Measuring and testing – Liquid level or depth gauge – Immersible electrode type
Reexamination Certificate
1997-12-29
2001-06-26
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid level or depth gauge
Immersible electrode type
C324S690000, C361S284000
Reexamination Certificate
active
06250152
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a sensor arrangement for determining the condition and level of a liquid in a container.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,646,070 discloses an arrangement for determining the aging condition of lubricating oil in internal combustion engines, the dielectric constant of the oil is determined by means of a capacitive sensor, whose electrode measuring chamber is filled entirely with the lubricating oil, and a statement regarding the aging condition of the oil is derived therefrom.
U.S. Pat. No. 4,629,334 discloses a sensor arrangement wherein, by measuring the resistance of an oil disposed between the electrodes of an electric sensor, the aging condition of the oil is inferred. By way of simultaneous measurement of the temperature with an integrated temperature sensor, it is possible to compensate for temperature dependencies of the oil resistance. The electrical evaluation device additionally provides a detector which triggers an alarm signal if conductive oil between the electrodes of the sensor is missing.
Electrical sensors are also used for the level measurement of liquids in containers, for example, U.S. Pat. No. 4,745,893 teaches that the capacitance of a partially liquid-filled capacitor can be evaluated as a level measure.
Further examples of level sensors are disclosed in U.S. Pat. No. 4,924,702 and EP-A 0 378 304. U.S. Pat. No. 4,924,702 describes a level sensor having a measuring capacitor and a reference capacitor. The ratio of the measured values of the measuring capacitor and the reference capacitor is used for determining the level of a liquid in the measuring capacitor. The reference capacitor serves to obtain a level measurement independently of the conductance and the dielectric constant. Further, EP-A 0 378 304 proposes a sensor for the level measurement having a measuring capacitance and a reference capacitance. The level signal is composed of the measuring capacitance and the reference capacitance and thus permits a more precise level determination.
SUMMARY OF THE INVENTION
It is the object of the present invention to propose an advantageous sensor arrangement for determining the condition and level of a liquid in a container.
The invention includes a sensor arrangement for determining the condition of a liquid in a container. The arrangement has a first sensor with electrodes forming a first measuring chamber filled with the liquid and has electrical devices for the measurement of the impedance of the first sensor and for the derivation of a condition signal. The arrangement further has a second sensor with electrodes forming a second measuring chamber and is provided as a level sensor having a measuring chamber partially filled with the liquid as a function of the level in the container. The electrical devices derive a level signal from the measurement of the impedance of the second sensor. The measured impedance of the first sensor is used for the calibration of the impedance measurement of the second sensor. The measuring chamber of the second sensor is in communication with the liquid in the container via the measuring chamber of the first sensor by way of an opening arranged at the foot of the first sensor.
Additionally, the sensor arrangement can include an auxiliary chamber that is in communication with the liquid in the container via the measuring chamber of the first sensor and is disposed above the measuring chamber of the first sensor. Further, the horizontal cross section of the auxiliary chamber is larger than that of the measuring chamber of the second sensor.
In addition, for the sensor arrangement, the first and second sensors are each comprised of coaxial cylindrical electrodes. The first and second sensors include a joint outer cylinder electrode and separate internal cylinder electrodes arranged axially inside the joint outer cylinder electrode. The internal cylinder electrodes with insulating elements are embodied as a structural unit that can be plugged into the outer electrode. Further, the sensor arrangement can be used as a lubricating oil sensor in an engine.
The invention provides an arrangement which can be executed in a compact manner and which, in a simple manner, permits a reliable measurement of quality and level of a liquid in a container. The arrangement can be implemented to be mechanically and electrically straightforward and robust and is therefore particularly suited for use in vehicle engines.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated in detail in the following by way of embodiments with reference to the figures.
FIG. 1
depicts a preferred embodiment of a sensor arrangement, and
FIG. 2
depicts an alternative embodiment.
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patent: 2949386 (1980-06-01), None
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patent: 3041914 (1982-06-01), None
patent: 0378304 (1990-07-01), None
patent: 110919 (1980-08-01), None
patent: 1538055 (1990-01-01), None
Klein Manfred
Knoll Anton
Land Klaus
Ott Harald
Thom Rudolf
Cygan Michael
Daimler-Chrysler AG
Kunitz Norman N.
Spencer George H.
Venable
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