Digital frequency meter

Claim 2

Apparatus for measuring the frequency of a periodic input signal comprising a downcounter, rate multiplier means responsive to a clock signal and the present state of said downcounter for providing an input rate to said downcounter proportional to the square of the present state of the downcounter, means for initializing said downcounter to a state corresponding to the full scale frequency of the apparatus and for applying said input rate to said downcounter at a time delayed from the beginning of a period of the input signal by a time interval equal to the period of said full scale frequency, and means for sensing the state of said downcounter at the end of the period of said input signal.

Claim 3

Apparatus for measuring the frequency of a periodic input signal comprising a k-bit binary upcounter, bistable switching means switchable from a first state to a second state when said upcounter overranges through one cycle, logic means for inverting the binary word stored in said upcounter, said logic means being disabled by said bistable switching means when in said first state and enabled by said bistable switching means when in said second state, clock means, first and second k-bit rate multipliers, the output of said clock means being applied to the input of said first rate multiplier, the output of said first rate multiplier being applied to the input of said second rate multiplier, the output of said logic means being applied as one input to each of said first and second rate multipliers, the output of said second rate multiplier being applied to the input of said upcounter, k-bit storage register means, trigger means responsive to said input signal for enabling said storage register means to store the output of said logic means after each period of said input signal, said trigger means including means for resetting said upcounter and resetting said flip-flop to its first state subsequent to the enabling of said storage register means, and utilization means responsive to the binary word stored in said storage register means.

Claim 4

Apparatus for measuring the frequency of a periodic input signal comprising a k-bit binary upcounter, bistable switching means switchable from a first state to a second state when said upcounter overranges through one cycle, logic means for inverting the binary word stored in said upcounter, said logic means being disabled by said bistable switching means when in said first state and enabled by said bistable switching means when in said second state, clock means, first and second k-bit rate multipliers, the output of said clock means being applied to the input of said first rate multiplier, the output of said first rate multiplier being applied to the input of said second rate multiplier, the output of said logic means being applied as one input to each of said first and second rate multipliers, the output of said second rate multiplier being applied to the input of said upcounter, k-bit storage register means, trigger means responsive to said input signal for enabling said storage register means to store the output of said logic means after each period of said input signal, said trigger means including means for resetting said upcounter and resetting said flip-flop to its first state subsequent to the enabling of said storage register means, and utilization means responsive to the binary word stored in said storage register means.

Claim 5

The apparatus defined in claim 2 wherein said utilization means includes digital-to-analog converter means responsive to the binary word stored in said storage register means for providing an analog voltage output and indicator means responsive to the output of said digital-to-Analog converter means for indicating the frequency of said input signal.