Patent US3783686A successfully refreshed from Google Patents.
US3783686A
Expired / Lapsed
US
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Magnetic flowmeter arrangement
Assignee: Fischer and Porter Co
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Filing: 1971-11-05
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Granted: 1974-01-08
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Expires: 1991-11-05
Abstract
Abstract A magnetic flowmeter in which a pair of metering electrodes is disposed at diametrically opposed points in a flow tube through which flows the fluid to be measured, a magnetic field being established at right angles to the direction of flow by an excitation winding. The winding is energized by a cyclical voltage derived from an a-c power line, the polarity of the cyclical voltage being reversed at a rate which is a sub-multiple of the line frequency whereby each interval between successive points of reversal contains the same number of full cycles and the polarity of the last half cycle in each interval is the same as the first half cycle in the succeeding interval. The arrangement is such as to cancel error voltage components resulting from line frequency disturbances.
Inventors
- 👤 R Hentschel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 14:58
CPC Classifications
G; G01; G01F; G01F1/00; G01F1/56; G01F1/58; G01F1/60
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
206 words
In a magnetic flowmeter provided with a flow tube for conducting the fluid to be measured, a pair of metering electrodes disposed at diametrically opposed positions in said tube, and an excitation coil to establish a magnetic field in said tube at right angles to the direction of fluid flow to produce a singal which is applied to an indicator; a circuit for applying an enegizing voltage to said coil comprising, a. means connecting said circuit to an a-c power line to provide a cyclical voltage whose frequency corresponds to the line frequency, a parasitic voltage derived from said line being produced across said metering electrodes, b. means to reverse the polarity of the cyclical voltage at a rate which is a sub-multiple of the line frequency whereby each interval between successive points of reversal contains the same number of full cycles, and the polarity of the last half cycle in each interval is the same as the first half cycle in the succeeding interval, and c. means to apply said periodically reversed cyclical voltage to said excitation coil to produce said signal across said metering electrodes which depends on flow rate and which reverses in phase each time said cyclical voltage is reversed in polarity.
Claim 2
Dependent Claim
206 words
In a magnetic flowmeter provided with a flow tube for conducting the fluid to be measured, a pair of metering electrodes disposed at diametrically opposed positions in said tube, and an excitation coil to establish a magnetic field in said tube at right angles to the direction of fluid flow to produce a singal which is applied to an indicator; a circuit for applying an enegizing voltage to said coil comprising, a. means connecting said circuit to an a-c power line to provide a cyclical voltage whose frequency corresponds to the line frequency, a parasitic voltage derived from said line being produced across said metering electrodes, b. means to reverse the polarity of the cyclical voltage at a rate which is a sub-multiple of the line frequency whereby each interval between successive points of reversal contains the same number of full cycles, and the polarity of the last half cycle in each interval is the same as the first half cycle in the succeeding interval, and c. means to apply said periodically reversed cyclical voltage to said excitation coil to produce said signal across said metering electrodes which depends on flow rate and which reverses in phase each time said cyclical voltage is reversed in polarity.
Claim 3
Dependent Claim
26 words
A circuit as set forth in claim 1, further including a low pass filter and means to apply said signal to said indicator through said filter.
Claim 4
Dependent Claim
110 words
A circuit as set forth in claim 1, wherein said means to reverse the polarity of the cyclical voltage is constituted by a rectifier bridge each of whose legs is constituted by a bi-directional rectifier, the input diagonals of said bridge being connected to said power line, the output diagonals being connected to said excitation coil, and means alternately at a rate in accordance with said sub-multiple frequency, to trigger a first pair of said legs to cause said line voltage to be applied to said coil in one direction and to trigger the second pair of legs to cause said line voltage to be applied in the reverse direction.
Claim 5
Dependent Claim
37 words
A circuit as set forth in claim 3, wherein said triggering means includes a counter which counts the cycles of the cyclical voltage, and after a predetermined number is counted, acts to effect said reversal in direction.
Claim 6
Dependent Claim
17 words
A circuit as set forth in claim 3, wherein each bi-directional rectifier is constituted by a triac.
Claim 7
Dependent Claim
24 words
A circuit as set forth in claim 5, further including an R-C network connected across each triac to prevent excessively rapid voltage changes thereacross.
Claim 8
Dependent Claim
20 words
A circuit as set forth in claim 3, further including a current-limiting resistor interposed between said line and said bridge.
Claim 9
Dependent Claim
45 words
A circuit as set forth in claim 1, further including a synchronous rectifier interposed between said indicator and said metering electrodes, and means including an auxiliary coil disposed in said magnetic field to produce a control voltage for governing the operation of said synchronous rectifier.
Claim 10
Dependent Claim
24 words
A circuit as set forth in claim 1, wherein said indicator has a relatively slow response time in comparison to the polarity reversing rate.
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) | 1977-01-07 | 1977-07-09 | 1978-01-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-07 | 1981-07-09 | 1982-01-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-07 | 1985-07-09 | 1986-01-08 | $7700.00 | Window Closed / Lapsed |