Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Nonquantitative
Patent
1994-05-16
1996-04-02
Regan, Maura K.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Nonquantitative
324658, G01R 130
Patent
active
055044220
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and a device for testing the polarity of wet aluminum electrolytic capacitors having a metallic housing and at least two terminal connections of differing polarity.
BACKGROUND OF THE INVENTION
When the final electrical inspection test is made, it is often very difficult and sometimes even impossible to detect aluminum electrolytic capacitors that have been installed with reversed polarity. This can lead to field losses of electrolytic capacitors due to polarity reversal. To prevent this, optical and mechanical polarity indicators have already been used on electrolytic capacitors, in order to recognize polarity on the basis of the different terminal leads or merely to allow correct insertion into a printed circuit board. For this purpose, in known methods heretofore, one uses different terminal leads that are distinguished by differences in crimping, bending, thickness, color, or the like. However, these optical and mechanical polarity indicators require additional manufacturing steps on the electrolytic capacitor, which not only can adversely affect the reliability of operation, but can also result in increased costs. While optical polarity indicators are often unreliable, and can often hardly be detected after being soldered into a printed-circuit board, the mechanical polarity indicators still require costly additional measures on the printed-circuit boards, such as differently sized bore holes or differently shaped openings, which are complicated and expensive to introduce.
SUMMARY OF THE INVENTION
The advantage of the method and apparatus of the present invention is that the polarity of all electrolytic capacitors can be detected independently of their type of construction and of the nature of the connections, thus, for example, both for radial as well as axial electrolytic capacitors, it merely being necessary for these electrolytic capacitors to have a metal housing. Thus, the polarity of nearly all commercially available electrolytic capacitors can be detected in accordance with the invention. For this reason, there is no need for specially designed electrolytic capacitors, nor for any variations in layout on the printed-circuit boards; this leads to a reduction in costs and manufacturing steps. The test can be performed on the individual component, as well as on the finished circuit, i.e., a final inspection test can also be made. Resistors, capacitors, diodes, transistors, and ICs situated parallel to the electrolytic capacitor to be tested in the circuit do not adversely affect the result, provided that the impedance that is parallel to the electrolytic capacitor lies under 10 ohms (given a measuring frequency of f=50 Hz). Due to the fact that small measuring voltages can be used, other components connected to the electrolytic capacitor are not damaged or destroyed. A device for detecting polarity can be realized simply and cost-effectively, it being possible to have very short measuring times of about 60 ms.
The measuring resistors are expediently connected to testing lines, which are capable of being joined to the pole terminals of the capacitor and consist of a cathode line and of an anode line, a corresponding display signal being able to be generated by the display means when the testing lines are correctly connected. As a result, a quick and simple testing is rendered possible, the appropriate allocation to the pole terminals of the capacitor being able to be established through identification of the testing lines.
The measuring principle is advantageously based on the fact that the evaluation circuit of the present invention has means for comparing the amplitude and/or the phase relation of the voltages at the two measuring resistors, the measuring resistor connected to the cathode terminal (negative terminal) of the capacitor, given measuring resistances of the same magnitude, having a higher and/or lagging voltage compared to the anode voltage (or the voltage, that drops across an appropriately connected measuring re
REFERENCES:
patent: 4447785 (1984-05-01), Wright
patent: 4745359 (1988-05-01), Leitz
patent: 4748401 (1988-05-01), Aldinger
patent: 4779040 (1988-10-01), Aldinger
patent: 5343135 (1994-08-01), Mathieson
IBM Technical Disclosure Bulletin vol. 26 No. 2 Jul. 1983 Reverse Capacitor Tester Roop et al.
Bundschuh Goetz
Sterzl Axel
Regan Maura K.
Robert & Bosch GmbH
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