US3934197A
Expired / Lapsed
US
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Automatic calibration system
Assignee: Corning Glass Works
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Filing: 1973-12-03
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Granted: 1976-01-20
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Expires: 1993-12-03
Abstract
Abstract An automatic calibration system for pH meters includes a digital counter and a digital-to-analog converter which produces an output voltage connected to compensate the zero offset DC voltage of the pH measurement system. During a calibration operation a switch is closed to reset the binary counters and to thereafter supply clock pulses to the counters. As these clock pulses are counted, the digital-to-analog converter produces a staircase output voltage. This is applied to one input of a difference amplifier and the measuring voltage of the pH probe is applied to the other input. A detector stops the application of clock pulses to the counter when the staircase voltage equals the DC offset voltage of the pH measuring probe.
Inventors
- 👤 Aage Pettersen
- 👤 Herbert Schulkind
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:20
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/26; G01N27/416; G01N27/4163; G01N27/4165; G01R; G01R17/00; G01R17/02; G01R17/06
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
204 words
An automatic calibration system for an electronic pH measuring system of the type which produces a measurement voltage in a predetermined range, which represents the pH of a sample being analyzed and which includes a fixed zero offset DC voltage comprising: a first difference amplifier, said measurement voltage being applied to one input to said difference amplifier, indicating means operable over the range and connected to the output of said first difference amplifier for producing an output indication representing the pH of a sample being analyzed, said indication being corrected for said fixed zero offset DC voltage, a source of clock pulses, a counter, switch means for resetting said counter at the start of a calibration and for supplying said clock pulses to said counter during said calibration, a digital-to-analog converter having its input connected to the output of said counter, the output of said converter being connected to the other input of said difference amplifier to algebraically add said output to said measurement voltage, and a detector connected to the output of said difference amplifier for stopping the supply of clock pulses to said counter when the algebraic sum of said measurement voltage and the output of said converter reaches a predetermined level.
Claim 2
Dependent Claim
204 words
An automatic calibration system for an electronic pH measuring system of the type which produces a measurement voltage in a predetermined range, which represents the pH of a sample being analyzed and which includes a fixed zero offset DC voltage comprising: a first difference amplifier, said measurement voltage being applied to one input to said difference amplifier, indicating means operable over the range and connected to the output of said first difference amplifier for producing an output indication representing the pH of a sample being analyzed, said indication being corrected for said fixed zero offset DC voltage, a source of clock pulses, a counter, switch means for resetting said counter at the start of a calibration and for supplying said clock pulses to said counter during said calibration, a digital-to-analog converter having its input connected to the output of said counter, the output of said converter being connected to the other input of said difference amplifier to algebraically add said output to said measurement voltage, and a detector connected to the output of said difference amplifier for stopping the supply of clock pulses to said counter when the algebraic sum of said measurement voltage and the output of said converter reaches a predetermined level.
Claim 3
Dependent Claim
51 words
The system recited in claim 1 wherein said detector comprises: a second difference amplifier, the output of said first difference amplifier being connected to one input of said second difference amplifier, and a source of bias voltage representing said predetermined level connected to the other input of said second difference amplifier.
References Cited (Backward Citations)
US3784912A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-01-19 | 1979-07-21 | 1980-01-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-01-19 | 1983-07-21 | 1984-01-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-01-19 | 1987-07-21 | 1988-01-20 | $7700.00 | Window Closed / Lapsed |