You are not registered yet. Please click here to register!


 
 
plc storereviewsdownloads
This board is for PLC Related Q&A ONLY. Please DON'T use it for advertising, etc.
 
Try our online PLC Simulator- FREE.  Click here now to try it.

---------->>>>>Get FREE PLC Programming Tips

New Here? Please read this important info!!!


Go Back   PLCS.net - Interactive Q & A > PLCS.net - Interactive Q & A > LIVE PLC Questions And Answers

PLC training tools sale

Reply
 
Thread Tools Display Modes
Old September 8th, 2004, 03:28 AM   #1
labingtone
Member
Philippines

labingtone is offline
 
Join Date: Aug 2002
Location: Manila, Philippines
Posts: 113
analog wire color scheme

hi to all,

Im bulding a panel that constitute a plc and analog io card.

discrete inputs like 24vdc, 110vac, 220vac and many more.... has a color coding scheme on the wiring.

my question is analog signal like 4-20ma, 0-10vdc, milivolt signal, has color coding scheme also?

any input related to my question is highly appreciated.


many thanks,

lovington dela cruz
  Reply With Quote
Old September 8th, 2004, 08:05 AM   #2
Tom Jenkins
Lifetime Supporting Member
United States

Tom Jenkins is offline
 
Tom Jenkins's Avatar
 
Join Date: Apr 2002
Location: Milwaukee, WI
Posts: 5,287
We use the same color on analog wiring that we use on DC discrete wiring. In our case, that's blue for both leads. It makes sense, since the analog signals are usually powered from 24 VDC wires. We rely on the wire numbers to differentiate between + and - signals.

I've seen lots of attempts to use a code, say red or white for +, black for - . The problem is that if you have multiple devices in the loop, like an indicator, an analog card, and a recorder, you have to go "+ to +" or "- to -" between devices at some point. This interferes with the consistency of the color code. If you have a loop powered device you start out with the power supply +24 VDC and this is blue anyway. I gave up trying to fight it, and went to our present scheme.
  Reply With Quote
Old September 8th, 2004, 09:01 PM   #3
Bruce99
Member
Canada

Bruce99 is offline
 
Bruce99's Avatar
 
Join Date: Jul 2004
Location: Prince George
Posts: 341
DC

We use standard DC wiring.
Black is neg or common or chassis ground.
Green or bare is power supply ground, bonding conductor, or shield.
Everything else is positive. Many cables use a combination of colours, like orange-blue, white-red, yellow-white. Some twist pairs
just to confuse you. On these you'll have to make up your own rules.
Tom is quite right. A loop can go through a meter, Input module, amp or transducer, good luck matching colours
Have fun!
Bruce
  Reply With Quote
Old September 8th, 2004, 09:22 PM   #4
jimbo3123
Member
United States

jimbo3123 is offline
 
Join Date: Sep 2003
Location: Detroit Area
Posts: 550
Like Tom said, this is a tough question, with the way that analog loops work.

However, we typically use two wire belden cable with a clear and black lead plus a bare shield. For basic loops, we generally use black for the negative and clear for the positive. Complex loops usually start that way, but in the end you end up having to cross things up. Your best bet is to rely on the wire numbers to keep things straight.

Thermocouple wires are a whole different animal. No one has mentioned them yet, but I feel like I should at least throw them in the discussion. Each type of thermocouple has its own associated wire type. The wire type is generally identified by the wire colors and labeling on the outside of the cable. There are typically two wires, one red and one another color which varies depending on the type of thermocouple that the wire is intended for. The red wire is always the Negative (which still strikes me as odd, but that's the way it is) AFAIK, these are always wired point-to-point. One end being the thermocouple itself, and one end being the controller/measuring device. Terminals can be used, but these need to be special terminals designed for the type of thermocouple to be used.
  Reply With Quote
Reply
Jump to Live PLC Question and Answer Forum

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Topics
Thread Thread Starter Forum Replies Last Post
S5 115U CPU943B ( how many analog can fit it ) teh LIVE PLC Questions And Answers 4 September 1st, 2006 08:38 AM
Analog out to analog in on same plc thierry2003 LIVE PLC Questions And Answers 6 January 25th, 2006 11:18 AM
simatic 135u analog value sahin2000 LIVE PLC Questions And Answers 1 January 13th, 2005 06:34 PM
460-7la12 CONTROLTESTGUY LIVE PLC Questions And Answers 1 October 9th, 2004 01:40 PM
Analog input issue! NoName LIVE PLC Questions And Answers 9 July 8th, 2004 04:10 AM


All times are GMT -5. The time now is 02:00 AM.


.