Null-balance servo system

Claim 2

A null-balance servo system for measuring an unknown electrical quantity as an input signal comprising: an adjustable circuit element for generating a position feedback signal representing the adjustable position of said adjustable circuit element; an input circuit responsive to an input signal and said position feedback signal applied thereto for generating an error signal representing the unbalance of said system; signal processing amplifier means having an input coupled to the output of said input circuit; power amplifier means having an input coupled to the output of said signal processing amplifier means and an output; a motor coupled to said output of said power amplifier means for adjusting said adjustable circuit element in a direction to restore balance to said system; means for reducing said error signal by small signal acceleration feedback and small signal velocity feedback signals, said small signal acceleration feedback signal being applied to the input of said signal processing amplifier; means for reducing said error signal by large signal velocity feedback when said rate of change of said adjustable circuit element exceeds a predetermined threshold so as to establish a velocity controlled mode of operation for said system, said large signal velocity feedback signal being applied to the input of said power amplifier in proper phase relationship; and means for decreasing the effect of at least one of said small signal feedback signals on said error signal relative to the effect of said large signal velocity feedback signal on said error signal when said large signal velocity feedback exceeds said threshold so as to permit the large signal velocity feedback to dominate said at least one small signal feedback thereby constraining the effective bandwidth of the system during said velocity controlled mode of operation, said means for decreasing the effect of said small signal feedback signals substantially limiting the small signal acceleration feedback that is applied to said siGnal processing amplifier when said rate of adjustment exceeds said threshold.

Claim 3

A null-balance servo system for measuring an unknown electrical quantity as an input signal comprising: an adjustable circuit element for generating a position feedback signal representing the adjustable position of said adjustable circuit element; an input circuit responsive to an input signal and said position feedback signal applied thereto for generating an error signal representing the unbalance of said system; signal processing amplifier means having an input coupled to the output of said input circuit; pulse modulation means having an input coupled to the output of said signal processing amplifier means; switch mode amplifier means having an input coupled to the output of said pulse modulating means and an output; a motor coupled to said output of said switch mode amplifier for adjusting said adjustable circuit element in a direction to restore balance to said system; means for reducing said error signal by small signal acceleration feedback and small signal velocity feedback signals; means for reducing said error signal by large signal velocity feedback when said rate of change of said adjustable circuit element exceeds a predetermined threshold so as to establish a velocity controlled mode of operation for said system; means for applying said small signal acceleration feedback signal and said large signal velocity feedback signal to the input of said signal processing amplifier means; and means for decreasing the effect of at least one of said small signal feedback signals on said error signal relative to the effect of said large signal velocity feedback signal on said error signal when said large signal velocity feedback exceeds said threshold so as to permit the large signal velocity feedback to dominate said at least one small signal feedback thereby constraining the effective bandwidth of the system during said velocity controlled mode of operation.

Claim 4

A null-balance servo system for measuring an unknown electrical quantity as an input signal comprising: an adjustable circuit element for generating a position feedback signal representing the adjustable position of said adjustable circuit element; an input circuit responsive to an input signal and said position feedback signal applied thereto for generating an error signal representing the unbalance of said system; signal processing amplifier means having an input coupled to the output of said input circuit; pulse modulation means having an input coupled to the output of said signal processing amplifier means; switch mode amplifier means having an input coupled to the output of said pulse modulating means and an output; a motor coupled to said output of said switch mode amplifier for adjusting said adjustable circuit element in a direction to restore balance to said system; means for reducing said error signal by small signal acceleration feedback and small signal velocity feedback signals; means for reducing said error signal by large signal velocity feedback when said rate of change of said adjustable circuit element exceeds a predetermined threshold so as to establish a velocity controlled mode of operation for said system; means for applying said small signal acceleration feedback signal and said large signal velocity feedback signal to the input of said signal processing amplifier means; and means for decreasing the effect of at least one of said small signal feedback signals on said error signal relative to the effect of said large signal velocity feedback signal on said error signal when said large signal velocity feedback exceeds said threshold so as to permit the large signal velocity feedback to dominate said at least one small signal feedback thereby constraining the effective bandwidth of the system during said velocity controlled mode of operation.

