CN102313622A - Capacitance detection circuit and capacitive type pressure transmitter - Google Patents
Capacitance detection circuit and capacitive type pressure transmitter Download PDFInfo
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- CN102313622A CN102313622A CN201110130290A CN201110130290A CN102313622A CN 102313622 A CN102313622 A CN 102313622A CN 201110130290 A CN201110130290 A CN 201110130290A CN 201110130290 A CN201110130290 A CN 201110130290A CN 102313622 A CN102313622 A CN 102313622A
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Abstract
The invention discloses a capacitance detection circuit and a capacitive type pressure transmitter, the capacitance detection circuit is a field-mounted pressure signal acquisition unit in an industrial instrument and comprises a capacitive type pressure sensor, a multi-way switch and a capacitance-frequency conversion circuit, and the capacitive type pressure sensor is used for converting external pressure change signals to capacitance change values; the multi-way switch is used for switching capacitance on the two sides; and the capacitance-frequency conversion circuit is a self-excited oscillation circuit and is used for converting capacitance signals on the driven side, which are outputted by the multi-way switch, to frequency signals. The multi-way switch is adopted, a same square wave self-excited oscillator is used for performing time division sampling, the charge and discharge characteristics of the capacitance are fully utilized, changes of the capacitance are reflected on the changes of oscillation frequency of the circuit, an oscillation circuit does not need to be additionally designed, an alternating current power supply is not required and only a direct current power supply is required, thereby simplifying a measuring circuit and avoiding introduction of alternating current interference.
Description
Technical field
The present invention relates to testing circuit and transmitter, be specifically related to a kind of capacitive detection circuit and capacitance pressure transmitter based on the WIA wireless network.
Background technology
Capacitance pressure transmitter has a wide range of applications in industrial process control.For capacitance pressure transmitter, its front-end circuit is capacitive detection circuit.The basic circuit of capacitance detecting has two types: the first as an impedor, carry out conversion according to the mode of resistance-voltage transitions, but wherein power supply must adopt AC power to electric capacity; It two is that the charge-discharge characteristic that makes full use of electric capacity carries out conversion.
At present, in capacitance pressure transmitter, adopt the method for capacitance-voltage conversion that capacitive detection circuit is set mostly, therefore need the design oscillatory circuit so that AC power to be provided; Yet this frequency is generally several KHzs, and; The too high meeting of frequency makes the influence of stray capacitance excessive, crosses the low difference that then is unfavorable for haggling over a capacitive reactance lock, therefore; Adopt the capacitive detection circuit of capacitance-voltage transfer principle design to have complicated circuit, huge characteristics, very unfavorable to the miniaturization of capacitance pressure transmitter; The colleague also gives the temperature drift compensation of circuit, and nonlinear compensation has been brought very big inconvenience.
A kind of pressure unit and measuring method thereof of Direct Digitalization, notification number are disclosed in being the Chinese patent of CN 1188678C; It adopts capacitance pressure transducer, and CB555 multi resonant oscillator to accomplish: convert the ambient pressure variable signal into the capacitance variations value; And convert the capacitance variations value into the concussion frequency signal, so that follow-up single-chip microcomputer calculates and changes.This patent utilization the capacitor charge and discharge characteristic wake up with a start capacitance measurement; But,, therefore cause consequence complicated on the structure owing to adopt two CB555 multivibrators respectively both sides electric capacity to be sampled; Thereby raise the cost; In addition, there is fit difference in two CB555 multivibrators, have influenced measuring accuracy thus.
70～eighties of last century, the wireless industrial technology still is a kind of simple means of communication, is purpose as the additional of cable technology with the data transmission that solves long distance, can realize point-to-point, point-to-multipoint delivery.In order to realize ubiquitous perception, promote the industrial measurement and control mode for reforming beginning of this century, and the information that solves is cheaply obtained, and the wireless industrial technology begins to realize large scale networkization.
Summary of the invention
The objective of the invention is to: a kind of capacitive detection circuit and capacitance pressure transmitter are provided, avoid adopting two CB555 multivibrators to carry out the front end capacitance measurement, cause cost low, measuring accuracy is high.
