Title: +038=360.000-OU045T_03-PCD2.m4160 PLS SBC - Hardware Manual.pdf
The relay contacts on this module are switched. However, it is still recommended to connect a suppressor element to the load.(Often obtainable as a standard component of certified gates and valves).When carrying direct current, it is recommended to install a protective diode across the load, even where an ohmic load is theoretically present. In practice, there will always be an inductive portion (connecting cable, resistor winding etc.). Note that the switch-off time will be extended.(Tau approx. L / RL * √ (RL * IL / 0.7).For direct current, the transistor output modules are recommended.A.3.4 Details of relay manufacturers for sizing of RC elementsContact protection circuits:The purpose of contact protection circuits is to suppress arcing and hence to increase the service life of the contact elements. Any protective circuit may have disadvantages as well as advantages. For how to suppress arcing with an RC element, see figure opposite.