High speed accurate low frequency counter
First Claim
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1. Apparatus for determining the frequency of an input signal by measuring an integral number of cycles of said input signals over a flexible measurement interval comprising:
- (a) input means, including first generating means, for receiving said input signal and for generating a series of trigger pulses wherein each trigger pulse is representative of the start of a cycle of said input signal;
(b) clock means for providing an elapsed time signal representative of the duration of said flexible interval;
(c) logic means, connected to said input means, for providing a cycle count signal representative of the number of integral cycles of said input signal occurring during said flexible interval, wherein said cycle count signal is a function of the number of trigger pulses in said series; and
(d) processing means, including second generating means, connected to said clock means and to said logic means, for computing the frequency of said input signal as a function of said cycle count signal and said elapsed time signal and for generating a frequency measurement signal indicative of the computed frequency.
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Abstract
A frequency counter is disclosed which determines the frequency of an input signal in a high speed and accurate manner. High speed is achieved by utilizing electronic digital processing circuitry. The high degree of accuracy is achieved by a combination of elements which perform period averaging of an integral number of periods of the input signal over a flexible measurement interval. The counter is particularly useful in accurately measuring low frequency signals.
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13 Claims
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1. Apparatus for determining the frequency of an input signal by measuring an integral number of cycles of said input signals over a flexible measurement interval comprising:
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(a) input means, including first generating means, for receiving said input signal and for generating a series of trigger pulses wherein each trigger pulse is representative of the start of a cycle of said input signal; (b) clock means for providing an elapsed time signal representative of the duration of said flexible interval; (c) logic means, connected to said input means, for providing a cycle count signal representative of the number of integral cycles of said input signal occurring during said flexible interval, wherein said cycle count signal is a function of the number of trigger pulses in said series; and (d) processing means, including second generating means, connected to said clock means and to said logic means, for computing the frequency of said input signal as a function of said cycle count signal and said elapsed time signal and for generating a frequency measurement signal indicative of the computed frequency. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for determining the frequency of a periodic input signal comprising the steps of:
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(a) measuring elapsed time over an integral number of periods of said input signal to provide an elapsed time measure T; (b) counting said integral number of periods to provide an integral period count N; and (c) electronically computing the frequency of said input signal according to the formula Frequency=N/T. - View Dependent Claims (8, 9)
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10. A method for determining the frequency of a periodic signal over a flexible measurement interval comprises the steps of:
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(a) inputting said periodic signal into a first generating means; (b) generating a series of trigger pulses in response to said input signal wherein each trigger pulse of said series is representative of the start of a cycle of said periodic signal; (c) accumulating elapsed time over said flexible measurement interval; (d) generating an elapsed time signal representative of said accumulated elapsed time; (e) generating a cycle count signal representative of the number of integral cycles of said input signal occurring during said flexible interval as a function of the number of trigger pulses in said series; and (f) electronically calculating the frequency of said input signal as a function of said cycle count signal and said elapsed time signal. - View Dependent Claims (11, 12, 13)
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Specification