Technical solution of the present invention is: capacitive detection circuit is a field erected pressure signal collecting unit in the industrial instrument, and it comprises capacitance pressure transducer,, multi-way switch and electric capacity freq converting circuit; Wherein, capacitance pressure transducer: be used for converting the ambient pressure variable signal into the capacitance variations value; Multi-way switch: its input end connects capacitance pressure transducer,, and its output terminal connects the electric capacity freq converting circuit, is used for that two of capacitance pressure transducer, is surveyed electric capacity and switches; Electric capacity freq converting circuit: be a self-maintained circuit; Be used for being become frequency signal by the lateral capacitance conversion of signals to what multi-way switch was exported; The electric capacity freq converting circuit links to each other with hysteresis loop comparator and latch through measured capacitance and constitutes self-maintained circuit; The size of said oscillation frequency embodies the size of measured capacitance, and follow-up circuit is sampled to this frequency values and promptly obtained its frequency values.
The present invention can also make up self-maintained circuit through amplifier, and the variation of said measured capacitance converts change of frequency output to.
Wherein, Said electric capacity freq converting circuit comprises amplifier, integrating resistor R, divider resistance R1, resistance R 2, resistance R 3; The output voltage of amplifier is sent into the repercussion input end of amplifier behind RC circuit integration; Its inverting input connects measured capacitance, and the amplifier output voltage gets into in-phase end through feedback resistance R3, and power supply VCC voltage as a reference is added to the amplifier in-phase input end through R1.
Wherein, ((R3+R2)/R3), oscillation frequency f are 1/T to the cycle T=2RCln of said amplifier input, and when the resistance of R2, R3, R was confirmed, frequency was determined by capacitor C.
Wherein, said resistance is precision resistance.
The present invention provides a kind of capacitance pressure transmitter; It comprises capacitive detection circuit, single-chip microcomputer, storer, input equipment and display unit; Capacitive detection circuit comprises: comprise capacitance pressure transducer,, multi-way switch and electric capacity freq converting circuit, capacitance pressure transducer: be used for converting the ambient pressure variable signal into the capacitance variations value; Multi-way switch: its input end connects capacitance pressure transducer,, and its output terminal connects the electric capacity freq converting circuit, is used for two lateral capacitances are switched; The electric capacity freq converting circuit: it is a self-maintained circuit, is used for the north side capacitance signal of multi-way switch output is converted to frequency signal; Single-chip microcomputer: be used for the control of multi-way switch and receive the frequency signal that the electric capacity freq converting circuit is seen off, and it is calculated and changes; Storer: be used to store the calculation result data that single-chip microcomputer produces; Input equipment: be used to adjust range and input measurement parameter; Display unit: the demonstration of daring to exporting measurement result and the setting of said parameter.
Wherein, said measured capacitance links to each other with hysteresis loop comparator and constitutes the self-excited oscillator circuit, and the size of said oscillation frequency embodies the size of measured capacitance.
Wherein, Said electric capacity freq converting circuit comprises that the output voltage of amplifier, integrating resistor R, divider resistance R1, resistance R 2, resistance R 3, amplifier sends into the reversed-phase output of amplifier behind RC circuit integration; Its reversed-phase output connects measured capacitance; The amplifier output voltage gets into in-phase end through feedback resistance R3, and power supply VCC voltage as a reference is added to the amplifier in-phase input end through R1.
The present invention has the following advantages:
1, the present invention adopts multi-way switch, carries out time sharing sampling with same square wave self-excited oscillator, has made full use of the charge-discharge characteristic of electric capacity; Changes in capacitance is embodied in the variation of circuit oscillation frequency; Need not to design in addition oscillatory circuit, need not AC power, only need direct supply; Thereby simplified metering circuit, also avoided exchanging the introducing of disturbing.
2, the present invention has improved the speed of comparer part amplifier, has reduced the size of resistance in the integral element, further improves the measuring accuracy of metering circuit, and the principle of this circuit has also determined than has been easier to realize non-linear and warm compensation of floating etc.
3, transmitter is based on intelligent wireless network WIA technology; Meet IEEE 802.15.4 wireless communication standard; The radio communication of information between main equipment oriented; Use meets the free frequency band of Chinese the Radio Management Commission regulation, solves the various large-scale apparatus that spreads all under the rugged surroundings, metallic conduit etc. to the reflection of wireless signal, the multipath effect that scattering causes, and produces the interference of electromagnetic noise to radio communication when motor, apparatus running; Highly reliable, the real-time radio communication service that can satisfy application demand are provided, have technical characterictics such as very strong antijamming capability, super low-power consumption, real-time Communication for Power.
