The overdrive of the coil is also a critical parameter in making the DCR measurement. Simply defined: it is the voltage ( or current) above the actual pull-in (or closure) point where the DCR measurement is made. If the reed contacts close with 3.0 volts applied, adding an increased voltage above 3.0 Volts and testing at that point would represent the overdrive level. A reasonable overdrive number is 40%. Here for 3.0 Volts this represents a voltage increase of 1.2 volts or a test level of 4.2 volts applied to the coil.