Claim 5

A null-balance servo system for measuring an unknown electrical quantity as an input signal comprising: an adjustable circuit element for generating a position feedback signal representing the adjustable position of said adjustable circuit element; an input circuit responsive to an input signal and said position feedback signal applied thereto for generating an error signal representing the unbalance of said system; amplifying means having an input coupled to the output of said input circuit and an output; a motor coupled to said output of said amplifying means for adjusting said adjustable circuit element in a direction to restore balance to said system; said amplifying means further having a local feedback path from its output to its input comprising a capacitor and a resistor connected in series circuit relationship; means for reducing said error signal by small signal acceleration feedback and small signal velocity feedback signals; means for reducing said error signal by small signal acceleration feedback and small signal velocity feedback signals; means for reducing said error signal by large signal velocity feedback when said rate of change of said adjustable circuit element exceeds a predetermined threshold so as to establish a velocity controlled mode of operation for said system; means for applying said large signal velocity feedback means to the input of said amplifying means and said small signal velocity feedback signal to the output of said input circuit; means for decreasing the effect of at least one of said small signal feedback signals on said error signal relative to the effect of said large signal velocity feedback signal on said error signal when said large signal velocity feedback exceeds said threshold so as to permit the large signal velocity feedback to dominate said at least one small signal feedback thereby constraining the effective bandwidth of the system during said velocity controlled mode of operatIon; and said means for decreasing the effect of said small signal feedback signals including attenuating means coupled between the output of said input circuit and the input of said amplifiying means.

Claim 6

A null-balance servo system for measuring an unknown electrical quantity as an input signal comprising: an adjustable circuit element for generating a position feedback signal representing the adjustable position of said adjustable circuit element; an input circuit responsive to an input signal and said position feedback signal applied thereto for generating an error signal representing the unbalance of said system; amplifying means having an input coupled to the output of said input circuit and an output; a motor coupled to said output of said amplifying means for adjusting said adjustable circuit element in a direction to restore balance to said system; said amplifying means further having a local feedback path from its output to its input comprising a capacitor and a resistor connected in series circuit relationship; means for reducing said error signal by small signal acceleration feedback and small signal velocity feedback signals; means for reducing said error signal by small signal acceleration feedback and small signal velocity feedback signals; means for reducing said error signal by large signal velocity feedback when said rate of change of said adjustable circuit element exceeds a predetermined threshold so as to establish a velocity controlled mode of operation for said system; means for applying said large signal velocity feedback means to the input of said amplifying means and said small signal velocity feedback signal to the output of said input circuit; means for decreasing the effect of at least one of said small signal feedback signals on said error signal relative to the effect of said large signal velocity feedback signal on said error signal when said large signal velocity feedback exceeds said threshold so as to permit the large signal velocity feedback to dominate said at least one small signal feedback thereby constraining the effective bandwidth of the system during said velocity controlled mode of operatIon; and said means for decreasing the effect of said small signal feedback signals including attenuating means coupled between the output of said input circuit and the input of said amplifiying means.

Claim 7

A null-balance servo system for measuring an unknown electrical quantity as an input signal comprising: an adjustable circuit element for generating a position feedback signal representing the adjustable position of said adjustable circuit element; an input circuit responsive to an input signal and said position feedback signal applied thereto for generating an error signal representing the unbalance of said system; integrating amplifying means having an input coupled to the output of said input circuit; pulse modulating means having an input coupled to the output of said integrating amplifying means; switch mode amplifying means having an input coupled to the output of said pulse modulating means and an output; a motor coupled to said output of said switch mode amplifying means for adjusting said adjustable circuit element in a direction to restore balance to said system; means for reducing said error signal by small signal acceleration feedback and small signal velocity feedback signal; means for reducing said error signal by large signal velocity feedback when said rate of change of said adjustable circuit element exceeds a predetermined threshold so as to establish a velocity controlled mode of operation for said system; means for coupling said small signal acceleration feedback and said large signal velocity feedback to the input of said integrating and amplifying means; and means for decreasing the effect of at least one of said small signal feedback signals on said error signal relative to the effect of said large signal velocity feedback signal on said error signal when said large signal velocity feedback exceeds said threshold so as to permit the large signal velocity feedback to dominate at least one small signal feedback thereby constraining the effective bandwidth of the system during said velocity controlled mode of operation, said means for decreasing the effect including attenuating means coupled between the output of said input circuit and the input of said amplifying means.