4, the size of said oscillation frequency embodies the size of measured capacitance; The size of the time that the present invention has determined just because of the size of electric capacity to discharge and recharge; Then determined the frequency size of comparer output waveform; The frequency of capacitive detection circuit output waveform has embodied the size of measured capacitance thus, and follow-up circuit only need be sampled to this frequency values can obtain its frequency values.
5, the front-end detection circuit of pressure unit of the present invention switches through multi-way switch; At the time sharing sampling that utilizes self-excited oscillator to two lateral capacitances; Obtain frequency values; Use identical oscillatory circuit owing to guarantee the conversion of both sides, and then simplified circuit, thereby avoided influencing the problem of measuring accuracy because of the individual difference that adopts the pressure survey multi-resonant oscillating circuit that two CB555 form.
Description of drawings
Fig. 1 is the structural representation of capacitance pressure transmitter of the present invention.
Fig. 2 is the capacitive detection circuit schematic diagram of Fig. 1.
Fig. 3 is data acquisition and the temperature-compensation circuit figure of Fig. 1.
Fig. 4 is data processing circuit and the wave point of Fig. 1.
Among the figure: 1, antenna, 2, LCD, 3, pipeline, 4, shell, 5, the capacitive transducer probe.
Embodiment
Further specify technical solution of the present invention below in conjunction with accompanying drawing and embodiment, embodiment should not be construed as the restriction to technical solution.
Capacitive detection circuit can be applicable to a lot of capacitance pressure transmitters; Below be that example is explained the capacitance pressure transmitter that adopts above-mentioned capacitive detection circuit with regard to several capacitance pressure transmitters; See also Fig. 1-4; It is the structure and the circuit theory diagrams of a kind of capacitance pressure transmitter of the present invention, and it comprises capacitive detection circuit, single-chip microcomputer, storer, input equipment and display unit, and capacitive detection circuit comprises capacitance pressure transducer,, multi-way switch and electric capacity freq converting circuit; Wherein, Capacitance pressure transducer, comprises high-pressure side pressure measurement electric capacity and low-pressure side pressure measurement electric capacity, utilize multi-way switch to switch and utilize the electric capacity freq converting circuit to realize time sharing sampling, and with sampled value C through converting frequency signal to; Wherein, capacitance pressure transducer: be used for converting the ambient pressure variable signal into the capacitance variations value; Multi-way switch: its first input end connects single-chip microcomputer P3.3 mouth, the break-make of control high-pressure side pressure measurement electric capacity and feedback resistance R1 one end; Second input end connects single-chip microcomputer P3.0 mouth, the break-make of control low-pressure side pressure measurement electric capacity and feedback resistance R1 one end; The 3rd input end connects single-chip microcomputer P3.1 mouth, controls the break-make of accurate capacitor C 1 and feedback resistance R1 one end; Four-input terminal connects single-chip microcomputer P3.2 mouth, the end of control socket XZ5 and the break-make of feedback resistance R1 one end; Electric capacity freq converting circuit: adopt amplifier and latch to make up self-maintained circuit; It comprises amplifier 1, amplifier 2, divider resistance R2, resistance R 3, resistance R 4, feedback resistance R1, Sheffer stroke gate 1, Sheffer stroke gate 2, filter capacitor C14, capacitor C 15, counter 1 sum counter 2; VCC is added to the in-phase input end of amplifier 1 through R1; Be added to the inverting input of amplifier 2 again through R3, after R4 arrives ground; The inverting input of the in-phase input end of amplifier 1 and amplifier 2 meets filter capacitor C14 respectively, and capacitor C 15 is to ground; The output terminal of amplifier 1 links to each other with an input end of Sheffer stroke gate 2; Another input end of Sheffer stroke gate 2 links to each other with the output terminal of Sheffer stroke gate 1; The output terminal of Sheffer stroke gate 2 links to each other with an input end of Sheffer stroke gate 1; Another input end of Sheffer stroke gate 1 links to each other with the output terminal of amplifier 2, and the output of amplifier 1 also drives input end with the clock of counter 1, and the end of feedback resistance R1 links to each other; The other end of