US3703002A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Analog to digital converter and indicator using recirculation of remainder
Assignee: Fluke Corp
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Filing: 1971-12-06
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Granted: 1972-11-14
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Expires: 1991-12-06
Abstract
Abstract A multi-digit analog to digital converter with digitizing means in the output of a differential amplifier to derive the digit value and also feedback applied to the amplifier input in nullifying balancing relation to an analog input signal, such feedback including a component proportional to the derived digit value of the analog input and a component proportional to the resultant arithmetic remainder of such digit value, said digitizing means further storing a recirculatable remainder in analog form proportional to said remainder component multiplied by the digit base, said remainder being substituted for the input analog signal at the end of each digitizing time period in order to operate the digitizing means similarly in the next succeeding digit-deriving cycle, such process being repeated until the analog signal conversion has been carried out to a predetermined number of digit places. The digitizing means comprises a digit base ratio divider connected in feedback relation to the amplifier input, including a counter-controlled ladder network and a feedback resistance, with said ladder network being digitally switched in response to the count of a signal controlled variable frequency oscillator operated, in turn, proportionally to amplifier output exceeding a reference, voltage proportional to the digit base, and with the recirculatable remainder analog feedback being derived in either of two condensers alternately during succeeding digitizing time periods proportionally to amplifier output limited at an upper value proportional to the digit base. Additional feedback means responsive to amplifier output exceeding a value proportional to the digit base supresses amplifier output during digitizing periods. Depending upon input and feedback connections the amplifier may be operated in a straight mode or in an operational mode for positive or negative polarity input signals and avoid common mode rejection errors. Virtual grounding of both differential input sides of the amplifier cyclically enables correction of differential gain drift errors.
Inventors
- 👤 Richard W Van Saun
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 21:16
CPC Classifications
H; H03; H03M; H03M1/00; H03M1/12; H03M1/34; H03M1/38; H03M1/40; H03M1/403
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
278 words
An analog to digital converter comprising: a differential amplifier having two inputs and an output; coupling means connected to said inputs of said differential amplifier for applying an input analog signal having a digit base to one of said inputs of said differential amplifier; a digital feedback path connected to the output of said differential amplifier and to one of said inputs of said differential amplifier, said digital feedback path being operable over a first digit period to derive from the output of said differential amplifier and apply to one of said inputs of said differential amplifier a first negative feedback signal comprising a variable voltage having any of at least three different values proportional to the first digit value of said input analog signal; a remainder feedback path connected to the output of said differential amplifier and to one of said inputs of said differential amplifier, said remainder feedback path being operable over said first digit period to apply in additive relation to the first negative feedback signal a second negative feedback signal proportional to the arithmetic difference between said first digit value and said input analog signal to one of said inputs of said differential amplifier; storage means connected to said remainder feedback path for deriving and storing a recirculatable remainder analog signal proportional to said arithmetic difference between said first digit value and said input analog signal multiplied by the digit base of said analog signal; and, control means connected to said storage means for applying said recirculatable remainder analog signal substitutionally for said input analog signal and causing reoperation of said differential amplifier to derive the second digit value of said input analog signal.
Claim 2
Dependent Claim
278 words
An analog to digital converter comprising: a differential amplifier having two inputs and an output; coupling means connected to said inputs of said differential amplifier for applying an input analog signal having a digit base to one of said inputs of said differential amplifier; a digital feedback path connected to the output of said differential amplifier and to one of said inputs of said differential amplifier, said digital feedback path being operable over a first digit period to derive from the output of said differential amplifier and apply to one of said inputs of said differential amplifier a first negative feedback signal comprising a variable voltage having any of at least three different values proportional to the first digit value of said input analog signal; a remainder feedback path connected to the output of said differential amplifier and to one of said inputs of said differential amplifier, said remainder feedback path being operable over said first digit period to apply in additive relation to the first negative feedback signal a second negative feedback signal proportional to the arithmetic difference between said first digit value and said input analog signal to one of said inputs of said differential amplifier; storage means connected to said remainder feedback path for deriving and storing a recirculatable remainder analog signal proportional to said arithmetic difference between said first digit value and said input analog signal multiplied by the digit base of said analog signal; and, control means connected to said storage means for applying said recirculatable remainder analog signal substitutionally for said input analog signal and causing reoperation of said differential amplifier to derive the second digit value of said input analog signal.
