpa) electric current (mA)
Claims (4)
1, a kind of ceramic double-capacitance pressure transmitter circuit, comprise two capacitance ceramic pressure-sensitive diaphragms (2), it is characterized in that: the public electrode of described pair of capacitance ceramic pressure-sensitive diaphragm (2), reference electrode and potential electrode connect with capacitance-voltage conversion chip (1) input end respectively through its lead-in wire, capacitance-voltage conversion chip (1) output terminal connects with the input end of instrument amplifier (3), the output terminal of instrument amplifier (3) connects with the input of single amplifier (4), the output of single amplifier (4) connects with the input end of voltage-to-current conversion chip (5) again, and voltage-to-current conversion chip (5) also connects with a reference voltage (6).
2, ceramic double-capacitance pressure transmitter circuit according to claim 1, it is characterized in that: described pair of capacitance ceramic pressure-sensitive diaphragm (2) changes pressure the capacitance variations input capacitance-voltage transitions chip (1) that causes, capacitance-voltage conversion chip (1) is converted into voltage form with electric capacity, and be input to instrument amplifier (3) by electric resistance partial pressure, single amplifier (4) adjustment is passed through in the output of instrument amplifier (3) again, and by being input to voltage-to-current conversion chip (5) behind the electric resistance partial pressure, voltage-to-current transforms chip (5) and carries out the V-I conversion, and do non-linear correction, export the dc current signal of 4-20mA at last.
3, ceramic double-capacitance pressure transmitter circuit according to claim 1 is characterized in that: pressure is changed the changes in capacitance amount that causes the two electric capacity of pottery, use capacitance-voltage to transform chip XE2004, capacitance signal is converted into voltage signal.
4, ceramic double-capacitance pressure transmitter circuit according to claim 1 is characterized in that: the non-linear adjustment of transducer signal transforms chip XTR106 by voltage-to-current and carries out.
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| CN200910144955A CN101655379A (en) | 2009-09-15 | 2009-09-15 | Ceramic double-capacitance pressure transmitter circuit |
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| CN200910144955A CN101655379A (en) | 2009-09-15 | 2009-09-15 | Ceramic double-capacitance pressure transmitter circuit |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103674407A (en) * | 2012-09-17 | 2014-03-26 | 昆山尚达智机械有限公司 | Novel pressure transmitter |
| CN104406732A (en) * | 2014-11-21 | 2015-03-11 | 广西智通节能环保科技有限公司 | Pressure gauge |
| CN108956005A (en) * | 2018-08-08 | 2018-12-07 | 陈德连 | pressure sensor |
| CN110319971A (en) * | 2019-08-02 | 2019-10-11 | 上海振太仪表有限公司 | A kind of bipolar condenser type vacuum meter and its corresponding measuring circuit |
-
2009
- 2009-09-15 CN CN200910144955A patent/CN101655379A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103674407A (en) * | 2012-09-17 | 2014-03-26 | 昆山尚达智机械有限公司 | Novel pressure transmitter |
| CN104406732A (en) * | 2014-11-21 | 2015-03-11 | 广西智通节能环保科技有限公司 | Pressure gauge |
| CN108956005A (en) * | 2018-08-08 | 2018-12-07 | 陈德连 | pressure sensor |
| CN108956005B (en) * | 2018-08-08 | 2024-03-22 | 陈德连 | Pressure sensor |
| CN110319971A (en) * | 2019-08-02 | 2019-10-11 | 上海振太仪表有限公司 | A kind of bipolar condenser type vacuum meter and its corresponding measuring circuit |
| CN110319971B (en) * | 2019-08-02 | 2024-04-23 | 上海振太仪表有限公司 | Measuring circuit for measuring pressure in bipolar capacitance type vacuum gauge |
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Open date: 20100224 |