feedback resistance links to each other with four input ends of multi-way switch, the inverting input of amplifier 1 and the in-phase input end of amplifier 2; The 4th output terminal of counter 1 drives input end with the clock of counter 2 and links to each other, and second of counter 2 links to each other with P1.2 mouth, the P1.3 mouth of single-chip microcomputer with the 3rd output terminal; Power supply: the 3.3V lithium battery power supply, use 3.3V to change 3V gate-controlled switch chip and to analog part and numerical portion required power supply be provided in the main controller circuit plate; 3.3V power supply is by C3, C14, C15, C16, C20, C21, C22, C24 filtering, the 3V power supply is by C1, C9, C10, C18 filtering; Single-chip microcomputer: the MSP430F149 chip of selecting the texas,U.S electric corporation for use; Crystal oscillator is selected 3.6264MHz for use, and program is downloaded use standard jtag interface; XT2IN, XT2OUT are connected with crystal oscillator, between connect resistance R 17, through C11, C12 to ground; 54,55,56,57 pin of MCU link to each other with 1,3,5,7 pin of double cab JP2 respectively, and 12 of MCU links to each other with 6 pin with 2 pin of JP2 respectively with 22 pin, and 58 pin of MCU link to each other with 11 pin of JP2; Eeprom memory: sheet external memory chip is selected the 24LC64 chip of MicroChip company for use, adopts the I2C interface; By the power supply of 3.3V power supply, 5, No. 6 pin links to each other with P4.5, the P4.6 mouth of MCU through R20, R21 pull-up resistor, and C25 is used for filtering, and 1,2,3, No. 4 pin ground connection is used for indicant reason address; Display: select for use 48 pin HT1621B of spi bus structure to drive LCD screen; Wherein SEG0～SEG23 and COM0～COM3 totally 24 pins be connected with liquid-crystalline glasses; The DATA pin connects an end that draws resistance R 52 and is connected with the P5.1 mouth of MCU; The CS pin connects an end that draws resistance R 53 and is connected with the P1.5 mouth of MCU, and the WR pin connects an end that draws resistance R 54 and is connected with the P1.6 mouth of MCU, and the RD pin connects an end that draws resistance R 55 and is connected with the P1.7 mouth of MCU; The other end of pull-up resistor R52, R53, R54, R55 is connected with VDD; Be connected the R51 variable resistor between VDD and the VLCD pin, VDD is connected with ground wire respectively at the 3.3V power supply on the main controller circuit plate with VSS, and all the other pins are unsettled; The P3.4 of radio communication: MCU, P3.5 mouth link to each other with the serial interface of WIAPA-M1800 wireless communication module.
Claims (10)
1. capacitive detection circuit, it is characterized in that: it comprises capacitance pressure transducer,, multi-way switch and electric capacity freq converting circuit, capacitance pressure transducer: be used for converting the ambient pressure variable signal into the capacitance variations value; Multi-way switch: its input end connects capacitance pressure transducer,, and its output terminal connects the electric capacity freq converting circuit, is used for two lateral capacitances are switched; Electric capacity freq converting circuit: be a self-maintained circuit, be used for being become frequency signal by the lateral capacitance conversion of signals to what multi-way switch was exported.
2. capacitive detection circuit as claimed in claim 1 is characterized in that: said measured capacitance links to each other with hysteresis loop comparator, and to constitute self-maintained circuit, the size of said oscillation frequency embodies the size of measured capacitance.
3. capacitive detection circuit as claimed in claim 1 is characterized in that: self-maintained circuit makes up through amplifier, and the variation of said measured capacitance converts change of frequency output to.
4. capacitive detection circuit as claimed in claim 3; It is characterized in that: said electric capacity freq converting circuit comprises amplifier, integrating resistor R, divider resistance R1, resistance R 2, resistance R 3; The output voltage of amplifier is sent into the repercussion input end of amplifier behind RC circuit integration; Its inverting input connects measured capacitance, and the amplifier output voltage gets into in-phase end through feedback resistance R3, and power supply VCC voltage as a reference is added to the amplifier in-phase input end through R1.
5. capacitive detection circuit as claimed in claim 4 is characterized in that: ((R3+R2)/R3), oscillation frequency f are 1/T to the cycle T=2RCln of said amplifier input, and when the resistance of R2, R3, R was confirmed, frequency was determined by capacitor C.
