I'm building a circuit to measure both voltage and current given to a solenoid valve 24V DC 15W. In parallel to the valve is a voltage divider with 470k + 100k Ohm resistors. In series with the valve is a 1 Ohm 4W resistor. In parallel with both valve and 1 Ohm resistor is a 1n4007 Diode correctly positioned in order to actuate as a Flyback Diode. But yet, whenever i remove the +24V contact of the valve, simulating a opening of a Relay, I still see some sparks flying around. They are easily noticeable. I've measured the peak voltage and indeed it has lowered: from -10V (minimum readable value) to -250mV. But there are still sparks! Is it ok or will it damage a operating relay?