US3921087A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrostatic field modulator having a tuning fork
Assignee: Individual
•
Filing: 1971-05-12
•
Granted: 1975-11-18
•
Expires: 1991-05-12
Abstract
Abstract A capacitive electrostatic modulator having a tuning fork arrangement including tines operatively associated with each end of the tuning fork. A driver is used to vibrate the tuning fork to alternately couple and decouple a sensitive electrode with the unknown quantity being measured such that a voltage corresponding to the unknown quantity is induced thereon. Associated circuitry enables connection of the electrostatic modulator as an electrostatic voltmeter or field meter.
Inventors
- 👤 Robert E Vosteen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 13:14
CPC Classifications
G; G01; G01R; G01R29/00; G01R29/12; G01R15/00; G01R15/14; G01R15/16; G01R15/165
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
161 words
An electrostatic measuring apparatus to measure unknowns such as the electrostatic potential of a surface in non-contacting manner or an electrostatic field with a capacitive detector having a sensitive electrode positionable in electrostatic coupling relationship with the surface or in the electrostatic field to produce a detector signal representative of the magnitude and polarity of the unknown being measured comprising: a tuning fork with first and second tines mounted to respective ends thereof, operatively postioned to be able to vary the coupling relationship, drive means to vibrate the tuning fork at a predetermined frequency to vary the coupling relationship and produce modulated detector signals having a carrier frequency equal to the predetermined frequency, a reference oscillator to produce reference signals at the predetermined frequency, a detector connected to receive the reference signals and modulated detector signals at a fixed phase relationship to demodulate the latter and produce an output signal indicative of the magnitude and polarity of the unknown being measured.
Claim 2
Dependent Claim
161 words
An electrostatic measuring apparatus to measure unknowns such as the electrostatic potential of a surface in non-contacting manner or an electrostatic field with a capacitive detector having a sensitive electrode positionable in electrostatic coupling relationship with the surface or in the electrostatic field to produce a detector signal representative of the magnitude and polarity of the unknown being measured comprising: a tuning fork with first and second tines mounted to respective ends thereof, operatively postioned to be able to vary the coupling relationship, drive means to vibrate the tuning fork at a predetermined frequency to vary the coupling relationship and produce modulated detector signals having a carrier frequency equal to the predetermined frequency, a reference oscillator to produce reference signals at the predetermined frequency, a detector connected to receive the reference signals and modulated detector signals at a fixed phase relationship to demodulate the latter and produce an output signal indicative of the magnitude and polarity of the unknown being measured.
Claim 3
Dependent Claim
55 words
The electrostatic measuring apparatus recited in claim 1 wherein the first and second tines are interposed between the sensitive electrode and the unknown quantity being measured and are caused to oscillate in opposite phase at equal amplitude by the tuning fork to alternately couple and decouple the sensitive electrode from the unknown quantity being measured.
Claim 4
Dependent Claim
37 words
The electrostatic measuring apparatus recited in claim 2 further comprising: a housing, the assembly and the sensitive electrode being mounted therein, the housing having a plate defining an aperture located opposite a surface of the sensitive electrode.
Claim 5
Dependent Claim
23 words
The electrostatic measuring apparatus recited in claim 3 wherein the first and second tines are interposed between the aperture and the seNsitive electrode.
Claim 6
Dependent Claim
39 words
The electrostatic measuring apparatus recited in claim 4 further comprising: first and second mounting means to mount the first and second tines to their respective ends of the tuning fork in offset manner to minimize the plate-to-sensitive electrode spacing.
Claim 7
Dependent Claim
23 words
The electrostatic measuring apparatus recited in claim 3 wherein the first and second tines each define right angle sections at their free ends.
Claim 8
Dependent Claim
22 words
The electrostatic measuring apparatus recited in claim 6 wherein the right angle sections are interposed between the aperture and the sensitive electrode.
Claim 9
Dependent Claim
20 words
The electrostatic measuring apparatus recited in claim 1 further comprising: a preamplifier interposed between the capacitive detector and the detector.