6. capacitance pressure transmitter; It is characterized in that: it comprises capacitive detection circuit, single-chip microcomputer, storer, input equipment and display unit; Capacitive detection circuit comprises: comprise capacitance pressure transducer,, multi-way switch and electric capacity freq converting circuit, capacitance pressure transducer: be used for converting the ambient pressure variable signal into the capacitance variations value; Multi-way switch: its input end connects capacitance pressure transducer,, and its output terminal connects the electric capacity freq converting circuit, is used for two lateral capacitances are switched; The electric capacity freq converting circuit: it is a self-maintained circuit, is used for the north side capacitance signal of multi-way switch output is converted to frequency signal; Single-chip microcomputer: be used for the control of multi-way switch and receive the frequency signal that the electric capacity freq converting circuit is seen off, and it is calculated and changes; Storer: be used to store the calculation result data that single-chip microcomputer produces; Input equipment: be used to adjust range and input measurement parameter; Display unit: the demonstration of daring to exporting measurement result and the setting of said parameter.
7. capacitance pressure transmitter as claimed in claim 6 is characterized in that: said measured capacitance links to each other with hysteresis loop comparator and constitutes the self-excited oscillator circuit, and the size of said oscillation frequency embodies the size of measured capacitance.
8. capacitance pressure transmitter as claimed in claim 6 is characterized in that: the self-sustained oscillation loop makes up through amplifier, and the variation of said measured capacitance converts change of frequency output to.
9. capacitance pressure transmitter as claimed in claim 8; It is characterized in that: said electric capacity freq converting circuit comprises that the output voltage of amplifier, integrating resistor R, divider resistance R1, resistance R 2, resistance R 3, amplifier sends into the reversed-phase output of amplifier behind RC circuit integration; Its reversed-phase output connects measured capacitance; The amplifier output voltage gets into in-phase end through feedback resistance R3, and power supply VCC voltage as a reference is added to the amplifier in-phase input end through R1.
10. capacitance pressure transmitter as claimed in claim 6; It is characterized in that: it comprises capacitive detection circuit, single-chip microcomputer, storer, input equipment and display unit; Capacitive detection circuit comprises capacitance pressure transducer,, multi-way switch and electric capacity freq converting circuit, and wherein, capacitance pressure transducer, comprises high-pressure side pressure measurement electric capacity and low-pressure side pressure measurement electric capacity; Utilize multi-way switch to switch and utilize the electric capacity freq converting circuit to realize time sharing sampling; And with sampled value C through converting frequency signal to, wherein, capacitance pressure transducer: be used for converting the ambient pressure variable signal into the capacitance variations value; Multi-way switch: its first input end connects single-chip microcomputer P3.3 mouth, the break-make of control high-pressure side pressure measurement electric capacity and feedback resistance R1 one end; Second input end connects single-chip microcomputer P3.0 mouth, the break-make of control low-pressure side pressure measurement electric capacity and feedback resistance R1 one end; The 3rd input end connects single-chip microcomputer P3.1 mouth, controls the break-make of accurate capacitor C 1 and feedback resistance R1 one end; Four-input terminal connects single-chip microcomputer P3.2 mouth, the end of control socket XZ5 and the break-make of feedback resistance R1 one end; Electric capacity freq converting circuit: adopt amplifier and latch to make up self-maintained circuit; It comprises amplifier 1, amplifier 2, divider resistance R2, resistance R 3, resistance R 4, feedback resistance R1, Sheffer stroke gate 1, Sheffer stroke gate 2, filter capacitor C14, capacitor C 15, counter 1 sum counter 2; VCC is added to the in-phase input end of amplifier 1 through R1; Be added to the inverting input of amplifier 2 again through R3, after R4 arrives ground; The inverting input of the in-phase input end of amplifier 1 and amplifier 2 meets filter capacitor C14 respectively, and capacitor C 15 is to ground; The output terminal of amplifier 1 links to each other with an input end of Sheffer stroke gate 2; Another input end of Sheffer stroke gate 2 links to each other with the output terminal of Sheffer stroke gate 1; The output terminal of Sheffer stroke gate 2 links to each other with an input end of Sheffer stroke gate 1; Another input end of Sheffer stroke gate 1 links to