Signal processing circuits

Claim 2

A signal processing circuit comprising means responsive to an input signal and a feedback signal to produce a first signal varying in accord with the difference between input and feedback signals, a pulse source providing a continuous train of pulses, a bistable device having set, reset and pulse input lines and which can be changed in state by set and reset signals only in response to a pulse on said pulse input line, means applying said continuous train of pulses to said pulse input line, means applying a logic reset signal to said reset input line, means applying said first signal to said set input line whereby the bistable device changes in state repetitively to produce a repetitive pulse output signal with a frequency proportional to the repetition frequency of the continuous train of pulses when the first signal is in a predetermined condition and means coupled to said bistable device for developing said feedback signal in accord with the mean frequency of the output pulse signal.

Claim 3

A circuit as claimed in claim 1 in which the means for developing the feedback signal comprises integrating means.

Claim 4

A circuit as claimed in claim 2 in which the integrating means comprises a passive integrator.

Claim 5

A circuit as claimed in claim 2 in which the integrating means is arranged to receive the pulses constituting the pulse output signal.

Claim 6

A circuit as claimed in claim 2 in which the means for developing the feedback signal comprises switch means for applying a reference signal to the integrating means at times temporally corresponding to the pulses of the pulse output signal.

Claim 7

A circuit as claimed in claim 5 in which the switch means comprises a switch for temporarily closing to apply the reference signal to the integrating means in response to each pulse of the said pulse output signal.

Claim 8

A circuit as claimed in claim 6 in which means are provided for varying the reference signal and thereby raising or lowering the pulse output frequency for an input signal of given magnitude.

Claim 9

A signal processing circuit comprising a difference amplifier for receiving an input signal and a feedback signal and for producing a first signal varying in accord with the difference between the input and feedback signals, a pulse signal source providing a continuous train of input pulses, a logic circuit response to the said first signal and to said train of input pulses for producing when said first signal is in a predetermined condition a repetitive output pulse signal, means including integrating means for developing the feedback signal in accord with the mean frequency of the output pulse signal; said logic circuit including a bistable device which can be changed in state only in response to a pulse in the input pulse train and which is adapted to switch repeatedly between states in response to pulses in the input train only if the said first signal is in the said predetermined condition.

Claim 10

A signal processing circuit comprising a difference amplifier for receiving an input signal and a feedback signal and for producing a first signal varying in accord with the difference between the input and feedback signals, a pulse signal source providing a continuous train of input pulses, a logic circuit response to the said first signal and to said train of input pulses for producing when said first signal is in a predetermined condition a repetitive output pulse signal, means including integrating means for developing the feedback signal in accord with the mean frequency of the output pulse signal; said logic circuit including a bistable device which can be changed in state only in response to a pulse in the input pulse train and which is adapted to switch repeatedly between states in response to pulses in the input train only if the said first signal is in the said predetermined condition.

Claim 11

A circuit as claimed in claim 8 in which the said difference amplifier is a chopper amplifier operated at a frequency corresponding to the pulses of the said input pulse train.

Claim 12

A circuit as claimed in claim 8 in which the difference amplifier is an alternating current amplifier and switching means are provided for interrupting the feeding of the input signal and the feedback signal to respective inputs of the alternating current amplifier.

Claim 13

A circuit as claimed in claim 10 in which the switching means comprise a switch operable by pulses from a pulse source arranged to provide the pulses of the said input pulse train.

Claim 14

A meter comprising means responsive to a first variable to provide an input signal of magnitude proportional to the first variable, means responsive to a second variable for producing a pulse train of repetition frequency proportional to the second variable, means responsive to the input signal and a feedback signal to produce a first signal varying in accord with the difference between the input and feedback signals, a logic circuit responsive to the said first signal for producing when said first signal is in a predetermined condition a repetitive output pulse signal, said logic circuit comprising a bistable device arranged to change state only in response to a pulse in said pulse train and to switch repeatedly between states only when said first signal is in the said predetermined condition, means including integrating means for developing said feedback signal in accord with the mean frequency of the output pulse signal and indicating means responsive to the said output pulse signal.