Claim 3
Dependent Claim
89 words
An analog to digital converter as claimed in claim 1 wherein one of said two inputs of said differential amplifier is a positive input and the other input is a negative input; and, wherein said coupling means comprises a positive analog terminal connected to the positive input of said differential amplifier and a negative analog input terminal connected to the negative input of said differential amplifier, said positive analog terminal being adapted to receive positive analog signals and said negative analog terminal being adapted to receive negative analog signals.
Claim 4
Dependent Claim
137 words
An analog to digital converter as claimed in Claim 2 wherein said digital feedback path comprises: a current controlled oscillator connected to the output of said differential amplifier so as to receive a signal from said differential amplifier when the output of said differential amplifier is above the digit base of said input analog signal; a counter connected to the output of said current controlled oscillator to count the pulses generated by said current controlled oscillator; and, a constant resistance, voltage variable network connected to the output of said counter, the output of said constant resistance, voltage variable network being connected to the negative input of said differential amplifier so as to apply a variable voltage having a level proportional to the number of pulses counted by said counter to the negative input of said differential amplifier.
Claim 5
Dependent Claim
68 words
An analog to digital converter as claimed in claim 3 wherein said remainder feedback path comprises: a clamping circuit connected to the output of said differential amplifier for clamping the output of said differential amplifier to a voltage value related to the digit base of said input analog signal; and, a resistor connected between the output of said clamping circuit and the negative input of said differential amplifier.
Claim 6
Dependent Claim
260 words
An analog to digital converter as claimed in claim 4 wherein said storage means comprises: a fiRst storage capacitor; a first switch connected between the junction between said clamping circuit and said resistor, and said first storage capacitor for charging said first storage capacitor in accordance with the voltage at said junction when said first switch is closed and preventing the charging of said first capacitor when said first switch is open; a second switch connected between said first storage capacitor and the positive input of said differential amplifier for applying the charge on said first storage capacitor to said positive input when said second switch is closed and preventing the application of any charge from said first storage capacitor to said positive input when said second switch is open; a second storage capacitor; a third switch connected between the junction between said clamping circuit and said resistor, and said second storage capacitor for charging said second storage capacitor in accordance with the voltage at said junction when said third switch is closed and preventing the charging of said second storage capacitor when said third switch is open; and, a fourth switch connected between said second storage capacitor and the positive input of said differential amplifier for applying the charge on said second storage capacitor to said positive input when said fourth switch is closed and preventing the application of any charge from said second storage capacitor to said positive input when said fourth switch is open, said first, second, third and fourth switches being controlled by said control means.
Claim 7
Dependent Claim
113 words
An analog to digital converter as claimed in claim 5 wherein said control means comprises: a control logic circuit suitable for generating a plurality of control signals at a plurality of control outputs, said control signals being adapted to control the operation of said analog to digital converter, certain of said plurality of control outputs being connected to said first, second, third and fourth switches so as to open and close said switches in a predetermined sequence; and a recirculatable shift register having a plurality of outputs connected to the inputs of said control logic circuit for causing said control logic circuit to generate said plurality of control signals in a predetermined sequence.
Claim 8
Dependent Claim
117 words
An analog to digital converter as claimed in claim 6 including an indicating means for providing a visual indication of the digital representation of the input analog signal, said indicating means comprising: a Nixie tube indicator formed of a plurality of Nixie tubes; a binary digital to decade digital driver circuit having its inputs connected to the output of said counter and having its outputs connected to the cathodes of the plurality of Nixie tubes forming said Nixie tube indicator; and, a Nixie tube anode strobe circuit having its inputs connected to the outputs of said recirculatable shift register and its outputs connected to the anodes of the plurality of Nixie tubes forming said Nixie tube indicator.
Claim 9
Dependent Claim
87 words
An analog to digital converter as claimed in claim 7 including a drift correction circuit having an input connected to sense the drift in the output of said differential amplifier and having an output connected to an input of said differential amplifier to correct for drift, said drift correction circuit having a control input connected to a control signal output of said control logic circuit so that drift correction is performed in a predetermined time period in the sequence of operation of said analog to digital converter.
