US3779378A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus and method for linearizing the output of a normally nonlinear radio frequency thickness gauge
Assignee: OI Glass Inc
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Filing: 1973-01-31
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Granted: 1973-12-18
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Expires: 1993-01-31
Abstract
Abstract Apparatus and method for producing a linear voltage versus thickness output for a radio frequency glass thickness gauge. One type of thickness measuring device for glass containers uses the attenuation of a radio frequency signal as a measure of thickness. The thickness signal is a voltage which varies nonlinearly as a function of thickness. This invention is a circuit for linearizing the nonlinear thickness signal. The input resistance to an operational amplifier is varied as a function of the thickness signal voltage. This creates a variable gain for the operational amplifier and consequently results in the generation of a linear thickness versus voltage relationship. Zener diodes are used as nonlinear variable resistors in two different thickness ranges to give a nonlinear, variable, input resistance to the operational amplifier.
Inventors
- 👤 G Scherf
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 03:40
CPC Classifications
G; G06; G06G; G06G7/00; G06G7/12; G06G7/26; G06G7/28; G01; G01B; G01B15/00; G01B15/02; G01B7/00; G01B7/02; G01B7/06
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
492 words
In an apparatus for measuring the thickness of an article formed from a dielectric material, wherein an antenna is used to establish a radio frequency field outwardly in the direction of an article positioned adjacent thereto; a probe is positioned in said field adjacent to said article; the voltage induced in said probe is a nonlinear index of the thickness of that portion of said article immediately in front of said probe; a compensated reference voltage is generated during periods when no article is present and held as a constant voltage during periods when an article is present; said induced voltage and said compensated reference voltage are summed to provide an output signal voltage which is a nonlinear voltage measure of the thickness of said article; said nonlinear thickness voltage is compared with a preselected minimum voltage level to provide a reject signal when the thickness of said article is below a pre-selected value represented by said pre-selected minimum voltage level; and said reject signal is transmitted to a reject control mechanism for rejecting articles exhibiting a thickness voltage below said preselected minimum voltage level, the improvement in said apparatus which comprises, in combination: a first operational amplifier having at least two inpUt terminals and one output terminal; a first input resistor connected in series with said probe and with a first input terminal of said first operational amplifier; a second input resistor connected in series with said compensated reference voltage and with a second input terminal of said first operational amplifier; a fixed feedback resistor connected between the output terminal of said first operational amplifier and said first input terminal of said first operational amplifier; a variable feedback resistor connected in series with said fixed feedback resistor for said first operational amplifier; a second operational amplifier having at least two input terminals and one output terminal; a fixed feedback resistor connected between a first input terminal of said second operational amplifier and the output terminal of said second operational amplifier; circuit means, connected in series between the output terminal of said first operational amplifier and said first input terminal of said second operational amplifier, for automatically varying the input resistance to said second operational amplifier as a function of the output voltage of said first operational amplifier, the minimum resistance of said circuit means being greater than the resistance value of said fixed feedback resistor for said second operational amplifier; a third operational amplifier having at least two input terminals and one output terminal; a fixed feedback resistor connected between the output terminal of said third operational amplifier and said first input terminal of said third operational amplifier, the resistance values of said input and feedback resistors for said third operational amplifier being substantially equal, whereby the output voltage from said third operational amplifier is a linear voltage measure of the thickness of said article and is connected to allow comparison of said linear voltage with said pre-selected minimum voltage level.
Claim 2
Dependent Claim
492 words
In an apparatus for measuring the thickness of an article formed from a dielectric material, wherein an antenna is used to establish a radio frequency field outwardly in the direction of an article positioned adjacent thereto; a probe is positioned in said field adjacent to said article; the voltage induced in said probe is a nonlinear index of the thickness of that portion of said article immediately in front of said probe; a compensated reference voltage is generated during periods when no article is present and held as a constant voltage during periods when an article is present; said induced voltage and said compensated reference voltage are summed to provide an output signal voltage which is a nonlinear voltage measure of the thickness of said article; said nonlinear thickness voltage is compared with a preselected minimum voltage level to provide a reject signal when the thickness of said article is below a pre-selected value represented by said pre-selected minimum voltage level; and said reject signal is transmitted to a reject control mechanism for rejecting articles exhibiting a thickness voltage below said preselected minimum voltage level, the improvement in said apparatus which comprises, in combination: a first operational amplifier having at least two inpUt terminals and one output terminal; a first input resistor connected in series with said probe and with a first input terminal of said first operational amplifier; a second input resistor connected in series with said compensated reference voltage and with a second input terminal of said first operational amplifier; a fixed feedback resistor connected between the output terminal of said first operational amplifier and said first input terminal of said first operational amplifier; a variable feedback resistor connected in series with said fixed feedback resistor for said first operational amplifier; a second operational amplifier having at least two input terminals and one output terminal; a fixed feedback resistor connected between a first input terminal of said second operational amplifier and the output terminal of said second operational amplifier; circuit means, connected in series between the output terminal of said first operational amplifier and said first input terminal of said second operational amplifier, for automatically varying the input resistance to said second operational amplifier as a function of the output voltage of said first operational amplifier, the minimum resistance of said circuit means being greater than the resistance value of said fixed feedback resistor for said second operational amplifier; a third operational amplifier having at least two input terminals and one output terminal; a fixed feedback resistor connected between the output terminal of said third operational amplifier and said first input terminal of said third operational amplifier, the resistance values of said input and feedback resistors for said third operational amplifier being substantially equal, whereby the output voltage from said third operational amplifier is a linear voltage measure of the thickness of said article and is connected to allow comparison of said linear voltage with said pre-selected minimum voltage level.
