Analog to digital converter for electrical signals

Claim 2

Apparatus for converting an unknown analog signal to an equivalent digital representation comprising a source of positive and negative reference signals, means capable of comparing input levels coupled thereto and producing an output indicative of the differential therebetween, switching means responsive to the polarity of the output of said comparing means for producing a said reference signal from said source as an output with a polarity which will cause the level of said comparing means output to approach a reference level, means for enabling said switching means following each polarity change of the output of said comparing means, network means having said unknown analog signal and said switching means output signal connected as inputs thereto for coupling said network means inputs as input levels to said comparing means so that at least one of said network means inputs is thus coupled as a cumulative time average thereof, and means for measuring the amount of time at least one of said reference signals is produced as an output by said switching means during a preselected time period.

Claim 3

Apparatus in accordance with claim 1 wherein said network means includes means for directly coupling said unknown analog signal as one input to said comparing means, and means for coupling a cumulative time average of said switching means output as a second input to said comparing means.

Claim 4

Apparatus in accordance with claim 2 wherein said cumulative time average coupling means includes a capacitor coupled for accumulating a charge from the said reference signal output from said switching means for providing said second input for said comparing means.

Claim 5

Apparatus in accordance with claim 1 which includes capacitor means, a standaRd signal level source, means for summing said unknown analog signal and said switching means output and for charging said capacitor as a function of the summation, and means for applying the charge contained in said capacitor to one of said comparing means input and said standard signal level to another of said comparing means inputs.

Claim 6

Apparatus in accordance with claim 1 which further includes means for providing a continuous stream of clock pulses, said enabling means being coupled to respond to transitions of said clock pulses to effect said reference signal switching, said measuring means including a. first counting means responsive to a start signal for counting a predetermined number of said clock pulses and for providing an output signal reflecting a count of said predetermined number, b. second counting means, and c. logic means operable during the time period between the start signal and said first counting means output for permitting said second counting means to count said clock pulses occurring during all times a preselected one of said reference signals is coupled to provide an input to said comparing means.

Claim 7

Apparatus for converting an unknown analog signal to an equivalent digital representation comprising a comparator capable of inspecting input signals thereto and producing an output reflecting the polarity of the difference between said input signals, first coupling means for coupling the unknown analog signal to one of the inputs to said comparator, means for producing a continuous train of clock pulses, a source of positive and negative reference signals, means connected to said source of reference signals and being actuated during at least a portion of each said clock pulse for inspecting the polarity of the output of said comparator and for producing as an output thereof a said reference signal from said source with a polarity opposite the polarity of said comparator output, second coupling means coupling said inspecting means output to said comparator input, at least one of said first and second coupling means including means for converting the input thereto into a time related function of the said input for providing the input to said comparator, means for producing a start signal, timer means for providing an output signal indicative that a preselected time period has passed following each said start signal, a counter, means for gating said clock pulses to said counter during all times between a said start signal and its following said timer means output that said inspecting means output is of a preselected polarity, digital data utilization means, and means responsive to said timer means output for enabling the transfer of the contents of said counter to said utilization means.

Claim 8

Apparatus for converting an unknown analog signal to an equivalent digital representation comprising a comparator capable of inspecting input signals thereto and producing an output reflecting the polarity of the difference between said input signals, first coupling means for coupling the unknown analog signal to one of the inputs to said comparator, means for producing a continuous train of clock pulses, a source of positive and negative reference signals, means connected to said source of reference signals and being actuated during at least a portion of each said clock pulse for inspecting the polarity of the output of said comparator and for producing as an output thereof a said reference signal from said source with a polarity opposite the polarity of said comparator output, second coupling means coupling said inspecting means output to said comparator input, at least one of said first and second coupling means including means for converting the input thereto into a time related function of the said input for providing the input to said comparator, means for producing a start signal, timer means for providing an output signal indicative that a preselected time period has passed following each said start signal, a counter, means for gating said clock pulses to said counter during all times between a said start signal and its following said timer means output that said inspecting means output is of a preselected polarity, digital data utilization means, and means responsive to said timer means output for enabling the transfer of the contents of said counter to said utilization means.

Claim 9

Apparatus in accordance with claim 6 wherein said comparator is a differential amplifier having one input connected to a ground reference, said first coupling means includes a first resistive element, said second coupling means includes a second resistive element, a capacitor connected on one side to said ground reference and commonly connected on the other side to (a) said first and second resistive elements and (b) a second input for said differential amplifier.

Claim 10

Apparatus in accordance with claim 7 wherein said second coupling means further includes means for changing the magnitude of the said reference signal being coupled to said capacitor.

Claim 11

Apparatus in accordance with claim 8 which further includes multiple sources of unknown analog signals, multiplex means connected to said analog signal sources, selecting means for causing said multiplex means to connect a particular one of said analog signals to said analog signal coupling means, and means for discharging said capacitor whenever a conversion cycle is not being performed.

Claim 12

Apparatus in accordance with claim 8 wherein said timer means incLudes a second counter for producing said output signal whenever a preselected count is present therein, and means responsive to said start signal for gating said clock pulses into said second counter until said preselected count is reached.

Claim 13

Apparatus in accordance with claim 6 which further includes multiple sources of unknown analog signals, a plurality of signal handling groups each including a said comparator, a said inspecting means, a first coupling means and a second coupling means, each said group being connected for receiving at least one of said multiple analog signals, said apparatus further including means for selecting one of said signal handling groups for performing a conversion cycle with said counter and said gating means in accordance with the state of the said inspecting means output for the selected said signal handling group.