Discussion in 'Programmer's Corner' started by Dave1971, May 17, 2007.
Thanks for your help
These questions appear to be part of a homework assignment or perhaps test questions.
I recommend you give them a shot and then post your answers for the membership to take a look at and comment upon.
They are part of a assignment, i haven`t a clue on how to answer these question, all i know is analogue signals have problems with noise.
I would start with Google or wikipedia in the absence of any other textual resources. Here is an article on current loops of which the 4-20 analog one is described
Here is one about PLCs
Get the idea?
Ugh, normally I hate it when people come to the forums for homework answers.
I will try to give you a little direction though.
i. What does a current loop have in common at every point (Think KCL)?. How would this be an advantage over a voltage signal with long (possibly unknown) wire runs/voltage drops?
ii. Look at the price difference between an analog input and digital input card for any PLC mfg.