Voltage controlled electronic filter
First Claim
1. An electronic filtering system comprising:
- an active filtering network having adjustable response characteristics;
means for varying the Q of the filtering network as a function of the magnitude of an applied DC voltage, andmeans for maintaining the gain of the filtering network constant as the Q is varied.
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Abstract
The response characteristics of an electronic filter are automatically adjusted as a function of the magnitude of an applied DC voltage to permit the same filter to be used for varying applications. Embodiments for varying the center frequency and Q of the filter are disclosed. The filter has particular utility in vibration monitoring systems wherein the center frequency may be selectively set at a value which is characteristic of the frequency of particular vibration signals of interest. In a disclosed vibration monitoring system incorporating the voltage controlled filter of this invention, which is particularly useful for monitoring vibration levels in gas turbine engines, the magnitude of the DC control voltage is varied as a function of gas turbine rotational velocity. In an alternate embodiment of the vibration monitoring system an adjustable feedback circuit is provided which may be set to reduce variations in phase shift as the center frequency of the filter is varied or alternatively to automatically track a particular center frequency.
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Citations
11 Claims
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1. An electronic filtering system comprising:
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an active filtering network having adjustable response characteristics; means for varying the Q of the filtering network as a function of the magnitude of an applied DC voltage, and means for maintaining the gain of the filtering network constant as the Q is varied.
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2. An electronic filtering system comprising:
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an active filtering network having adjustable response characteristics; means for varying the center frequency of the filtering network as a function of the magnitude of an applied DC voltage; wherein the filtering network comprises a cascade of two integrators which includes first and second operational amplifiers interconnected by a first resistor, and a third operational amplifier; and the center frequency varying means comprises a first two input analog multiplier having one input connected to the output of the third operational amplifier, the other input connected to a DC control voltage and an output connected to the input of the first operational amplifier through a second series resistor, and a second two input analog multiplier having one input connected to the output of the second operational amplifier, the other input connected to the DC control voltage and an output connected through a third series resistor to the input of the third operational amplifier. - View Dependent Claims (3, 4)
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5. A system for monitoring vibration levels in gas turbine engines comprising:
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transducer means for producing AC output signals having a frequency content and amplitude proportional to the velocity of measured vibration levels, bandpass filtering means having a center frequency which may be varied as a function of an applied DC voltage for receiving the signals output from the transducer means and outputting vibration signals within the filter pass band, and means for automatically controlling the center frequency of the bandpass filtering means as a function of the rotational velocity of the gas turbine engine. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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Specification