Liquid level sensor and electrode assembly therefor
First Claim
1. Apparatus for detecting the level of fluid in a non-conducting container and comprising:
- a. detector means mountable against the exterior surface of said container and having three spaced capacitance plate members, namely an upper member, a lower member and a middle member between said upper and lower members, the capacity between said upper and middle members being C1, the capacity between said lower and middle members being C2, and the value of C1 being greater than that of C2 when said detector means is located in air and also when said detector means is mounted on said container with the fluid level in said container above or below said detector means,b. circuit means including a bias capacitance of capacity C3 detachably connected between said lower and middle members, the value of C3 being such that when said detector means is located in air or on said container with the fluid level in said container below said upper member, the value of C1 is less than the combined values of C2 and C3, and when said detector means is on said container with the fluid level in said container above said upper member, C1 is greater than the combined values of C2 and C3,c. said circuit means including means for comparing the value of C1 with the combined values of C2 and C3 and operative to produce an alarm signal when the value of C1 is less than the combined values of C2 and C3.
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Accused Products
Abstract
A system for detecting the fluid level in an intravenous bottle wherein a disposable electrode assembly, consisting of a piece of tape having upper, middle and lower electrode strips, is adhered to the bottle and connected to sensing equipment. The upper strip is longer than the middle strip and the middle strip is longer than the lower strip, so that the capacity between the upper and middle strips (C1) is normally greater than that between the middle and lower strips (C2). The sensing equipment includes a bias capacity (C3) connected between the middle and lower strips so that C1 is less than C2 plus C3 except when the tape is on a bottle with the fluid level in the bottle above the top strip. Pulses having a gradually sloped leading edge and a steep trailing edge are fed to the centre strip. The received pulses at the top and bottom strips are differentiated and fed to the inputs of a differential amplifier which produces an output which changes in polarity when the fluid drops below the upper electrode strip. A delay circuit generates an alarm signal after the changed polarity output signal has persisted for a predetermined interval. If the tape falls off the bottle or becomes disconnected from the sensing equipment, the alarm signal will be produced.
61 Citations
15 Claims
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1. Apparatus for detecting the level of fluid in a non-conducting container and comprising:
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a. detector means mountable against the exterior surface of said container and having three spaced capacitance plate members, namely an upper member, a lower member and a middle member between said upper and lower members, the capacity between said upper and middle members being C1, the capacity between said lower and middle members being C2, and the value of C1 being greater than that of C2 when said detector means is located in air and also when said detector means is mounted on said container with the fluid level in said container above or below said detector means, b. circuit means including a bias capacitance of capacity C3 detachably connected between said lower and middle members, the value of C3 being such that when said detector means is located in air or on said container with the fluid level in said container below said upper member, the value of C1 is less than the combined values of C2 and C3, and when said detector means is on said container with the fluid level in said container above said upper member, C1 is greater than the combined values of C2 and C3, c. said circuit means including means for comparing the value of C1 with the combined values of C2 and C3 and operative to produce an alarm signal when the value of C1 is less than the combined values of C2 and C3. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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- 9. A disposable electrode assembly for use with apparatus for detecting the level of fluid in a non-conducting container and comprising a piece of adhesive tape, three flexible electrode strips adhered to said tape, said strips being an upper strip, a lower strip, and a middle strip located between said upper and lower strips, the capacity between said upper and middle strips being greater than that between said middle and lower strips when said assembly is located in air or is adhered to said container with the fluid level in said container above or below said assembly, and terminal means connected to each strip for detachably connecting a lead to each electrode strip.
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12. A disposable electrode assembly for use with apparatus for detecting the level of fluid in a non-conducting container for intravenous fluid, said assembly comprising:
- a flexible backing member, three flexible electrode strips mounted on said backing member and spaced apart from each other, said strips being an upper strip, a lower strip, and a middle strip located between said upper and lower strips, said assembly thus having a first capacitance between said upper and middle strips and a second capacitance between said middle and lower strips, each said strip including means adapted to be detachably connected to a lead, said assembly having an adhesive thereon so that said assembly can be adhered to the outside surface of said container with said electrode strips in close proximity to said outside surface, and so that said assembly may be removed from said container after use.
- View Dependent Claims (13, 14)
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15. Apparatus for detecting the level of fluid in a non-conducting intravenous container and comprising:
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1. a disposable electrode assembly comprising;
a flexible backing member, three flexible electrode strips mounted on said backing member and spaced apart from each other, said strips being an upper strip, a lower strip, and a middle strip located between said upper and lower strips, said assembly thus having a first capacitance between said upper and middle strips and a second capacitance between said middle and lower strips, each said strip including connection means adapted to be detachably connected to a lead, said assembly having an adhesive thereon and being removably adhered to the outside surface of said container with said electrode strips in close proximity to said outside surface, and so that said assembly may be removed from said container after use,2. circuit means, and means detachably connected to said connection means and connecting said electrode assembly to said circuit means, 3. said circuit means including means for comparing said first and second capacitances and for producing an alarm signal consequent upon a selected change in the relative values of said capacitances when the fluid level in said container falls to a selected level below the top of said upper strip.
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Specification