| 摘要 |
PROBLEM TO BE SOLVED: To realize an electromagnetic flowmeter, capable of reducing constant- current control errors generated due to the stray capacitance of a remote cable. SOLUTION: The electromagnetic flowmeter supplies an excitation current from a converter to an excitation coil, provided in a detector via a remote cable means. The converter has a DC voltage source; a switching means for intermittently applying the voltage of the voltage source to the coil via the remote cable means; an excitation current detecting means for converting a current flowing through the coil into a voltage signal and detecting it; an error amplifier for amplifying a difference between the output voltage of the detecting means and a reference voltage; an oscillator for generating a triangular signal, having a constant amplitude and a constant period; a comparator for comparing the output of the amplifier with the triangular signal to conduct on and off controls the switching means according to a compared output; and a holding circuit provided at a front stage of the amplifier.
|
