Cyclically operating analog to digital converter

Claim 2

A converter providing a digital output representation of an analog input voltage comprising, a high-gain amplifier, first and second capacitors, one side of said first capacitor being permanently and directly connected to one side of said second capacitor to form a common junction, the output of said amplifier being coupled directly to said common junction, a source of reference voltage, switching means for selectively interconnecting said reference source, the other sides of each of said first and second capacitors, said analog input voltage and said amplifier to sequentially charge one of said capacitors to a voltage related to said analog input voltage and thereafter repetitively interchange the positions of each of said capacitors to repetitively decrease the voltage stored on each of said capacitors by an increment having a fixed relation to the value of said reference voltage, until the voltage at the output of said amplifier changes polarity, and display means for displaying the number of times said switching means interchanges said capacitors as a digital output representation of said analog input voltage.

Claim 3

A converter in accordance with claim 1 and further including remainder amplifying means operable only after each change of polarity of said amplifier output signal to amplify by a specific factor the voltage difference between the voltage across the capacitor which was last charged prior to the change of polarity and said subtractive increment and to charge the other of said capacitors to a voltage equal to said amplified remainder, and wherein said switching means is thereafter operated to again interchange repetitively said capacitors to repetitively decrease said amplified remainder voltage by said increment until the amplifier output again changes polarity, the number of times said capacitors are interchanged between successive changes of polarity at said amplifier output providing additional digit information in a multidigit representation of said analog input voltage.

Claim 4

A converter in accordance with claim 2 and further including a series of independent display elements, the number of elements in said series being equal to the number of digits in said multidigit representation, and multiplexing means for coupling the number of switch interchanges to only said initial display element when said number Of interchanges represents said first digit and to thereafter couple the number of capacitor interchanges occurring between each successive change of polarity at the output of said amplifier only to that one of said display element series corresponding to the represented digit.

Claim 5

A converter in accordance with claim 3 wherein said remainder multiplying factor is a factor of 10 and wherein each of said display elements is a decimal indicator and wherein said switching means is operated on a time cycle such that after each change of polarity at the output of said amplifier, a sufficient time is allowed before the next succession of capacitor interchanges to allow the number of capacitor interchanges occurring prior to this change of polarity to be recorded on the appropriate one of said display elements.

Claim 6

A converter for providing a digital output representation of an analog input voltage comprising, a high-gain amplifier having an input and an output, a first capacitor, a second capacitor, said first and second capacitors each having one side connected to the other at a common junction, said common junction being coupled to said amplifier output, a reference voltage source, sampling means for charging said first capacitor to a voltage related to said analog input voltage, first coupling means for coupling and decoupling the other side of one of said capacitors to said amplifier input and the other side of the remaining one of said capacitors to a point of potential reference, switching means for interchanging the connections between the other sides of said capacitors, said point of potential reference and said amplifier input, second coupling means for coupling said reference voltage source into the circuit including said amplifier, said capacitors, as said point of potential reference such that, in one position of said switching means said switching means said reference voltage source changes the potential of the noncommon side of one of said capacitors with respect to said point of potential reference and in another position of said switching means it changes the potential of the noncommon side of the other one of said capacitors with respect to said point of potential reference, and program means to sequence the operation of said first and second coupling means, said sampling means and said switching means to initially charge said first capacitor to said voltage related to the analog input and thereafter to repetitively decrease the voltage stored on each of said capacitors by an increment equal to the value of said reference voltage until the voltage on said amplifier output changes polarity, the number of times said switching means is operated to interchange said capacitors providing a digital value of said analog input voltage.

Claim 7

A converter for providing a digital output representation of an analog input voltage comprising, a high-gain amplifier having an input and an output, a first capacitor, a second capacitor, said first and second capacitors each having one side connected to the other at a common junction, said common junction being coupled to said amplifier output, a reference voltage source, sampling means for charging said first capacitor to a voltage related to said analog input voltage, first coupling means for coupling and decoupling the other side of one of said capacitors to said amplifier input and the other side of the remaining one of said capacitors to a point of potential reference, switching means for interchanging the connections between the other sides of said capacitors, said point of potential reference and said amplifier input, second coupling means for coupling said reference voltage source into the circuit including said amplifier, said capacitors, as said point of potential reference such that, in one position of said switching means said switching means said reference voltage source changes the potential of the noncommon side of one of said capacitors with respect to said point of potential reference and in another position of said switching means it changes the potential of the noncommon side of the other one of said capacitors with respect to said point of potential reference, and program means to sequence the operation of said first and second coupling means, said sampling means and said switching means to initially charge said first capacitor to said voltage related to the analog input and thereafter to repetitively decrease the voltage stored on each of said capacitors by an increment equal to the value of said reference voltage until the voltage on said amplifier output changes polarity, the number of times said switching means is operated to interchange said capacitors providing a digital value of said analog input voltage.

