All of our Reed switches are 100% tested in our Standard Test Coils and measured in ampere-turns (AT). Put simply, we have coils wound in a specific coil form, with a given number of turns. We supply a ramp of current to the coil. When the contacts close, we calculate the number of turns of the coil multiplied by the current flowing when the contacts actually closed, to give us the pull-in AT for that Reed switch. Correspondingly, when measuring the point at which the contacts open, also in AT, we similarly measure the current flowing in the coil at the point of opening and calculate it.
Care must be taken when buying Reed switches or Reed sensors from vendors other than Standex Electronics. There is no standardised test coil. All companies have their own test coils and therefore their own AT ranges specific to their test coils.
In this section we describe our test coils so that comparisons can be made with other manufacturers’ test coils and AT ranges. It is also very important to note that the AT measurements refer to uncut, unbent Reed switches. Bending and/or cutting the Reed switches will dramatically alter their opening and closing AT points. When we know the final cutting and bending of a Reed switch or Reed sensor, we typically supply that modified value.
