Question { Exxon Mobil, 12033 }

When a field input to plc is coming from 400 to 600 meters
and the input is in 24 V DC? So signal cable of which cross
section i should select for proper signal to plc?

Answer

you can use 0.5 Sq mm shieled for analog .....Upto 600 m no
problem ....but generally as per standerds above 500m you
will have to go with Fibre optic cable

Question { 6666 }

I want to take temp. data from recorder to computer. Which
communication system is best from this option(Rs 232-
485/ethernet/USB)?

Answer

It all depents upon your computer or monitering Equipment
distance and also the purpose i.e.to control or to monitor.

the distance limitations and speed of responce is as
follows for
1)RS 232 --distance =20 feet--speed limited to KBPS
2)RS 485 --Distance upto 1500 feet --Speed Limited to KBPS
3)ETHERNET PORT ---DISTANCE UPTO 500 METERS --sPEED LIMITED
TO 100mbps..BUT now a days it is enhancet to GBPS provided
that the connectivity should be Fibreoptic
4)I haven seen instruments with USB compatibility ,but we
can convert many ports to USB