Claim 10
Dependent Claim
18 words
The electrostatic measuring apparatus recited in claim 8 wherein the sensitive electrode is connected to the preamplifier input.
Claim 11
Dependent Claim
27 words
The electrostatic measuring apparatus recited in claim 1 wherein the reference oscillator is connected to the drive means to apply reference signals thereto at the predetermined frequency.
Claim 12
Dependent Claim
34 words
The electrostatic measuring apparatus recited in claim 8 further comprising: a compact probe housing containing the preamplifier, capacitive detector, and the drive means, shield means to shield the capacitive detector from stray capacitive effects.
Claim 13
Dependent Claim
22 words
An electrostatic measuring apparatus recited in claim 1 further comprising a high gain operational amplifier connected to the output of the detector.
Claim 14
Dependent Claim
99 words
The electrostatic measuring apparatus recited in claim 12 for measurement of the electro static potential of a surface further comprising: a housing of conductive material, said capacitive detector being mounted in the housing which provides a substantially isolated environment therefor, a feedback circuit connected between the output of the operational amplifier and the housing to drive the latter and the sensitive electrode very close to the electrostatic potential being measured to create a substantially zero field condition which does not disturb the electrostatic charge distribution of the surface to produce an accurate replica of the electrostatic potential under measurement.
Claim 15
Dependent Claim
23 words
The electrostatic measuring apparatus recited in claim 13 wherein the housing comprises a bottom plate defining an aperture located opposite the sensitive electrode.
Claim 16
Dependent Claim
112 words
In a capacitive modulator having a tuning fork with drive means to vibrate the tuning fork at a predetermined frequency and a sensitive electrode subject to capacitive coupling, the improvement comprising: a tuning fork having first and second ends, first and second mounting means respectively mounted in offset manner to the first and second ends, first and second tines respectively attached to the first and second mounting means extending therefrom in substantially opposite direction relative respectively to the first and second ends, operative to vary the coupling relationship to which the sensitive electrode is subject and produce modulated signals at the sensitive electrode having a carrier frequency equal to the predetermined frequency.
Claim 17
Dependent Claim
112 words
In a capacitive modulator having a tuning fork with drive means to vibrate the tuning fork at a predetermined frequency and a sensitive electrode subject to capacitive coupling, the improvement comprising: a tuning fork having first and second ends, first and second mounting means respectively mounted in offset manner to the first and second ends, first and second tines respectively attached to the first and second mounting means extending therefrom in substantially opposite direction relative respectively to the first and second ends, operative to vary the coupling relationship to which the sensitive electrode is subject and produce modulated signals at the sensitive electrode having a carrier frequency equal to the predetermined frequency.
Claim 18
Dependent Claim
42 words
In the capacitive modulator recited in claim 15, wherein the first and second tines are caused to oscillate in opposite phase at equal amplitude by the tuning fork to alternately couple and decouple the sensitive electrode which is subject to capacitive coupling.
Claim 19
Dependent Claim
32 words
In the capacitive modulator recited in claim 16, a housing, the sensitive electrode being mounted therein, the housing having a plate defining an aperture located opposite the surface of the sensitive electrode.
Claim 20
Dependent Claim
22 words
In the capacitive modulator recited inclaim 17, wherein the first and second tines are interposed between the aperture and the sensitive electrode.
Claim 21
Dependent Claim
23 words
In the capacitive modulator recited in claim 18, wherein the first and second mounting means are operative to minimize the plate-to-sensitive electrode spacing.
Claim 22
Dependent Claim
22 words
In the capacitive modulator recited in claim 17, wherEin the first and second tines define right angle sections at their free ends.
Claim 23
Dependent Claim
22 words
In the capacitive modulator recited in claim 20, wherein the right angle sections are interposed between the aperture and the sensitive electrode.
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) | 1978-11-17 | 1979-05-19 | 1979-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-17 | 1983-05-19 | 1983-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-17 | 1987-05-19 | 1987-11-18 | $7700.00 | Window Closed / Lapsed |