US3819864A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Digital dc offset removal method for data systems
Assignee: Halliburton Co
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Filing: 1973-03-30
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Granted: 1974-06-25
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Expires: 1993-03-30
Abstract
Abstract This disclosure relates to dc removal in data systems and in particular to multichannel, multiplexed data, gain ranging, seismic data acquisition systems. A medium drift dc amplifier (approximately + OR - 2.5 Mu v/*C) replaces the chopper stabilized amplifier. An overrange capability is provided in both the A/D converter and the gain ranging amplifier so the combined drift of the medium drift amplifier and the gain ranging amplifier over the system temperature is less than the overrange. This eliminates the necessity for rezeroing as the temperature changes or from using part of the converter range for dc drift. The digital filter has at least one word of memory per input channel plus one for each gain of the gain ranging amplifier. The input of the gain ranging amplifier is shorted periodically by Switch S and the average dc offset for each gain of the gain ranging amplifier is accumulated by filtering. An average is also accumulated by filtering for each of the data channels while they are in normal operation. Two cascaded one pole filters which share common hardware are used. The first removes the portion of offset due to the gain ranging amplifier and the second removes the dc offset due to the stabilized amplifier and multiplexer.
Inventors
- 👤 P Carroll
- 👤 R Harris
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 08:43
CPC Classifications
G; G01; G01V; G01V1/00; G01V1/24; G01V1/245; G08; G08C; G08C15/00; G08C15/06; H; H04; H04L; H04L25/00; H04L25/02; H04L25/06; H04L25/061
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
175 words
A data acquisition system having a plurality of input channels for supplying input data in the form of analog signals, comprising: a. first amplifying means for receiving and amplifying the input signals and having an output; b. second amplifying means having an input; c. switching means, connected to the output of the first amplifying means and to the input of the second amplifying means, and to a reference voltage for selectively permitting the output of the first amplifier means or the reference voltage to be presented to the input of the second amplifying means, the reference voltage being selected to provide an output signal from the second amplifying means representative of the DC offset of the second amplifying means; d. analog-to-digital conversion means, connected to receive the output of the second amplifying means for conversion into digital form; and e. comparison means, for comparing a digital signal from the analog-to-digital conversion means, representative of the DC offset with a digital signal representative of input data and DC offset, the difference being supplied as an output.
Claim 2
Dependent Claim
175 words
A data acquisition system having a plurality of input channels for supplying input data in the form of analog signals, comprising: a. first amplifying means for receiving and amplifying the input signals and having an output; b. second amplifying means having an input; c. switching means, connected to the output of the first amplifying means and to the input of the second amplifying means, and to a reference voltage for selectively permitting the output of the first amplifier means or the reference voltage to be presented to the input of the second amplifying means, the reference voltage being selected to provide an output signal from the second amplifying means representative of the DC offset of the second amplifying means; d. analog-to-digital conversion means, connected to receive the output of the second amplifying means for conversion into digital form; and e. comparison means, for comparing a digital signal from the analog-to-digital conversion means, representative of the DC offset with a digital signal representative of input data and DC offset, the difference being supplied as an output.
Claim 3
Dependent Claim
35 words
The data acquisition system of claim 1 wherein the comparison means further comprises a digital filter having a first storage means for storing digital signals representative of the DC oFfset from the second amplifying means.
Claim 4
Dependent Claim
25 words
The data acquisition system of claim 2 wherein the digital filter has a second storage means for storing DC offset from the first amplifying means.
Claim 5
Dependent Claim
76 words
The data acquisition system of claim 3 wherein the digital filter further comprises: e. i. a first subtraction circuit connected to subtract the contents of the first storage means from the digital signal from the analog-to-digital conversion means to provide a first difference signal; and ii. a second subtraction circuit, connected to receive the first difference signal and to subtract the contents of the second storage means from the first differential signal providing an output signal.
Claim 6
Dependent Claim
63 words
The data acquisition system of claim 1 wherein the switching means further comprise: c. i. a timing circuit for providing timing pulses; ii. a plurality of switches corresponding to the input channels, responsive to the timing circuit; and iii. a shorting circuit, responsive to the timing circuit to close when the switches open to present the reference voltage to the second amplifying means.
Claim 7
Dependent Claim
63 words
The data acquisition system of claim 4 wherein the switching means further comprise: c. i. a timing circuit for providing timing pulses; ii. a plurality of switches corresponding to the input channels, responsive to the timing circuit; and iii. a shorting circuit, responsive to the timing circuit to close when the switches open to present the reference voltage to the second amplifying means.
Claim 8
Independent Claim
108 words
A method of processing data, in the form of electrical analog signals, acquired from a plurality of input channels comprising the steps of: a. presenting a reference voltage to the input of a second amplifying means to provide a value of DC offset at the output of the second amplifying means; b. converting the DC offset to a digital representation; c. storing the digital DC offset; d. amplifying the input analog signals through a first amplifier and through the second amplifying means; e. converting the amplified input signal to digital form; and f. subtracting the digital DC offset from the digital input signal to provide a digital output.
Claim 9
Independent Claim
108 words
A method of processing data, in the form of electrical analog signals, acquired from a plurality of input channels comprising the steps of: a. presenting a reference voltage to the input of a second amplifying means to provide a value of DC offset at the output of the second amplifying means; b. converting the DC offset to a digital representation; c. storing the digital DC offset; d. amplifying the input analog signals through a first amplifier and through the second amplifying means; e. converting the amplified input signal to digital form; and f. subtracting the digital DC offset from the digital input signal to provide a digital output.
Claim 10
Dependent Claim
60 words
The method of claim 7 further comprising the steps of: g. averaging the output signal from the first amplifier to obtain the DC offset from the first amplifier; h. digitizing the first amplifier DC offset; i. storing the first amplifier digital DC offset; and j. subtracting the first amplifier digital DC offset from the first difference to provide an output.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-06-24 | 1977-12-24 | 1978-06-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-24 | 1981-12-24 | 1982-06-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-24 | 1985-12-24 | 1986-06-25 | $7700.00 | Window Closed / Lapsed |