Claim 8

A converter in accordance with claim 5 and further including remainder amplifying means, operative upon the change of polarity of said amplifier output voltage to charge the one of said first and said second capacitors which is not coupled to said amplifier input to a voltage equal to 10 times the difference between the voltage across the one of said capacitors coupled to said amplifier input and said reference source potential, and program means operating thereafter to again sequence the operation of said first and second coupling means and said switching means to repetitively decrease the voltage stored on each of said capacitors by an increment equal to the value of said reference voltage until the voltage on said amplifier output terminal again changes polarity, the number of times said switching means is operated between said first and second changes of polarity providing an output indication of the nine''s complement of a digital value for the second decimal place of a digital representation of said analog input voltage.

Claim 9

A converter in accordance with claim 5 wherein said sampling means comprises, means for coupling said analog input voltage between said amplifier input and said point of potential reference for a period sufficient to charge said first capacitor to said analog input voltage.

Claim 10

A converter in accordance with claim 5 wherein said sampling means includes means for initially charging said first capacitor to a voltage equal to 10 times the sampled analog input voltage, independent of the polarity of the sampled analog input voltage.

Claim 11

A converter for providing a digital output representation of an analog input voltage comprising, a high-gain amplifier having two input terminals and an output terminal; a first capacitor; a second capacitor, one side of said first capacitor being connected to one side of said second capacitor at a common junction, said common junction being coupled to said amplifier output terminal, a reference voltage source, first coupling means for coupling and decoupling said reference voltage source between a first one of said amplifier input terminals and a point of potential reference, sampling means for charging said first capacitor to a voltage related to said analog input voltage, second coupling means for coupling and decoupling the other side of said first capacitor to the second one of said amplifier input terminals and the other side of said second capacitor to said point of potential reference, switching means for interchanging the connections between the other sides of said capacitors and said point of potential reference and said second amplifier input terminal, and program means to sequence the operation of said first and second coupling means, said sampling means and said switching means to initially charge said first capacitor to said voltage related to the analog input and thereafter to repetitively decrease the voltage stored on each of said capacitors by an increment equal to the value of said reference voltage until the voltage on said amplifier output terminal changes polarity, and means providing a digital output indication of the number of times said switching means is operated to interchange said capacitors, as a digital value of said analog input voltage.

Claim 12

A converter for providing a digital output representation of an analog input voltage comprising, a high-gain amplifier having two input terminals and an output terminal; a first capacitor; a second capacitor, one side of said first capacitor being connected to one side of said second capacitor at a common junction, said common junction being coupled to said amplifier output terminal, a reference voltage source, first coupling means for coupling and decoupling said reference voltage source between a first one of said amplifier input terminals and a point of potential reference, sampling means for charging said first capacitor to a voltage related to said analog input voltage, second coupling means for coupling and decoupling the other side of said first capacitor to the second one of said amplifier input terminals and the other side of said second capacitor to said point of potential reference, switching means for interchanging the connections between the other sides of said capacitors and said point of potential reference and said second amplifier input terminal, and program means to sequence the operation of said first and second coupling means, said sampling means and said switching means to initially charge said first capacitor to said voltage related to the analog input and thereafter to repetitively decrease the voltage stored on each of said capacitors by an increment equal to the value of said reference voltage until the voltage on said amplifier output terminal changes polarity, and means providing a digital output indication of the number of times said switching means is operated to interchange said capacitors, as a digital value of said analog input voltage.

Claim 13

A converter in accordance with claim 9 and further including remainder amplifying means, operative upon the change of polarity of said amplifier output voltage, to charge the one of said first and second capacitors which is not coupled to said amplifier second input terminal, to a voltage equal to 10 times the difference between the voltage across the one of said capacitors coupled to said amplifier second input terminal and said reference source potential, said program means operating thereafter to again sequence the operation of said first and second coupling means, and said switching means to repetitively decrease the voltage stored on each of said capacitors by an increment equal to the value of said reference voltage until the voltage on said amplifier output terminal again changes polarity and wherein said means providing a digital output indication, provides an output indication of the nine''s complement of the number of times said switching means is operated between said first and second changes of polarity, as a digital value of the second decimal place of a digital representation of said analog input voltage.

Claim 14

A converter in accordance with claim 9 wherein said sampling means comprises, means for coupling said analog input voltage between said amplifier first input terminal and said point of potential reference for a period sufficient to charge said first capacitor, said reference voltage source being decoupled from said amplifier first input terminal during said charging period.