Claim 8

A null-balance servo system for measuring an unknown electrical quantity as an input signal comprising: an adjustable circuit element for generating a position feedback signal representing the adjustable position of said adjustable circuit element; an input circuit responsive to an input signal and said position feedback signal applied thereto for generating an error signal representing the unbalance of said system; integrating amplifying means having an input coupled to the output of said input circuit; pulse modulating means having an input coupled to the output of said integrating amplifying means; switch mode amplifying means having an input coupled to the output of said pulse modulating means and an output; a motor coupled to said output of said switch mode amplifying means for adjusting said adjustable circuit element in a direction to restore balance to said system; means for reducing said error signal by small signal acceleration feedback and small signal velocity feedback signal; means for reducing said error signal by large signal velocity feedback when said rate of change of said adjustable circuit element exceeds a predetermined threshold so as to establish a velocity controlled mode of operation for said system; means for coupling said small signal acceleration feedback and said large signal velocity feedback to the input of said integrating and amplifying means; and means for decreasing the effect of at least one of said small signal feedback signals on said error signal relative to the effect of said large signal velocity feedback signal on said error signal when said large signal velocity feedback exceeds said threshold so as to permit the large signal velocity feedback to dominate at least one small signal feedback thereby constraining the effective bandwidth of the system during said velocity controlled mode of operation, said means for decreasing the effect including attenuating means coupled between the output of said input circuit and the input of said amplifying means.

Claim 9

A null-balance servo system for measuring an unknown electrical quantity as an input signal comprising: an adjustable circuit element for generating a position feedback signal representing the adjustable position of said adjustable circuit element; an input circuit responsive to an input signal and said position feedback signal applied thereto for generating an error signal representing the unbalance of said system; a motor coupled to said input circuit for adjusting said adjustable circuit element in a direction to restore balance to said system; means for reducing said error signal by small signal acceleration feedback and small signal velocity feedback signals; means for reducing said error signal by large signal velocity feedback when said rate of change of said adjustable circuit element exceeds a predetermined threshold so as to establish a velocity controlled mode of operation for said system, said means for reducing comprising a velocity feedback loop including adjustable gain amplifier means in series relationship with a threshold network comprising: first and second inverting amplifiers; an adjustable reference signal source having a negative terminal and a positive terminal; an input of said first inverting amplifier being connected to said negative terminal and having a feedback path including a diode and a resistor in parallel circuit configuration, said diode being poled for current flow from the output of said first inverting amplifier to its input; an input of said second inverting amplifier being connected to said positive terminal and having a feedback path including a diode and resistor in parallel circuit configuration, said diode being poled for current flow from the input of said second inverting amplifier to its output; transformer means for coupling said adjustable circuit element and each said output to said first and second inverting amplifiers, said transformer means providing simultaneous differentiation and direct isolation; and resistive means for combining the outputs of said first and second inverting amplifiers for applying the output signals from said first and second inverting amplifiers between the output of said signal processing amplifiers and the input of said power amplifier; and means for decreasing the effect of at least one of said small signal feedback signals on said error signal relative to the effect of said large signal velocity feedback signal on said error signal when said large signal velocity feedback exceeds said threshold so as to permit the large signal velocity feedback to dominate said at least one small signal feedback thereby constraining the effective bandwidth of the system during said velocity controlled mode of operation.

Claim 10

A null-balance servo system for measuring an unknown electrical quantity as an input signal comprising: an adjustable circuit element for generating a position feedback signal representing the adjustable position of said adjustable circuit element; an input circuit responsive to an input signal and said position feedback signal applied thereto for generating an error signal representing the unbalance of said system; a motor coupled to said input circuit for adjusting said adjustable circuit element in a direction to restore balance to said system; means for reducing said error signal by small signal acceleration feedback and small signal velocity feedback signals; means for reducing said error signal by large signal velocity feedback when said rate of change of said adjustable circuit element exceeds a predetermined threshold so as to establish a velocity controlled mode of operation for said system, said means for reducing comprising a velocity feedback loop including adjustable gain amplifier means in series relationship with a threshold network comprising: first and second inverting amplifiers; an adjustable reference signal source having a negative terminal and a positive terminal; an input of said first inverting amplifier being connected to said negative terminal and having a feedback path including a diode and a resistor in parallel circuit configuration, said diode being poled for current flow from the output of said first inverting amplifier to its input; an input of said second inverting amplifier being connected to said positive terminal and having a feedback path including a diode and resistor in parallel circuit configuration, said diode being poled for current flow from the input of said second inverting amplifier to its output; transformer means for coupling said adjustable circuit element and each said output to said first and second inverting amplifiers, said transformer means providing simultaneous differentiation and direct isolation; and resistive means for combining the outputs of said first and second inverting amplifiers for applying the output signals from said first and second inverting amplifiers between the output of said signal processing amplifiers and the input of said power amplifier; and means for decreasing the effect of at least one of said small signal feedback signals on said error signal relative to the effect of said large signal velocity feedback signal on said error signal when said large signal velocity feedback exceeds said threshold so as to permit the large signal velocity feedback to dominate said at least one small signal feedback thereby constraining the effective bandwidth of the system during said velocity controlled mode of operation.

