Configuration and Installation Chapter 2SCXI-1160 User Manual 2-10 © National Instruments CorporationFront Connector Signal DescriptionsPin Signal Name DescriptionA1, A3, A5, A7, NO <15..0> Normally Open Contact – These are theA9, A11, A13, normally open contacts of the relaysA15, A17, A19, 15 through 0.A21, A23, A25,A27, A29, A31B2, B4, B6, B8, COM <15..0> Common Contact – These are the commonB10, B12, B14, contacts of the relays 15 through 0.B16, B18, B20,B22, B24, B26,B28, B30, B32C1, C3, C5, C7, NC <15..0> Normally Closed Contact – These are theC9, C11, C13, normally closed contacts of the relaysC15, C17, C19, 15 through 0.C21, C23, C25,C27, C29, C31All contacts have a working common mode voltage of 250 VAC or VDC. The contact-to-contact breakdown voltage is 750 Vrms. The contact-to-coil breakdown voltage is 1,500 Vrms.Please refer to the module specifications listed in Appendix A for further details beforeconnecting the signals to the relay contacts.Contact Protection for Inductive Load ConnectionsWhen inductive loads are connected to the relays, a large counter electromotive force may occurat relay switching time due to the energy stored in the inductive load. These flyback voltages canseverely damage the relay contacts and greatly shorten the life of the relay.It is best to limit these flyback voltages at your inductive load by installing a flyback diode forDC loads or an MOV for AC loads. Refer to the section, 3. Contact Protection, in Appendix F,Aromat Relay Technical Data , for further details.In addition, the module contains pads on which you can place an arc suppressor protection circuitto limit the voltage spike generated during the switching of inductive loads. These pads arelocated between the COM position and the NO position and between the COM position and theNC position of the relays.
