| 摘要 |
PROBLEM TO BE SOLVED: To shorten a switching phase and to enhance a uniform magnetic field switching frequency by supplying an additional current to a field winding of an electromagnet immediately after a half wave of each time of a field current of a pulse-like DC by using an additional current source. SOLUTION: A magnetic induction type flowmeter comprises, for example, an additional voltage source 15, and an additional current source 14 having a storage capacitor 16 and a power supply switch 17. The current source 14 is controllable depending upon a field winding of a field current I flowing through an electromagnet. At a steady state time of the case that the current I corresponds to a target value, the switch 17 is in a stopped state, and the switch 17 is controlled to a continuity state immediately after start of a half wave of each time of a pulse-like DC flowing to a field winding 5 at a switching time continued to the steady state at each time. Thus, an electromagnetic energy of the winding 5 is obtained from an electrostatic energy stored in a storage capacitor, and the current I is abruptly raised by a reaction with the electromagnetic energy existing in the winding 5 at the initial time.
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