Claim 3
Dependent Claim
199 words
The apparatus of claim 1, wherein said circuit means comprises, in combination: a first fixed resistor, for reducing, in combination with said second operational amplifier feedback resistor, the gain of said second operational amplifier by a fixed amount in a first pre-selected range of article thicknesses; a first Zener diode biased to be off so long as said article thickness, as indicated by said induced voltage in said probe, is within said first pre-selected range of thicknesses and to be on when said thickness is within a second pre-selected range of article thicknesses having a minimum value substantially equal to the maximum value of said first pre-selected range of thicknesses and connected in parallel with said first fixed resistor; and a second fixed resistor, connected in series with said first Zener diode, for limiting the current to said first Zener diode to a pre-selected amount to force the voltage across said Zener diode to vary nonlinearly, in said second pre-selected range of article thicknesses, in approximately inverse relationship to the voltage variation of said voltage induced in said probe, the voltage across said Zener diode being fixed when the maximum value of said second range of thicknesses is reached.
Claim 4
Dependent Claim
157 words
The apparatus of claim 2, further including: a second Zener diode, connected in parallel with said first Zener diode, biased to be off so long as said article thickness, as indicated by said induced voltage in said probe, is within a third pre-selected range of article thicknesses having a minimum value substantially equal to the maximum value of said second range of thicknesses and to be on when said thicknesses is within said third range of article thicknesses; and a third fixed resistor, connected in series with said second Zener diode, for limiting the current to said second Zener diode to a pre-selected amount to force the voltage across said Zener diode to vary non-linearly, in said third range of article thicknessEs, in approximately inverse relationship to the voltage variation of said voltage induced in said probe, the voltage across said Zener diode being fixed when the maximum value of said third range of thicknesses is reached.
Claim 5
Dependent Claim
209 words
In a method for inspecting dielectric articles wherein a radio-frequency field is provided at an inspection station; an attenuated signal of said field is detected as an index of the thickness of an article placed in said field; a compensated reference signal is generated during periods when no article is present in said inspection station and held as a constant value when articles are present in said inspection station; and said attenuated signal and said compensated reference signal are summed to give a nonlinear output signal which is a measure of the thickness of said article, the improvement in said method which comprises the steps of: a. electronically decreasing said output signal, in a first range of thicknesses of said articles, by a fixed amount to generate a linear voltage versus thickness relationship having a pre-selected slope; and b. electronically decreasing said output signal, in a second range of thicknesses of said articles having a minimum value substantially equal to the maximum value of said first thickness range, by a variable amount as a function of said output signal to coincide with said slope of said linear voltage versus thickness relationship in said second range of thicknesses of said articles as well as in said first range of thicknesses.
Claim 6
Dependent Claim
209 words
In a method for inspecting dielectric articles wherein a radio-frequency field is provided at an inspection station; an attenuated signal of said field is detected as an index of the thickness of an article placed in said field; a compensated reference signal is generated during periods when no article is present in said inspection station and held as a constant value when articles are present in said inspection station; and said attenuated signal and said compensated reference signal are summed to give a nonlinear output signal which is a measure of the thickness of said article, the improvement in said method which comprises the steps of: a. electronically decreasing said output signal, in a first range of thicknesses of said articles, by a fixed amount to generate a linear voltage versus thickness relationship having a pre-selected slope; and b. electronically decreasing said output signal, in a second range of thicknesses of said articles having a minimum value substantially equal to the maximum value of said first thickness range, by a variable amount as a function of said output signal to coincide with said slope of said linear voltage versus thickness relationship in said second range of thicknesses of said articles as well as in said first range of thicknesses.
Claim 7
Dependent Claim
80 words
The method of claim 4, further including the step of: c. electronically decreasing said output signal, in a third range of thicknesses of said articles having a minimum value substantially equal to the maximum value of said second thickness range, by a variable amount as a function of said output signal to coincide with said slope of said linear voltage versus thickness relationship in said third range of thicknesses as well as in said first and second range of thicknesses.
References Cited (Backward Citations)
US3393799A
Cited
US3708064A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-12-17 | 1977-06-18 | 1977-12-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-17 | 1981-06-18 | 1981-12-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-17 | 1985-06-18 | 1985-12-18 | $7700.00 | Window Closed / Lapsed |