Electricity: measuring and testing – Electrolyte properties – Using a battery testing device
Reexamination Certificate
2001-06-11
2002-07-09
Toatley, Gregory (Department: 2888)
Electricity: measuring and testing
Electrolyte properties
Using a battery testing device
Reexamination Certificate
active
06417669
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to measuring an ac dynamic parameter (e.g., impedance, admittance, resistance, reactance, conductance, susceptance) of an electrochemical cell/battery or other electrical element under conditions of possible interference from potential sources such as ac magnetic fields and/or ac currents at the powerline frequency and its harmonics. More specifically, it relates to evaluating a signal component at a known frequency under conditions of possible hum, noise, or other spurious interference at other known frequencies.
Electrochemical cells and batteries, such as primary cells/batteries, secondary (i.e., storage) cells/batteries, and fuel cells/batteries are important sources of electrical energy. Ac dynamic parameter measurements have proven very useful for cell/battery diagnostics and testing. However because of their extremely small impedances, most cells/batteries require large amplification of the time-varying voltage developed across their terminals during measurement. Accordingly, measurements are highly susceptible to corruption by ac hum at the powerline frequency and its harmonics. In a typical industrial setting, ac hum can be coupled into measurement circuitry by ac magnetic fields of nearby motors and transformers. In the case of on-line measurements, ac currents from poorly filtered rectifiers, chargers, and power inverters can introduce ac hum into the measurements.
The conventional approach to suppressing ac hum is to place appropriate notch filter circuitry in the high-gain amplifier chain. Such circuitry has been described in many literature references including Burr-Brown Application Bulletin AB-071, “Design a 60 hz Notch Filter with the UAF42”, published by Texas Instruments Incorporated; Linear Brief 5, “High Q Notch Filter”, published by National Semiconductor Corporation; and data sheets for the “LMF90 4
th
-Order Elliptic Notch Filter”, published by National Semiconductor Corporation.
There are, however, several disadvantages to the notch filter approach to hum suppression. First of all, maintaining the notch at exactly the powerline frequency generally requires precision components and/or trimming adjustments. Secondly, a single notch filter suppresses signals at only one frequency. Ac hum however, usually comprises a multitude of harmonically related frequencies. Third, although 60 Hz is the standard powerline frequency in most of the United States, 50 Hz is standard throughout much of the rest of the world, and 400 Hz is standard in many military and aircraft installations. Accordingly, apparatus manufactured for each of these markets would require different notch filters. Fourth, unless the notch is extremely narrow, the filter itself can affect measurements. Finally, a hardware notch filter can add substantially to manufacturing cost.
SUMMARY OF THE INVENTION
Methods and apparatus for measuring complex impedance and admittance of electrochemical cells/batteries and general electrical elements have recently been disclosed by Champlin in U.S. Pat. Nos. 6,002,238, 6,172,483, U.S. patent application Ser. No. 09/503,015 filed Feb. 12, 2000, now U.S. Pat. No. 6,262,563 and U.S. patent application Ser. No. 09/710,031 filed Nov. 10, 2000, now U.S. Pat. No. 6,294,876. Among the innovations disclosed therein is a novel technique for evaluating time-averaged fundamental-frequency Fourier coefficients of signals at a known measurement frequency. This new technique utilizes synchronous sampling, A/D conversion, summing or averaging over an integer number of periods, and computing the desired Fourier coefficients from the resulting sums or averages.
An inherent property of the disclosed evaluation procedure is the existence of perfect nulls in the frequency response of the Fourier coefficients. These perfect nulls occur at an infinite number of evenly spaced frequencies whose precise values are determined by both the fundamental measurement frequency f
1
and the number N of periods over which the digital samples are acquired. For a given measurement frequency f
1
, the nulls can be placed at exactly the powerline frequency and its harmonics by appropriately choosing N. Particular values of N can even be found that place nulls at fundamental and harmonic frequencies of 50 Hz, 60 Hz, and 400 Hz simultaneously. Thus, a single measuring apparatus can be implemented that suppresses all components of powerline hum in substantially all U.S., foreign, and military/aircraft markets. Since the perfect nulls are, themselves, an intrinsic property of the Fourier evaluation procedure, they introduce no errors into the measurements. Additionally, the disclosed solution to the hum problem uses only software. It can therefore be applied to appropriately designed measuring apparatus essentially “free of charge”. A specific application—that of suppressing powerline hum in ac measurements on electrochemical cells/batteries—is employed herein to demonstrate this novel technique. The technique, however, is more general than this particular application and can be applied to ac measurements on any electrical element. The disclosed method and apparatus are, in fact, universally applicable whenever one desires to evaluate a signal component at a known frequency in the presence of possible hum, noise, or other spurious interference at other known frequencies.
