Method for liquid level detection

• US 5,613,399 A
• Filed: 04/17/1995
• Issued: 03/25/1997
• Est. Priority Date: 10/27/1993
• Status: Expired due to Term

• Current Assignee: Hannan - Nickolin Intellectual Properties, LLC
• Original Assignee: L3 Fuzing & Ordnance Systems, Inc. (L3Harris Technologies, Inc.)
• Inventors: Nickolin, Thomas M., Hannan, Alan R.
• Primary Examiner(s): GUTIERREZ, DIEGO F
• Application Number:
  US08/422,859
• Time in Patent Office: 708 Days
• Field of Search: 73/304 C, 73/292, 364/509
• US Class Current: 73/304.00C
• CPC Class Codes: G01F 23/265 for discrete levels
• CPC Class Codes: G01F 23/266 measuring circuits therefor
• CPC Class Codes: G01F 23/268 mounting arrangements of probes

Abstract

A digital liquid level sensing apparatus and method for detecting variations in the dielectric of a substance being sensed. The apparatus includes a capacitive element array which is disposed in a fluid to be measured and which includes a plurality of individual (i.e., segmented) input plates positioned along an axis of measurement of the fluid to be detected. The array also includes a common output plate having a length sufficient to span the entire accumulated length of the input plates. A controller sequentially applies DC excitation pulses to the input plates which cause a series of output currents to be coupled onto the output plate. The output currents are input to a current-to-voltage amplifier which generates a series of corresponding analog output voltages. The analog output voltages are then input to a peak voltage detector circuit to generate a series of peak voltage signals representative of the magnitudes of the analog output voltages. The controller converts each of the peak voltage signals into a corresponding digital value and stores each of the digital values in an on-board memory. The controller then sequentially compares each of the values against at least one predetermined reference value indicative of an output produced by an input plate disposed in air until a predetermined difference is detected between the reference value and any one of the stored digital values. This indicates a predetermined difference in the dielectric, thus indicating that a corresponding input plate is at least partially submerged in fluid.

Claims

1. A method for detecting a level of a fluid within a fluid reservoir, the method comprising:

disposing a probe in said reservoir, wherein said probe includes a plurality of individually excitable input plates and a common output plate, said probe being positioned in said reservoir such that at least a portion of said output plate and a sub-plurality of said plurality of input plates are disposed in said fluid;

determining an electrical reference signal representative of the electrical output signal which would be generated by one of said input plates when said one input plate is disposed completely above an upper level of said fluid;

applying an electrical signal to each one of said input plates, sequentially, one at a time, to electrically excite each of said input plates and to generate a series of electrical signals;

sequentially reading said output signals generated on said output plate as said input plates are electrically excited;

comparing said output signals sequentially with said electrical reference signal;

determining from said comparison which ones of said input plates are not disposed completely above said upper level of said fluid disposed in said fluid; and

extrapolating from said input plates that are not disposed above said upper level of said fluid what a level of said fluid is within said reservoir relative to a known full level.

2. The method of claim 1, further comprising the step of determining what percentage of each of said input plates is submerged in said fluid;

and

from said percentage coverage of each of said input plates, further extrapolating a precise level of said fluid within said fluid reservoir.

3. A method for detecting a level of a fluid within a fluid reservoir, method comprising:

disposing a probe in said reservoir, wherein said probe includes a plurality of individually excitable input plates and a common output plate, said probe being positioned in said reservoir such that a least a portion of said output plate and a sub-plurality of said input plates are disposed in said fluid;

providing an electrical reference signal being indicative of an input plate being disposed above an upper level of said fluid;

applying an electrical signal to each one of said input plates, sequentially, one at a time, to electrically excite each said input plate and to generate a series of electrical signals;

sequentially reading said output signals generated on said output plate as said input plates are electrically excited;

comparing said output signals sequentially with said electrical reference signal to determine which one or ones of said input plates are not disposed completely above said upper level of said fluid; and

extrapolating, from said comparison of said output signals and said electrical reference signal, without measuring the capacitance at any one of said input plates, what an approximate level of said fluid is within said reservoir to a known full level.