Controlling current flow through magnet coil of magnetic valve - involves measuring continuously voltage drop over magnet coil and power switch

摘要

The current is measured by a resistor in series with the magnet coil according to the dropping voltage. The coil (2) is alternately switched-on and -off by a power switch (3). The switched-off coil is short circuited. The voltage drop across the coil and switch is continuously measured. The current is precisely measured, when the magnet coil is ON, and the measured current and the simultaneously measured voltage are used to determine the ohmic resistance of the coil. With a fixed switching frequency, the magnet coil is ON for different time periods in dependence on the actual voltage and the determined ohmic resistance. ADVANTAGE - Low appts. expenditure, suitable for different currents and for different ohmic resistances and inductivities.