each other with the output terminal of amplifier 2, and the output of amplifier 1 also drives input end with the clock of counter 1, and the end of feedback resistance R1 links to each other; The other end of feedback resistance links to each other with four input ends of multi-way switch, the inverting input of amplifier 1 and the in-phase input end of amplifier 2; The 4th output terminal of counter 1 drives input end with the clock of counter 2 and links to each other, and second of counter 2 links to each other with P1.2 mouth, the P1.3 mouth of single-chip microcomputer with the 3rd output terminal; Power supply: the 3.3V lithium battery power supply, use 3.3V to change 3V gate-controlled switch chip and to analog part and numerical portion required power supply be provided in the main controller circuit plate; 3.3V power supply is by C3, C14, C15, C16, C20, C21, C22, C24 filtering, the 3V power supply is by C1, C9, C10, C18 filtering; Single-chip microcomputer: the MSP430F149 chip of selecting the texas,U.S electric corporation for use; Crystal oscillator is selected 3.6264MHz for use, and program is downloaded use standard jtag interface; XT2IN, XT2OUT are connected with crystal oscillator, between connect resistance R 17, through C11, C12 to ground; 54,55,56,57 pin of MCU link to each other with 1,3,5,7 pin of double cab JP2 respectively, and 12 of MCU links to each other with 6 pin with 2 pin of JP2 respectively with 22 pin, and 58 pin of MCU link to each other with 11 pin of JP2; Eeprom memory: sheet external memory chip is selected the 24LC64 chip of MicroChip company for use, adopts the I2C interface; By the power supply of 3.3V power supply, 5, No. 6 pin links to each other with P4.5, the P4.6 mouth of MCU through R20, R21 pull-up resistor, and C25 is used for filtering, and 1,2,3, No. 4 pin ground connection is used for indicant reason address; Display: select for use 48 pin HT1621B of spi bus structure to drive LCD screen; Wherein SEG0～SEG23 and COM0～COM3 totally 24 pins be connected with liquid-crystalline glasses; The DATA pin connects an end that draws resistance R 52 and is connected with the P5.1 mouth of MCU; The CS pin connects an end that draws resistance R 53 and is connected with the P1.5 mouth of MCU, and the WR pin connects an end that draws resistance R 54 and is connected with the P1.6 mouth of MCU, and the RD pin connects an end that draws resistance R 55 and is connected with the P1.7 mouth of MCU; The other end of pull-up resistor R52, R53, R54, R55 is connected with VDD; Be connected the R51 variable resistor between VDD and the VLCD pin, VDD is connected with ground wire respectively at the 3.3V power supply on the main controller circuit plate with VSS, and all the other pins are unsettled; The P3.4 of radio communication: MCU, P3.5 mouth link to each other with the serial interface of WIAPA-M1800 wireless communication module.
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| CN103575306A (en) * | 2013-11-18 | 2014-02-12 | 东南大学 | Passive wireless multi-parameter sensor system and multi-parameter measurement method thereof |
| CN103674352A (en) * | 2013-12-18 | 2014-03-26 | 惠州盛太克仪表有限公司 | Pressure transmitter signal processing chip and capacitive differential pressure transmitter |
| CN104267746A (en) * | 2014-09-26 | 2015-01-07 | 杭州墨锐机电科技有限公司 | Large-caliber ultra-thin self-adaptation secondary mirror control system |
| CN107631829A (en) * | 2017-09-15 | 2018-01-26 | 武汉中航传感技术有限责任公司 | Differential pressure pickup |
| CN108225495A (en) * | 2016-12-12 | 2018-06-29 | 中国航空工业集团公司西安航空计算技术研究所 | A kind of capacitance level transducer on-line measurement system and its method |
| CN111492234A (en) * | 2018-11-09 | 2020-08-04 | 广东美的白色家电技术创新中心有限公司 | Movable electric device |
| CN112074718A (en) * | 2018-03-07 | 2020-12-11 | Ifm电子股份有限公司 | Capacitive pressure measuring cell and method for operating a capacitive pressure measuring device |
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| CN103575306A (en) * | 2013-11-18 | 2014-02-12 | 东南大学 | Passive wireless multi-parameter sensor system and multi-parameter measurement method thereof |
| CN103674352A (en) * | 2013-12-18 | 2014-03-26 | 惠州盛太克仪表有限公司 | Pressure transmitter signal processing chip and capacitive differential pressure transmitter |
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| CN112074718A (en) * | 2018-03-07 | 2020-12-11 | Ifm电子股份有限公司 | Capacitive pressure measuring cell and method for operating a capacitive pressure measuring device |
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| CN111492234A (en) * | 2018-11-09 | 2020-08-04 | 广东美的白色家电技术创新中心有限公司 | Movable electric device |
| US12042106B2 (en) | 2018-11-09 | 2024-07-23 | Guangdong Midea White Home Appliance Technology Innovation Center Co., Ltd. | Movable electronic apparatus |
| CN112267549A (en) * | 2020-10-10 | 2021-01-26 | 浙江飞创环境科技有限公司 | Integrated pump station |
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Application publication date: 20120111 |