Pulse width - dc converter compensating for pulse repetition rate changes

Claim 3

An apparatus as recited in claim 1, wherein said integrating means includes a source of a reference voltage, an integrator including an input and an output, a switching means operative to connect said source of reference voltage to the input of said integrator for the duration of each of said rectangular pulses, whereby said output signal is provided on said integrator output. 3. A signal conditioner for a motorless fuel flow transmitter which includes first and second means providing electrical output signals representing, respectively, the speed of rotation of drum and impeller assemblies of the transmitter, wherein the relative time displacement between said first and second electrical signals is proportional to the mass flow rate of fuel through the transmitter, including: a. pulse shaping means providing a series of rectangular output pulses from said first and said second electrical signals, the width of each of said rectangular output pulses being proportional to the instantaneous time displacement between said first and said second electrical signals, b. an integrating means for producing an output signal having a ramp waveform in response to each of said rectangular output pulses, c. timing means for developing from each of said rectangular output pulses a timing pulse and a sample pulse, said sample pulse being produced for a short time interval following the termination of each of said rectangular output pulses, and said timing pulse being produced a short time after the termination of each of said sample pulses, d. means sampling said output signal in response to each of said sample pulses, e. means storing said sampled output signals to thereby provide a continuous DC output proportional to mass flow rate, and f. means resetting said integrating means in response to each of said timing pulses.

Claim 4

A signal conditioner as recited in claim 3, wherein said pulse shaping means includes first and second filter networks for removing noise from said first and second electrical signals, first and second transistor switches, each of said transistor switches having input, output and control terminals, the input terminal of said first transistor switch being coupled to said first filter network and the input terminal of said second transistor switch being coupled to said second filter network, a comparator having input and output terminals, means coupling the output terminals of said first and second transistor switches in common to the input terminal of said comparator, said comparator providing an output pulse whenever the level of either of said first or said second electrical signals passes a predetermined threshold value, a bistable switching means having an input terminal and first and second output terminals and being operative to switch an output pulse from one of said output terminals to the other of said output terminals in Response to each of said output pulses from said comparator, and means connecting said first output terminal to the control terminal of said first transistor switch and said second output terminal to the control terminal of said second transistor switch, whereby said series of rectangular output pulses are produced on one of said first or second output terminals.

Claim 5

The signal conditioner as recited in claim 3, wherein said integrating means comprises a source of a constant reference voltage, an operational amplifier having inverting and non-inverting inputs, and an output, a switching means coupling said source of constant reference voltage across said amplifier inputs for the duration of each of said rectangular output pulses, and a feedback capacitor connected between said amplifier''s output and inverting input, and wherein said resetting means comprises a third transistor switch having input, output and control terminals, said input and output terminals of said transistor switch being connected in parallel with said feedback capacitor, and said timing pulses being supplied to said control terminal such that said third transistor switch shunts said feedback capacitor in response to each of said timing pulses, whereby said output signal is provided at the output of said amplifier.

Claim 6

The signal conditioner as recited in claim 3, further comprising a transmitter rotation detector which includes a timing means for providing a control signal at a predetermined time after the termination of each of said rectangular output pulses, means inhibiting said timing circuit if the initiation of each of said rectangular output pulses occurs before said predetermined time period, and means responsive to said control signal to maintain the level of said DC output signal proportional to zero mass flow rate.

Claim 7

A signal conditioner as recited in claim 6, wherein said transmitter rotation detector further includes means establishing a threshold signal value, and detector means providing said control signal when the level of said output signal of said integrating means exceeds said threshold signal value.