@Kris: As far as Base-T is concerned, Ethernet in industrial applications is the same as in other applications except for the physical media. The spacings between contact pins of the jack and plug are the same, outline of the mating interfaces internally is also the same but the outer mechanical outlines of the connectors are different. This is due to the required ingress protection ratings (IP65/67).
Honestly, communicating at the fieldbus level implies the capacity to convey time-senstive traffic required with sensors, controllers and actuators in an automobile. Ethernet was not intended to support such traffic because of its nondeterministic arbitration mechanism and packet re-transmission. Even with Switching, some kind of higher-level coordination is needed as in datacenter bridging Ethernet (DCE) where Ethernet co-habitates Fiberchannel and becomes lossless.
Interesting point @docdivakar...what are the examples of industrial Ethernet applications that you mention? and what does it mean that Ethernet application is industrialized? I presume Ethernet packet is Ethernet packet and teh ways to process the packet (including managing colliosions) is always the same...Kris
@Prabhakar: for the redundancies you brought up, the additional pair/s are the way to go. The cables are not as fragile as the regular unshielded twisted pair so I think they do meet criteria for system criticality. Moreover, there are many examples of industrial ethernet deployed in mission-critical installations.
Single twisted pair is fine. But some redundancy is required . The critical systems such as engine control etc need to be separated atleast from this common twisted pair communication channel , in my opinon
There are no industrial Ethernet connectors for just one twisted pair. 2 or 4 pairs are standard and it therefore makes sense to use what is already available in mass production. They are already IP65/67 qualified and are used in industrial automation today.