US Patent: 5,677,632
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| Automatic Calibration for a Capacitive Pickup Circuit
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Patentee:
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| Michael B. Meeker (exact or similar names) - Kenosha, WI |
| Manufacturer: |
| Not known to have been produced |
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Patent Dates:
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| Applied: |
Feb. 27, 1995 |
| Granted: |
Oct. 14, 1997 |
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Stan Schulz
Snap-On Tools Company History
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Description: |
| Emrich & Dithmar - patent attorneys
Abstract
A calibrating pickup circuit detects, using primary and secondary pickups, the primary and secondary voltages of an ignition coil of known turns ratio. The pickup circuit includes a programmable gain amplifier, responsive to the detected secondary voltage waveform signal and to a gain control feedback signal for generating an amplified secondary voltage waveform signal wherein the feedback signal has an initial predetermined value in calibration mode and has a calibration value in signal monitor mode. A waveform multiplexing circuit is selectively operable in calibration mode to alternately sample the primary and the amplified secondary voltage waveform signals over a predetermined period to generate a single interlaced waveform signal. Waveform comparison is then performed by evaluating the single interlaced waveform signal and a secondary-to-primary ratio calculated representative of the signal strength difference between analogous portions of the primary and the amplified secondary voltage waveform signals A calibration value is then determined on the basis of the secondary-to-primary ratio and the known turns ratio of the ignition coil.
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