Claim 15

A converter in accordance with claim 9 wherein said second coupling means includes, a third capacitor, having one side connected to said amplifier second input terminal, means for selectively coupling the other side of said third capacitor to either said point of potential reference or through said first switching means to the other side of said first and second capacitors, and shorting means operable to provide a short circuit between said amplifier output terminal and said amplifier input terminal, said program means operating said selective coupling means and said shorting means prior to the initial charging of said first capacitor to couple the other side of said third capacitor to said point of potential reference and short said output terminal to said input terminal thereby charging said third capacitor to the offset voltage of said amplifier.

Claim 16

A converter in accordance with claim 10 wherein said remainder amplifying means comprises, a first resistor connected between said common junction of said first and second capacitors and said point of potential reference, a second resistor, said second resistor being characterized by a resistance substantially 10 times that of said first resistor, a first diode connected in series with said second resistor between said amplifier output terminal and said common junction to pass current in a first direction, a second diode connected between said amplifier output terminal and said common junction to pass current in the opposite direction, and third switching means operative when the voltage at said amplifier output terminal changes polarity to decouple the other sides of said first and second capacitors from said point of potential reference and to couple the other side of that one of said capacitors which was connected to the point of potential reference to the junction between said second resistor and said first diode for a period sufficient to charge the connected one of said capacitors to the potential across said second resistor and thereafter to disconnect said other side from said junction and reconnect it to said point of potential reference.

Claim 17

A converter in accordance with claim 10 wherein said sampling means includes means for initially charging said first capacitor to a voltage equal to 10 times the sampled analog input voltage, independent of the polarity of the sampled analog input voltage.

Claim 18

A converter in accordance with claim 14 wherein said remainder amplifying means for amplifying the difference in voltage and for charging the first capacitor to 10 times the sampled analog input voltage comprises, first, second and third resistors, first and second diodes, and a second switching element, said first resistor being connected between said point of potential reference and the junction between said second and third resistors, said first diode being coupled between said amplifier output terminal and said capacitor''s common junction in a direction to pass current in a first direction, said second diode being connected in series combination with second and third resistors between said amplifier output terminal and said capacitors common junction in a direction to pass current in the opposite direction, said second and third resistors each being characterized by a resistance value substantially 10 times the resistance value of said first resistor, said second switching element being connected from the junction of said second diode and said second resistor to said second coupling means, said program means operating said switching element such that when said sampling means is operated to initially charge said first capacitor, said switching element is connecting the other side of said first capacitor to the junction between said second diode and said second resistor.

Claim 19

A converter providing a digital output representation of an analog input voltage comprising, sampling means for sampling the instantaneous value of said analog input voltage periodically, a source of reference voltage, cyclically operable subtraction means for repetitively subtracting from said sampled analog input a voltage increment related to said source of reference potential, a register coupled to said subtraction means, a series of display elements coupled to said Register, each of said display elements representing one digit in a decimal digit display, and program means for controlling the repetition rate of said sampling means and for cyclically operating said subtraction means and said display means such that said register accumulates from said subtraction means a number of pulses representing the first digit in a decimal digit representation of said sampled analog input voltage during a first cycle of operation of said subtraction means and provides a signal indicating said number to a first digit display element of said series and thereafter accumulates from a second cycle of operation of said subtraction means a number of pulses related to the value of the second decimal digit of a decimal digital representation of said analog input voltage and provides this number to a second display element of said series each of said display elements being actuated only when said register is providing a number to it, the time sequence of operation of said program means being such that said display element provides a visual display appearing to maintain the proper digital value at each display element during the operation of said converter.

Claim 20

A converter providing a digital output representation of an analog input voltage comprising, sampling means for sampling the instantaneous value of said analog input voltage periodically, a source of reference voltage, cyclically operable subtraction means for repetitively subtracting from said sampled analog input a voltage increment related to said source of reference potential, a register coupled to said subtraction means, a series of display elements coupled to said Register, each of said display elements representing one digit in a decimal digit display, and program means for controlling the repetition rate of said sampling means and for cyclically operating said subtraction means and said display means such that said register accumulates from said subtraction means a number of pulses representing the first digit in a decimal digit representation of said sampled analog input voltage during a first cycle of operation of said subtraction means and provides a signal indicating said number to a first digit display element of said series and thereafter accumulates from a second cycle of operation of said subtraction means a number of pulses related to the value of the second decimal digit of a decimal digital representation of said analog input voltage and provides this number to a second display element of said series each of said display elements being actuated only when said register is providing a number to it, the time sequence of operation of said program means being such that said display element provides a visual display appearing to maintain the proper digital value at each display element during the operation of said converter.