The coils for any given reed switch must have a certain number of Ampere turns to develop adequate magnetic field to close the contacts (switch’s blades).

It is essential there is a margin of overdrive so the device doesn’t operate at around the nominal coil voltage to ensure stable operation. The common rule is that at 25°C the operate voltage of the device will be less than 75% of the nominal voltage and the release greater than 10%. This ensures stable operation up to the maximum working temperature.

Most OEMs, including Pickering, sell catalog relays that can be driven at 3, 5, 12 or 24V (custom voltage levels can also be quoted). For a given coil power, a higher voltage means a lower current, which in turn means thinner coil wire can be used to balance the number of ampere turns needed.

With high voltage reed switches, the contact gap defines the high voltage performance, the wider this is, the higher the working voltage. However, the wider the contact gap, the less sensitive the reed switch. As it is the current flowing through the coil that generates the magnetic field, lower coil resistances are necessary in higher voltage relays.

If you would like advice on this or any of the other issues discussed above, please contact us.