Magnetic flowmeter
First Claim
1. In an electromagnetic flowmeter provided with a flow tube through which the fluid to be metered is conducted, the tube having a pair of electrodes mounted at diametrically-opposed positions thereon and including excitation coils to establish a magnetic field in the tube which is transverse to the direction of flow, the combination comprising:
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Accused Products
Abstract
A magnetic flowmeter wherein liquid to be metered is conducted through a flow tube to intersect a transverse magnetic field established by an electromagnet. The voltage induced in the fluid is transferred to a pair of electrodes mounted at diametrically-opposed positions on the flow tube. The electromagnet is energized by a low-frequency wave which is produced by applying the output of a full-wave rectifier to the excitation coils of the electromagnet through a switching element. The switching element acts to chop the full-wave rectified output in accordance with high-frequency pulses whose frequency is higher than that of a commercial electric power line, the duty cycle thereof being modulated by a low-frequency, sinusoidal wave whose frequency is less than that of the commercial line.
15 Citations
6 Claims
- 1. In an electromagnetic flowmeter provided with a flow tube through which the fluid to be metered is conducted, the tube having a pair of electrodes mounted at diametrically-opposed positions thereon and including excitation coils to establish a magnetic field in the tube which is transverse to the direction of flow, the combination comprising:
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2. A. switching means interposed between said coils and a power source;
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B. control means to effect "on-off" control of said switching means at a rate which is higher than a predetermined commercial a-c power frequency; and C. means gradually to change the duty ratio of said control means at a low-frequency rate which is less than said commercial frequency.
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Specification