Liquid level detection system
First Claim
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1. A system for detecting the presence and absence of an electrically-conductive liquid at a particular level in a vessel comprising:
- (a) first and second metallic probe members for mounting at a fixed location within the interior of a vessel containing electrically-conductive liquid;
(b) first and second capacitor means connected to the first and second probe members, respectively;
(c) first switch means to selectively couple the first capacitor means to ground, and second switch means to concomitantly couple a constant voltage source to the second capacitor means;
(d) comparator means connected to said second capacitor means to sense the magnitude of the electrical charge thereon at predetermined times following coupling of the second capacitor means to the voltage source, the sensed charge magnitude being indicative of the presence of electrically-conductive liquid surrounding the second probe member; and
(e) indicator means coupled to the comparator means and responsive thereto to indicate the presence of electrically-conductive liquid at the level in the vessel at which the second probe member is mounted.
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Abstract
A detector system for sensing the presence, or absence, of electrically-conductive liquid in contact with two probe members. The system includes switchable voltage sources to selectively establish a potential across capacitors connected to the probe members, and detection systems for sensing the magnitudes of charges on the capacitors. The magnitudes of the sampled charge at given intervals is indicative of the presence, or absence, of ionic liquid in contact with the probe members.
49 Citations
21 Claims
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1. A system for detecting the presence and absence of an electrically-conductive liquid at a particular level in a vessel comprising:
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(a) first and second metallic probe members for mounting at a fixed location within the interior of a vessel containing electrically-conductive liquid; (b) first and second capacitor means connected to the first and second probe members, respectively; (c) first switch means to selectively couple the first capacitor means to ground, and second switch means to concomitantly couple a constant voltage source to the second capacitor means; (d) comparator means connected to said second capacitor means to sense the magnitude of the electrical charge thereon at predetermined times following coupling of the second capacitor means to the voltage source, the sensed charge magnitude being indicative of the presence of electrically-conductive liquid surrounding the second probe member; and (e) indicator means coupled to the comparator means and responsive thereto to indicate the presence of electrically-conductive liquid at the level in the vessel at which the second probe member is mounted. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for detecting the presence or absence of an electrically-conductive liquid at a particular level within a vessel comprising the steps of:
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(a) mounting first and second metallic probe members at a fixed location within a vessel for containing electrically-conductive liquid; (b) connecting first and second capacitor means to the first and second probe members, respectively; (c) at a first predetermined time, connecting the second probe member to a constant voltage source, connecting the first probe member to ground, and providing diode means between the first and second capacitor means so that current can only flow through the diode from the first capacitor means to the second capacitor means; (d) comparing the magnitude of electrical charge on the second capacitor means with a first constant value and, thereby, discriminating between the presence or absence of ionic liquid surrounding the second probe member. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A method for detecting the presence or absence of ionic liquid surrounding first and second adjacent metallic probe members comprising the steps of:
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(a) connecting first and second capacitor means to the first and second probe members respectively, (b) connecting diode means between the first and second capacitor means so that current can only flow through the diode from the first capacitor means to the second capacitor means; in a first state, coupling the first capacitor means to a constant voltage source while concommitantly coupling the second capacitor means to ground, and determining whether the voltage at the first capacitor means equals the expected voltage drop across the diode means; in a second state, subsequently coupling both the first and second capacitor means to ground, so that when the first probe means is surrounded by ionic liquids there is no net charge electrochemically transferred to the first probe member during the first and second states taken together; in a third state, coupling the second probe means to a constant voltage source and determining, at a predetermined time, whether the voltage at the second capacitor means exceeds a first constant value, thereby discriminating between a condition where ionic liquid surrounds the second probe means and the condition where ionic liquid does not surround the second probe means; and in a fourth state, coupling both the first and second capacitor means to ground so that, when the second probe means is surrounded by ionic liquid, there is no net charge electrochemically transferred to the second probe member during the third and fourth states taken together. - View Dependent Claims (20, 21)
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Specification