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→Measuring of Contact Resistance
For contacts designed to cover multiple load ranges, the measuring category for the lowest range must be used. Contact resistance measurement usually is carried out following the 4-wire method at a temperature of 27°C ± 1°C and relative humidity of 63 – 67% RH.
By adding an upper threshold value (for ex. the 90% contact resistance value of the statistical cumulative frequency), it can be assured that that those contacts are fulfilling the requirement from their new state for the respective application. The current carrying in normal dynamical operating devices is also assured by this measurement procedure. It is however not a valid indicator for the further behavior in a given application. To determine this, electrical life tests have to be performed under real electrical loads.
<figure id="fig:Relation between the breaking currents of relays and electrical life requirements of switching systems">
