Electricity: measuring and testing – Electrolyte properties – Using a battery testing device
Reexamination Certificate
2001-10-12
2002-10-15
Tso, Edward H. (Department: 2838)
Electricity: measuring and testing
Electrolyte properties
Using a battery testing device
Reexamination Certificate
active
06466026
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to electronically testing electrochemical cells and batteries. More specifically, it relates to method and apparatus for passing a programmably-determined periodic current through an electrochemical cell or battery to facilitate measurement of at least one component of its ac immittance (i.e., either ac impedance or ac admittance) at a specific frequency.
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. As such, their complex impedance/admittance is of both theoretical and practical interest. Recent U.S. patents issued to Champlin disclose methods and apparatus for. accurately measuring components of complex impedance (U.S. Pat. No. 6,002,238; U.S. Pat. No. 6,172,483) and complex admittance (U.S. Pat. No. 6,262,563) of cells/batteries at a specific frequency. A common feature of these inventions is that they all employ a periodic current—a current that need not be sinusoidal—to excite the cell/battery undergoing test.
Consider FIG.
1
. This figure depicts immittance-measuring apparatus disclosed in the prior art U.S. Pat. Nos. 6,002,238, 6,172,483, and 6,262,563 and shows details of current excitation circuitry disclosed therein. Current exciter
5
comprises a series combination of load resistor
25
and controlled switch (i.e. transistor)
30
connected to cell/battery
10
through current-carrying contacts A and B. A symmetrical timing signal
70
outputted by microprocessor/controller
20
turns controlled switch
30
“on” and “off” at the measurement frequency f. Accordingly, a square-wave current −i(t) at frequency f flows through: the cell/battery in the discharging direction as shown. (By convention, cell/battery current is assumed positive in the charging direction.) The peak to peak amplitude and average value of this generated square wave are |V
B
/R
L
| amps and −(V
B
/2R
L
) amps, respectively, where V
B
is the cell/battery voltage and R
L
is the load resistance. Current exciter
5
also outputs a signal voltage R
L
i(t)
35
for processing by the remaining measurement circuitry. The function and operation of all other elements depicted in
FIG. 1
have been fully explained in the referenced Champlin patents and will not be repeated herein.
One problem with this prior art current exciter is that the excitation current is inevitably a discharging current. There is, however, ample theoretical basis for believing that immittance measured with zero net current, or even with a net charging current, is equally important. Furthermore, the amplitude: of the generated square-wave in this prior art circuit is fixed at a value determined by the cell/battery voltage and the resistance of the load resistor. This fixed amplitude may not be large enough to develop sufficient ac voltage across low-impedance cells/batteries for accurate measurement. Or, it may be so large that high-impedance cells/batteries are driven into nonlinearity. All of these objections to the method disclosed in the prior art are surmounted by the inventions disclosed herein.
The programmable current exciter disclosed herein bears some resemblance to the “flying bridge” circuit disclosed in
FIG. 5
of PCT Application WO 99/18448. However, a careful comparison of the two inventions reveals very significant differences in the objectives, implementation and results achieved.
SUMMARY OF THE INVENTION
The present invention comprises an exciter of periodic square-wave current for use in measuring one or more components of complex ac impedance or admittance of a cell or battery. A microcontroller/processor outputs two digital words that define upper and lower current levels. These words are latched and converted to analog voltages by D/A converter circuitry. A timing signal at the measurement frequency, also outputted by the microprocessor/controller, controls a multiplexer arranged to select either analog voltage. The multiplexer output thus toggles between the two programmed analog voltages at the measurement frequency.
By virtue of negative feedback, the toggled multiplexer output voltage equals the voltage developed across a resistance in series with the cell/battery. Two complementary transistors and a dc voltage source are arranged such that a positive multiplexer output directs a programmed current through this resistance in the “discharge” direction, and a negative multiplexer output directs a programmed current through it in the “charge” direction. Accordingly, the current through the cell/battery is a symmetrical square wave having frequency, amplitude, average value, and average flow direction completely under program control.
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: 3936774 (1976-02-01), Perlmutter
patent: 3946299 (1976-03-01), Christianson 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: 3984768 (1976-10-01), Staples
patent: 3989544 (1976-11-01), Santo
patent: 4008619 (1977-02-01), Alcaide et al.
patent: 4024953 (1977-05-01), Nailor, III
patent: 4047091 (1977-09-01), Hutchines et al.
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: 4297639 (1981-10-01), Branham
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: 4351405 (1982-09-01), Fields 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: 4667143 (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), Liebermann
patent: 4743855 (1988-05-01), Randin et al.
patent: 4745349 (1988-05-01), Palanisamy et al.
patent: 4816768 (1989-03-01), Champlin
patent: 4820966 (1989-04-01), Fridman
patent: 4825170 (1989-04-01), Champlin
patent: 4847547 (1989-07-01), Eng, Jr. et al.
patent: 4849700 (1989-07-01), Morioka et al.
patent: 4876495 (1989-10-01), Palanisamy et al.
patent: 4881038 (1989-11-01), Champlin
patent: 4912416 (1990-03-01), C
Tso Edward H.
Westman Champlin & Kelly
LandOfFree
Programmable current exciter for measuring AC immittance of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Programmable current exciter for measuring AC immittance of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Programmable current exciter for measuring AC immittance of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2968721