Tachometer circuit

Claim 2

A frequency converter responsive to a variable frequency signal comprising: a. squaring circuit means responsive to said variable signal for generating a first train of squared pulses having time displacement related to the frequency of said variable signal and having an amplitude switching between first and second states; b. pulse generator means responsive to said first train of pulses for generating a second train of pulses, each pulse thereof chAracterized as having time displacement related to a change of state of said first train and having a selectively programmable pulse width; c. logic means for providing an exclusive OR logic combination of said first and second pulse trains to thereby generate a third pulse train having pulses of width determined by said time displacement between said first and second pulse trains; and d. integrator means responsive to said third pulse train for integrating said third pulse train into a DC signal having magnitude related to and varying with the frequency of said variable frequency signal.

Claim 3

The combination of claim 1 wherein said pulse generator means comprises: a. storage means including a capacitor having a controlled rate of charge and discharge; and b. a differential comparator for generating said second pulse train responsive to the relationship between the charge on said capacitor exceeding a predetermined threshold level.

Claim 4

The combination of claim 2 wherein the components comprising the frequency converter are included in an integrated circuit.

Claim 5

The combination of claim 3 and including a first current source responsive to said first pulse for generating a first control signal for actuating said capacitor and thereby controlling the pulse width of said second pulse train.

Claim 6

The combination of claim 4 wherein said integrator includes an integrating capacitor coupled to receive said third pulse train.

Claim 7

The combination of claim 5 and further including a second current source for generating a second control signal of magnitude substantially equal to said first control signal for controlling the amplitude of said third pulse train proportional to the pulse width of said second pulse train.

Claim 8

The combination of claim 6 wherein said second current source includes an output transistor having a collector coupled to said integrator for providing a relatively high impedance thereto.

Claim 9

The combination of claim 7 wherein said squaring circuit means comprises: a. a first differential amplifier having first and second inputs with said first input coupled to receive said variable frequency signal; b. a second differential amplifier coupled to said first differential amplifier for generating said first train of squared pulses; and c. a hysteresis circuit coupling the second input of said first differential amplifier with said second differential amplifier providing hysteresis feedback therebetween.

Claim 10

The combination of claim 8 wherein said integrator further comprises: a. an operational amplifier coupled to said integrating capacitor for providing said DC signal; and b. a filter coupled to said operational amplifier for smoothing said DC signal.

Claim 11

A frequency converter responsive to a variable frequency signal comprising: a. a squaring circuit responsive to said variable signal for generating a first train of squared pulses having time displacement related to the frequency of said variable signal and having an amplitude switching between first and second states; b. a first current source gated by said first pulse train to thereby generate a second pulse train having pulses of uniform magnitude; c. a differential comparator for generating a third pulse train when the amplitude of the pulses of said second pulse train exceeds a predetermined level; d. an exclusive OR circuit for providing an exclusive OR combination of said first and third pulse trains to thereby provide a fourth pulse train having pulses with time displacement relative to a change of state of said first pulse train; e. a second current source providing an output signal matched in magnitude to that of said first current source; f. switching means responsive to said fourth pulse train for gating said output signal of said second current source to thereby provide a fifth pulse train having pulses characterized by pulse width determined by said first current source and pulse amplitudes determined by said second current source; and g. an integrator including a capacitor responsive to said output signal of said second current source for integrating said fifth pulse train and providing a DC output signal having magnitude related to and varying with the frequency of said variable frequency signal.

Claim 12

A frequency converter responsive to a variable frequency signal comprising: a. a squaring circuit responsive to said variable signal for generating a first train of squared pulses having time displacement related to the frequency of said variable signal and having an amplitude switching between first and second states; b. a first current source gated by said first pulse train to thereby generate a second pulse train having pulses of uniform magnitude; c. a differential comparator for generating a third pulse train when the amplitude of the pulses of said second pulse train exceeds a predetermined level; d. an exclusive OR circuit for providing an exclusive OR combination of said first and third pulse trains to thereby provide a fourth pulse train having pulses with time displacement relative to a change of state of said first pulse train; e. a second current source providing an output signal matched in magnitude to that of said first current source; f. switching means responsive to said fourth pulse train for gating said output signal of said second current source to thereby provide a fifth pulse train having pulses characterized by pulse width determined by said first current source and pulse amplitudes determined by said second current source; and g. an integrator including a capacitor responsive to said output signal of said second current source for integrating said fifth pulse train and providing a DC output signal having magnitude related to and varying with the frequency of said variable frequency signal.

Claim 13

The combination of claim 10 including an output transistor coupling said fifth pulse train to said integrator with its collector coupled to said integrator for providing high impedance thereto.