Device and method for measuring the height of a liquid in a container
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
G01F-023/00
G01F-023/26
G01F-025/00
G01R-027/26
출원번호
US-0184651
(2016-06-16)
등록번호
US-10175086
(2019-01-08)
우선권정보
FR-15 55464 (2015-06-16)
발명자
/ 주소
Munoz, Régis
출원인 / 주소
AKWEL SA
대리인 / 주소
Oliff PLC
인용정보
피인용 횟수 :
0인용 특허 :
10
초록▼
A measurement device has two electrodes in the liquid forming a capacitor the capacitance of which depends on the height of the liquid, a microcontroller connected to an electrode and having a capacitance determination circuit for determining first and second values of the capacitance of the capacit
A measurement device has two electrodes in the liquid forming a capacitor the capacitance of which depends on the height of the liquid, a microcontroller connected to an electrode and having a capacitance determination circuit for determining first and second values of the capacitance of the capacitor respectively during charging and discharging of the capacitor, an oscillator circuit for generating signals at a reference frequency when the electrodes are not connected to the microcontroller, then at a variable frequency dependent on the height of the liquid when the electrodes are connected to the microcontroller. The microcontroller further includes a programmable logic device configured into a comparator circuit, and a frequency determination circuit connected to the programmable logic device so as to determine the variable frequency from the reference frequency and from the signals of the programmable logic device.
대표청구항▼
1. A measurement device, for measuring a height of liquid in a container, the liquid being an aqueous urea solution, the measurement device comprising at least: two electrodes intended to be at least partially immersed in the liquid when the liquid is introduced in the container, so that the electro
1. A measurement device, for measuring a height of liquid in a container, the liquid being an aqueous urea solution, the measurement device comprising at least: two electrodes intended to be at least partially immersed in the liquid when the liquid is introduced in the container, so that the electrodes and the liquid present between the electrodes form a variable capacitor the capacitance of which depends on the height of the liquid in the container,a microcontroller configured to be connected to at least one of the electrodes, the microcontroller comprising a capacitance determination circuit configured to determine: i) a first value of the capacitance of the variable capacitor from voltages measured between the electrodes during a charging phase of the variable capacitor, andii) a second value of the capacitance of the variable capacitor from voltages measured between the electrodes during a discharging phase of the variable capacitor,wherein the measurement device further comprises an oscillator circuit configured: i) to generate signals at a reference frequency when the electrodes are not connected to the microcontroller, andii) to generate signals at a variable frequency dependent on the height of the liquid in the container when the electrodes are connected to the microcontroller and immersed in the liquid;the microcontroller further comprising: a programmable logic device configured to form an inverter logic gate, the inverter logic gate being arranged so as to induce voltage oscillations at the variable frequency in the oscillator circuit , anda frequency determination circuit connected to the programmable logic device and configured to determine the variable frequency from the reference frequency and from the signals derived from the programmable logic device . 2. The measurement device according to claim 1, wherein the microcontroller is configured to generate: a first measurement signal which is formed from the first and second values of the capacitance of the variable capacitor so that the first measurement signal is representative of the height of the liquid; anda second measurement signal which is formed from the variable frequency so that the second measurement signal is representative of the height of the liquid; the microcontroller being further configured to generate a height signal which is formed:from the first measurement signal when the first measurement signal corresponds to a height of liquid which is larger than a predetermined height threshold; orfrom the second measurement signal when the first measurement signal corresponds to a height of liquid which is smaller than the predetermined height threshold. 3. The measurement device according to claim 1, wherein the frequency determination circuit comprises: a counter configured to count the number of oscillations of the oscillator circuit for a predetermined duration, anda phase-locked loop configured to generate stable-frequency signals so as to define a time base. 4. The measurement device according to claim 3, wherein the phase-locked loop is configured to operate at a stable frequency comprised between 8 MHz and 32 MHz and wherein the phase-locked loop is configured to increment the counter according to a period comprised between 125 nanoseconds and 31.25 nanoseconds. 5. The measurement device according to claim 1, further comprising a communication module configured to generate radioelectric signals representative of the height of the liquid in the container. 6. The measurement device according to claim 1, wherein the programmable logic device comprises an inverter circuit with a Schmitt comparator input. 7. The measurement device according to claim 1, wherein the microcontroller further comprises an analog-digital converter connected to the capacitance determination circuit, the analog-digital converter being configured to perform analog measurements of said voltages measured between the electrodes. 8. The measurement device according to claim 1, wherein the capacitance determination circuit is configured: i) to determine the first value of the capacitance of the variable capacitor from at least two voltages measured between the electrodes at respective instants during the charging phase of the variable capacitor, andii) to determine the second value of the capacitance of the variable capacitor from at least two voltages measured between the electrodes at two respective instants during the discharging phase of the variable capacitor. 9. The measurement device according to claim 1, wherein the electrodes are distant from each other, and wherein the electrodes are formed by cylinders having axes parallel to each other. 