Liquid concentration measuring device
First Claim
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1. A liquid concentration measuring device comprising:
- a detection electrode pair including a pair of electrodes facing each other;
a switching section connected to switch charging and discharging of the detection electrode pair;
an operation signal outputting section configured to produce operation signals of a predetermined frequency to control switching operation of the switching section at a predetermined period; and
a measured value outputting section configured to produce a voltage for charging the detection electrode pair through the switching section and to produce a detection voltage corresponding to a static electric capacity of the detection electrode pair as a measured value,wherein the operation signal outputting section is configured to produce alternately a first operation signal of a first frequency and a second operation signal of a second frequency different from the first frequency for operating the switching section during a first period and a second period, respectively, the first and the second period being determined such that the detection voltage is converged in each period;
wherein the measured value outputting section is configured to produce a first detection voltage and a second detection voltage when the switching section is operated at the first frequency in the first period and the second frequency in the second period, respectively; and
wherein the device further comprises a difference calculating section configured to produce a difference between the first detection voltage and the second detection voltage, which are produced when the frequency for operating the switching section is switched over between the first frequency and the second frequency, and the difference is produced as the measured value.
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Abstract
A liquid concentration measuring device has first and second switches, which are turned on and off at two frequencies. When the first switch is turned on and the second switch is turned off, a detection electrode pair is charged. When the first switch is turned off and the second switch is turned on, the positive side of the detection electrode pair is grounded so that the charged detection electrode pair discharges. The difference between the output voltages of an amplifier produced by charging and discharging the detection electrode pair at the two frequencies is used to determine an alcohol concentration in gasoline.
59 Citations
20 Claims
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1. A liquid concentration measuring device comprising:
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a detection electrode pair including a pair of electrodes facing each other; a switching section connected to switch charging and discharging of the detection electrode pair; an operation signal outputting section configured to produce operation signals of a predetermined frequency to control switching operation of the switching section at a predetermined period; and a measured value outputting section configured to produce a voltage for charging the detection electrode pair through the switching section and to produce a detection voltage corresponding to a static electric capacity of the detection electrode pair as a measured value, wherein the operation signal outputting section is configured to produce alternately a first operation signal of a first frequency and a second operation signal of a second frequency different from the first frequency for operating the switching section during a first period and a second period, respectively, the first and the second period being determined such that the detection voltage is converged in each period; wherein the measured value outputting section is configured to produce a first detection voltage and a second detection voltage when the switching section is operated at the first frequency in the first period and the second frequency in the second period, respectively; and wherein the device further comprises a difference calculating section configured to produce a difference between the first detection voltage and the second detection voltage, which are produced when the frequency for operating the switching section is switched over between the first frequency and the second frequency, and the difference is produced as the measured value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A liquid concentration measuring device comprising:
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a detection electrode pair including a pair of electrodes facing each other; a switching section connected to switch charging and discharging of the detection electrode pair; an operation signal outputting section configured to produce operation signals of a predetermined frequency to control switching operation of the switching section at a predetermined period; and a measured value outputting section configured to produce a voltage for charging the detection electrode pair through the switching section and to produce a detection voltage corresponding to a static electric capacity of the detection electrode pair as a measured value, wherein the operation signal outputting section is configured to produce alternately a first operation signal of a first frequency and a second operation signal of a second frequency different from the first frequency for operating the switching section during a first period and a second period, respectively, the second period being determined such that the detection voltage is converged in each period, wherein the measured value outputting section is configured to produce a first detection voltage and a second detection voltage when the switching section is operated at the first frequency in the first period and the second frequency in the second period, respectively; and wherein the device further comprises a calculating section configured to subtract the second detection voltage from the first detection voltage, which are produced when the frequency for operating the switched section is switched over between the first frequency and the second frequency, and a result of the subtraction is produced as the measured value.
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19. A liquid concentration measuring device comprising:
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a detection electrode pair including a pair of electrodes facing each other; an operation signal outputting section configured to produce a first operation signal in a pulse form of a first predetermined frequency and a second operation signal in a pulse form of a second predetermined frequency, the first predetermined frequency and the second predetermined frequency being different from each other; a switching section connected to the detection electrode pair to repeat charging and discharging of the detection electrode pair in response to a frequency of an operation signal produced by the operation signal outputting section, the switching section controlling the repeating and discharging by the first operation signal during a first period and the second operation signal during a second period alternately; and a measured value outputting section configured to produce a voltage for charging the detection electrode pair through the switching section and to produce a detection voltage corresponding to a static electric capacity of the detection electrode pair as a measured value, wherein the measured value outputting section is configured to produce a first detection voltage and a second detection voltage when the switching section is operated by the first operation signal and the second operation signal, respectively, and wherein the first period and the second period have time lengths, in which the first detection voltage and the second detection voltage are converged, respectively. - View Dependent Claims (20)
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Specification