Claim 10
Dependent Claim
73 words
An analog to digital converter as claimed in claim 8 including: a fifth switch connected between said positive analog input terminal and the positive input of said differential amplifier; and, a sixth switch connected between said negative analog input terminal and said the negative input of said differential amplifier, said fifth and sixth switchs being connected to said control logic circuit so as to be opened and closed by said coNtrol logic circuit.
Claim 11
Dependent Claim
43 words
An analog to digital converter as claimed in claim 9 including an initial saturation prevention feedback path connected between the output of said differential amplifier and the negative input of said differential amplifier so as to prevent initial saturation of said differential amplifier.
Claim 12
Dependent Claim
137 words
An analog to digital converter as claimed in claim 1 wherein said digital feedback path comprises: a current controlled oscillator connected to the output of said differential amplifier so as to receive a signal from said differential amplifier when the output of said differential amplifier is above the digit base of said input analog signal; a counter connected to the output of said current controlled oscillator to count the pulses generated by said current controlled oscillator; and, a constant resistance, voltage variable network connected to the output of said counter, the output of said constant resistance, voltage variable network being connected to said one input of said differential amplifier so as to apply a variable voltage having a level proportional to the number of pulses counted by said counter to said one input of said differential amplifier.
Claim 13
Dependent Claim
67 words
An analog to digital converter as claimed in claim 11 wherein said remainder feedback path comprises: a clamping circuit connected to the output of said differential amplifier for clamping the output of said differential amplifier to a voltage value related to the digit base of said input analog signal; and, a resistor connected between the output of said clamping circuit and said one input of said differential
Claim 14
Dependent Claim
260 words
An analog to digital converter as claimed in claim 12 wherein said storage means comprises: a first storage capacitor; a first switch connected between the junction between said clamping circuit and said resistor, and said first storage capacitor for charging said first storage capacitor in accordance with the voltage at said junction when said first switch is closed and preventing the charging of said first capacitor when said first switch is open; a second switch connected between said first storage capacitor and the other input of said differential amplifier for applying the charge on said first storage capacitor to said other input when said second switch is closed and preventing the application of any charge from said first storage capacitor to said other input when said second switch is open; a second storage capacitor; a third switch connected between the junction between said clamping circuit and said resistor, and said second storage capacitor for charging said second storage capacitor in accordance with the voltage of said junction when said third switch is closed and preventing the charging of said second storage capacitor when said third switch is open; and, a fourth switch connected between said second storage capacitor and said other input of said differential amplifier for applying the charge on said second storage capacitor to said other input when said fourth switch is closed and preventing the application of any charge from said second storage capacitor to said other input when said fourth switch is open, said first, second, third and fourth switches being controlled by said control means.
Claim 15
Dependent Claim
43 words
An analog to digital converter as claimed in claim 13 including an initial saturation prevention feedback path connected between the output of said differential amplifier and said one input of said differential amplifier so as to prevent initial saturation of said differential amplifier.
Claim 16
Dependent Claim
68 words
An analog to digital converter as claimed in claim 1 wherein said remainder feedback path comprises; a clamping circuit connected to the output of said differential amplifier for clamping the output of said differential amplifier to a voltage value related to the digit base of said input analog signal; and, a resistor connected between the output of said clamping circuit and said one input of said differential amplifier.
Claim 17
Dependent Claim
43 words
An analog to digital converter as claimed in claim 15 incluiding an initial saturation prevention feedback path connected between the output of said differential amplifier and said one input of said differential amplifier so as to prevent initial saturation of said differential amplifier.
Claim 18
Dependent Claim
43 words
An analog to digital converter as claimed in claim 1 including an initial saturation prevention feedback path connected between the output of said differential amplifier and said one input of said differential amplifier so as to prevent initial saturation of said differential amplifier.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-11-14 | 1976-05-15 | 1976-11-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-11-14 | 1980-05-15 | 1980-11-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-11-14 | 1984-05-15 | 1984-11-14 | $7700.00 | Window Closed / Lapsed |