| 摘要 |
An automatic tracking filter for use in conjunction with fluid flowmeters automatically locks onto the largest signal in a given frequency spectrum. The filter comprises a narrow band-pass filter having input and output filter circuits (e.g., a low-pass and a high-pass filter) connected in series. The output of the input filter circuit is combined in a control circuit with the input signal to generate an error signal which is used to tune each of the filter circuits to the input signal. In one embodiment disclosed the filter sections are two-pole active R-C filters in which a field-effect transistor is used as a voltage variable resistor.
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