Claim 15

A meter comprising means responsive to a first variable to provide an input signal of magnitude proportional to the first variable, means responsive to a second variable for producing a pulse train of repetition frequency proportional to the second variable, means responsive to the input signal and a feedback signal to produce a first signal varying in accord with the difference between the input and feedback signals, a logic circuit responsive to the said first signal for producing when said first signal is in a predetermined condition a repetitive output pulse signal, said logic circuit comprising a bistable device arranged to change state only in response to a pulse in said pulse train and to switch repeatedly between states only when said first signal is in the said predetermined condition, means including integrating means for developing said feedback signal in accord with the mean frequency of the output pulse signal and indicating means responsive to the said output pulse signal.

Claim 16

A signal processing circuit comprising a difference amplifier having means for receiving an input signal and a feedback signal and means for adding a reference signal to one of said input and feedback signals, said difference amplifier producing a first signal varying in accord with the difference between the input and feedback signals as modified by the addition of said reference signal, a logic circuit responsive to said first signal for producing when said first signal is in a predetermined condition a repetitive output pulse signal, means including integrating means for developing the feedback signal in accord with the mean frequency of the output pulse signal, and means for providing an input pulse train; said logic circuit including a bistable device which can be changed in state only in response to a pulse in the input pulse train and which is adapted to switch repeatedly between states only if the said first signal is in the said predetermined condition.

Claim 17

A signal processing circuit comprising a difference amplifier having means for receiving an input signal and a feedback signal and means for adding a reference signal to one of said input and feedback signals, said difference amplifier producing a first signal varying in accord with the difference between the input and feedback signals as modified by the addition of said reference signal, a logic circuit responsive to said first signal for producing when said first signal is in a predetermined condition a repetitive output pulse signal, means including integrating means for developing the feedback signal in accord with the mean frequency of the output pulse signal, and means for providing an input pulse train; said logic circuit including a bistable device which can be changed in state only in response to a pulse in the input pulse train and which is adapted to switch repeatedly between states only if the said first signal is in the said predetermined condition.

Claim 18

A signal processing circuit comprising means responsive to an input signal and a feedback signal to produce a first signal varying in accord with the difference between the input and feedback signals, means responsive to the said first signal for producing when said first signal is in a predetermined condition a repetitive output pulse signal, and means for developing the feedback signal in accord with the mean frequency of the output pulse signal and means for dividing the frequency of the said repetitive output pulse signal.

Claim 19

A signal processing circuit comprising means responsive to an input signal and a feedback signal to produce a first signal varying in accord with the difference between the input and feedback signals, means responsive to the said first signal for producing when said first signal is in a predetermined condition a repetitive output pulse signal, and means for developing the feedback signal in accord with the mean frequency of the output pulse signal and means for dividing the frequency of the said repetitive output pulse signal.

Claim 20

A meter as claimed in claim 14, further comprising a counter arranged for counting the pulse output.

Claim 21

A meter comprising a temperature measuring bridge responsive to a temperature to provide an input signal of magnitude proportional to said temperature, means responsive to the rate of flow of a fluid for producing a pulse train of repetition frequency proportional to the rate of flow, means responsive to the input signal and a feedback signal to produce a first signal varying in accord with the difference between the input and feedback signals, a logic circuit responsive to the said first signal for producing when said first signal is in a predetermined condition a repetitive output pulse signal, said logic circuit comprising a bistable device arranged to change state only in response to a pulse in said pulse train and to switch repeatedly between states only when said first signal is in the said predetermined condition, means including integrating means for developing said feedback signal in accord with the mean frequency of the output pulse signal and indicating means responsive to the said output pulse signal.

Claim 22

A meter comprising a temperature measuring bridge responsive to a temperature to provide an input signal of magnitude proportional to said temperature, means responsive to the rate of flow of a fluid for producing a pulse train of repetition frequency proportional to the rate of flow, means responsive to the input signal and a feedback signal to produce a first signal varying in accord with the difference between the input and feedback signals, a logic circuit responsive to the said first signal for producing when said first signal is in a predetermined condition a repetitive output pulse signal, said logic circuit comprising a bistable device arranged to change state only in response to a pulse in said pulse train and to switch repeatedly between states only when said first signal is in the said predetermined condition, means including integrating means for developing said feedback signal in accord with the mean frequency of the output pulse signal and indicating means responsive to the said output pulse signal.