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.

hgmjr

 

These questions appear to be part of a assignment.

I recommend you give them a shot and then post your answers for the membership to take a look at and comment upon.

hgmjr

Hi,

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
http://en.wikipedia.org/wiki/Current_loop
Here is one about PLCs
http://en.wikipedia.org/wiki/Programmable_logic_controller
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.