Claim 11

A null-balance servo system for measuring an unknown electrical quantity as an input signal comprising: an adjustable circuit element for generating a position feedback signal representing the adjustable position of said adjustable circuit element; an input circuit responsive to an input signal and said position feedback signal applied thereto for generating an error signal representing the unbalance of said system; a motor coupled to said input circuit for adjusting said adjustable circuit element in a direction to restore balance to said system; means for reducing said error signal by small signal acceleration feedback and a small signal velocity feedback signal; means for reducing said error signal by large signal velocity feedback when said rate of change of said adjustable circuit element exceeds a predetermined threshold so as to establish a velocity controlled mode of operation for said system, said means for reducing including a threshold determining reference signal source, means for comparing a velocity signal with said reference signal so as to apply said velocity signal to reduce said error signal when said velocity feedback signal exceeds said threshold determined by said reference signal, a pair of parallel, oppositely poled diode means coupled to said reference signal source so as to block the large velocity feedback unless said velocity feedback exceeds said threshold, a first pair of parallel resistive means respectively coupled to terminals of said pair of diode means, and a second pair of parallel resistive means respectively coupling said terminals to said reference signal source; and means for decreasing the effect of at least one of said small signal feedback signals on said error signal relative to the effect of said large signal velocity feedback signal on said error signal when said large signal velocity feedback exceeds said threshold so as to permit the large signal velocity feedback to dominate said at least one small signal feedback thereby constraining the effective bandwidth of the system during said velocity controlled mode of operation.

Claim 12

A null-balance servo system for measuring an unknown electrical quantity as an input signal comprising: an adjustable circuit element for generating a position feedback signal representing the adjustable position of said adjustable circuit element; an input circuit responsive to an input signal and said position feedback signal applied thereto for generating an error signal representing the unbalance of said system; a motor coupled to said input circuit for adjusting said adjustable circuit element in a direction to restore balance to said system; means for reducing said error signal by small signal acceleration feedback and a small signal velocity feedback signal; means for reducing said error signal by large signal velocity feedback when said rate of change of said adjustable circuit element exceeds a predetermined threshold so as to establish a velocity controlled mode of operation for said system, said means for reducing including a threshold determining reference signal source, means for comparing a velocity signal with said reference signal so as to apply said velocity signal to reduce said error signal when said velocity feedback signal exceeds said threshold determined by said reference signal, a pair of parallel, oppositely poled diode means coupled to said reference signal source so as to block the large velocity feedback unless said velocity feedback exceeds said threshold, a first pair of parallel resistive means respectively coupled to terminals of said pair of diode means, and a second pair of parallel resistive means respectively coupling said terminals to said reference signal source; and means for decreasing the effect of at least one of said small signal feedback signals on said error signal relative to the effect of said large signal velocity feedback signal on said error signal when said large signal velocity feedback exceeds said threshold so as to permit the large signal velocity feedback to dominate said at least one small signal feedback thereby constraining the effective bandwidth of the system during said velocity controlled mode of operation.

Claim 13

The improved null-balance servo system of claim 3 wherein said attenuating means comprise: a series arm including resistive means connected in series between said input circuit and said amplifying means; a shunt arm including resistive means and a field effect transistor connected in series relationship between said series arm and circuit common; and means for rendering said field effect transistor conductive when the rate of adjustment of said adjustable circuit element exceeds said threshold for attenuating the output of said input circuit.