REFERENCES:
patent: 2514745 (1950-07-01), Dalzell
patent: 3356936 (1967-12-01), Smith
patent: 3562634 (1971-02-01), Latner
patent: 3593099 (1971-07-01), Scholl
patent: 3607673 (1971-09-01), Seyl
patent: 3676770 (1972-07-01), Sharaf et al.
patent: 3729989 (1973-05-01), Little
patent: 3753094 (1973-08-01), Furuishi et al.
patent: 3808522 (1974-04-01), Sharaf
patent: 3811089 (1974-05-01), Strezelewicz
patent: 3873911 (1975-03-01), Champlin
patent: 3876931 (1975-04-01), Godshalk
patent: 3886443 (1975-05-01), Miyakawa et al.
patent: 3889248 (1975-06-01), Ritter
patent: 3906329 (1975-09-01), Bader
patent: 3909708 (1975-09-01), Champlin
patent: 3936744 (1976-02-01), Perlmutter
patent: 3946299 (1976-03-01), Christanson et al.
patent: 3947757 (1976-03-01), Grube et al.
patent: 3969667 (1976-07-01), McWilliams
patent: 3979664 (1976-09-01), Harris
patent: 3984762 (1976-10-01), Dowgiallo, Jr.
patent: 3989544 (1976-11-01), Santo
patent: 4008619 (1977-02-01), Alcaide et al.
patent: 4024953 (1977-05-01), Nailor, III
patent: 4053824 (1977-10-01), Dupuis et al.
patent: 4070624 (1978-01-01), Taylor
patent: 4086531 (1978-04-01), Bernier
patent: 4112351 (1978-09-01), Back et al.
patent: 4114083 (1978-09-01), Benham et al.
patent: 4126874 (1978-11-01), Suzuki et al.
patent: 4178546 (1979-12-01), Hulls et al.
patent: 4193025 (1980-03-01), Frailing et al.
patent: 4207611 (1980-06-01), Gordon
patent: 4217645 (1980-08-01), Barry et al.
patent: 4315204 (1982-02-01), Sievers et al.
patent: 4316185 (1982-02-01), Watrous et al.
patent: 4322685 (1982-03-01), Frailing et al.
patent: 4363407 (1982-12-01), Barkler et al.
patent: 4369407 (1983-01-01), Korbell
patent: 4379989 (1983-04-01), Kurz et al.
patent: 4379990 (1983-04-01), Sievers et al.
patent: 4390828 (1983-06-01), Converse et al.
patent: 4392101 (1983-07-01), Saar et al.
patent: 4396880 (1983-08-01), Windebank
patent: 4408157 (1983-10-01), Beaubien
patent: 4412169 (1983-10-01), Dell'Orto
patent: 4423378 (1983-12-01), Marino et al.
patent: 4423379 (1983-12-01), Jacobs et al.
patent: 4424491 (1984-01-01), Bobbett et al.
patent: 4459548 (1984-07-01), Lentz et al.
patent: 4514694 (1985-04-01), Finger
patent: 4520353 (1985-05-01), McAuliffe
patent: 4633418 (1986-12-01), Bishop
patent: 4659977 (1987-04-01), Kissel et al.
patent: 4663580 (1987-05-01), Wortman
patent: 4667146 (1987-05-01), Cooper et al.
patent: 4667279 (1987-05-01), Maier
patent: 4678998 (1987-07-01), Muramatsu
patent: 4679000 (1987-07-01), Clark
patent: 4680528 (1987-07-01), Mikami et al.
patent: 4697134 (1987-09-01), Burkum et al.
patent: 4707795 (1987-11-01), Alber et al.
patent: 4709202 (1987-11-01), Koenck et al.
patent: 4710861 (1987-12-01), Kanner
patent: 4719428 (1988-01-01), Li
Toatley Gregory
Westman Champlin & Kelly P.A.
LandOfFree
Suppressing interference in AC measurements of cells,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Suppressing interference in AC measurements of cells,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Suppressing interference in AC measurements of cells,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2841141