US4404481A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Capacitance to voltage conversion apparatus
Assignee: Panasonic Holdings Corp
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Filing: 1981-10-19
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Granted: 1983-09-13
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Expires: 2001-10-19
Abstract
Abstract A C-V(capacitance-to-voltage) conversion apparatus usable e.g. for detecting physical parameters such as pressure, distance and angle. The apparatus comprises a capacitive sensor, a C-PW(capacitance-to-pulse width) conversion circuit, and a PW-V(pulse width-to-voltage) conversion circuit. The capacitive sensor converts a physical parameter to a capacitance, but has a non-linear conversion characteristic. The C-PW conversion circuit converts the capacitance to a pulse signal whose mean value is proportional to the capacitance, by controlling a charging-discharging cycle of the capacitive sensor and a reference capacitor. The PW-V conversion circuit converts the pulse signal to a d.c. voltage and at the same time compensates for the non-linearity of the capacitive sensor's conversion characteristic so that the d.c. voltage is proportional to the physical parameter.
Inventors
- 👤 Toshimine Ide
- 👤 Takeshi Shimamoto
- 👤 Yoshiaki Igarashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 00:16
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/94; H03K17/965; H03K17/975; G; G01; G01D; G01D3/00; G01D3/02; G01D5/00; G01D5/12; G01D5/14; G01D5/24; G01D5/241; G01D5/2417; G01L; G01L9/00; G01L9/0041; G01L9/0072; G01L9/12
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
211 words
A C-V conversion apparatus comprising: a capacitive sensor whose capacitance is changed corresponding to a change of a physical parameter; a reference capacitor; a first charging circuit for charging said capacitive sensor; a second charging circuit for charging said reference capacitor; a first discharging circuit for discharging said capacitive sensor; a second discharging circuit for discharging said reference capacitor; a charging/discharging control means for controlling a charging and discharging cycle of said capacitive sensor and said reference capacitor; a reference voltage source for generating a reference voltage; a first comparator for comparing a voltage of said capacitive sensor with said reference voltage and for generating a control signal to control said charging/discharging control means; a second comparator for comparing a voltage of said reference capacitor with said reference voltage and for generating a pulse signal whose mean value is proportional to a capacitance of said capacitive sensor; and a pulse width-voltage conversion circuit for convertng said pulse signal to a d.c. voltage signal, said pulse width-voltage conversion circuit having a characteristic for compensating for a non-linear conversion characteristic of said capacitive sensor by selecting a charging time constant and a discharging time constant of said pulse width-voltage conversion circuit so that said d.c. voltage signal is proportional to said physical parameter.
Claim 2
Dependent Claim
211 words
A C-V conversion apparatus comprising: a capacitive sensor whose capacitance is changed corresponding to a change of a physical parameter; a reference capacitor; a first charging circuit for charging said capacitive sensor; a second charging circuit for charging said reference capacitor; a first discharging circuit for discharging said capacitive sensor; a second discharging circuit for discharging said reference capacitor; a charging/discharging control means for controlling a charging and discharging cycle of said capacitive sensor and said reference capacitor; a reference voltage source for generating a reference voltage; a first comparator for comparing a voltage of said capacitive sensor with said reference voltage and for generating a control signal to control said charging/discharging control means; a second comparator for comparing a voltage of said reference capacitor with said reference voltage and for generating a pulse signal whose mean value is proportional to a capacitance of said capacitive sensor; and a pulse width-voltage conversion circuit for convertng said pulse signal to a d.c. voltage signal, said pulse width-voltage conversion circuit having a characteristic for compensating for a non-linear conversion characteristic of said capacitive sensor by selecting a charging time constant and a discharging time constant of said pulse width-voltage conversion circuit so that said d.c. voltage signal is proportional to said physical parameter.
Claim 3
Dependent Claim
17 words
A C-V conversion apparatus according to claim 1, wherein said charging/discharging control means comprises a monostable multivibrator.
Claim 4
Dependent Claim
75 words
A C-V conversion apparatus according to claim 1, wherein said charging/discharging control means comprises: a second reference voltage source for generating a second reference voltage; a third comparator for comparing the voltage of said capacitive sensor with said second reference voltage and for generating a second control signal; and a flip-flop circuit for controlling said charging and discharging cycle, said flip-flop circuit being set by said control signal and reset by said second control signal.
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) | 1986-09-12 | 1987-03-14 | 1987-09-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-09-12 | 1991-03-14 | 1991-09-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-09-12 | 1995-03-14 | 1995-09-13 | $7700.00 | Window Closed / Lapsed |