anologue and digital signals for plc

hi my name is ian and i am working on plc course for my hnc
my question is what is the differnce between anologue signal and digital signals for plc an example for each type would be helpful e.g input and output signal.if any body can help with direction especilly on the web.

I think you'll find your answers in the tutorial on this site.

Help you to help yourself -
If you think about the basic differences between analogue and digital signals (and I hope you do if your are studying for HNC) , then you will be able to answer the first part of your question , now the second part - what would a PLC be used for in industry and how would the PLC gain information necessary for controlling the process .
I think you can answer your own questions.

Digital signals are of the type On or Off, Open or Closed, 1 or 0.
Analog signals have a variable level that ranges between some minimum and maximum level. Analog signals are used to input variable levels such as level of liquid in a tank, temperature measurement, and analog outputs are used to control valve positions for example. Digital inputs are switches and any two-state device. Digital outputs control things like magnetic motor starters, relays, solenoid valves.

That's it , encourage people to think for themselves.
Just what does HNC stand for ?
Hardly Never (at) College ?

Mr Floggle
Apparently HNC stands for Hardly Never Cracked (book). He should get an A at this rate.

MR student
I must admit I have told my instructor I have no idea of what I am doing. That maybe happens one time out of ten and he is patient with me. BUT at least I read the book or other info he gave me. Next week I have to tell him I read the chapter on PID and I am still thoroughly confused and ignorant. He will probably tell me well lets just do it and you will see then.

There are several things you can do.

1. Look at the top of the web page here and look at the tutorial.
2. Spend $40 for the book (also mentioned at top of page). Not very technical but your are not ready for technical yet. Very good book - I used it.
3. AFTER you have done 1 and 2 THEN read the Siemens manual
4. AFTER you get frustrated with the Siemens manual spend the money and take a class at a community college. I am. Best money spent. They have ALL the Allen Bradley small 10 IO up to the SLCs.

Incidentally the outputs do not put out a voltage as such. They are simply relays (switches). A power supply either integral with PLC or separate provides the power. You need to stay within the design paramters fo the output relay and the total load on power supply. Yes you can turn other relays off and on with these.

A hint to get all the help with these guys. When you ask a question have an answer or theory or hypothesis -- whatever -- you think is right. ALSO list brand make model and all that nameplate stuff of equpment. ALSO make model and all that for the relays or loads you want PLC to control. The more info you give em on what you have in mind the more they will help.

Another student.
Dan Bentler