Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
1998-12-08
2001-08-21
Assouad, Patrick (Department: 2862)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
Reexamination Certificate
active
06278952
ABSTRACT:
CROSS REFERENCES
Revised in February 2001
Subject matter herein is, in part, related to U.S. Pat. No. 3,768,011 and application Ser. No. 08/579,395, both by William H. Swain, inventor.
FEDERAL SPONSORSHIP
None
BACKGROUND OF THE INVENTION
We make large and small sensitive non-contact ammeters, mostly clamp-on, called Swain Meter®, to measure DC and/or AC flowing in conductors from #22 wire to 60 inch diameter pipe.
Basic concepts are shown in U.S. Pat. No. 3,768,011: “Means for measuring magnitude and direction of a direct current or permanent magnet, including clip-on direct current sensing inductor”.
Improvements (MER Meter and MEC Meter) are described in U.S. patent application Ser. No. 08/579,395: “Error Correction by Selective Modulation”.
DC Amp Clips are described on the website of the William H. Swain Co: www.SwainMeter.com
Some time ago I received a call from Paris asking about permanent installation of a sensor clamp at the base of a 13 inch pipe on an oil producing platform in a lake in Africa. In effect I declined because of the possibility of unexplained readings at the output of the indicator on the surface. I did not know how to economically find out if the clamp was still working well, or was damaged to where it could not be trusted.
To answer this question, I have discovered, designed and built a machine called Rgage™ for estimating the reliability of a non-contact ammeter by measuring and comparing the merit of its parts with references. Rgage is also useful for improving the quality of new meters, measuring the quality of meters in calibration or service, preferably without seriously disturbing their normal function, and locating and appraising damage should it occur. Hence the name “Reliability Gage for non-contact ammeters”, or Rgage for short. The process for making an Rgage machine has been generalized to where it will be useful for ammeters other than Swain Meters.
I use the word reliable in the sense that the Swain Meter can be counted upon to do what is expected—provide an accurate measure of the electrical current flowing in the aperture of the sensor.
This definition of “reliable” is from webster. I am also aware of the science of Reliability assessment, partly in terms of component failure rates, etc. This is outside the scope of my invention. I here use the word “reliable” as I believe was intended by a customer when he said “I think the (newer) MER Meter is much more reliable”. He appreciated a dependable, accurate and user-friendly clamp-on ammeter.
Swain Meters have proven reliable—beyond my expectations—even when buried in earth or used subsea. The Rgage has been built for assurance that a specific ammeter is now reliable and is expected to stay that way.
This patent application teaches how to estimate reliability for future use, locate a fault, and assess the present best use of a faulty non-contact ammeter.
Rgage is also for a production quality control tool for a calibration lab or a repair facility. Typical 2 wire in—2 wire out construction facilitates installation and removal.
The Rgage process includes measuring specific merits which are indicative of the quality or value of parts or parameters. An example is the total sensor plus cable DC resistance &Sgr;r
s
. The measurement is preferably automated, with computer control and analysis of the “spreadsheet”.
Measurements are normalized and compared for inclusion in a “Rgage spreadsheet” or computer file equivalent. Results are combined, correlated, and processed with design and experience reference files of merit magnitudes representative of a clean or faulty ammeter so as to output estimated reliability, fault location, and assess present use.
SUMMARY OF THE INVENTION
The teaching of this invention is how to build a machine outputting an estimate of: reliability, location of a fault, and best present use of a non-contact ammeter.
The machine is called an Rgage.
To build an Rgage machine, you need:
a) means measuring merits of the ammeter apparatus. Examples are:
&rgr;
v
o
in
FIG. 3
, and
Z
s
in FIG.
6
.
Generally one specific merit measurement result is influenced by the quality or value of several parameters of an ammeter. For example, transfer resistance &rgr;
v
o
is changed by an air gap in the sensor core or by an increase in cable resistance.
b) Comparing and reference means so that in a gaged ammeter, a measured merit magnitude can be evaluated by comparing it with a file reference merit magnitude representative of an ammeter in a good “clean” state or a bad “fault” state. And each fault merit magnitude needs to be tagged as representative of a specific fault: “clean”, fault short, fault gap, etc. Example of comparison and processing coupled to an output means are shown table 1 for DC and table 4 for AC Swain Meter type non-contact ammeters. These Rgage spreadsheets can be used manually—a person calculates and compares and correlates to get the outputs. Or they can be used as models to specify measurement steps and calculations needed to be performed by a computer with appropriate software, i.e., programs.
The Rgage is useful for gaging the reliability of non-contact ammeter apparatus, especially of sensors which are buried and thus difficult to evaluate by standard methods. It is also useful as a production or laboratory quality control tool—judging ammeter excellence by a lot more than just present calibration accuracy.
Rgage merit measurement is designed to minimize disturbance to normal ammeter use in the field. All this while obtaining numbers representative of at least one and likely several parameters of ammeter sensor, cable, and indicator. This is done with economical and well known tools and implements. For example; the Fluke meters shown in
FIG. 1
do a good job at moderate cost, and they are readily available. Moreover, the ammeter can function normally. The use of the Rgage machine does not change the output of the ammeter apparatus. The Rgage in
FIG. 1
can be used continually, so it can also be rigged as an alarm to show ammeter malfunction automatically.
Each process for Rgage merit measurement is designed with ease of installation in mind. Most can be installed by separating the cable from the indicator and inserting the Rgage in between. This 2 wire in—2 wire out arrangement is a time saving convenience in quality control—calibration laboratory testing and servicing. This is also true for temporary field service should a buried sensor need calibration verification or damage assessment. Moreover, it is a labor saver when adding an Rgage to the internal part of an indicator. There is no need to position an Rgage outside of the indicator.
REFERENCES:
patent: 5920197 (1999-07-01), Price
patent: 6005383 (1999-12-01), Savary
patent: 6014301 (2000-01-01), Schweitzer
patent: 6043641 (2000-03-01), Singer
patent: 6058354 (2000-05-01), Adame
patent: 6121768 (2000-09-01), Taurand
patent: 6147484 (2000-11-01), Smith
Assouad Patrick
Duong Khoi Hung
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