National Instruments 1191 User Manual

National Instruments 1191 User Manual Manual pdf 26 page image

Chapter 2 Using the SCXI-119XSCXI-1190/1191/1192 User Manual 2-4 ni.comSCXI backplane. National Instruments is not liable for any damages or injuries resultingfrom exceeding maximum voltage ratings. Refer to Appendix A, Specifications, forspecific information.Caution Always disconnect all signals from the front connectors and power off the SCXIchassis before removing the SCXI-119X from the chassis. Observe electrostatic dischargehandling precautions during and after removal of the module, or when connecting anddisconnecting signals on the front panel.Contact ProtectionCaution The contacts of the relays are rated for a life of 5 × 10 6 mechanical operationswhen operated with no signal or a very small signal present. When high-power loads areswitched, arcing can occur across the relay contacts that will reduce their useful life. SeeAppendix A, Specifications, for lifetime ratings for each module. If your setup allows, it isalways best to turn off the input signals connected to the switch module during theswitching operation to avoid contact arcing within the switch. Switching large inductiveloads can also cause contact arcing. In such instances, install a flyback diode or varistoracross the inductance to protect the switch.