The invention relates to a high /
low voltage switching excitation
system of an
electromagnetic flowmeter with a bypass and an
energy feedback circuit. The excitation
system comprises an adjustable
low voltage source circuit, a high /
low voltage switching circuit, a constant-current circuit, a bypass circuit, an H-bridge excitation circuit, an excitation
control circuit, a logic switching circuit, apower supply detection circuit, the
energy feedback circuit and an
energy leakage circuit. A practical
excitation current detected on a current detecting
resistor is compared with an
excitation current threshold set in the logic switching circuit, thereby obtaining a
control logic which is used for controlling the high / low
voltage switching circuit and the bypass circuit, so as to select an excitation work
voltage; introduction of the bypass circuit accelerates the response velocity of the
excitation current in a coil obviously; the
energy feedback circuit stores the energy fed back from an
excitation coil; the power supply detection circuit, the
energy leakage circuit and a switching protection circuit perform
electrification, outage and error protection on the excitation
system. The excitation system related to the invention improves the
utilization rate of power supply, accelerates the response speed of excitation current, broadens the range of excitation frequency and provides circuit fault protection.