10. The measurement device according to claim 1, wherein the microcontroller further comprises a temperature sensor, and wherein the microcontroller is configured to apply a temperature correction factor on the measurement of the height of the liquid. 11. A measurement method, for measuring a height of liquid in a container, the liquid being an aqueous urea solution, wherein the measurement method comprises at least the steps of: providing a measurement device according to claim 1,generating, by means of the oscillator circuit, signals at a reference frequency when the electrodes are not connected to the microcontroller,connecting the electrodes to the microcontroller, one of the electrodes being connected to the ground,introducing the liquid in the container so as to immerse at least partially the electrodes in the liquid,generating, by means of the oscillator circuit, signals at a variable frequency dependent on the height of the liquid in the container when the electrodes are immersed in the liquid, the voltage oscillations at the variable frequency being induced in the oscillator circuit by the inverter logic gate formed by the programmable logic device,determining, by means of the frequency determination circuit, at least one first value of the variable frequency from the reference frequency and from the signals obtained from the programmable logic device,determining, by means of the capacitance determination circuit, a first value of the capacitance of the variable capacitor from voltages measured between the electrodes during a charging phase of the variable capacitor, anddetermining, by means of the capacitance determination circuit, a second value of the capacitance of the variable capacitor from voltages measured between the electrodes during a discharging phase of the variable capacitor. 12. The measurement method according to claim 11, further comprising the steps of: generating, by means of the microcontroller, a first measurement signal which is formed from the first and second values of the capacitance of the variable capacitor so that the first measurement signal is representative of the height of the liquid; andgenerating, by means of the microcontroller, a second measurement signal which is formed from the variable frequency so that the second measurement signal is representative of the height of the liquid;generating, by means of the microcontroller, a height signal which is formed: from the first measurement signal when the first measurement signal corresponds to a height of liquid which is larger than a predetermined height threshold; orfrom the second measurement signal when the first measurement signal corresponds to a height of liquid which is smaller than the predetermined height threshold. 13. The measurement method according to claim 11, further comprising the steps of: disconnecting the electrode initially connected to the ground,bringing the thus disconnected electrode to a positive potential, andgenerating again, by means of the oscillator circuit, signals at a variable frequency dependent on the height of the liquid in the container when the electrodes are immersed in the liquid, the voltage oscillations at the variable frequency being induced in the oscillator circuit by the inverter logic gate formed by the programmable logic device. 14. The measurement method according to claim 13, further comprising the steps of: determining, by means of the frequency determination circuit, at least one second value of the variable frequency from the reference frequency and from the signals derived from the programmable logic device, andcalculating an average value of the variable frequency from the first value of the variable frequency and from the second value of the variable frequency. 15. The measurement method according to claim 11, further comprising a step consisting in connecting each electrode to the ground. 16. The measurement method according to claim 11, wherein in the measurement device, the frequency determination circuit comprises: a counter configured to count the number of oscillations of the oscillator circuit for a predetermined duration, anda phase-locked loop configured to generate stable-frequency signals so as to define a time base, the microcontroller further comprises an analog-digital converter connected to the capacitance determination circuit, the analog-digital converter being configured to perform analog measurements of said voltages measured between the electrodes, andthe capacitance determination circuit is configured:i) to determine the first value of the capacitance of the variable capacitor from at least two voltages measured between the electrodes at respective instants during the charging phase of the variable capacitor, andii) to determine the second value of the capacitance of the variable capacitor from at least two voltages measured between the electrodes at two respective instants during the discharging phase of the variable capacitor,the measurement method further comprising the steps of:resetting the time base defined by the phase-locked loop,connecting an electrode to the analog-digital converter and connecting an electrode to the ground,determining, by means of the capacitance determination circuit, the first value of the capacitance of the variable capacitor from at least two voltages measured between the electrodes at two respective instants during the charging phase of the variable capacitor, the voltages being converted into digital values by the analog-digital converter,resetting the time base defined by the phase-locked loop, anddetermining, by means of the capacitance determination circuit, the second value of the capacitance of the variable capacitor from at least two voltages measured between the electrodes at respective instants during the discharging phase of the variable capacitor, said voltages being converted into digital values by the analog-digital converter. 17. The measurement method according to claim 16, wherein the measurement device further comprises an oscillator resistor and an oscillator capacitor, charging of the variable capacitor and discharging of the variable capacitor being carried out through the oscillator resistor, and wherein: during the charging phase of the variable capacitor, the oscillator resistor is brought to a positive potential, andduring the discharging phase of the variable capacitor, the oscillator resistor is connected to the ground.
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이 특허에 인용된 특허 (10)
Worthington Ralph T. (4733 Mt. St. Helens Ct. San Diego CA 92117), Capacitance liquid level sensing and touch control system.
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