US3624541A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Oscillator circuit
Assignee: MOISTURE REGISTER CO
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Filing: 1969-11-03
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Granted: 1971-11-30
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Expires: 1989-11-03
Abstract
Abstract A field-effect transistor connected in a class C Hartley oscillator circuit has a diode connected to the gate to provide bias. A similar diode is connected in series with the source to provide temperature stabilization of the operating point. Further temperature stabilization is obtained by means of a thermistorcompensated load network. The biasing diode protects against positive high-voltage transients developed in the vicinity of moisture-sensing electrodes coupled to the tank circuit. A second diode is reverse-biased and coupled to the gate with opposite polarity to protect against negative transients. A zener diode connected to the drain prevents it from developing transients of negative voltage. To further protect against high-voltage transients, the moisture-sensing electrodes are coupled to the tank circuit through low-pass filters loaded by neon glowtubes.
Inventors
- 👤 John W Lundstrom
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 23:48
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/20; G; G01; G01N; G01N27/00; G01N27/02; G01N27/22; G01N27/223; H03; H03B; H03B5/00; H03B5/08; H03B5/12; H03B5/1203; H03B5/1228; H03B2200/00; H03B2200/0002; H03B2200/001; H03B5/02; H03B5/04
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
136 words
An oscillator circuit for a moisture content measuring system wherein radiofrequency energy in a tank circuit is coupled to materials containing moisture through fringe-field capacitance electrodes, the Q of said tank circuit being reduced as a measure of moisture content, said oscillator circuit comprising: a field effect transistor having a source, a drain, and a gate, said transistor being connected to said tank circuit in a Class C oscillator configuration; stabilization means for stabilizing said oscillator circuit as the Q of said tank circuit is reduced, said stabilization means including a diode connected in the gate circuit of said transistor in a rectifying configuration for a portion of the radiofrequency energy in said tank circuit whereby self-bias is provided for said oscillator circuit which is proportional to the reduction in the Q of said tank circuit.
Claim 2
Dependent Claim
136 words
An oscillator circuit for a moisture content measuring system wherein radiofrequency energy in a tank circuit is coupled to materials containing moisture through fringe-field capacitance electrodes, the Q of said tank circuit being reduced as a measure of moisture content, said oscillator circuit comprising: a field effect transistor having a source, a drain, and a gate, said transistor being connected to said tank circuit in a Class C oscillator configuration; stabilization means for stabilizing said oscillator circuit as the Q of said tank circuit is reduced, said stabilization means including a diode connected in the gate circuit of said transistor in a rectifying configuration for a portion of the radiofrequency energy in said tank circuit whereby self-bias is provided for said oscillator circuit which is proportional to the reduction in the Q of said tank circuit.
Claim 3
Dependent Claim
47 words
The oscillator circuit of claim 1 wherein: said stabilization means further includes a diode connected in the source circuit of said transistor for cooperation with said diode connected in the gate circuit of said transistor to provide for temperature stabilization of the operating point of said transistor.
Claim 4
Dependent Claim
49 words
The oscillator circuit of claim 1 wherein: said stabilization means further includes a thermistor connected in the drain circuit of said transistor for cooperation with said diode connected in the gate circuit of said transistor to provide temperature stabilization of the sensitivity of the oscillator to tank circuit loading.
Claim 5
Dependent Claim
54 words
The oscillator of claim 3 wherein: said stabilization means further includes a diode connected in the source circuit of said transistor for cooperation with said diode connected in the gate circuit and said thermistor connected in the drain circuit of said transistor to provide for temperature stabilization of the operating point of said transistor.
Claim 6
Dependent Claim
61 words
The oscillator circuit of claim 1 including: means for dissipating transient voltage pulses appearing on said fringe-field capacitance electrodes due to operation of said moisture content measuring system in the vicinity of static electric fields, said dissipating means having a back-biased diode connected in the gate circuit of said transistor whereby negative high voltage transients are shunted through said back-biased diode.
Claim 7
Dependent Claim
38 words
The oscillator circuit of claim 5 wherein: said dissipating means includes a zener diode connected in the drain circuit of said transistor for preventing the voltage at the drain from exceeding the avalanche voltage of said zener diode.
Claim 8
Dependent Claim
165 words
The oscillator circuit of claim 1 including coupling means for coupling each of said fringe-field capacitance electrodes to said tank said coupling means allowing radiofrequency energy to pass to and froM said tank to said electrodes but preventing the pasing of high-voltage transients appearing on said electrodes due to operation of said moisture content measuring system in the vicinity of static electric fields, said coupling means comprising: a first gas discharge tube connected across each of said electrodes, said discharge tube being ionized when high-voltage transients appear on said electrodes; a pi-section low-pass filter connected between each electrode and said tank circuit, said low-pass filter passing the radiofrequencies generated by said oscillator circuit and substantially attenuating the radiofrequencies associated with high-voltage transient pulses; and a second gas discharge tube connected across the junction of said low-pass filter and said tank circuit, said second discharge tube being ionized when remaining high-voltage transient pulses appear at said junction to effectively shunt said transients through said discharge tube.
Claim 9
Dependent Claim
27 words
The oscillator circuit of claim 7 including: a back-biased diode connected in the gate circuit of said transistor for dissipating negative high-voltage transients in the gate circuit.
Claim 10
Dependent Claim
29 words
The oscillator circuit of claim 8 including: a thermistor in the drain circuit of said transistor for temperature stabilization of the sensitivity of the oscillator to tank circuit loading.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-11-29 | 1975-05-31 | 1975-11-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-29 | 1979-05-31 | 1979-11-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-29 | 1983-05-31 | 1983-11-30 | $7700.00 | Window Closed / Lapsed |